WEBVTT 00:00:00.840 --> 00:00:03.180 The following content is provided under a Creative 00:00:03.180 --> 00:00:04.570 Commons license. 00:00:04.570 --> 00:00:06.780 Your support will help MIT OpenCourseWare 00:00:06.780 --> 00:00:10.870 continue to offer high quality educational resources for free. 00:00:10.870 --> 00:00:13.440 To make a donation or to view additional materials 00:00:13.440 --> 00:00:17.400 from hundreds of MIT courses, visit MIT OpenCourseWare 00:00:17.400 --> 00:00:18.286 at ocw.mit.edu. 00:00:22.770 --> 00:00:26.190 GABRIEL SANCHEZ-MARTINEZ: Today we have two guest lecturers. 00:00:26.190 --> 00:00:29.820 The one I invited is Professor Peter Furth. 00:00:29.820 --> 00:00:35.070 He's an expert on transit signal priority. 00:00:35.070 --> 00:00:41.466 His own work on reliability before time and then how people 00:00:41.466 --> 00:00:42.924 budget for their travel times, he's 00:00:42.924 --> 00:00:44.790 a really good teacher on that. 00:00:44.790 --> 00:00:46.400 And he's also a bike expert. 00:00:46.400 --> 00:00:48.233 He's really interested in all bicycle stuff, 00:00:48.233 --> 00:00:49.920 but let's not do this publicly. 00:00:49.920 --> 00:00:53.220 Maybe you can get him out of this class 00:00:53.220 --> 00:00:54.390 and ask him something. 00:00:54.390 --> 00:00:56.550 Then we also have-- he dragged someone else 00:00:56.550 --> 00:01:00.280 in from the Netherlands who also knows a lot about transit 00:01:00.280 --> 00:01:01.190 signal priorities. 00:01:01.190 --> 00:01:03.780 So I don't really know what to say about him, 00:01:03.780 --> 00:01:06.274 but we'll find out. 00:01:06.274 --> 00:01:07.440 Maybe you can introduce him. 00:01:07.440 --> 00:01:09.023 PETER FURTH: Yeah, I'll introduce him. 00:01:09.023 --> 00:01:09.810 Yeah, OK. 00:01:09.810 --> 00:01:10.350 Hi all. 00:01:10.350 --> 00:01:10.680 Thanks. 00:01:10.680 --> 00:01:11.670 It's great to be here. 00:01:14.540 --> 00:01:16.050 Before I get into transit priority, 00:01:16.050 --> 00:01:18.900 I just want to tell you a bit more about my background. 00:01:18.900 --> 00:01:21.990 So, I studied here at MIT, and my focus 00:01:21.990 --> 00:01:24.030 was on public transportation. 00:01:24.030 --> 00:01:26.250 Then, I became a professor at Northeastern. 00:01:26.250 --> 00:01:29.295 And after several years, for one thing 00:01:29.295 --> 00:01:31.420 there weren't enough jobs in public transportation. 00:01:31.420 --> 00:01:34.360 And my students needed more training in traffic engineering 00:01:34.360 --> 00:01:36.550 because there were more jobs in that. 00:01:36.550 --> 00:01:39.550 But then the other thing is that our buses were getting 00:01:39.550 --> 00:01:44.079 stuck in traffic all the time, and I wanted to learn, well, 00:01:44.079 --> 00:01:46.120 can't we figure out a way to make the lights turn 00:01:46.120 --> 00:01:47.020 green for a bus. 00:01:47.020 --> 00:01:49.990 I mean if we can get a man on the moon surely 00:01:49.990 --> 00:01:53.540 we should be able to get the lights to turn green for a bus. 00:01:53.540 --> 00:01:57.110 So I got the chance to go to the Netherlands 00:01:57.110 --> 00:01:59.310 for a year, a sabbatical year. 00:01:59.310 --> 00:02:02.210 And almost did a second PhD there, 00:02:02.210 --> 00:02:08.590 studying traffic signal control for transit priority. 00:02:08.590 --> 00:02:10.789 So you have to learn all the traffic signal control, 00:02:10.789 --> 00:02:13.910 and then you can learn, OK, now how do you do transit priority? 00:02:13.910 --> 00:02:15.842 Then I came back to the United States, 00:02:15.842 --> 00:02:17.300 and it took me several years to try 00:02:17.300 --> 00:02:21.240 to figure out how the Dutch traffic signal control-- 00:02:21.240 --> 00:02:24.240 they use different language but it's really about the same. 00:02:24.240 --> 00:02:26.780 There are some differences but it's mostly the same, 00:02:26.780 --> 00:02:30.695 how to say that in American traffic signal control. 00:02:30.695 --> 00:02:32.570 And since then, I've done a lot more work now 00:02:32.570 --> 00:02:37.580 in traffic signal control and transit priority. 00:02:37.580 --> 00:02:40.430 So that's how I come here. 00:02:40.430 --> 00:02:43.160 My title is, Is it help or is it hype? 00:02:43.160 --> 00:02:48.950 And I really mean that because if you go to Zurich 00:02:48.950 --> 00:02:52.590 transit signal priority is real help. 00:02:52.590 --> 00:02:56.420 I went there once on an official visit, 00:02:56.420 --> 00:02:58.490 and I told the people I was visiting, 00:02:58.490 --> 00:03:04.820 I came here because I've heard it said that the trams never 00:03:04.820 --> 00:03:06.290 have a red light. 00:03:06.290 --> 00:03:09.430 He said, Yeah, well that's just about true. 00:03:09.430 --> 00:03:11.750 There are some exceptions he said, of course, 00:03:11.750 --> 00:03:13.802 like at the main square there are so many trams. 00:03:13.802 --> 00:03:15.260 They come from different directions 00:03:15.260 --> 00:03:18.560 so one tram has a red light for another tram. 00:03:18.560 --> 00:03:21.710 But otherwise, there are only one or two intersections 00:03:21.710 --> 00:03:24.710 in the whole city where the trams don't just 00:03:24.710 --> 00:03:26.075 get a green light. 00:03:26.075 --> 00:03:28.700 I learned that in Portland, when they designed their light rail 00:03:28.700 --> 00:03:33.650 in the 1980s, station to station green waves 00:03:33.650 --> 00:03:36.710 are programmed into the traffic signal control. 00:03:36.710 --> 00:03:39.830 Now it doesn't mean zero delay because what that means is when 00:03:39.830 --> 00:03:43.010 a light rail train is at a station, 00:03:43.010 --> 00:03:45.649 there'll be a countdown clock for the driver. 00:03:45.649 --> 00:03:47.690 So there's no point in leaving now because you're 00:03:47.690 --> 00:03:48.773 going to have a red light. 00:03:48.773 --> 00:03:50.870 But if you wait until the appointed time to leave, 00:03:50.870 --> 00:03:57.390 then you will have a green wave to the next station. 00:03:57.390 --> 00:04:00.840 But then we come to applications of transit signal 00:04:00.840 --> 00:04:03.000 priority in the US. 00:04:03.000 --> 00:04:06.990 And you hear these great pronouncements, oh, we're 00:04:06.990 --> 00:04:08.440 doing transit signal priority. 00:04:08.440 --> 00:04:11.850 But when you look into it, there's almost no benefit. 00:04:11.850 --> 00:04:15.150 Sometimes they're saving the bus two seconds 00:04:15.150 --> 00:04:17.610 per intersection or less. 00:04:17.610 --> 00:04:19.269 Often they're not measuring at all. 00:04:19.269 --> 00:04:23.760 So then I have to ask, is it really a help or is it hype? 00:04:23.760 --> 00:04:27.810 And so what I'm going to tell you today 00:04:27.810 --> 00:04:30.090 is some of the standard ways of doing transit signal 00:04:30.090 --> 00:04:32.400 priority, how they work, and how they 00:04:32.400 --> 00:04:35.620 don't work very [AUDIO OUT] have to do to really 00:04:35.620 --> 00:04:43.780 be able to have our buses or trams have nearly zero delay. 00:04:43.780 --> 00:04:46.630 So before we get into detail, why 00:04:46.630 --> 00:04:48.200 are we doing transit priority? 00:04:48.200 --> 00:04:49.990 This is a class on public transportation 00:04:49.990 --> 00:04:53.590 so it probably doesn't need a lot of argument 00:04:53.590 --> 00:04:57.160 but we start with a societal objective. 00:04:57.160 --> 00:05:01.690 Transit offers many benefits to society 00:05:01.690 --> 00:05:04.510 in terms of congestion, air quality, livable communities, 00:05:04.510 --> 00:05:05.680 and so on. 00:05:05.680 --> 00:05:09.610 And transit is mostly competing with car use. 00:05:09.610 --> 00:05:13.620 And what transit can do is break the vicious cycle. 00:05:13.620 --> 00:05:14.690 There's a vicious cycle. 00:05:14.690 --> 00:05:16.930 This is especially strong in developing countries. 00:05:16.930 --> 00:05:19.060 Whereas people get more money, one 00:05:19.060 --> 00:05:22.060 of the first things they want to buy when they have more money 00:05:22.060 --> 00:05:23.020 is a car. 00:05:23.020 --> 00:05:26.920 And then with the car the car roads become congested 00:05:26.920 --> 00:05:28.480 and then that slows down transit. 00:05:28.480 --> 00:05:31.090 So then people don't want to use transit 00:05:31.090 --> 00:05:33.820 so then they get more cars and it just keeps going. 00:05:33.820 --> 00:05:38.950 If you can do priority for a bus, then 00:05:38.950 --> 00:05:41.200 that breaks that cycle and now people will say, 00:05:41.200 --> 00:05:44.930 I'm going to use the bus or the train to have priority. 00:05:44.930 --> 00:05:51.770 And then having priority for transit makes a lot of sense 00:05:51.770 --> 00:05:58.400 because the tradition in Boston has been a very extreme all 00:05:58.400 --> 00:06:00.020 or nothing priority. 00:06:00.020 --> 00:06:02.690 We know one way to give transit priority. 00:06:02.690 --> 00:06:04.970 Total grade separation. 00:06:04.970 --> 00:06:10.460 We build a subway, and they're protected from congestion. 00:06:10.460 --> 00:06:13.930 So we know how to do the $2 billion priority 00:06:13.930 --> 00:06:17.170 and we also know the other extreme, which is nothing. 00:06:17.170 --> 00:06:18.910 Buses you're welcome to use our roads. 00:06:18.910 --> 00:06:21.610 I mean when the light turns green everybody else can go, 00:06:21.610 --> 00:06:23.780 I guess you can too. 00:06:23.780 --> 00:06:27.160 It doesn't make sense to only have those two extremes. 00:06:27.160 --> 00:06:30.130 And that's what the city of Zurich did. 00:06:30.130 --> 00:06:34.750 The main planners for Zurich wanted to build a subway. 00:06:34.750 --> 00:06:36.190 This was in the 1970s. 00:06:36.190 --> 00:06:38.620 Big cities that didn't have subway systems 00:06:38.620 --> 00:06:40.060 then were building them. 00:06:40.060 --> 00:06:45.852 But the citizens said, no, spend a tenth of the money-- 00:06:45.852 --> 00:06:47.560 because subways are incredibly expensive, 00:06:47.560 --> 00:06:49.660 spend about a tenth of that money 00:06:49.660 --> 00:06:53.680 to give our trams priority, and then we 00:06:53.680 --> 00:06:56.270 don't have to walk down in the basement. 00:06:56.270 --> 00:06:59.830 And instead we like how the trams are right. 00:06:59.830 --> 00:07:01.900 It's almost like an extension of the sidewalk. 00:07:01.900 --> 00:07:05.140 You just step on, ride, step off. 00:07:05.140 --> 00:07:08.800 So it makes sense to have some means of priority that's 00:07:08.800 --> 00:07:11.360 in between all or nothing. 00:07:11.360 --> 00:07:13.380 And we have two ways of doing priority. 00:07:13.380 --> 00:07:14.860 It's priority in space. 00:07:14.860 --> 00:07:19.480 That means you give the buses or the trams their own lane, 00:07:19.480 --> 00:07:20.420 their own space. 00:07:20.420 --> 00:07:22.360 And then there's priority at time, 00:07:22.360 --> 00:07:26.340 which comes at traffic signals. 00:07:26.340 --> 00:07:31.790 Priority, it's easy to see what it means to a transit user. 00:07:31.790 --> 00:07:35.210 It means you get a faster ride and a more reliable ride. 00:07:35.210 --> 00:07:38.120 So it saves you time. 00:07:38.120 --> 00:07:41.900 The reliability means it also saves you in buffer time. 00:07:41.900 --> 00:07:44.300 But it's important to know what transit priority means 00:07:44.300 --> 00:07:45.950 to a transit operator. 00:07:45.950 --> 00:07:47.990 The savings in time means they might 00:07:47.990 --> 00:07:54.170 be able to run their route with fewer vehicles and less labor. 00:07:54.170 --> 00:07:56.540 And the improved reliability means 00:07:56.540 --> 00:08:01.100 they don't have to have as much recovery time. 00:08:01.100 --> 00:08:07.800 So in Portland they had a case at Tri-Mat Line 12. 00:08:07.800 --> 00:08:10.751 The transit priority they put in didn't reduce the running time 00:08:10.751 --> 00:08:11.250 that much. 00:08:11.250 --> 00:08:13.920 But it reduced the variability of running time 00:08:13.920 --> 00:08:18.810 so much that they were able to reduce the cycle 00:08:18.810 --> 00:08:22.140 time by 11 minutes. 00:08:22.140 --> 00:08:24.930 And if you reduce the cycle time by 11 minutes on a route 00:08:24.930 --> 00:08:27.360 that runs every 11 minutes or every-- 00:08:27.360 --> 00:08:31.730 then you save one bus and one operator. 00:08:31.730 --> 00:08:35.049 And that lowers your cost tremendously. 00:08:35.049 --> 00:08:37.260 So priority is important for passengers, 00:08:37.260 --> 00:08:40.690 it's important for the operator. 00:08:40.690 --> 00:08:48.770 And I told you I studied traffic signals in the Netherlands 00:08:48.770 --> 00:08:53.660 and it was in the context of transit priority-- 00:08:53.660 --> 00:08:55.590 how can we make transit service better? 00:08:55.590 --> 00:09:01.760 So here you have two graphs, each line 00:09:01.760 --> 00:09:04.310 represents the trajectory of a vehicle. 00:09:04.310 --> 00:09:05.810 On the bottom is space. 00:09:05.810 --> 00:09:09.200 We're going from station CL across to station S. 00:09:09.200 --> 00:09:12.260 And on the vertical axis is how far off schedule are we? 00:09:12.260 --> 00:09:14.930 So if you're at the 0 line, that means 00:09:14.930 --> 00:09:17.790 you're perfectly on schedule. 00:09:17.790 --> 00:09:24.600 And as you go above the line, you're earlier and earlier. 00:09:24.600 --> 00:09:27.720 And as you go below the line your later and later. 00:09:27.720 --> 00:09:30.810 So this is what the operation was, kind of 00:09:30.810 --> 00:09:33.510 if you just let it be. 00:09:33.510 --> 00:09:35.642 The buses will start pretty close to on time 00:09:35.642 --> 00:09:38.100 but they got later and later and later, and the spread just 00:09:38.100 --> 00:09:39.391 gets worse and worse and worse. 00:09:39.391 --> 00:09:40.680 This is nothing new. 00:09:40.680 --> 00:09:42.690 If you know about transit service 00:09:42.690 --> 00:09:47.700 you know how there's these random shocks 00:09:47.700 --> 00:09:48.617 could make a bus late. 00:09:48.617 --> 00:09:51.033 And once you're late you become later and later and later. 00:09:51.033 --> 00:09:53.320 And once you're early you become earlier and earlier 00:09:53.320 --> 00:09:53.850 and earlier. 00:09:53.850 --> 00:09:58.544 But here they put in a system with priority 00:09:58.544 --> 00:09:59.460 at the traffic lights. 00:09:59.460 --> 00:10:02.130 And it's conditional priority. 00:10:02.130 --> 00:10:06.630 If the bus is early, no priority for you but if the bus is late, 00:10:06.630 --> 00:10:09.090 we're going to give very aggressive priority 00:10:09.090 --> 00:10:11.880 so that bus can cruise right through the intersection. 00:10:11.880 --> 00:10:14.970 So if the average time to get through an intersection 00:10:14.970 --> 00:10:18.000 is let's say half a minute, but with priority 00:10:18.000 --> 00:10:20.700 that's going to be 10 seconds and without priority 00:10:20.700 --> 00:10:22.320 that's going to be 50 seconds. 00:10:22.320 --> 00:10:26.760 That's a 40 second difference that I 00:10:26.760 --> 00:10:30.390 can make my bus 20 seconds later by not giving it priority. 00:10:30.390 --> 00:10:33.960 I can make my bus 50 seconds earlier by giving it priority. 00:10:33.960 --> 00:10:36.990 So with that you see how much tighter the lines are, 00:10:36.990 --> 00:10:40.920 how much better the reliability is 00:10:40.920 --> 00:10:44.970 because the priority system is able to keep those buses 00:10:44.970 --> 00:10:45.910 right on schedule. 00:10:45.910 --> 00:10:46.110 Yeah. 00:10:46.110 --> 00:10:48.109 AUDIENCE: [INAUDIBLE] people driving on the road 00:10:48.109 --> 00:10:49.975 would have to use that traffic light 00:10:49.975 --> 00:10:52.584 and they know it normally takes them 30 seconds and all 00:10:52.584 --> 00:10:56.210 of a sudden it's 50 seconds or is this a separate thing? 00:10:56.210 --> 00:10:59.300 PETER FURTH: No, this is not let's 00:10:59.300 --> 00:11:01.280 hold the light red extra long. 00:11:01.280 --> 00:11:04.550 This is just we won't give priority, that's all. 00:11:04.550 --> 00:11:08.480 So, yeah when I say we won't give priority, 00:11:08.480 --> 00:11:11.130 I'm not talking about holding. 00:11:11.130 --> 00:11:13.170 So we're not deliberately holding the light red. 00:11:13.170 --> 00:11:16.920 It's just, if the bus arrives in the light is green, OK bus you 00:11:16.920 --> 00:11:17.670 get to go through. 00:11:17.670 --> 00:11:19.381 But if you arrive when it's red, I'm 00:11:19.381 --> 00:11:21.630 not going to hurry up and turn the light green for you 00:11:21.630 --> 00:11:22.650 if you're early. 00:11:22.650 --> 00:11:24.358 I'm only going to do that if you're late. 00:11:27.430 --> 00:11:32.050 And priority makes transit more competitive 00:11:32.050 --> 00:11:36.340 because after all if transit has to stop to pick people up, 00:11:36.340 --> 00:11:40.060 that slows it down, you have to walk to get to the station that 00:11:40.060 --> 00:11:41.350 adds more travel time. 00:11:41.350 --> 00:11:43.330 How can we compete with car? 00:11:43.330 --> 00:11:48.537 Well one way we can compete is we can give transit priority 00:11:48.537 --> 00:11:49.870 and it makes it more acceptable. 00:11:49.870 --> 00:11:52.180 And because I got late, I get don't get to tell you 00:11:52.180 --> 00:11:55.120 the story about my great aunt. 00:11:55.120 --> 00:11:58.840 So there are different levels of priority. 00:11:58.840 --> 00:12:00.940 One of the things you'll often hear if you ever 00:12:00.940 --> 00:12:03.040 hear a presentation about priority, they'll say, 00:12:03.040 --> 00:12:05.170 it's not preemption. 00:12:05.170 --> 00:12:09.520 Preemption is a technical term in traffic signal control, 00:12:09.520 --> 00:12:13.770 and preemption is what we'll do for a fire truck. 00:12:13.770 --> 00:12:18.150 And that just means oh, preempt the signal, just stop. 00:12:18.150 --> 00:12:22.530 Every conflicting movement goes to yellow, goes to red, 00:12:22.530 --> 00:12:25.820 and we just stop everything so the fire truck can go through. 00:12:25.820 --> 00:12:29.160 And by the way the street that the fire truck is on we 00:12:29.160 --> 00:12:33.952 don't turn that one red, we would make that one green. 00:12:33.952 --> 00:12:35.910 It's not like we ask everybody to pull over out 00:12:35.910 --> 00:12:37.118 of the way of the fire truck. 00:12:37.118 --> 00:12:39.630 We ask everybody just keep driving, go, go, go, go, go, 00:12:39.630 --> 00:12:40.170 go, go. 00:12:40.170 --> 00:12:41.940 Give them green wave, go, go, go, 00:12:41.940 --> 00:12:44.400 and then the fire engine comes along. 00:12:44.400 --> 00:12:45.930 So that's preemption. 00:12:45.930 --> 00:12:47.310 We do that for fire engines. 00:12:47.310 --> 00:12:52.860 And we do that for trains because trains can't brake. 00:12:52.860 --> 00:12:56.280 You get a train coming along at 40, 50 miles an hour, 00:12:56.280 --> 00:12:58.320 trains-- that steel wheel on steel rail, 00:12:58.320 --> 00:13:01.060 they can't brake very quickly. 00:13:01.060 --> 00:13:05.580 So we will preempt a light for a train. 00:13:05.580 --> 00:13:08.340 So priority is something short of preemption. 00:13:08.340 --> 00:13:11.970 For instance, with transit priority 00:13:11.970 --> 00:13:14.205 we will not cut off a pedestrian phase. 00:13:17.470 --> 00:13:19.320 There's a certain clearance for pedestrians 00:13:19.320 --> 00:13:20.940 to be able to cross the street. 00:13:20.940 --> 00:13:23.250 You've seen the countdown signals. 00:13:23.250 --> 00:13:25.990 So for a fire engine they'll just-- 00:13:25.990 --> 00:13:30.710 it could be 15, 14, 0. 00:13:30.710 --> 00:13:34.190 But we won't do that for transit. 00:13:34.190 --> 00:13:41.060 And preemption it doesn't think a moment about the impact 00:13:41.060 --> 00:13:42.520 on the other traffic. 00:13:42.520 --> 00:13:44.286 We got to save a life. 00:13:44.286 --> 00:13:46.160 Somebody's life is at stake, somebody's house 00:13:46.160 --> 00:13:48.020 is burning down, and there's a train 00:13:48.020 --> 00:13:50.160 coming that would kill everybody in its way. 00:13:50.160 --> 00:13:53.120 So when it comes to saving a life you don't worry about, 00:13:53.120 --> 00:13:56.540 is it costing people a few extra seconds, minutes of time? 00:13:56.540 --> 00:13:59.090 But transit priority we're going to give 00:13:59.090 --> 00:14:02.390 priority to transit vehicle every five minutes every, 00:14:02.390 --> 00:14:03.650 three minutes. 00:14:03.650 --> 00:14:05.330 You can't be completely disrupting 00:14:05.330 --> 00:14:08.300 and screwing up traffic every three minutes. 00:14:08.300 --> 00:14:11.420 You have to think about how it affects others. 00:14:11.420 --> 00:14:14.424 So there are some standard tactics. 00:14:14.424 --> 00:14:16.340 The main ones I'll talk about are listed here. 00:14:16.340 --> 00:14:18.920 Green extension and early green, but I'll 00:14:18.920 --> 00:14:22.640 also talked about some more intelligent tactics 00:14:22.640 --> 00:14:24.740 and some ways of changing the background. 00:14:27.450 --> 00:14:31.080 So let's look at the most popular tactic, which 00:14:31.080 --> 00:14:33.330 is green extension. 00:14:33.330 --> 00:14:37.140 Green extension means the street that the bus is on, 00:14:37.140 --> 00:14:38.870 the light is green. 00:14:38.870 --> 00:14:42.440 It's about to turn yellow, but we detect, 00:14:42.440 --> 00:14:45.950 oh, there's a bus coming and it's only 12 seconds away. 00:14:45.950 --> 00:14:48.950 All right, then we'll just delay turning yellow. 00:14:48.950 --> 00:14:51.350 We'll just extend the green, and then the bus 00:14:51.350 --> 00:14:52.940 will come right through. 00:14:52.940 --> 00:14:57.360 And then the light can turn yellow and turn red. 00:14:57.360 --> 00:15:02.360 So that offers, as I have there on the slide, a very 00:15:02.360 --> 00:15:07.680 large benefit to the buses who take advantage of this. 00:15:07.680 --> 00:15:11.510 I mean, because the bus who gets the green extension, that's 00:15:11.510 --> 00:15:14.090 the bus that if they didn't get that extension 00:15:14.090 --> 00:15:17.060 they would arrive right near the beginning of red. 00:15:17.060 --> 00:15:19.480 And they'd have the longest wait of anybody in the cycle. 00:15:19.480 --> 00:15:22.430 They'd have to wait whole red period until they can finally 00:15:22.430 --> 00:15:23.700 go on. 00:15:23.700 --> 00:15:25.730 So if the red period is 70 seconds long, 00:15:25.730 --> 00:15:28.810 you just save that bus about 70 seconds. 00:15:28.810 --> 00:15:32.170 So it's a very large benefit, but it's a benefit only 00:15:32.170 --> 00:15:33.910 to a few buses. 00:15:33.910 --> 00:15:37.690 Because which buses get to enjoy that benefit? 00:15:37.690 --> 00:15:42.370 Only the ones arriving during the first few seconds of red. 00:15:42.370 --> 00:15:45.730 Let's say you're willing to give a 15 second green extension, 00:15:45.730 --> 00:15:49.720 then any bus arriving in the first 15 seconds of red that 00:15:49.720 --> 00:15:50.950 gets a benefit. 00:15:50.950 --> 00:15:53.680 But if the cycle is 100 seconds long 00:15:53.680 --> 00:15:56.500 and buses arrive at random, well that's only 15% 00:15:56.500 --> 00:15:59.000 of the arrivals that are in that window. 00:15:59.000 --> 00:16:02.740 So green extension is a large benefit 00:16:02.740 --> 00:16:05.410 but to a small number of buses. 00:16:05.410 --> 00:16:08.470 And we can model that benefit this way. 00:16:11.444 --> 00:16:16.520 On the horizontal axis is time in the cycle. 00:16:16.520 --> 00:16:23.360 And on the vertical axis, I have arrivals 00:16:23.360 --> 00:16:25.760 and so you have cumulative vehicles arriving. 00:16:25.760 --> 00:16:29.890 And then the red lines going across, that's-- 00:16:29.890 --> 00:16:31.156 you're raising your hand? 00:16:31.156 --> 00:16:31.520 AUDIENCE: I have a question. 00:16:31.520 --> 00:16:32.270 PETER FURTH: Yeah. 00:16:32.270 --> 00:16:33.979 AUDIENCE: So but now that you said, 00:16:33.979 --> 00:16:36.020 it's a large benefit to a small number of buses-- 00:16:36.020 --> 00:16:36.780 PETER FURTH: Yeah. 00:16:36.780 --> 00:16:39.440 AUDIENCE: --per intersection because if the whole bus run 00:16:39.440 --> 00:16:45.080 is 10-20 signal intersection, then over time 00:16:45.080 --> 00:16:48.070 the probability of every single bus enjoying that and every bus 00:16:48.070 --> 00:16:49.441 that runs [INAUDIBLE] 00:16:49.441 --> 00:16:50.190 PETER FURTH: Sure. 00:16:50.190 --> 00:16:50.815 AUDIENCE: Yeah. 00:16:50.815 --> 00:16:53.630 You say it's only 15% of buses, it's actually a lot more 00:16:53.630 --> 00:16:54.260 and it's-- 00:16:54.260 --> 00:16:57.135 PETER FURTH: So let's say 15% of bus arrivals at a signal. 00:16:57.135 --> 00:16:58.260 AUDIENCE: At a signal but-- 00:16:58.260 --> 00:16:58.410 PETER FURTH: Yeah. 00:16:58.410 --> 00:16:59.260 AUDIENCE: --over a lot of signals? 00:16:59.260 --> 00:17:00.100 PETER FURTH: Yeah. 00:17:00.100 --> 00:17:00.600 Yeah. 00:17:00.600 --> 00:17:03.490 If I'm running a route in which I'm going through 20 signals 00:17:03.490 --> 00:17:06.704 and I'm going to get the benefit of 15% of them on average, 00:17:06.704 --> 00:17:08.329 I'll get that benefit, well, that would 00:17:08.329 --> 00:17:10.670 be three times 15% of 20. 00:17:10.670 --> 00:17:11.810 Yeah. 00:17:11.810 --> 00:17:17.380 So the red lines here represent the time 00:17:17.380 --> 00:17:18.940 that a person is in the queue. 00:17:18.940 --> 00:17:23.619 So like the car arrival-- 00:17:23.619 --> 00:17:25.720 here's arrival number one and then 00:17:25.720 --> 00:17:27.369 this line is the departure curve. 00:17:27.369 --> 00:17:30.430 Cars arrive at a relatively slow rate, 00:17:30.430 --> 00:17:32.830 let's say one car every five seconds. 00:17:32.830 --> 00:17:36.250 And they pull out at a much faster rate, say one car 00:17:36.250 --> 00:17:38.300 every two seconds. 00:17:38.300 --> 00:17:43.690 So each horizontal line represents a certain vehicle. 00:17:43.690 --> 00:17:47.950 So let's say the vehicle number two arrives here. 00:17:47.950 --> 00:17:50.950 And vehicle number two doesn't depart until here. 00:17:50.950 --> 00:17:53.830 So that horizontal line is the waiting time 00:17:53.830 --> 00:17:54.790 of vehicle number two. 00:17:54.790 --> 00:17:58.570 So in this representation, horizontal distance 00:17:58.570 --> 00:18:00.190 is waiting time. 00:18:00.190 --> 00:18:04.570 So for the bus with a green extension, 00:18:04.570 --> 00:18:08.680 instead of red starting at times throw, 00:18:08.680 --> 00:18:11.290 the red actually doesn't start until here. 00:18:11.290 --> 00:18:15.130 So a bus that would have arrived and had been delayed, 00:18:15.130 --> 00:18:16.690 now those buses aren't-- 00:18:16.690 --> 00:18:19.690 buses that arrive after the extension time 00:18:19.690 --> 00:18:20.980 still are delayed. 00:18:20.980 --> 00:18:28.930 So the possibility for delay, which 00:18:28.930 --> 00:18:31.970 is represented by the red area, there is less of it. 00:18:31.970 --> 00:18:37.450 And you find the average horizontal length 00:18:37.450 --> 00:18:39.100 between these lines. 00:18:39.100 --> 00:18:43.450 And then you do a little bit of geometry. 00:18:43.450 --> 00:18:48.350 And we find that the expected delay in the first case, 00:18:48.350 --> 00:18:51.200 this is the standard delay for cars, 00:18:51.200 --> 00:18:54.890 has to do with the length of the [AUDIO OUT] car, the cycle 00:18:54.890 --> 00:18:59.090 length, C, and the ratio of the arrival rate 00:18:59.090 --> 00:19:02.090 to the discharge rate, that's v over s. 00:19:02.090 --> 00:19:04.340 And when we put in a green extension, 00:19:04.340 --> 00:19:08.430 we have that same term minus this term here. 00:19:08.430 --> 00:19:10.670 And I give that the name the priority push. 00:19:10.670 --> 00:19:18.190 So that's the reduction in delay thanks to green extension. 00:19:18.190 --> 00:19:20.680 And that reduction in delay has to do 00:19:20.680 --> 00:19:23.710 with how long an extension are you willing to give. 00:19:23.710 --> 00:19:26.320 In some places though they say, well, I'm 00:19:26.320 --> 00:19:28.480 willing to extend for 10 seconds. 00:19:28.480 --> 00:19:30.700 In Toronto, they often say, I'm willing to extend 00:19:30.700 --> 00:19:33.050 for 30 seconds. 00:19:33.050 --> 00:19:37.100 So it depends on how long is your extension. 00:19:37.100 --> 00:19:40.280 But it also depends a lot on how long is your red 00:19:40.280 --> 00:19:42.750 and how long is your cycle. 00:19:42.750 --> 00:19:45.680 So just so you can have some numbers of-- 00:19:45.680 --> 00:19:46.306 Yeah. 00:19:46.306 --> 00:19:46.972 AUDIENCE: Sorry. 00:19:46.972 --> 00:19:57.390 [INAUDIBLE] why is the order [INAUDIBLE] assigned to that? 00:19:57.390 --> 00:20:02.220 PETER FURTH: So this line here? 00:20:02.220 --> 00:20:02.844 AUDIENCE: Mhm. 00:20:02.844 --> 00:20:03.510 PETER FURTH: OK. 00:20:03.510 --> 00:20:09.910 So that represents the cumulative departing cars, OK? 00:20:09.910 --> 00:20:13.309 So at a certain point in time, the light turns green 00:20:13.309 --> 00:20:14.600 and then the first car departs. 00:20:14.600 --> 00:20:17.420 The second car doesn't depart until about two seconds later. 00:20:17.420 --> 00:20:19.110 The cars follow one another. 00:20:19.110 --> 00:20:24.560 So this line has a slope of about one car 00:20:24.560 --> 00:20:27.170 every two seconds as they depart. 00:20:27.170 --> 00:20:28.500 This is as they arrive. 00:20:28.500 --> 00:20:34.160 It's maybe one car every five, six, seven, eight seconds, OK? 00:20:34.160 --> 00:20:36.890 And where the two lines meet, that 00:20:36.890 --> 00:20:40.610 means the last car in the queue is now gone. 00:20:40.610 --> 00:20:48.350 And after that, as cars arrive and depart without any joining 00:20:48.350 --> 00:20:51.970 acuity, just go through. 00:20:51.970 --> 00:20:55.420 So to put some numbers on that priority push, 00:20:55.420 --> 00:20:58.420 let's consider a sort of typical intersection 00:20:58.420 --> 00:21:00.610 with a cycle length of 100 seconds, 00:21:00.610 --> 00:21:04.810 50 seconds of red time, and the v over s. 00:21:04.810 --> 00:21:08.260 That v over s term is such that the degree of saturation 00:21:08.260 --> 00:21:11.600 is 85% which that's pretty typical. 00:21:11.600 --> 00:21:14.170 So this shows how the priority push varies 00:21:14.170 --> 00:21:15.700 with the green extension. 00:21:15.700 --> 00:21:18.310 The longer an extension you're willing to give 00:21:18.310 --> 00:21:19.760 the more of a priority push. 00:21:19.760 --> 00:21:22.640 But notice they're not equal to each other. 00:21:22.640 --> 00:21:25.840 For instance, when the green extension is 15 seconds 00:21:25.840 --> 00:21:29.180 that gives me a priority push of about eight seconds. 00:21:29.180 --> 00:21:35.740 So often if anybody does try to describe the priority tactics 00:21:35.740 --> 00:21:38.000 they're using, they'll say something like, oh, when we 00:21:38.000 --> 00:21:41.279 give 15 second green extension. 00:21:41.279 --> 00:21:43.570 Well that doesn't mean it's going to speed the buses up 00:21:43.570 --> 00:21:46.180 by 15 seconds. 00:21:46.180 --> 00:21:50.470 In this case, how it affects each individual bus 00:21:50.470 --> 00:21:56.290 varies but on average that will reduce the delay of buses-- 00:21:56.290 --> 00:21:59.710 this is averaged over all buses, reduce the delay 00:21:59.710 --> 00:22:01.330 by eight seconds. 00:22:01.330 --> 00:22:04.870 And then it has a lot to do also with the cycling. 00:22:04.870 --> 00:22:08.680 So let's again consider 100 second cycle, 00:22:08.680 --> 00:22:10.210 degree saturation 85. 00:22:10.210 --> 00:22:14.080 This time hold the green extension period 00:22:14.080 --> 00:22:15.760 fixed to 15 seconds. 00:22:15.760 --> 00:22:20.080 And look at different amounts of red time. 00:22:20.080 --> 00:22:24.130 So if you're red time is low, that's 00:22:24.130 --> 00:22:26.200 like the buses on the through road that 00:22:26.200 --> 00:22:27.465 gets green most of the time. 00:22:27.465 --> 00:22:30.090 We're green most of the time and only a small part of the cycle 00:22:30.090 --> 00:22:31.720 is for the cross street. 00:22:31.720 --> 00:22:34.750 Well then the priority push is pretty small, 00:22:34.750 --> 00:22:36.460 only about five seconds. 00:22:36.460 --> 00:22:41.170 But if the red time is long, if it's 100 second cycle 00:22:41.170 --> 00:22:45.640 and the light is red for you 90 out of those 100 seconds, 00:22:45.640 --> 00:22:51.850 well then getting pushed ahead 15 seconds will save you a lot. 00:22:51.850 --> 00:22:57.460 Now when is the light red for 90 out of 100 seconds? 00:22:57.460 --> 00:23:00.190 Under what kind of traffic movement 00:23:00.190 --> 00:23:03.340 would it be that is red almost all the time 00:23:03.340 --> 00:23:04.390 with a very short green? 00:23:04.390 --> 00:23:09.201 AUDIENCE: Maybe like a city center pedestrian plaza? 00:23:09.201 --> 00:23:10.450 PETER FURTH: No, probably not. 00:23:10.450 --> 00:23:12.444 Because if you only give the cars 10 seconds 00:23:12.444 --> 00:23:14.110 you just can't get much traffic through. 00:23:14.110 --> 00:23:14.610 Yeah? 00:23:14.610 --> 00:23:16.240 AUDIENCE: D street in South Boston. 00:23:16.240 --> 00:23:18.250 PETER FURTH: Ho, ho, ho, ho, ho you got it. 00:23:18.250 --> 00:23:19.390 You got it. 00:23:19.390 --> 00:23:22.303 But that's not a typical case. 00:23:22.303 --> 00:23:26.584 AUDIENCE: The cross streets of a major thoroughfare? 00:23:26.584 --> 00:23:28.000 PETER FURTH: So the cross streets, 00:23:28.000 --> 00:23:30.925 even they get more like 25-30 seconds. 00:23:30.925 --> 00:23:32.830 AUDIENCE: Like a protected class. 00:23:32.830 --> 00:23:34.870 PETER FURTH: A left turn, that's it. 00:23:34.870 --> 00:23:37.450 This is the one that really, really could 00:23:37.450 --> 00:23:40.990 benefit from a green extension. 00:23:40.990 --> 00:23:44.830 So right next to Northeastern is Ruggles Station, 00:23:44.830 --> 00:23:47.710 and you got all these buses making left turns. 00:23:47.710 --> 00:23:50.840 And if they don't make it, uh sorry, 00:23:50.840 --> 00:23:57.600 120 second cycle, 100 seconds of red. 00:23:57.600 --> 00:24:02.830 So that's a situation where a green extension would be-- 00:24:02.830 --> 00:24:07.550 it's valuable in all these cases but it's especially valuable 00:24:07.550 --> 00:24:11.150 when there's a really long red time. 00:24:11.150 --> 00:24:13.550 So I'm glad you mentioned D Street. 00:24:13.550 --> 00:24:15.080 I'll be talking about D Street. 00:24:15.080 --> 00:24:17.300 All right. 00:24:17.300 --> 00:24:20.570 OK, how do we do detection? 00:24:20.570 --> 00:24:24.514 Technically to detect the bus, it's almost trivial. 00:24:24.514 --> 00:24:26.180 There's so many different ways to do it. 00:24:30.370 --> 00:24:34.870 I'll say something about technologies, but where 00:24:34.870 --> 00:24:36.130 we want to detect the bus. 00:24:36.130 --> 00:24:39.280 So we want to have a check-in detector so the bus reports in. 00:24:39.280 --> 00:24:40.330 Hello, I'm a bus. 00:24:40.330 --> 00:24:42.840 Can you give me priority? 00:24:42.840 --> 00:24:44.670 And there is a trade-off. 00:24:44.670 --> 00:24:47.700 The sooner we know, the better because then 00:24:47.700 --> 00:24:50.460 we can prepare for it and get that light to be red. 00:24:50.460 --> 00:24:54.810 But if you tell me two minutes in advance 00:24:54.810 --> 00:24:59.010 there's a bus coming, bus travel time is not deterministic. 00:24:59.010 --> 00:24:59.510 All right? 00:24:59.510 --> 00:25:03.680 So there might be stops in between and random dwell time. 00:25:03.680 --> 00:25:05.770 There might be other traffic signals in between. 00:25:05.770 --> 00:25:11.210 So usually we want our check-in to be 00:25:11.210 --> 00:25:15.260 as far away as can be but no farther than the next stop 00:25:15.260 --> 00:25:17.810 or the next intersection so there's a pretty 00:25:17.810 --> 00:25:22.070 deterministic travel time. 00:25:22.070 --> 00:25:24.460 We also want there to be a check-out detector. 00:25:24.460 --> 00:25:27.320 Some systems omit the check-out detector. 00:25:27.320 --> 00:25:30.750 So if you omit the check-out detector, 00:25:30.750 --> 00:25:32.520 here's how inefficient you are. 00:25:32.520 --> 00:25:34.270 You say, oh, there's a bus coming. 00:25:34.270 --> 00:25:36.760 I'll give it a 15 second extension. 00:25:36.760 --> 00:25:38.860 The bus goes through after three seconds, 00:25:38.860 --> 00:25:41.754 and you still hold the light green for the full 15. 00:25:41.754 --> 00:25:42.920 That doesn't make any sense. 00:25:42.920 --> 00:25:44.830 So have a check-out detector. 00:25:44.830 --> 00:25:46.780 As soon as the bus hits that, you 00:25:46.780 --> 00:25:50.710 cancel the extension request, let the light turn yellow. 00:25:53.520 --> 00:25:57.040 The traditional technology for extension 00:25:57.040 --> 00:26:00.610 is we bury in the ground a loop-- 00:26:00.610 --> 00:26:03.100 not just a dumb loop of cable but a loop 00:26:03.100 --> 00:26:04.460 that acts like an antenna. 00:26:04.460 --> 00:26:09.310 So the bus is coming along, giving along a very low energy 00:26:09.310 --> 00:26:09.820 signal. 00:26:09.820 --> 00:26:10.690 I'm a bus. 00:26:10.690 --> 00:26:14.800 I'm bus number 2356 so you can check my ID to make sure 00:26:14.800 --> 00:26:18.580 that this is not a stolen unit. 00:26:18.580 --> 00:26:20.320 And it could give off some information 00:26:20.320 --> 00:26:23.290 like, I'm turning left so I need the left arrow. 00:26:23.290 --> 00:26:27.190 There's another bus route coming along that's going straight. 00:26:27.190 --> 00:26:29.920 So that's one way of doing it. 00:26:29.920 --> 00:26:36.640 Nowadays, we'll be doing it with GPS and basically cell phone 00:26:36.640 --> 00:26:38.280 technology, texting. 00:26:38.280 --> 00:26:41.809 The bus sets up text messages with the controller and says, 00:26:41.809 --> 00:26:43.850 here are my coordinates, here are my coordinates, 00:26:43.850 --> 00:26:47.740 and just keep sending essentially the packets of cell 00:26:47.740 --> 00:26:50.800 data like text messages. 00:26:50.800 --> 00:26:55.150 And then we know where the bus is, and we can take action. 00:26:57.660 --> 00:26:59.960 So I can skip that. 00:26:59.960 --> 00:27:04.190 So one difficulty of giving priority 00:27:04.190 --> 00:27:07.240 is, well, what if there's a near side stop? 00:27:07.240 --> 00:27:11.030 If you looked at locating stops for buses, 00:27:11.030 --> 00:27:14.360 you know there's a basic choice between the near side, 00:27:14.360 --> 00:27:18.420 the upstream side intersection or the far side. 00:27:18.420 --> 00:27:20.180 Well, if you're on the near side, 00:27:20.180 --> 00:27:23.300 remember stop dwell time is random. 00:27:23.300 --> 00:27:25.280 So I don't even want to check the bus 00:27:25.280 --> 00:27:27.590 in until it's left the stop. 00:27:27.590 --> 00:27:29.330 Well, that means my check-in point 00:27:29.330 --> 00:27:31.310 is going to be awfully close. 00:27:31.310 --> 00:27:31.820 So what? 00:27:31.820 --> 00:27:35.230 I'm going to find out two seconds before the bus comes 00:27:35.230 --> 00:27:37.250 that a bus is coming? 00:27:37.250 --> 00:27:39.840 If you only have two seconds advance notice, 00:27:39.840 --> 00:27:43.654 how long a green extension can you give? 00:27:43.654 --> 00:27:44.650 AUDIENCE: Two seconds. 00:27:44.650 --> 00:27:45.691 PETER FURTH: Two seconds. 00:27:45.691 --> 00:27:46.900 Think about it. 00:27:46.900 --> 00:27:49.600 You can't give a 15 second extension 00:27:49.600 --> 00:27:53.500 if you're only detecting the bus two seconds early, right? 00:27:53.500 --> 00:27:56.290 If I was going to end the green at time-- 00:27:56.290 --> 00:27:58.980 let's just pick a number at time 50 00:27:58.980 --> 00:28:02.580 and I said, oh, I'm willing to wait till time 65. 00:28:02.580 --> 00:28:05.700 But I don't know when the bus is there until time 63, 00:28:05.700 --> 00:28:08.290 how would I know to extend the green? 00:28:08.290 --> 00:28:08.790 Yeah. 00:28:08.790 --> 00:28:13.270 You cannot give a green extension longer than 00:28:13.270 --> 00:28:16.310 the advance notice that you have. 00:28:16.310 --> 00:28:19.240 So this is a killer. 00:28:19.240 --> 00:28:19.740 Yeah. 00:28:19.740 --> 00:28:21.948 AUDIENCE: I'm just curious about the actual mechanics 00:28:21.948 --> 00:28:23.170 of the signal extension. 00:28:23.170 --> 00:28:23.410 PETER FURTH: Yeah. 00:28:23.410 --> 00:28:24.785 AUDIENCE: Is this a signal you're 00:28:24.785 --> 00:28:27.370 sending to just that one traffic intersection or are you 00:28:27.370 --> 00:28:29.330 sending a signal to some central control that's 00:28:29.330 --> 00:28:31.690 controlling the whole city's traffic lights? 00:28:31.690 --> 00:28:33.070 PETER FURTH: A single place. 00:28:33.070 --> 00:28:35.650 Now, it can work through the central place, 00:28:35.650 --> 00:28:39.600 but I'm talking about, yeah, a bus 00:28:39.600 --> 00:28:43.280 is detected for a particular light, 00:28:43.280 --> 00:28:46.590 hold that particular light green for me. 00:28:46.590 --> 00:28:50.450 It doesn't do anything to any other intersection. 00:28:50.450 --> 00:28:52.346 AUDIENCE: But I meant does it send a signal 00:28:52.346 --> 00:28:54.470 to some central control which then tells that light 00:28:54.470 --> 00:28:57.320 to change? 00:28:57.320 --> 00:28:59.130 PETER FURTH: That's an option. 00:28:59.130 --> 00:29:03.930 So in Zurich, yes, they do that but man you need 00:29:03.930 --> 00:29:05.180 all kinds of cabling for that. 00:29:05.180 --> 00:29:11.420 In Zurich the controllers on the street are 100% slaves. 00:29:11.420 --> 00:29:13.910 All they do is, when the central computer 00:29:13.910 --> 00:29:16.850 tells them to change from green to yellow they just say, yes. 00:29:16.850 --> 00:29:19.220 And the only other software they have running in them 00:29:19.220 --> 00:29:23.630 is some kind of checking to make sure that they're not 00:29:23.630 --> 00:29:24.590 violating something. 00:29:24.590 --> 00:29:29.760 But that's a very unusual setup that was done ages ago. 00:29:29.760 --> 00:29:32.690 Nowadays we have very reliable microcomputers 00:29:32.690 --> 00:29:34.130 in the controllers. 00:29:34.130 --> 00:29:37.070 So the central computer will make 00:29:37.070 --> 00:29:40.940 sure every intersection is on the clock, 00:29:40.940 --> 00:29:43.730 every intersection is supposed to have its certain offset-- 00:29:43.730 --> 00:29:47.310 you turn green at a certain time in the cycle. 00:29:47.310 --> 00:29:49.980 And it will give them the basic parameters-- 00:29:49.980 --> 00:29:53.690 30 seconds for this street, 20 seconds for this phase, 00:29:53.690 --> 00:29:55.790 20 seconds for this phase, and so on. 00:29:55.790 --> 00:29:57.650 And it will say, and you're allowed 00:29:57.650 --> 00:30:00.530 to give a 15 second green extension. 00:30:00.530 --> 00:30:02.840 And then it's the local controller 00:30:02.840 --> 00:30:05.900 that will actually do it. 00:30:05.900 --> 00:30:06.639 Yeah. 00:30:06.639 --> 00:30:12.280 AUDIENCE: [INAUDIBLE] means that the detector is right there 00:30:12.280 --> 00:30:13.940 at the intersection? 00:30:13.940 --> 00:30:16.190 PETER FURTH: Well it means that the stop is just 00:30:16.190 --> 00:30:17.240 before the intersection. 00:30:17.240 --> 00:30:18.720 AUDIENCE: OK. 00:30:18.720 --> 00:30:21.110 PETER FURTH: So if I put my detector-- 00:30:21.110 --> 00:30:24.380 normally, let's say I want to give a 15 second extension, 00:30:24.380 --> 00:30:28.910 I locate my detector 15 seconds upstream of the traffic light. 00:30:28.910 --> 00:30:31.760 Well, what's 15 seconds ahead when 00:30:31.760 --> 00:30:34.420 there is a dwell time in there? 00:30:34.420 --> 00:30:39.840 So you know how random dwell times are, right? 00:30:39.840 --> 00:30:43.409 Are there going to be one, two, five people getting off? 00:30:43.409 --> 00:30:44.700 How many people are getting on? 00:30:44.700 --> 00:30:48.270 Maybe somebody who needs assistance or having 00:30:48.270 --> 00:30:51.140 trouble with their fares. 00:30:51.140 --> 00:30:55.884 So because of that we won't usually call for an extension 00:30:55.884 --> 00:30:57.800 if there is a stop in between because we don't 00:30:57.800 --> 00:30:59.091 know how long it's going to be. 00:30:59.091 --> 00:31:07.230 So near side stops, not entirely but they get some benefit. 00:31:07.230 --> 00:31:10.670 If the bus is pulling out two seconds of extension, 00:31:10.670 --> 00:31:13.860 that's nice but it's only two seconds. 00:31:13.860 --> 00:31:16.200 So it nearly kills the effectiveness 00:31:16.200 --> 00:31:17.940 of green extension. 00:31:17.940 --> 00:31:21.864 So that's a reason if you want to do transit priority, 00:31:21.864 --> 00:31:23.280 you review your route and you say, 00:31:23.280 --> 00:31:26.830 can I move the stops to the far side. 00:31:26.830 --> 00:31:29.980 There are a lot of other reasons to move stops to the far side. 00:31:29.980 --> 00:31:33.250 Transit agencies around the country where they can 00:31:33.250 --> 00:31:34.840 are moving stops to the far side. 00:31:34.840 --> 00:31:36.970 So in the NBTA recently they did a review 00:31:36.970 --> 00:31:38.260 of all their key routes. 00:31:38.260 --> 00:31:41.650 And one thing they looked at is, can we relocate stops? 00:31:41.650 --> 00:31:43.690 But they have criteria-- 00:31:43.690 --> 00:31:47.230 where there's a stop there has to be a level landing place. 00:31:47.230 --> 00:31:50.500 There can't be fire hydrants and telephone poles in the way. 00:31:50.500 --> 00:31:53.440 There can't be driveways. 00:31:53.440 --> 00:31:57.430 So some of the streets that I've looked at for, could we 00:31:57.430 --> 00:32:01.090 do transit priority, and first thing I would say, oh no, it's 00:32:01.090 --> 00:32:02.170 a near side stop. 00:32:02.170 --> 00:32:04.582 We've got to move it to the other side of the street. 00:32:04.582 --> 00:32:06.040 But on the other side of the street 00:32:06.040 --> 00:32:07.840 there's a driveway every 30 feet, 00:32:07.840 --> 00:32:10.210 you can't put a bus stop there. 00:32:10.210 --> 00:32:13.550 Or there's a firehouse, you can't put a bus stop there. 00:32:13.550 --> 00:32:16.870 So sometimes we're stuck with near side stops. 00:32:16.870 --> 00:32:18.926 And then green extension just ain't 00:32:18.926 --> 00:32:20.050 going to help us very much. 00:32:25.250 --> 00:32:25.750 OK. 00:32:25.750 --> 00:32:33.720 Before I go into more tactics, let 00:32:33.720 --> 00:32:37.080 me go through this list of common weaknesses 00:32:37.080 --> 00:32:38.680 in trying to do it. 00:32:38.680 --> 00:32:42.540 So one weakness that I've seen a lot here in the US 00:32:42.540 --> 00:32:45.270 is what I call cautious priority. 00:32:45.270 --> 00:32:49.240 So all this equipment they put in this transit priority 00:32:49.240 --> 00:32:49.740 system. 00:32:49.740 --> 00:32:52.110 But the traffic engineers are so afraid it's 00:32:52.110 --> 00:32:54.930 going to screw up traffic that they'll say, 00:32:54.930 --> 00:32:56.760 once we give priority to a bus we 00:32:56.760 --> 00:32:58.710 inhibit the whole system for five minutes 00:32:58.710 --> 00:33:01.050 to give the signal a chance to recover 00:33:01.050 --> 00:33:03.840 or we inhibit at least for another cycle. 00:33:06.820 --> 00:33:12.370 Or if the traffic level on the cross street is too much, 00:33:12.370 --> 00:33:15.870 just turn off the signal priorities. 00:33:15.870 --> 00:33:16.370 OK. 00:33:16.370 --> 00:33:20.510 So the Silver Line running on Washington Street 00:33:20.510 --> 00:33:22.190 has a priority system. 00:33:26.310 --> 00:33:29.040 Some of the cross streets have so much traffic 00:33:29.040 --> 00:33:31.950 that they have this rule-- if the cross street volume is 00:33:31.950 --> 00:33:32.940 too much, turn it off. 00:33:32.940 --> 00:33:34.140 Well it's turned off, OK. 00:33:34.140 --> 00:33:36.420 So the bus never gets priority at Melnea Cass, 00:33:36.420 --> 00:33:39.660 it never gets priority at Mass Ave. 00:33:39.660 --> 00:33:42.630 Many of the cross streets bus has the green light 00:33:42.630 --> 00:33:45.180 for like 70 out of 90 seconds in the cycle. 00:33:45.180 --> 00:33:47.280 So it's almost always green so the bus almost 00:33:47.280 --> 00:33:48.370 never needs priority. 00:33:48.370 --> 00:33:53.460 So there is priority, but the benefit is very time. 00:33:53.460 --> 00:33:56.002 So in the end, what do you get? 00:33:56.002 --> 00:33:56.960 You get almost nothing. 00:34:00.140 --> 00:34:04.880 And then a second weakness is not 00:34:04.880 --> 00:34:07.910 thinking about the impact of priority on traffic 00:34:07.910 --> 00:34:09.889 and then unnecessarily hurting traffic, 00:34:09.889 --> 00:34:13.669 like not having a check-out detector that I mentioned. 00:34:13.669 --> 00:34:16.880 But the second bullet there, that's 00:34:16.880 --> 00:34:21.840 an important one I want you to think about, is compensation. 00:34:21.840 --> 00:34:26.130 Compensation is a key to making priority not 00:34:26.130 --> 00:34:28.020 hurt traffic so bad. 00:34:28.020 --> 00:34:29.670 And by compensation what do I mean? 00:34:29.670 --> 00:34:33.239 What I mean is if I'm going to give the bus street 15 seconds, 00:34:33.239 --> 00:34:36.420 I'm taking those 15 seconds away from somebody. 00:34:36.420 --> 00:34:39.510 Are you going to give it back? 00:34:39.510 --> 00:34:41.834 The language that traffic engineers use 00:34:41.834 --> 00:34:43.060 is they use the word borrow. 00:34:43.060 --> 00:34:47.139 They say, oh, we'll just borrow 15 seconds from phase two. 00:34:47.139 --> 00:34:49.630 And then I ask are you going to give it back? 00:34:49.630 --> 00:34:50.909 And they say, well, no. 00:34:50.909 --> 00:34:55.690 I say, well, then it's not borrowing, that's stealing. 00:34:55.690 --> 00:34:59.560 So if you take away 15 seconds from phase two, 00:34:59.560 --> 00:35:07.480 and phase two now they can't clear its queue. 00:35:07.480 --> 00:35:09.640 So now it's going to have a long queue. 00:35:09.640 --> 00:35:12.550 And then the traffic engineers will say, oh no, 00:35:12.550 --> 00:35:16.570 now if we let them have priority in the next cycle as well, 00:35:16.570 --> 00:35:19.210 oh no, what a disaster. 00:35:19.210 --> 00:35:20.750 So that's why you get these rules, 00:35:20.750 --> 00:35:23.620 like if we do priority, no priority for the next cycle 00:35:23.620 --> 00:35:26.660 or the next five minutes. 00:35:26.660 --> 00:35:32.380 But if I hold the light green for let's say East Street 00:35:32.380 --> 00:35:35.470 for the bus, so I hold the light green 15 seconds 00:35:35.470 --> 00:35:39.110 for East Street, who's going to get through 00:35:39.110 --> 00:35:40.510 in addition to the bus? 00:35:40.510 --> 00:35:42.370 A bunch of cars, right? 00:35:42.370 --> 00:35:45.880 A bunch of cars who otherwise would have been in the queue 00:35:45.880 --> 00:35:47.524 for the next cycle. 00:35:47.524 --> 00:35:49.690 So that means when we come around to the next cycle, 00:35:49.690 --> 00:35:51.400 East Street is not going to need as much 00:35:51.400 --> 00:35:55.690 green because some of their cars already got through. 00:35:55.690 --> 00:35:57.810 Meanwhile, other streets whose green we took they 00:35:57.810 --> 00:35:58.800 need more green. 00:35:58.800 --> 00:36:03.810 So hey, why not just be reasonable and fair about it. 00:36:03.810 --> 00:36:07.004 Since we gave East Street some extra green, in the next cycle 00:36:07.004 --> 00:36:08.670 we'll give the other streets extra green 00:36:08.670 --> 00:36:10.860 and we'll take some away from East Street. 00:36:10.860 --> 00:36:12.690 That's compensation. 00:36:12.690 --> 00:36:14.820 That's a sensible way of doing things. 00:36:14.820 --> 00:36:18.570 And what you'll see is we don't do that. 00:36:18.570 --> 00:36:23.640 We can't do that with much of the standard way of controlling 00:36:23.640 --> 00:36:26.730 lights that we follow here in the US. 00:36:26.730 --> 00:36:29.490 And that's the inflexibility that I'll 00:36:29.490 --> 00:36:33.170 be explaining later on. 00:36:33.170 --> 00:36:36.770 Then another weakness is we'll do the easy things. 00:36:36.770 --> 00:36:38.030 Green extension is easy. 00:36:38.030 --> 00:36:40.100 So we just do green extension. 00:36:40.100 --> 00:36:42.920 And then, like I said, if you have near side stops, 00:36:42.920 --> 00:36:44.570 well you don't get any benefit. 00:36:44.570 --> 00:36:46.790 And there are other tactics that are harder to do, 00:36:46.790 --> 00:36:48.890 but we only do the easy ones. 00:36:48.890 --> 00:36:52.860 And then the last weakness is failing to collect data. 00:36:52.860 --> 00:36:54.740 In something like this, it's hard to get it 00:36:54.740 --> 00:36:55.650 right the first time. 00:36:55.650 --> 00:36:58.280 You need to do it, collect data. 00:36:58.280 --> 00:37:00.950 See, are my buses getting the priority they're supposed to? 00:37:00.950 --> 00:37:03.860 If they're not, make some fixes. 00:37:03.860 --> 00:37:06.080 Is car traffic doing all right? 00:37:06.080 --> 00:37:09.140 Are there places where huge queues are building up? 00:37:09.140 --> 00:37:10.970 And try to fix it. 00:37:10.970 --> 00:37:14.000 So take the objective seriously. 00:37:14.000 --> 00:37:19.250 So now I need to move away from transit priority 00:37:19.250 --> 00:37:21.500 and just tell you something about traffic signal 00:37:21.500 --> 00:37:24.440 control in general because it's something 00:37:24.440 --> 00:37:27.440 that isn't covered in a lot of the standard transportation 00:37:27.440 --> 00:37:29.190 planning curriculum. 00:37:29.190 --> 00:37:33.350 So there are two basic paradigms for signal control. 00:37:33.350 --> 00:37:37.250 One is fully actuated and the other is coordinated. 00:37:37.250 --> 00:37:43.400 So fully actuated that's uncoordinated. 00:37:43.400 --> 00:37:46.700 With fully actuated that means every approach 00:37:46.700 --> 00:37:47.960 I've got detectors. 00:37:47.960 --> 00:37:50.480 And the standard detector it's a loop 00:37:50.480 --> 00:37:52.400 of copper in the street, a couple 00:37:52.400 --> 00:37:54.500 rounds that goes to a box. 00:37:54.500 --> 00:37:57.770 And through the miracles of electromagnetism 00:37:57.770 --> 00:38:01.940 if a vehicle drives over it, it induces a voltage. 00:38:01.940 --> 00:38:03.470 And you can pick up that voltage, 00:38:03.470 --> 00:38:05.300 and so you know there's a car there. 00:38:05.300 --> 00:38:05.800 Yeah. 00:38:05.800 --> 00:38:08.220 AUDIENCE: [INAUDIBLE] 00:38:08.220 --> 00:38:10.440 PETER FURTH: So there is a setting 00:38:10.440 --> 00:38:16.260 of how much of a voltage change is enough because it 00:38:16.260 --> 00:38:17.240 has to become digital. 00:38:17.240 --> 00:38:19.750 It's either 0 or 1. 00:38:19.750 --> 00:38:22.050 So if we increase the sensitivity, 00:38:22.050 --> 00:38:23.730 then it'll detect a bike. 00:38:23.730 --> 00:38:25.890 But then the danger is it will also detect 00:38:25.890 --> 00:38:28.810 a car in the next lane over. 00:38:28.810 --> 00:38:30.460 So there is a trade off there. 00:38:30.460 --> 00:38:34.900 So then if we want to detect bikes, 00:38:34.900 --> 00:38:37.570 we use a figure 8 configuration. 00:38:37.570 --> 00:38:42.010 And then we try to educate the bicyclists, drive right down 00:38:42.010 --> 00:38:43.750 the middle of that figure 8. 00:38:43.750 --> 00:38:47.450 And that's where you'll get picked up the most. 00:38:47.450 --> 00:38:49.175 Hardly anybody knows that though. 00:38:52.900 --> 00:38:55.620 There's another solution to bike detection, which 00:38:55.620 --> 00:39:02.860 is if you're a bicyclist like me, I like green. 00:39:02.860 --> 00:39:04.250 I like red. 00:39:04.250 --> 00:39:05.020 I like yellow. 00:39:05.020 --> 00:39:06.400 I like all colors. 00:39:06.400 --> 00:39:06.960 I just go. 00:39:15.081 --> 00:39:15.580 All right. 00:39:15.580 --> 00:39:19.130 So with fully actuated control I've got detectors. 00:39:19.130 --> 00:39:21.440 And based on those detectors, I will 00:39:21.440 --> 00:39:24.560 know how many seconds has it been since a car 00:39:24.560 --> 00:39:27.730 passed through and [AUDIO OUT] gap. 00:39:27.730 --> 00:39:30.060 And once the gap reaches a certain threshold, 00:39:30.060 --> 00:39:34.410 2 and 1/2 seconds, 3 seconds, then you have gapped out. 00:39:34.410 --> 00:39:36.660 Boom, your turn is over. 00:39:36.660 --> 00:39:39.420 And it's the next one's turn. 00:39:39.420 --> 00:39:41.430 So there's no fixed cycle length. 00:39:41.430 --> 00:39:42.000 Who knows? 00:39:42.000 --> 00:39:45.270 If traffic volume is light, we serve you, we serve the next, 00:39:45.270 --> 00:39:47.280 we serve the next, and now we're back. 00:39:47.280 --> 00:39:48.330 Traffic is heavy. 00:39:48.330 --> 00:39:51.460 It might take 90 seconds to cycle around. 00:39:51.460 --> 00:39:54.600 But it's completely flexible like that. 00:39:54.600 --> 00:39:59.640 And if I interrupt something like that for transit 00:39:59.640 --> 00:40:03.790 priority and now there's a longer queue-- 00:40:03.790 --> 00:40:06.790 OK, everybody's been waiting an extra 15 seconds because 00:40:06.790 --> 00:40:09.160 of this transit priority. 00:40:09.160 --> 00:40:13.570 Well, when their turn comes up if they've got more cars, 00:40:13.570 --> 00:40:16.300 well the detector will say, hey, they still have cars, 00:40:16.300 --> 00:40:17.590 still have cars, yeah. 00:40:17.590 --> 00:40:19.280 So keep them going, keep them going. 00:40:19.280 --> 00:40:19.780 OK. 00:40:19.780 --> 00:40:22.850 Now we finally have a gap you're over, onto the next one. 00:40:22.850 --> 00:40:26.110 And if East Street like I was saying 00:40:26.110 --> 00:40:30.340 has less traffic, the street that the bus was on because it 00:40:30.340 --> 00:40:34.890 got that green extension, when its turn comes up instead 00:40:34.890 --> 00:40:37.680 of holding the light for 35 seconds 00:40:37.680 --> 00:40:40.290 like it usually does it'll hold the light for 25 seconds 00:40:40.290 --> 00:40:42.070 and then say, I'm all done. 00:40:42.070 --> 00:40:43.510 No more traffic. 00:40:43.510 --> 00:40:50.970 So fully actuated control is a great background for priority 00:40:50.970 --> 00:40:55.710 because it's inherently flexible, it's cycle free, 00:40:55.710 --> 00:40:59.660 it has that built in compensation. 00:40:59.660 --> 00:41:03.980 But then there's another way of doing control, 00:41:03.980 --> 00:41:06.380 another basic paradigm for control, 00:41:06.380 --> 00:41:09.590 which is coordinated control. 00:41:09.590 --> 00:41:13.910 In the US, I'm showing the most kind 00:41:13.910 --> 00:41:16.940 of the basic paradigm, which is the dual ring with eight 00:41:16.940 --> 00:41:17.986 phases. 00:41:17.986 --> 00:41:20.360 I'm not including right turns because right turns usually 00:41:20.360 --> 00:41:21.710 don't have their own lights. 00:41:21.710 --> 00:41:25.100 The right turns just go with the through movements. 00:41:25.100 --> 00:41:27.320 And with coordinated control like this 00:41:27.320 --> 00:41:34.460 we have EBL, that means eastbound left, westbound 00:41:34.460 --> 00:41:37.370 through, WBT, westbound through. 00:41:37.370 --> 00:41:40.380 So the east-west street has its time. 00:41:40.380 --> 00:41:42.740 There's an upper ring and a lower ring. 00:41:42.740 --> 00:41:44.990 And the rings that are in parallel they 00:41:44.990 --> 00:41:46.110 can move together. 00:41:46.110 --> 00:41:48.590 So when the light starts green, eastbound left 00:41:48.590 --> 00:41:51.800 and westbound left, one and five, they're green together. 00:41:51.800 --> 00:41:53.900 What comes next, two or six? 00:41:53.900 --> 00:41:55.220 That depends. 00:41:55.220 --> 00:41:57.980 Whichever one has more traffic, one or five, 00:41:57.980 --> 00:42:02.510 that will stay green because it has detectors 00:42:02.510 --> 00:42:04.280 while the other one gaps out. 00:42:04.280 --> 00:42:07.430 So maybe five gaps out first because it had less traffic. 00:42:07.430 --> 00:42:10.220 Then six becomes green along with one. 00:42:10.220 --> 00:42:14.090 Eventually one gaps out, and now six is green along with two. 00:42:14.090 --> 00:42:16.620 But then six and two have to end together. 00:42:16.620 --> 00:42:20.150 And then we have the same thing for the north-south street. 00:42:20.150 --> 00:42:24.530 So this could be fully actuated, but when 00:42:24.530 --> 00:42:26.240 I say it's coordinated what I mean 00:42:26.240 --> 00:42:30.840 is phases two and six those are the coordinated phases. 00:42:30.840 --> 00:42:35.310 And the cycle goes from the end of two and six 00:42:35.310 --> 00:42:37.380 until the next end of two and six. 00:42:37.380 --> 00:42:39.180 And that is a fixed amount of time. 00:42:39.180 --> 00:42:41.550 So if it's 110 second cycle, it's 00:42:41.550 --> 00:42:44.790 always 110 seconds from this point 00:42:44.790 --> 00:42:48.960 until when it comes around again. 00:42:48.960 --> 00:42:51.132 These phases can have some actuation. 00:42:51.132 --> 00:42:52.340 They can have some detectors. 00:42:52.340 --> 00:42:55.430 And so they might run shorter than scheduled. 00:42:55.430 --> 00:42:58.160 And if they gap out quicker, run short, 00:42:58.160 --> 00:43:01.640 and this one gaps out, it runs short, this one gaps out, 00:43:01.640 --> 00:43:05.360 it runs short that means two and six are going to start early. 00:43:05.360 --> 00:43:07.550 But if they start early, they never end early. 00:43:07.550 --> 00:43:09.590 They run their full length because that's 00:43:09.590 --> 00:43:12.140 how we have the full cycle. 00:43:12.140 --> 00:43:14.390 And the advantage to do that is when 00:43:14.390 --> 00:43:18.410 you have many signals in a line on an arterial 00:43:18.410 --> 00:43:20.870 and you want a green wave, you have them 00:43:20.870 --> 00:43:22.370 all on the same cycle. 00:43:22.370 --> 00:43:24.870 And then you have their different offsets. 00:43:24.870 --> 00:43:29.330 So let's say signal 1 it's green starts at time 0. 00:43:29.330 --> 00:43:33.050 The next one that's maybe 20 seconds away, well it's green 00:43:33.050 --> 00:43:34.440 starts at time 20. 00:43:34.440 --> 00:43:36.590 And that way the cars can get a green wave. 00:43:36.590 --> 00:43:37.760 That's the idea. 00:43:37.760 --> 00:43:38.260 Yeah. 00:43:38.260 --> 00:43:41.620 AUDIENCE: Are these doing that while left turns [INAUDIBLE]?? 00:43:41.620 --> 00:43:42.370 PETER FURTH: Yeah. 00:43:42.370 --> 00:43:44.930 As I drew it here, it's protected left turns. 00:43:44.930 --> 00:43:46.650 You can have protected plus permitted. 00:43:46.650 --> 00:43:48.624 I mean there are variations. 00:43:48.624 --> 00:43:51.290 If there might be no left turns, then you can just take them out 00:43:51.290 --> 00:43:54.390 but that's the basic scheme. 00:43:54.390 --> 00:43:58.250 Now, what I want you to think about is suppose 00:43:58.250 --> 00:44:03.580 the bus is on phase two which is a common case. 00:44:03.580 --> 00:44:07.750 That's your Main Street the street that's coordinated. 00:44:07.750 --> 00:44:10.500 And the bus says, I need an extension. 00:44:10.500 --> 00:44:11.231 Extend the green. 00:44:11.231 --> 00:44:11.730 All right. 00:44:11.730 --> 00:44:16.680 We're going to borrow some time from the later phases. 00:44:16.680 --> 00:44:19.692 So we're going to hold the light green an extra 15 seconds. 00:44:22.650 --> 00:44:27.660 But remember we are guaranteeing that at the end 00:44:27.660 --> 00:44:28.950 we've got to be on time again. 00:44:28.950 --> 00:44:34.730 So now we've only got 85 seconds left to complete the cycle. 00:44:34.730 --> 00:44:37.790 And phase two and six, they are not only 00:44:37.790 --> 00:44:39.350 guaranteed their ending time, they're 00:44:39.350 --> 00:44:41.270 also guaranteed they're starting time. 00:44:41.270 --> 00:44:45.282 So that means we have to take those 15 seconds out of 3, 7, 00:44:45.282 --> 00:44:47.850 4, 8, and 1, 5. 00:44:47.850 --> 00:44:52.020 So to make things simple let's only look at the bottom ring. 00:44:52.020 --> 00:44:56.400 So I have to take 15 seconds. 00:44:56.400 --> 00:44:58.770 The first generation, they would take the whole 15 00:44:58.770 --> 00:45:01.080 seconds out of phase seven and then phase seven 00:45:01.080 --> 00:45:01.950 would get canceled. 00:45:01.950 --> 00:45:03.220 Well that caused big problems. 00:45:03.220 --> 00:45:05.490 So now what they'll do is they'll proportionally 00:45:05.490 --> 00:45:06.120 take it out. 00:45:06.120 --> 00:45:11.070 So let's say phase seven is normally 00:45:11.070 --> 00:45:13.450 scheduled to have 20 seconds, and this one is normally 00:45:13.450 --> 00:45:16.410 scheduled at 30 seconds, and this one is normally 00:45:16.410 --> 00:45:18.130 scheduled to have 20 seconds. 00:45:18.130 --> 00:45:22.530 So 20, 30, 20, that's sums up to 70. 00:45:22.530 --> 00:45:24.960 So I'm taking 15 seconds out. 00:45:24.960 --> 00:45:27.940 So a portion of that I'd take from you, I'd take from you, 00:45:27.940 --> 00:45:29.370 I'd take from you. 00:45:29.370 --> 00:45:31.750 You get the idea. 00:45:31.750 --> 00:45:34.030 Is there any compensation going on here? 00:45:34.030 --> 00:45:36.580 None at all. 00:45:36.580 --> 00:45:43.170 Phase six, the coordinated phase, got an extra 15 seconds. 00:45:43.170 --> 00:45:47.920 But the competing phases, they all got cut short. 00:45:47.920 --> 00:45:53.000 And now phase six comes up for a full phase. 00:45:53.000 --> 00:45:57.501 That's the way our coordinated systems are programmed to work. 00:45:57.501 --> 00:45:59.250 They don't have to be programmed that way, 00:45:59.250 --> 00:46:00.560 but that's the way they are. 00:46:00.560 --> 00:46:03.740 If you buy them from any American supplier, 00:46:03.740 --> 00:46:07.450 that's how they're programmed to work. 00:46:07.450 --> 00:46:10.570 So when you say let's add transit priority 00:46:10.570 --> 00:46:12.430 on top of that, now you can understand 00:46:12.430 --> 00:46:14.440 why the traffic engineers say, I don't know 00:46:14.440 --> 00:46:16.900 about a 30 second extension. 00:46:16.900 --> 00:46:19.630 Or oh, after giving priority in one cycle 00:46:19.630 --> 00:46:21.760 we better not give priority in the next. 00:46:21.760 --> 00:46:24.880 Because it can really screw up traffic. 00:46:24.880 --> 00:46:28.560 It lacks this mechanism for compensation. 00:46:28.560 --> 00:46:30.120 And compensating would be easy. 00:46:30.120 --> 00:46:36.110 It would be say, let seven run for its full scheduled time 00:46:36.110 --> 00:46:37.230 unless it gaps out. 00:46:37.230 --> 00:46:39.610 I mean if it gaps out if there's no traffic, don't. 00:46:39.610 --> 00:46:43.140 And allow six to start late because six 00:46:43.140 --> 00:46:44.220 got some extra time. 00:46:44.220 --> 00:46:47.940 It probably doesn't need its full amount. 00:46:47.940 --> 00:46:49.754 But we don't do that. 00:46:52.580 --> 00:46:56.150 And then if we do a longer extension, 00:46:56.150 --> 00:46:58.340 we get out of coordination, we have to return back, 00:46:58.340 --> 00:46:59.570 and I won't go into that. 00:47:03.925 --> 00:47:05.800 I'll talk about a second tactic, and then I'm 00:47:05.800 --> 00:47:10.240 going to take a break so you can hear about how they've done 00:47:10.240 --> 00:47:12.130 priority in the Netherlands. 00:47:12.130 --> 00:47:16.210 A second tactic is Early Green, OK? 00:47:16.210 --> 00:47:21.250 So in this diagram, the phase that's green, 00:47:21.250 --> 00:47:24.540 that's the phase in which the bus is coming, OK? 00:47:24.540 --> 00:47:26.250 And the phases that precede it, those 00:47:26.250 --> 00:47:29.280 are competing phases, the cross street or left turns 00:47:29.280 --> 00:47:31.380 that are waiting, OK? 00:47:31.380 --> 00:47:36.496 And the red dash line, that's when in the cycle 00:47:36.496 --> 00:47:37.620 the bus is going to arrive. 00:47:37.620 --> 00:47:41.280 So I've got a situation where the bus 00:47:41.280 --> 00:47:44.070 is expected to arrive near the beginning of the left turn 00:47:44.070 --> 00:47:45.184 phase. 00:47:45.184 --> 00:47:47.100 And then it would have to wait through the end 00:47:47.100 --> 00:47:48.480 of the left turn phase. 00:47:48.480 --> 00:47:52.140 And finally its phase would be green. 00:47:52.140 --> 00:48:01.450 So with early green, I could shorten the left turn phase. 00:48:01.450 --> 00:48:06.040 I could even shorten the north-south phase before it. 00:48:06.040 --> 00:48:09.850 So that now it's a shorter wait until the bus's green comes up. 00:48:09.850 --> 00:48:11.710 Maybe I even skip the left turn. 00:48:11.710 --> 00:48:14.530 I shorten the through, phase skip the left turn 00:48:14.530 --> 00:48:19.990 and really make things better for the bus that way. 00:48:19.990 --> 00:48:22.630 So an interesting way to look at early green 00:48:22.630 --> 00:48:24.830 compared to green extension. 00:48:24.830 --> 00:48:29.410 It's a small benefit because if I make the green start 00:48:29.410 --> 00:48:32.230 10 seconds early, that will reduce the delay for the bus 00:48:32.230 --> 00:48:33.550 by 10 seconds. 00:48:36.120 --> 00:48:39.120 Remember with green extension, 10 second extension 00:48:39.120 --> 00:48:41.430 could save a bus 90 seconds. 00:48:41.430 --> 00:48:46.950 But this-- it's a small benefit, but who benefits? 00:48:46.950 --> 00:48:48.530 Any bus arriving on red. 00:48:48.530 --> 00:48:53.240 And red is usually a long time, and a large percentage of buses 00:48:53.240 --> 00:48:54.230 arrive on red. 00:48:54.230 --> 00:48:58.070 Actually, the early part of green, buses can also benefit. 00:48:58.070 --> 00:49:02.030 So it's a small benefit to a large number of buses. 00:49:02.030 --> 00:49:02.530 Yeah. 00:49:02.530 --> 00:49:04.488 AUDIENCE: For skip you have the question marks. 00:49:04.488 --> 00:49:07.280 Why wouldn't you just flip the two cycles, flip the left-- 00:49:07.280 --> 00:49:08.930 PETER FURTH: Well that's a great idea. 00:49:08.930 --> 00:49:11.040 Flipping them, but now then you'd 00:49:11.040 --> 00:49:13.070 have to give that tactic a different name. 00:49:13.070 --> 00:49:16.900 And that name is called phase rotation. 00:49:16.900 --> 00:49:17.830 So yeah. 00:49:17.830 --> 00:49:22.330 And some people think phase rotation is an invitation 00:49:22.330 --> 00:49:23.990 to traffic Armageddon. 00:49:23.990 --> 00:49:25.090 It's going to be disaster. 00:49:25.090 --> 00:49:27.160 Cars are going to be smashing into each other 00:49:27.160 --> 00:49:30.220 because people expect their phase 00:49:30.220 --> 00:49:31.450 to come up at a certain time. 00:49:31.450 --> 00:49:33.580 And if it doesn't, they're going to think the light is broken 00:49:33.580 --> 00:49:34.463 and go through. 00:49:37.850 --> 00:49:39.885 This is something that can be tested. 00:49:39.885 --> 00:49:40.510 AUDIENCE: Yeah. 00:49:40.510 --> 00:49:41.840 I was just going to ask whether or not-- 00:49:41.840 --> 00:49:43.784 I think I've been at a light before where 00:49:43.784 --> 00:49:46.350 I had a skipped left turn and I was pretty pissed off. 00:49:46.350 --> 00:49:48.294 I was just curious how that goes down. 00:49:48.294 --> 00:49:51.830 How many people does it-- 00:49:51.830 --> 00:49:55.820 PETER FURTH: So in Zurich when the traffic signal programmers 00:49:55.820 --> 00:49:59.490 said, we can give better priority if we can do this. 00:49:59.490 --> 00:50:02.619 The higher ups were worried about so they 00:50:02.619 --> 00:50:04.160 said, what we're going to do is we're 00:50:04.160 --> 00:50:06.410 going to have a campaign in which we're going to let 00:50:06.410 --> 00:50:09.140 the people in the city know that for the next six months 00:50:09.140 --> 00:50:11.240 the sequence of traffic signals is 00:50:11.240 --> 00:50:13.700 going to be completely random. 00:50:13.700 --> 00:50:17.830 Just wait until your green comes up. 00:50:17.830 --> 00:50:19.480 And they did that. 00:50:19.480 --> 00:50:24.935 And then they went to having a phase rotation. 00:50:27.980 --> 00:50:30.080 AUDIENCE: Isn't it the law that you're supposed 00:50:30.080 --> 00:50:31.710 to wait until the green light? 00:50:31.710 --> 00:50:33.470 And they're assuming people-- 00:50:33.470 --> 00:50:34.480 PETER FURTH: Yeah. 00:50:34.480 --> 00:50:37.920 So in my life-- and my life is a little longer than yours, so 00:50:37.920 --> 00:50:42.360 in my lifetime of being out on the streets 00:50:42.360 --> 00:50:47.090 and I do drive a car sometimes, once I went through a red light 00:50:47.090 --> 00:50:50.360 because I waited like two whole cycles 00:50:50.360 --> 00:50:51.800 and my phase never came up. 00:50:51.800 --> 00:50:53.300 So I figured the detector was broken 00:50:53.300 --> 00:50:56.720 and there's no traffic around here anyway, so I'm going. 00:50:56.720 --> 00:51:00.616 So people will do that now and then. 00:51:00.616 --> 00:51:04.010 It doesn't happen often though. 00:51:04.010 --> 00:51:05.810 But what you say about won't people wait, 00:51:05.810 --> 00:51:08.780 there is one class of people who won't wait. 00:51:08.780 --> 00:51:10.310 And that's called bicyclists. 00:51:10.310 --> 00:51:13.160 So you got to watch out for them. 00:51:13.160 --> 00:51:14.260 Think about their safety. 00:51:16.850 --> 00:51:22.590 Now, in practice, often you can't get much benefit 00:51:22.590 --> 00:51:26.530 from early green because who's green 00:51:26.530 --> 00:51:28.494 are you trying to cut short? 00:51:28.494 --> 00:51:29.910 If what you're trying to cut short 00:51:29.910 --> 00:51:32.220 is the cross streets green, the cross streets green 00:51:32.220 --> 00:51:36.060 is often determined by pedestrians. 00:51:36.060 --> 00:51:38.040 And we don't cut pedestrian phases. 00:51:38.040 --> 00:51:42.100 Pedestrians and transit you know we're on the same team. 00:51:42.100 --> 00:51:45.480 We don't want to hurt one to help the other because all 00:51:45.480 --> 00:51:48.510 of our transit passengers become pedestrians as soon as they 00:51:48.510 --> 00:51:50.130 get off the bus. 00:51:50.130 --> 00:51:55.230 So a lot of times you just can't do early green because you've 00:51:55.230 --> 00:51:59.400 got a wide street, the cars need about 15 seconds of green 00:51:59.400 --> 00:52:01.830 to get through, but the pedestrians need 24 seconds. 00:52:01.830 --> 00:52:04.170 So the green light's 24 seconds, it's 00:52:04.170 --> 00:52:06.180 entirely because it's what the pedestrians need. 00:52:06.180 --> 00:52:09.150 You can't cut that short. 00:52:09.150 --> 00:52:14.100 So that's a practical issue that early green there 00:52:14.100 --> 00:52:18.420 are limitations unless you can detect the bus really 00:52:18.420 --> 00:52:22.320 far in advance and cut something else short. 00:52:22.320 --> 00:52:36.360 So let me take a break now and introduce Jan Nederveen. 00:52:36.360 --> 00:52:42.330 Jan is a senior transportation planner with the city of Delft. 00:52:42.330 --> 00:52:48.070 And I get the privilege every summer for the last 10 years, 00:52:48.070 --> 00:52:51.240 I've been taking 20 or 25 Northeastern students 00:52:51.240 --> 00:52:54.690 to Delft for five weeks for a course in sustainable 00:52:54.690 --> 00:52:56.100 transportation. 00:52:56.100 --> 00:52:59.720 And there they get to enjoy incredible bike paths, 00:52:59.720 --> 00:53:05.040 incredible roundabouts, streets rebuilt 00:53:05.040 --> 00:53:08.310 to be safe for public transportation 00:53:08.310 --> 00:53:11.220 systems, new train station, fantastic stuff. 00:53:11.220 --> 00:53:13.530 And it turns out the guy who plans a lot of this stuff 00:53:13.530 --> 00:53:14.910 is sitting right here. 00:53:14.910 --> 00:53:16.620 And he often speaks to our students 00:53:16.620 --> 00:53:18.790 and explains it and the philosophy behind it. 00:53:18.790 --> 00:53:23.100 So Jan, would you come and say something about how do you 00:53:23.100 --> 00:53:27.250 do transit priority in Delft. 00:53:27.250 --> 00:53:28.000 JAN NEDERVEEN: OK. 00:53:28.000 --> 00:53:28.499 Welcome. 00:53:28.499 --> 00:53:31.010 Thank you for having me here. 00:53:31.010 --> 00:53:34.270 I'm going to tell you something that works that I don't do 00:53:34.270 --> 00:53:35.710 but my colleagues do. 00:53:35.710 --> 00:53:39.670 I've got three people in my department doing traffic 00:53:39.670 --> 00:53:41.200 engineering, traffic lights. 00:53:41.200 --> 00:53:44.440 They design it, they build it, and they maintain it. 00:53:44.440 --> 00:53:47.500 So what I'll show you here is part of the thoughts 00:53:47.500 --> 00:53:51.400 they have done and I only focus on public transport. 00:53:51.400 --> 00:53:54.730 Peter offers many times a lot about cycling 00:53:54.730 --> 00:53:59.060 but this time it will be public transport. 00:53:59.060 --> 00:54:02.040 First I'll give you some views about the network. 00:54:02.040 --> 00:54:04.580 And then I'll show you the two current types of priority 00:54:04.580 --> 00:54:05.100 we give. 00:54:05.100 --> 00:54:08.510 We do physical priority, and we do time priority. 00:54:08.510 --> 00:54:12.760 I'll show you some slides for some examples of Delft. 00:54:12.760 --> 00:54:19.710 First our city Delft, 100,000 residents close to 00:54:19.710 --> 00:54:23.190 of The Hague with 600,000 residents. 00:54:23.190 --> 00:54:25.470 That's how we oriented in the busiest part, 00:54:25.470 --> 00:54:28.120 dense part of the Netherlands. 00:54:28.120 --> 00:54:32.950 First we had one system to try to serve everybody. 00:54:32.950 --> 00:54:36.310 And we didn't succeed in it because our public transport 00:54:36.310 --> 00:54:39.010 system was too slow. 00:54:39.010 --> 00:54:41.080 And then we figured out, oh, that's good. 00:54:41.080 --> 00:54:44.500 We have two kinds of groups we like to facilitate. 00:54:44.500 --> 00:54:48.130 One group are the commuters going to their work. 00:54:48.130 --> 00:54:51.680 And what they love is speed as soon as possible 00:54:51.680 --> 00:54:53.380 going to destination. 00:54:53.380 --> 00:54:57.080 In their view they only need one stop between their front door 00:54:57.080 --> 00:54:58.500 and at their destination. 00:54:58.500 --> 00:55:02.280 And everything between is not needed for them. 00:55:02.280 --> 00:55:05.850 Well, I need to collect so much more passengers 00:55:05.850 --> 00:55:08.340 that we say, we make straight lines, 00:55:08.340 --> 00:55:12.750 few stops, serving high dense volume housing 00:55:12.750 --> 00:55:15.920 with high dense jobs together. 00:55:15.920 --> 00:55:18.390 And then you can go for the high speed, the high quality, 00:55:18.390 --> 00:55:22.050 and we see that we attract more passengers. 00:55:22.050 --> 00:55:25.410 The second group is everybody else-- usually elderly people, 00:55:25.410 --> 00:55:27.420 people without a job. 00:55:27.420 --> 00:55:31.200 And we focus on them, as you say, they need coverage. 00:55:31.200 --> 00:55:34.120 They have to go to many local locations. 00:55:34.120 --> 00:55:37.670 So we make a citywide network covering every area. 00:55:37.670 --> 00:55:40.620 And that is located on a lower speed 00:55:40.620 --> 00:55:44.400 because I have to cover everything low frequency. 00:55:44.400 --> 00:55:47.200 That's the way we handle public transport. 00:55:47.200 --> 00:55:49.110 The first group is growing, the second group 00:55:49.110 --> 00:55:51.840 is stable If you look at the data. 00:55:54.700 --> 00:55:57.230 This is how our network works. 00:55:57.230 --> 00:55:59.440 I've got a purple line. 00:55:59.440 --> 00:56:02.800 That's the Delft railway system connecting all major cities 00:56:02.800 --> 00:56:03.610 of the Netherlands. 00:56:03.610 --> 00:56:05.860 If you get in Delft central station, 00:56:05.860 --> 00:56:08.590 within an hour you're standing on the central market 00:56:08.590 --> 00:56:11.800 in Amsterdam, within 10 minutes to 50 minutes 00:56:11.800 --> 00:56:13.510 you're in Rotterdam or The Hague. 00:56:13.510 --> 00:56:18.377 Nationwide system very good quality, 11 trains each hour 00:56:18.377 --> 00:56:19.800 each direction. 00:56:19.800 --> 00:56:22.090 So it's perfect. 00:56:22.090 --> 00:56:24.940 If you live in Delft, you can reach 1 million jobs 00:56:24.940 --> 00:56:26.900 within 45 minutes. 00:56:26.900 --> 00:56:32.340 So if you need a place, live in Delft. 00:56:32.340 --> 00:56:33.610 That's our first system. 00:56:33.610 --> 00:56:37.080 The second one, if I asked the people what do they like, 00:56:37.080 --> 00:56:39.990 most people like light rail like tram. 00:56:39.990 --> 00:56:44.130 There's a large group of car drivers who love light rail 00:56:44.130 --> 00:56:45.300 and don't like buses. 00:56:45.300 --> 00:56:49.340 So I tried to convert my complete network to light rail. 00:56:49.340 --> 00:56:51.590 That is the dotted lines over here. 00:56:51.590 --> 00:56:54.660 The red ones are already built. And we're still 00:56:54.660 --> 00:56:56.290 talking with the regional government 00:56:56.290 --> 00:56:58.830 to get funding for the black one. 00:56:58.830 --> 00:57:01.350 And if that's done, you see a spider kind 00:57:01.350 --> 00:57:04.810 of network covering most of the city. 00:57:04.810 --> 00:57:08.590 And I add some regional bus lines through its radial lines. 00:57:08.590 --> 00:57:10.992 That's the next coverage of our system. 00:57:10.992 --> 00:57:12.325 And that's the commuter network. 00:57:16.580 --> 00:57:19.700 And that's the last network covering everything. 00:57:19.700 --> 00:57:22.380 Step on a bus, pay $2, you've got the whole city 00:57:22.380 --> 00:57:24.980 to view if you've got the time. 00:57:24.980 --> 00:57:28.110 That's how we cover the complete area. 00:57:28.110 --> 00:57:32.130 And the last group is transport on demand. 00:57:32.130 --> 00:57:36.720 If you're unable to use a public bus, we use smaller buses. 00:57:36.720 --> 00:57:38.945 You have to phone every one hour, search 00:57:38.945 --> 00:57:42.780 a bus driving through, and you were picked up and delivered 00:57:42.780 --> 00:57:45.030 door to door transport. 00:57:45.030 --> 00:57:49.100 It's a fantastic system but it's awful expensive. 00:57:49.100 --> 00:57:52.680 So what we're trying to do is get people out of this system, 00:57:52.680 --> 00:57:55.710 this market is growing, and getting them back 00:57:55.710 --> 00:57:56.640 in a normal bus. 00:57:56.640 --> 00:57:59.640 So we modify the bus so they are more attractive for people 00:57:59.640 --> 00:58:02.610 with light handicaps. 00:58:02.610 --> 00:58:04.650 And the other thing we are thinking about, maybe 00:58:04.650 --> 00:58:07.860 we can offer a discount to the buses as a sort of timetable. 00:58:07.860 --> 00:58:11.320 We have a line structure for driving that kind of business. 00:58:11.320 --> 00:58:13.230 So it looks like more public transport which 00:58:13.230 --> 00:58:18.230 makes it more cheaper to run. 00:58:18.230 --> 00:58:20.590 Physical priority. 00:58:20.590 --> 00:58:22.600 That's the first thing we do. 00:58:22.600 --> 00:58:26.340 If a bus is in the same lane as a car or if there's many 00:58:26.340 --> 00:58:28.630 bicycles usually there's the same speed, 00:58:28.630 --> 00:58:31.265 and I cannot give them any priority, 00:58:31.265 --> 00:58:33.640 let's give them bus lines. 00:58:36.490 --> 00:58:39.060 Where the center of city, center is city Delft, that 00:58:39.060 --> 00:58:41.380 is the downtown area, the central market square, 00:58:41.380 --> 00:58:43.870 this is where all the shops are and all the restaurants. 00:58:43.870 --> 00:58:45.490 That's the most historical center. 00:58:45.490 --> 00:58:47.455 It's a lovely place to be. 00:58:47.455 --> 00:58:51.370 You see the square over there, that is the central railroad 00:58:51.370 --> 00:58:52.270 station. 00:58:52.270 --> 00:58:55.020 If you'd like to leave the city, go there. 00:58:55.020 --> 00:58:56.620 And we designed all the bus lines 00:58:56.620 --> 00:58:59.440 going to the central railroad station. 00:58:59.440 --> 00:59:02.130 We can give them good priority on that location. 00:59:04.790 --> 00:59:06.920 When do we need a bus lane? 00:59:06.920 --> 00:59:13.230 We need it if there is a delay of driving with the cars. 00:59:13.230 --> 00:59:15.790 So on busy streets I like to have a bus lane. 00:59:15.790 --> 00:59:19.640 And that's difficult because if it's a busy street, 00:59:19.640 --> 00:59:23.290 you need probably four lanes or two lanes of car traffic. 00:59:23.290 --> 00:59:26.470 And I'm asking one lane for six or eight buses 00:59:26.470 --> 00:59:28.340 per hour in each direction. 00:59:28.340 --> 00:59:31.280 So then we have to compete, as I said, in the busiest areas. 00:59:31.280 --> 00:59:34.900 We start searching for a bus lane or a light rail lane 00:59:34.900 --> 00:59:37.180 so we can give them priority. 00:59:37.180 --> 00:59:40.210 And elsewhere-- this is a residential area, 00:59:40.210 --> 00:59:44.880 it's nice to have but you don't need to have it. 00:59:44.880 --> 00:59:47.300 This was thought in the 80s, OK, let's 00:59:47.300 --> 00:59:49.880 make a bus lane everywhere so we get the bus 00:59:49.880 --> 00:59:51.830 lane in a residential area. 00:59:51.830 --> 00:59:54.500 And the only place we need it that it's 00:59:54.500 --> 00:59:57.280 crossing the highway in that location 00:59:57.280 --> 00:59:59.976 is because that's our big intersections. 01:00:03.190 --> 01:00:09.960 Another part of priority is at the central station of Delft. 01:00:09.960 --> 01:00:11.895 This area, if you look at Delft and you 01:00:11.895 --> 01:00:14.210 take in Delft area, urban development, 01:00:14.210 --> 01:00:17.260 railroad you see a huge development in the downtown 01:00:17.260 --> 01:00:17.760 area. 01:00:17.760 --> 01:00:20.790 Over here is the old station. 01:00:20.790 --> 01:00:22.110 Over there is a new one. 01:00:22.110 --> 01:00:26.380 We have spent 500 million Euros to get the railroad tracks 01:00:26.380 --> 01:00:29.970 under the ground for 1 and 1/2 miles. 01:00:29.970 --> 01:00:34.380 And we built a complete railroad station, a new bus platform, 01:00:34.380 --> 01:00:38.460 and we did a complete separation of all the transfer flows. 01:00:38.460 --> 01:00:41.695 On the surface level we offered public transport. 01:00:41.695 --> 01:00:44.670 So in the open air, that's public transport. 01:00:44.670 --> 01:00:47.130 On minus one, in the basement, we 01:00:47.130 --> 01:00:50.850 have the huge parking facility with parking lanes 01:00:50.850 --> 01:00:53.020 underground to bus platform. 01:00:53.020 --> 01:00:56.580 So we have a physical separation of the bike transport 01:00:56.580 --> 01:00:59.505 going to the railroad station and the bus transport. 01:00:59.505 --> 01:01:03.270 Now on level minus two, we have the railroad tracks. 01:01:03.270 --> 01:01:06.510 That's one way of separation. 01:01:06.510 --> 01:01:10.690 You can see it here in the picture. 01:01:10.690 --> 01:01:12.640 This is the town hall, the glass building. 01:01:12.640 --> 01:01:14.494 And the first floor, the ground floor, 01:01:14.494 --> 01:01:15.660 that's the railroad station. 01:01:15.660 --> 01:01:18.100 We have the name Delft on it. 01:01:18.100 --> 01:01:19.960 And underneath in it right, you can 01:01:19.960 --> 01:01:24.340 see people standing at the entrance of the parking garage. 01:01:24.340 --> 01:01:27.760 We've got 100,000 people living in Delft. 01:01:27.760 --> 01:01:31.480 This parking garage for bicycles is today 8,000 places, 01:01:31.480 --> 01:01:33.520 and it's not enough. 01:01:33.520 --> 01:01:36.260 So a few years later there will be 10,000 places 01:01:36.260 --> 01:01:39.270 for 100,000 residents. 01:01:39.270 --> 01:01:41.337 So bike parking is very important. 01:01:41.337 --> 01:01:43.170 AUDIENCE: There's also the university there, 01:01:43.170 --> 01:01:47.181 so they're not all residents. 01:01:47.181 --> 01:01:47.680 Yeah. 01:01:47.680 --> 01:01:49.817 Not all the students are residents [INAUDIBLE].. 01:01:49.817 --> 01:01:50.650 JAN NEDERVEEN: Yeah. 01:01:50.650 --> 01:01:51.490 It's students. 01:01:51.490 --> 01:01:52.531 It's also residents now. 01:01:52.531 --> 01:01:53.030 Yes. 01:01:53.030 --> 01:01:54.670 OK. 01:01:54.670 --> 01:02:00.230 But when the students are at the university 01:02:00.230 --> 01:02:04.360 and you look at the parking facility, it's also full. 01:02:04.360 --> 01:02:06.400 And other people leaving Delft. 01:02:06.400 --> 01:02:09.250 Some of them are also students going 01:02:09.250 --> 01:02:12.250 into a university in Leiden or in Rotterdam 01:02:12.250 --> 01:02:16.480 but also normal people like myself are parking there. 01:02:16.480 --> 01:02:19.540 It's not a student parking garage. 01:02:19.540 --> 01:02:21.070 Yeah. 01:02:21.070 --> 01:02:24.780 It's true that a large group of them are students. 01:02:24.780 --> 01:02:27.570 Well minus one is for the bikes and the bus platform 01:02:27.570 --> 01:02:29.940 is operational on this level. 01:02:29.940 --> 01:02:34.900 So buses don't have to deal with cars or with pedestrians 01:02:34.900 --> 01:02:36.300 or with bikes. 01:02:36.300 --> 01:02:37.094 Yes. 01:02:37.094 --> 01:02:39.070 AUDIENCE: So if minus one is parking for bikes, 01:02:39.070 --> 01:02:44.510 do they also travel on that level or do they [INAUDIBLE]?? 01:02:44.510 --> 01:02:47.280 JAN NEDERVEEN: The bikes also travel on minus one. 01:02:47.280 --> 01:02:51.180 The bike lane goes here under this bridge 01:02:51.180 --> 01:02:52.570 and then entering the park. 01:02:52.570 --> 01:02:54.750 You can see there's a rim over it. 01:02:54.750 --> 01:02:57.390 So he has a complete separation to minus one 01:02:57.390 --> 01:03:01.640 in the most busiest area. 01:03:01.640 --> 01:03:04.630 And that saves me a lot of time because the first traffic 01:03:04.630 --> 01:03:07.620 light, very close to the railroad station, 01:03:07.620 --> 01:03:12.700 should otherwise have to deal with 10,000 bicycles a day. 01:03:12.700 --> 01:03:14.350 But I've offered them a tunnel so I've 01:03:14.350 --> 01:03:17.050 got a normal intersection with a normal traffic light. 01:03:17.050 --> 01:03:20.880 All the rest I cannot handle that amount of cyclists, 01:03:20.880 --> 01:03:24.100 and this Peter here among this group, he will not stop. 01:03:27.970 --> 01:03:29.870 Here's an aerial view of the system. 01:03:29.870 --> 01:03:31.630 The town hall is in the front. 01:03:31.630 --> 01:03:33.860 And we have also an east-west separation. 01:03:33.860 --> 01:03:38.190 On the down inner city side that's over here, 01:03:38.190 --> 01:03:42.560 we put the bus lane, the light rail lane. 01:03:42.560 --> 01:03:46.810 And on the other side, we've got the lane with the car traffic. 01:03:46.810 --> 01:03:48.870 And that's very important because at the top 01:03:48.870 --> 01:03:51.420 of the picture on the left side, I 01:03:51.420 --> 01:03:54.120 have an intersection where all public transport has to make 01:03:54.120 --> 01:03:56.436 all the left or right turns. 01:03:56.436 --> 01:03:57.810 And that's the only one that make 01:03:57.810 --> 01:04:00.320 that turn because the car route is blocked 01:04:00.320 --> 01:04:02.820 and the bike lane is underground in a tunnel. 01:04:02.820 --> 01:04:06.330 So I have an intersection where only public transport 01:04:06.330 --> 01:04:08.539 makes left and right turns. 01:04:08.539 --> 01:04:10.830 And on the other intersection that's almost falling off 01:04:10.830 --> 01:04:12.288 the picture on the right side, that 01:04:12.288 --> 01:04:17.040 is my car intersection where all the light rail traffic only 01:04:17.040 --> 01:04:19.520 has to cross, they go straight through. 01:04:19.520 --> 01:04:23.430 So it was much easier to handle if a separate public transport 01:04:23.430 --> 01:04:26.950 and car transport on different intersections. 01:04:26.950 --> 01:04:31.000 And my transport engineers were interested in traffic lights. 01:04:31.000 --> 01:04:33.550 I took them, let me have a look if this is the same. 01:04:33.550 --> 01:04:37.900 Can you build a traffic light for this location? 01:04:37.900 --> 01:04:41.680 Because the alternative was one big crossing with everything, 01:04:41.680 --> 01:04:44.900 and that didn't work. 01:04:44.900 --> 01:04:48.830 I do also have some discussions with my urban planners. 01:04:48.830 --> 01:04:52.610 And they love the light rail and the green grass in the middle. 01:04:55.480 --> 01:05:01.230 And my public transport here, lots 01:05:01.230 --> 01:05:07.090 of asphalt. What do you like? 01:05:07.090 --> 01:05:08.980 I pick you out. 01:05:08.980 --> 01:05:12.000 Which one would you like and why? 01:05:12.000 --> 01:05:15.920 AUDIENCE: I'd prefer the light lines because I feel 01:05:15.920 --> 01:05:18.370 like you're more in tune with-- 01:05:18.370 --> 01:05:22.520 you experience the road better that way. 01:05:22.520 --> 01:05:24.120 You can serve the demand like that. 01:05:24.120 --> 01:05:25.324 You should go green. 01:05:25.324 --> 01:05:26.740 JAN NEDERVEEN: So which one do you 01:05:26.740 --> 01:05:28.865 like, the light rail in the green or the light rail 01:05:28.865 --> 01:05:30.182 in the asphalt? 01:05:30.182 --> 01:05:32.184 AUDIENCE: In the green. 01:05:32.184 --> 01:05:33.350 JAN NEDERVEEN: In the green. 01:05:33.350 --> 01:05:36.035 It's lovely, nicer. 01:05:36.035 --> 01:05:36.910 AUDIENCE: [INAUDIBLE] 01:05:36.910 --> 01:05:37.743 JAN NEDERVEEN: Yeah. 01:05:37.743 --> 01:05:40.100 Well we had that discussion also. 01:05:40.100 --> 01:05:43.270 I also think the top picture is the most beautiful. 01:05:43.270 --> 01:05:46.940 But this has one big disadvantage. 01:05:46.940 --> 01:05:51.030 If I have a bus link or a public transport link 01:05:51.030 --> 01:05:55.220 but I like to operate buses as well as light rail, 01:05:55.220 --> 01:05:59.720 in this situation they can both use the same line. 01:05:59.720 --> 01:06:01.550 And I've got one platform, and you 01:06:01.550 --> 01:06:04.720 can decide if you take a bus or light rail. 01:06:04.720 --> 01:06:08.780 And the one on top, if I would like to add the bus lane, 01:06:08.780 --> 01:06:12.260 well that would be a bus stop without priority 01:06:12.260 --> 01:06:14.300 on the normal street. 01:06:14.300 --> 01:06:15.740 I [INAUDIBLE] that one because it 01:06:15.740 --> 01:06:18.560 doesn't have a bus lane anymore because I replaced it 01:06:18.560 --> 01:06:19.240 by a light rail. 01:06:22.120 --> 01:06:22.760 Yes. 01:06:22.760 --> 01:06:25.970 AUDIENCE: What is the typical frequency of light rail lines? 01:06:25.970 --> 01:06:28.810 JAN NEDERVEEN: The minimum is four light rail vehicles 01:06:28.810 --> 01:06:29.950 an hour each direction. 01:06:29.950 --> 01:06:31.670 That's the minimum. 01:06:31.670 --> 01:06:32.170 Otherwise-- 01:06:32.170 --> 01:06:33.540 AUDIENCE: Rush hour? 01:06:33.540 --> 01:06:37.080 JAN NEDERVEEN: It goes up to 6 or 8 in Delft. 01:06:37.080 --> 01:06:39.920 And in other cities it can be more. 01:06:39.920 --> 01:06:44.770 But eight is all pretty much for city with 100,000 people. 01:06:44.770 --> 01:06:47.470 And it has to compete with cycling. 01:06:47.470 --> 01:06:50.710 So many people who cycle you take them out 01:06:50.710 --> 01:06:54.180 from the public transport system. 01:06:54.180 --> 01:06:58.490 These guys, cab drivers always ask me, 01:06:58.490 --> 01:07:01.250 may I use your bus lanes? 01:07:01.250 --> 01:07:05.030 Because they are so fast and they have beautiful traffic 01:07:05.030 --> 01:07:06.230 lights. 01:07:06.230 --> 01:07:09.700 I couldn't find a letter size bigger than this one. 01:07:12.740 --> 01:07:14.240 I said no! 01:07:14.240 --> 01:07:16.720 Absolutely not! 01:07:16.720 --> 01:07:22.740 I've got maybe 2018 cabs in Delft, but it's no, no. 01:07:22.740 --> 01:07:25.627 AUDIENCE: It's not more efficient than driving. 01:07:25.627 --> 01:07:27.460 JAN NEDERVEEN: Oh, they love to drive my bus 01:07:27.460 --> 01:07:30.160 lanes like the fire department, who is pretty fast, 01:07:30.160 --> 01:07:34.360 but no way I want it. 01:07:34.360 --> 01:07:38.530 Because if they enter a huge intersection 01:07:38.530 --> 01:07:41.260 and there is a bus going at that intersection, 01:07:41.260 --> 01:07:44.620 I know that bus will make a left turn. 01:07:44.620 --> 01:07:47.680 Because every bus on that intersection will make a left 01:07:47.680 --> 01:07:48.620 turn. 01:07:48.620 --> 01:07:52.970 And that means all other directions can get green. 01:07:52.970 --> 01:07:55.736 I don't know where that cab is going. 01:07:55.736 --> 01:07:59.810 So you have to completely block the intersection for one cab. 01:07:59.810 --> 01:08:00.560 Yes? 01:08:00.560 --> 01:08:04.851 AUDIENCE: Why is that London lets taxis use the bus lanes? 01:08:04.851 --> 01:08:06.830 Are you familiar with that? 01:08:06.830 --> 01:08:08.020 JAN NEDERVEEN: In London? 01:08:08.020 --> 01:08:08.644 AUDIENCE: Yeah. 01:08:08.644 --> 01:08:11.150 JAN NEDERVEEN: Yeah, maybe they block out 01:08:11.150 --> 01:08:15.270 all the other directions to give them the priority. 01:08:15.270 --> 01:08:19.229 And that will seriously harm all other modes of transport. 01:08:19.229 --> 01:08:23.290 It would harm car traffic and bike traffic. 01:08:23.290 --> 01:08:27.560 And we like to give priority to the buses with many people, 01:08:27.560 --> 01:08:29.290 but this is one taxi who have maybe 01:08:29.290 --> 01:08:30.990 one or two people inside it. 01:08:30.990 --> 01:08:34.015 That's not worth the effort. 01:08:34.015 --> 01:08:36.090 And it's a big risk to give him green 01:08:36.090 --> 01:08:37.454 and see what is happening. 01:08:41.170 --> 01:08:41.950 Time priority. 01:08:41.950 --> 01:08:46.340 Peter already taught some things but that is what we do. 01:08:46.340 --> 01:08:49.689 You have special traffic lights, the [INAUDIBLE] traffic 01:08:49.689 --> 01:08:56.580 lights that's in the picture on the black/white border column. 01:08:56.580 --> 01:08:59.890 That's showing if you get green to left or to right or straight 01:08:59.890 --> 01:09:01.340 through for our bus. 01:09:01.340 --> 01:09:04.990 And we have two kinds of detection. 01:09:04.990 --> 01:09:07.270 The first one is the intelligent one. 01:09:07.270 --> 01:09:13.189 So every vehicle says, I'm bus 24 vehicle number, 01:09:13.189 --> 01:09:18.520 so I should be here 20 minutes past five. 01:09:18.520 --> 01:09:21.439 So it's also telling it's time per table. 01:09:21.439 --> 01:09:25.300 And then we know, OK, you're one minute early, 01:09:25.300 --> 01:09:29.979 we will not give you priority That's the expensive one. 01:09:29.979 --> 01:09:32.720 And the other one, that's a simple detection. 01:09:32.720 --> 01:09:35.080 Some vehicle is crossing a detector and notice, oh, 01:09:35.080 --> 01:09:36.490 this is a vehicle. 01:09:36.490 --> 01:09:37.960 I even don't know which bus it is. 01:09:37.960 --> 01:09:40.450 Even if you are a car you are detected 01:09:40.450 --> 01:09:42.640 and then you get some priority. 01:09:42.640 --> 01:09:44.200 That's the way of detection. 01:09:44.200 --> 01:09:45.399 The top one is the best. 01:09:45.399 --> 01:09:48.460 So if we are in charge and it's our traffic light, 01:09:48.460 --> 01:09:50.439 we put in the intelligent one. 01:09:50.439 --> 01:09:52.390 If somebody is else doing the design, 01:09:52.390 --> 01:09:55.610 a regional government, sometimes you get the cheap one. 01:09:55.610 --> 01:09:58.960 Especially in the Delft University, top technology 01:09:58.960 --> 01:10:01.480 campus, the cheap one is installed. 01:10:04.630 --> 01:10:05.840 Traffic light priority. 01:10:05.840 --> 01:10:10.120 Peter showed you a bus stop close to an intersection. 01:10:10.120 --> 01:10:14.360 Well, here's an example of a traffic light priority 01:10:14.360 --> 01:10:16.070 at a huge intersection. 01:10:16.070 --> 01:10:19.170 The term has to make a turn to the left. 01:10:19.170 --> 01:10:23.550 And what we do, we put in to two lines. 01:10:23.550 --> 01:10:26.220 The first one is the location where 01:10:26.220 --> 01:10:29.940 the light rail, the [AUDIO OUT] for handling the passengers. 01:10:29.940 --> 01:10:33.770 I don't know how long that will take. 01:10:33.770 --> 01:10:36.540 And I don't want to stop all the other traffic because he 01:10:36.540 --> 01:10:37.850 is still handling passengers. 01:10:37.850 --> 01:10:40.400 If I do so, I get many letters from people 01:10:40.400 --> 01:10:41.970 waiting for nothing. 01:10:41.970 --> 01:10:44.270 So there's a second stop line, go 01:10:44.270 --> 01:10:46.850 straightforward on the intersection. 01:10:46.850 --> 01:10:49.530 And then the light rail will [INAUDIBLE],, 01:10:49.530 --> 01:10:51.350 hey, hello I'm here. 01:10:51.350 --> 01:10:54.220 Please can you give me what priority. 01:10:54.220 --> 01:10:57.560 And what this system does, he will not break off 01:10:57.560 --> 01:10:58.610 all the other signals. 01:10:58.610 --> 01:11:00.900 He says, oh, I've finished my phase, 01:11:00.900 --> 01:11:04.370 I then add in the phase with public transport, 01:11:04.370 --> 01:11:06.530 and then I continue with all the rest. 01:11:06.530 --> 01:11:09.260 I don't take out any time from the others, 01:11:09.260 --> 01:11:13.410 just merge in a priority for the traffic lights. 01:11:13.410 --> 01:11:15.395 So this intersection is four phases 01:11:15.395 --> 01:11:18.300 so there are four chances to give him priority. 01:11:18.300 --> 01:11:21.710 So the waiting time is not a full cycle but only 01:11:21.710 --> 01:11:24.360 a quarter of it. 01:11:24.360 --> 01:11:26.860 That's how it works. 01:11:26.860 --> 01:11:31.510 This is that same intersection from the air. 01:11:31.510 --> 01:11:33.640 So it's a huge one, the biggest intersection 01:11:33.640 --> 01:11:35.543 we have in the built up area. 01:11:35.543 --> 01:11:38.440 We have total detection all directions. 01:11:38.440 --> 01:11:41.950 Also the bicycles are detected. 01:11:41.950 --> 01:11:43.000 We have a detector. 01:11:43.000 --> 01:11:44.020 We don't use an eight. 01:11:44.020 --> 01:11:46.010 We've got a good detector. 01:11:46.010 --> 01:11:48.190 So we detect bikes. 01:11:48.190 --> 01:11:51.070 There also is a button if you like, but most of the time 01:11:51.070 --> 01:11:53.290 you're already detected. 01:11:53.290 --> 01:11:59.010 We have a fixed sequence which groups go together. 01:11:59.010 --> 01:12:01.190 And what the sequence is? 01:12:01.190 --> 01:12:04.460 We have defined a maximum green time 01:12:04.460 --> 01:12:07.440 that might be possible for each direction. 01:12:07.440 --> 01:12:11.960 And we stop giving green if we achieve a free flow situation. 01:12:11.960 --> 01:12:15.830 So I don't give green to free flow traffic. 01:12:15.830 --> 01:12:17.490 And if the traffic's still congested 01:12:17.490 --> 01:12:20.570 after a certain amount of time we say, OK, now it's enough, 01:12:20.570 --> 01:12:23.560 now the others have to go. 01:12:23.560 --> 01:12:26.950 You have bus priority and light rail priority and fire truck 01:12:26.950 --> 01:12:28.420 priority. 01:12:28.420 --> 01:12:31.090 And we don't build intersections in Delft. 01:12:31.090 --> 01:12:34.720 We have a traffic light sequence of 120 seconds. 01:12:34.720 --> 01:12:36.160 That's the max. 01:12:36.160 --> 01:12:39.610 So if the area is congested, the maximum cycle time 01:12:39.610 --> 01:12:42.610 is 1 minute and 20 seconds. 01:12:42.610 --> 01:12:46.700 And my [INAUDIBLE] if you look at our intersections, 01:12:46.700 --> 01:12:48.770 I'm trying to bring back the cycle 01:12:48.770 --> 01:12:55.050 time for as many intersections back to 90 seconds. 01:12:55.050 --> 01:12:57.660 And they did and for most intersections it worked. 01:12:57.660 --> 01:13:01.260 And it was a huge benefit for everybody. 01:13:01.260 --> 01:13:04.840 The maximum waiting time is reduced 30 seconds. 01:13:04.840 --> 01:13:07.650 So if you missed going first 30 seconds, 01:13:07.650 --> 01:13:10.420 you're simply reducing the cycle time. 01:13:10.420 --> 01:13:12.000 You can also do it physically, make 01:13:12.000 --> 01:13:14.790 your intersections smaller. 01:13:14.790 --> 01:13:17.776 That's a huge benefit for the cycling time. 01:13:17.776 --> 01:13:20.870 And we noticed some intersections 01:13:20.870 --> 01:13:23.370 were pretty sharp, 90 seconds. 01:13:23.370 --> 01:13:25.150 People get used to it so they didn't 01:13:25.150 --> 01:13:27.340 miss the first second of green. 01:13:27.340 --> 01:13:30.120 They were green, [INAUDIBLE],, driving. 01:13:30.120 --> 01:13:33.860 So we could handle the same number of cars 01:13:33.860 --> 01:13:35.890 in a shorter green time. 01:13:35.890 --> 01:13:39.880 A special one was the fire truck priority. 01:13:39.880 --> 01:13:43.980 The fire department has a depot exactly at that intersection. 01:13:43.980 --> 01:13:46.910 And they've got a beautiful red button. 01:13:46.910 --> 01:13:49.870 So if I press that red button, the intersection 01:13:49.870 --> 01:13:53.410 will stand in a way that the order directions 01:13:53.410 --> 01:13:57.490 are blocked that the fire department has to cross. 01:13:57.490 --> 01:13:59.770 So if you're not in the direction of a fire 01:13:59.770 --> 01:14:01.810 that the fire department has to go, 01:14:01.810 --> 01:14:06.130 you still get green because it is an intelligence red button. 01:14:06.130 --> 01:14:10.090 So I press this button showing I have a fire in Delft North, 01:14:10.090 --> 01:14:12.880 and they will follow this route. 01:14:12.880 --> 01:14:15.810 Then that route will get green for the fire truck 01:14:15.810 --> 01:14:18.190 on the time we think he will be there. 01:14:18.190 --> 01:14:21.950 So while driving North, he continues detected, 01:14:21.950 --> 01:14:24.750 and the traffic lights are switched that way 01:14:24.750 --> 01:14:27.000 that we will get green. 01:14:27.000 --> 01:14:30.270 We do not block completely all these intersections 01:14:30.270 --> 01:14:32.910 for the fire trucks since he knows if we do so, 01:14:32.910 --> 01:14:36.180 we might cause a traffic jam because all the directions 01:14:36.180 --> 01:14:37.680 are blocked. 01:14:37.680 --> 01:14:39.180 And that's the way how we get there. 01:14:39.180 --> 01:14:43.410 And we also detect if you pressed the right button 01:14:43.410 --> 01:14:47.225 and if we make a system that is going perfectly to the north. 01:14:47.225 --> 01:14:51.020 Maybe he didn't use that route but in certain times 01:14:51.020 --> 01:14:53.590 the system arguments, OK, I did the measuring 01:14:53.590 --> 01:14:57.160 so somebody has disappeared or gone somewhere else. 01:14:57.160 --> 01:14:59.470 Well let's switch back to normal. 01:14:59.470 --> 01:15:01.760 That's the fire priority we've got in Delft. 01:15:01.760 --> 01:15:05.160 And it was very important when we built the railroad tunnel 01:15:05.160 --> 01:15:09.540 because the whole area was under construction 01:15:09.540 --> 01:15:12.633 with all the traffic lights kept to that priority. 01:15:15.580 --> 01:15:17.481 And that's the example from Delft. 01:15:17.481 --> 01:15:17.980 Thank you. 01:15:24.354 --> 01:15:25.520 PETER FURTH: My new graphic. 01:15:29.130 --> 01:15:29.630 Yeah. 01:15:35.380 --> 01:15:41.050 So I told you that [AUDIO OUT] are green extension, which 01:15:41.050 --> 01:15:43.240 is great if you've got a far side stop 01:15:43.240 --> 01:15:44.650 and you can predict events. 01:15:44.650 --> 01:15:46.900 Early green, which is a little more limited 01:15:46.900 --> 01:15:48.440 but we need more flexibility. 01:15:48.440 --> 01:15:51.010 So like what Jan was describing there, 01:15:51.010 --> 01:15:56.270 they have these four phases in the cycle. 01:15:56.270 --> 01:15:58.700 To make it simple, let's just say 01:15:58.700 --> 01:16:07.820 we have east and west left and then east and west through 01:16:07.820 --> 01:16:14.710 and then north and south left and north and south 01:16:14.710 --> 01:16:20.580 through, phase one, two, three, four, and the tram, 01:16:20.580 --> 01:16:22.110 in this case, because it actually 01:16:22.110 --> 01:16:23.830 conflicts with all of them. 01:16:23.830 --> 01:16:28.140 So the normal thinking of a traffic engineer would be, 01:16:28.140 --> 01:16:30.534 OK, and then we'll have a tram phase here. 01:16:30.534 --> 01:16:31.575 And now that's the cycle. 01:16:34.540 --> 01:16:37.475 But the Delft thinking is, we'll put a tram phase here, 01:16:37.475 --> 01:16:39.850 we'll put a tram phase here, we'll put a tram phase here, 01:16:39.850 --> 01:16:41.650 and a tram phase here. 01:16:41.650 --> 01:16:43.390 And if there's no tram, well we skip it. 01:16:43.390 --> 01:16:46.060 And if there is a tram, then the tram gets to go. 01:16:46.060 --> 01:16:48.460 So the tram never has to wait long. 01:16:48.460 --> 01:16:52.480 So that's part of the, if we can get a man on the moon, 01:16:52.480 --> 01:16:54.890 we can turn the light green. 01:16:54.890 --> 01:17:01.710 So let me say something. 01:17:01.710 --> 01:17:04.090 I'll leave the rest of these plans. 01:17:04.090 --> 01:17:06.330 They have some details there. 01:17:06.330 --> 01:17:09.720 But let me tell you something about D Street and the Silver 01:17:09.720 --> 01:17:11.580 Line, OK? 01:17:11.580 --> 01:17:17.622 So the Waterfront Silver Line-- 01:17:17.622 --> 01:17:19.740 AUDIENCE: [INAUDIBLE] 01:17:19.740 --> 01:17:20.448 PETER FURTH: Huh? 01:17:20.448 --> 01:17:21.700 AUDIENCE: Do you have a video? 01:17:21.700 --> 01:17:22.533 PETER FURTH: No, no. 01:17:22.533 --> 01:17:25.000 I'm not going to do the video. 01:17:25.000 --> 01:17:27.490 This is something new. 01:17:27.490 --> 01:17:29.740 How many of you are familiar with the Silver Line that 01:17:29.740 --> 01:17:31.260 goes to and from the airport? 01:17:31.260 --> 01:17:33.130 Yeah. 01:17:33.130 --> 01:17:35.470 D street is where, if you're going toward the airport, 01:17:35.470 --> 01:17:38.707 it comes out of the tunnel and then it stops at a red light. 01:17:38.707 --> 01:17:41.040 And while you're waiting at the red light you can watch, 01:17:41.040 --> 01:17:42.310 and there's no cars going by. 01:17:42.310 --> 01:17:44.180 And you think, why is the light red? 01:17:44.180 --> 01:17:50.140 So on a map here's Congress Street. 01:17:52.720 --> 01:17:55.120 This is D Street. 01:17:55.120 --> 01:17:58.180 And then this is Silver Line Way. 01:17:58.180 --> 01:18:00.970 So the traffic engineers are concerned 01:18:00.970 --> 01:18:02.800 that that's a short distance. 01:18:02.800 --> 01:18:05.320 And if they turn the light red for Congress Street, 01:18:05.320 --> 01:18:06.890 two bad things can happen. 01:18:06.890 --> 01:18:08.680 One is spill back. 01:18:08.680 --> 01:18:11.770 Traffic comes to here, oh, the light is red, 01:18:11.770 --> 01:18:16.240 and now queue spills back, and it hurts the capacity. 01:18:16.240 --> 01:18:18.880 And the second one is starvation. 01:18:18.880 --> 01:18:22.480 The light turns green here for northbound traffic, 01:18:22.480 --> 01:18:24.580 but the light is still red here. 01:18:24.580 --> 01:18:28.430 So cars start to go, but nobody can go because they're stuck. 01:18:28.430 --> 01:18:29.620 It's starved. 01:18:29.620 --> 01:18:35.410 So they don't want to close D Street while either 01:18:35.410 --> 01:18:37.280 of those things can happen. 01:18:37.280 --> 01:18:40.330 So there is a cycle; it's a 120 second cycle. 01:18:40.330 --> 01:18:42.370 This time I'll draw the cycle in a circle. 01:18:42.370 --> 01:18:44.380 And they've decided here is the time 01:18:44.380 --> 01:18:46.790 in the cycle the bus can go. 01:18:46.790 --> 01:18:48.970 So that's why you just wait, you just wait. 01:18:48.970 --> 01:18:52.870 You arrive and you just wait until your time in the cycle. 01:18:52.870 --> 01:18:55.660 So I just recently had some students 01:18:55.660 --> 01:18:59.380 study it in my advanced traffic control class. 01:18:59.380 --> 01:19:01.870 We actually took the whole class there for a field trip 01:19:01.870 --> 01:19:05.350 during morning peak hour because I had to see it myself. 01:19:05.350 --> 01:19:08.530 Is it really the disaster people talk about? 01:19:08.530 --> 01:19:10.000 It is not a traffic disaster. 01:19:10.000 --> 01:19:14.980 It is a transit disaster because the frequency the Silver Line, 01:19:14.980 --> 01:19:16.629 it's about one bus every two minutes, 01:19:16.629 --> 01:19:17.920 and they go in both directions. 01:19:17.920 --> 01:19:22.870 So that means in a 120 second cycle, 01:19:22.870 --> 01:19:24.310 if they're perfectly on schedule, 01:19:24.310 --> 01:19:26.610 you'd have one bus at most one per direction. 01:19:26.610 --> 01:19:27.670 Of course they're not. 01:19:27.670 --> 01:19:29.470 So often you've got two buses, sometimes 01:19:29.470 --> 01:19:32.004 three buses waiting to go. 01:19:32.004 --> 01:19:34.042 And they wait, and they wait, and they wait, 01:19:34.042 --> 01:19:35.500 and they wait, and most of the time 01:19:35.500 --> 01:19:37.450 there is no conflicting traffic. 01:19:37.450 --> 01:19:42.050 So my students learn how to do traffic simulations. 01:19:42.050 --> 01:19:43.990 There's some standard packages for that. 01:19:43.990 --> 01:19:46.670 They learn how to program their own traffic control. 01:19:46.670 --> 01:19:51.910 And they said, let's try just all out aggressive priority. 01:19:51.910 --> 01:19:55.090 When we detect the bus, we just stop the street, 01:19:55.090 --> 01:19:56.800 let the bus go through. 01:19:56.800 --> 01:20:01.840 The bus only needs like 14 seconds, and then it goes back. 01:20:01.840 --> 01:20:05.210 And I can hear people saying, oh, 01:20:05.210 --> 01:20:08.290 but sometimes you've got to serve two or three buses. 01:20:08.290 --> 01:20:11.630 Yeah, when buses have to wait two minutes till their turn 01:20:11.630 --> 01:20:12.130 comes. 01:20:12.130 --> 01:20:14.200 But when they don't have to wait, 01:20:14.200 --> 01:20:16.580 you're never going to be serving more than one at a time. 01:20:16.580 --> 01:20:19.210 And it only takes 15 seconds. 01:20:19.210 --> 01:20:21.280 We put that into the simulation to see, OK, 01:20:21.280 --> 01:20:23.080 how's it going to affect cars? 01:20:23.080 --> 01:20:26.070 How is it going to affect buses? 01:20:26.070 --> 01:20:29.430 Average delay for bus goes from 50 seconds down 01:20:29.430 --> 01:20:31.330 to four seconds. 01:20:31.330 --> 01:20:33.140 Why four? 01:20:33.140 --> 01:20:36.020 That's only because if we do turn the light green for a bus, 01:20:36.020 --> 01:20:40.664 for the cars a minimum 20 second before the next bus. 01:20:40.664 --> 01:20:42.080 So there's a bus in one direction, 01:20:42.080 --> 01:20:44.020 the bus coming in the other direction 01:20:44.020 --> 01:20:47.920 15 seconds later might have to wait a few seconds. 01:20:47.920 --> 01:20:50.120 So delay for bus goes down almost zero. 01:20:50.120 --> 01:20:55.140 Delay for cars also goes down because the system 01:20:55.140 --> 01:20:59.662 they have now will stop the cars even when there's no bus. 01:21:03.540 --> 01:21:06.440 I don't know why. 01:21:06.440 --> 01:21:08.960 And there's another thing about the system they have now 01:21:08.960 --> 01:21:10.410 that is not so intelligent. 01:21:10.410 --> 01:21:16.390 So the main message I want to get across 01:21:16.390 --> 01:21:22.780 is the old way I said is if we can put a man on the moon, 01:21:22.780 --> 01:21:25.960 we can get the light to turn green for the bus. 01:21:25.960 --> 01:21:32.020 That is if you use intelligent tactics, 01:21:32.020 --> 01:21:35.350 we can almost always reduce the delay 01:21:35.350 --> 01:21:39.910 for a bus down to near zero without really 01:21:39.910 --> 01:21:42.290 increasing the delay for cars. 01:21:42.290 --> 01:21:44.790 Bus only needs a few seconds to get through. 01:21:44.790 --> 01:21:47.720 They just need a few seconds at the right time. 01:21:47.720 --> 01:21:50.810 Just rearrange the time a little bit. 01:21:50.810 --> 01:21:53.960 Give the bus the green when it needs. 01:21:53.960 --> 01:21:57.740 And what's in the way is this inflexible paradigm 01:21:57.740 --> 01:22:03.890 of fixed time control with a fixed cycle, long fixed cycles. 01:22:03.890 --> 01:22:06.605 Like Jan was saying, the long cycles are killer. 01:22:06.605 --> 01:22:10.190 If you have short cycles, the delay won't be too much. 01:22:14.320 --> 01:22:19.810 So what Europe has done with transit priority 01:22:19.810 --> 01:22:20.586 is just amazing. 01:22:20.586 --> 01:22:22.210 Some of the things that I saw there, it 01:22:22.210 --> 01:22:25.390 just blew my mind how they're just 01:22:25.390 --> 01:22:26.770 giving priority to transit. 01:22:26.770 --> 01:22:27.436 They just do it. 01:22:27.436 --> 01:22:28.255 They just do it. 01:22:28.255 --> 01:22:30.150 They just do it. 01:22:30.150 --> 01:22:32.680 There was an intersection in The Hague, 01:22:32.680 --> 01:22:36.460 right near Delft, where a tram line was intersecting 01:22:36.460 --> 01:22:38.050 the main ring road. 01:22:38.050 --> 01:22:42.710 Lots of traffic and big traffic jams. 01:22:42.710 --> 01:22:45.740 And my friends are telling me, oh yeah, big traffic jams here. 01:22:45.740 --> 01:22:46.550 How come? 01:22:46.550 --> 01:22:49.100 Well because we have to give the tram priority. 01:22:49.100 --> 01:22:53.040 It's like you just have to. 01:22:53.040 --> 01:22:57.080 You drink coffee in the morning, and you give the tram priority. 01:22:57.080 --> 01:22:59.990 Who would ever think of making the tram wait at a red light? 01:22:59.990 --> 01:23:00.800 No! 01:23:00.800 --> 01:23:02.660 You have to give the tram priority. 01:23:02.660 --> 01:23:04.010 And there are lots of trams. 01:23:04.010 --> 01:23:06.480 And it's causing a big traffic jam. 01:23:06.480 --> 01:23:08.390 So what's the solution? 01:23:08.390 --> 01:23:12.290 Spend a lot of money, grade separation, and now the tram 01:23:12.290 --> 01:23:14.434 has absolutely zero delay. 01:23:14.434 --> 01:23:16.850 And the cars go underneath, and they have no delay either, 01:23:16.850 --> 01:23:18.170 and everybody's happy. 01:23:18.170 --> 01:23:21.670 But it started because of this attitude 01:23:21.670 --> 01:23:26.620 that we just give priority to our important transit lines. 01:23:26.620 --> 01:23:31.240 So if we have that attitude, we can 01:23:31.240 --> 01:23:34.800 do it a lot better than what we're doing.