WEBVTT - How Traffic Lights Work 0:00:00.320 --> 0:00:02.880 Brought to you by the reinvented two thousand twelve camera. 0:00:03.200 --> 0:00:08.920 It's ready. Are you get in touch with technology with 0:00:09.080 --> 0:00:17.800 tech Stuff from how stuff works dot com. Hello again, everyone, 0:00:17.920 --> 0:00:20.919 welcome to tech stuff. My name is Chris Poette and 0:00:20.920 --> 0:00:23.960 I am an editor here at how stuff works dot com. 0:00:24.000 --> 0:00:27.160 As usual, sitting across from me is the lovely smiling 0:00:27.160 --> 0:00:31.640 face of senior writer Jonathan Strickland. Do go on now, 0:00:31.680 --> 0:00:35.839 I think I should stop nice hammer time. All right? 0:00:35.920 --> 0:00:38.199 This uh, this episode is brought to us courtesy of 0:00:38.200 --> 0:00:46.160 a little listener mail. This listener mail comes from Nate. 0:00:46.520 --> 0:00:49.879 He says, Hi, I'm a teenage listener from Colorado and 0:00:49.960 --> 0:00:53.680 just received my learners permit. I'm often frustrated by stoplights 0:00:53.680 --> 0:00:56.400 that are too long or short for the intersection. That 0:00:56.440 --> 0:00:59.560 got me wondering about how these things actually work. So 0:00:59.600 --> 0:01:01.440 I'm hope thing that you can do a podcast on 0:01:01.520 --> 0:01:07.119 how stop lights work. Thanks from your best listener in Colorado, Nate. Alright, Nate, 0:01:07.120 --> 0:01:11.320 we're gonna talk about some some traffic lights. Yes, and 0:01:11.480 --> 0:01:15.640 uh do you like traffic lights? I like traffic lights 0:01:15.680 --> 0:01:22.559 only when they're green. Apparently Nate does. Alright, so um, well, 0:01:22.680 --> 0:01:24.959 let's you know we all know what traffic lights are. 0:01:25.200 --> 0:01:27.080 I don't think we need to do the breakdown that 0:01:27.120 --> 0:01:31.240 we usually do. Yes, Uh, It's it's funny because when 0:01:31.240 --> 0:01:34.520 this email came in, I started thinking, Um, you know 0:01:34.560 --> 0:01:37.759 how very simple this idea is. You know, you've got 0:01:37.760 --> 0:01:39.959 a box and it's got some lights in it, and 0:01:40.000 --> 0:01:42.000 they have very red light or yellow light and green 0:01:42.080 --> 0:01:45.880 light at least here in America, and they switched from 0:01:45.880 --> 0:01:48.600 one another. Well that's pretty simple. Then I thought, well, 0:01:48.640 --> 0:01:50.560 you know, there really is a lot more to it 0:01:50.600 --> 0:01:52.720 than that, because it's not just the lights, it's also 0:01:52.800 --> 0:01:54.920 the controller in the whole system that goes behind it. Yeah, 0:01:55.000 --> 0:01:57.000 especially when you look at it from a macro level 0:01:57.040 --> 0:02:01.880 like a city, a city size level, it becomes unbelievably 0:02:02.000 --> 0:02:04.920 complex because you're not just talking about one intersection. You're 0:02:04.920 --> 0:02:08.440 talking about traffic patterns that go across an entire city. Well, yeah, 0:02:08.440 --> 0:02:11.400 and you can use uh, if you've got the system 0:02:11.440 --> 0:02:13.800 that can handle it, you can use uh, you know, 0:02:14.000 --> 0:02:18.440 a whole computer network of traffic lights to uh to 0:02:18.639 --> 0:02:22.280 arrange the way traffic would flow. That is, assuming everybody 0:02:22.360 --> 0:02:26.120 is obeying the law right. Well, and and that's important 0:02:26.160 --> 0:02:29.160 to remember because you know, in the old days, making 0:02:29.200 --> 0:02:33.799 adjustments to traffic lights was pretty difficult, I mean, or 0:02:33.800 --> 0:02:36.200 at least it was more involved than what it is today. Today. 0:02:36.360 --> 0:02:38.959 You know, there are fully automated systems where you can 0:02:39.480 --> 0:02:43.040 walk into a room and see the redoubts and kind 0:02:43.080 --> 0:02:45.880 of get a real life, real time picture of what's 0:02:45.880 --> 0:02:48.440 going on. And if traffic is really bad in one 0:02:48.480 --> 0:02:50.960 part of town for one reason or another, you can 0:02:50.960 --> 0:02:54.639 actually make adjustments on the fly in many systems and 0:02:54.639 --> 0:02:58.200 and alleviate some of that traffic snarl. And and that's 0:02:58.360 --> 0:03:02.200 and it's crazy the sort of things that cause traffic jams. 0:03:02.360 --> 0:03:06.680 I've written about how traffic works for the site article. 0:03:07.639 --> 0:03:10.560 It's and it's really things that you would never expect 0:03:11.160 --> 0:03:13.520 to cause traffic jams can in fact cause them. And 0:03:13.560 --> 0:03:17.280 sometimes it's just poorly timed intersections. You know, you could 0:03:17.280 --> 0:03:19.919 have two intersections that are even a mile and a 0:03:19.960 --> 0:03:22.959 half apart, but because of the way they're timed, traffic 0:03:23.000 --> 0:03:24.800 starts to back up. So we're gonna talk a little 0:03:24.800 --> 0:03:28.920 bit about what goes into making these lights work. I 0:03:28.960 --> 0:03:31.239 wanted to to step back a little bit and talk 0:03:31.280 --> 0:03:34.320 about the the older systems because some some towns in 0:03:34.320 --> 0:03:38.800 in the United states still use these. Before the solid 0:03:38.840 --> 0:03:43.839 state electronics controllers for traffic lights became really the thing, 0:03:44.720 --> 0:03:49.040 we had mechanical controllers. Now, the lights themselves are electrical, 0:03:50.120 --> 0:03:52.840 and they're also modular in most cases, so that you 0:03:52.880 --> 0:03:57.760 can build a larger set of lights using the same 0:03:57.800 --> 0:04:00.240 basic units, so that lets you do things like create 0:04:00.320 --> 0:04:02.880 the you know, the turn signal lights versus the straight 0:04:02.960 --> 0:04:06.040 up and down you know, red yellow green lights that 0:04:06.080 --> 0:04:09.520 we we know and love. Um Now, the old lights 0:04:09.520 --> 0:04:14.040 were halogen lamp lights, but usually between fifty watts and 0:04:14.080 --> 0:04:16.800 a hundred and fifty wats, depending on the size of 0:04:16.839 --> 0:04:19.160 the light. I would I would have thought that they 0:04:19.160 --> 0:04:22.880 would be incandescent, did you I would have you would 0:04:22.920 --> 0:04:25.840 have Apparently I would be wrong. Well, the current ones 0:04:25.839 --> 0:04:29.040 are LEDs. Yes, they're much more efficient, and you can 0:04:29.040 --> 0:04:31.760 tell those apart two because it looks like they're a 0:04:31.839 --> 0:04:35.480 batch of little tiny lights in the circle where an 0:04:35.520 --> 0:04:37.440 older one of the older lights would be with the 0:04:37.480 --> 0:04:42.400 giant limbs. Right, So these older very cool that they're 0:04:42.400 --> 0:04:45.400 doing that because there's so much more energy efficient. No, yes, 0:04:45.520 --> 0:04:48.360 they're energy efficient, and you don't have to replace them 0:04:48.400 --> 0:04:50.840 nearly as often the old ones. You would actually have 0:04:50.880 --> 0:04:53.200 to replace almost on a monthly basis, which of course 0:04:53.320 --> 0:04:55.600 could cause even more problems with traffic because it means 0:04:55.640 --> 0:04:58.760 that someone has to guts to go out there. And yeah, 0:04:58.839 --> 0:05:02.240 so these older MCCA Nicole controllers, they actually if you 0:05:02.279 --> 0:05:04.640 were to open up one of these boxes, here's where 0:05:04.680 --> 0:05:09.800 we have our standard, do not open a traffic control box. 0:05:10.720 --> 0:05:13.640 It's a bad idea, but probably against the law if 0:05:13.640 --> 0:05:16.640 you're not exactly Oh well, if you're authorized to do it, 0:05:16.680 --> 0:05:20.280 then yes, by all these please yes. But inside these 0:05:20.320 --> 0:05:24.200 mechanical controllers, you would find a series of switches, uh. 0:05:24.240 --> 0:05:26.080 And at the base of each switch would be a 0:05:26.120 --> 0:05:30.440 little wheel. Now the wheel would have uh, twelve sections. 0:05:30.440 --> 0:05:34.960 Think of it like pi. So it's got essentially a 0:05:35.160 --> 0:05:39.760 twelve twelve areas sliced and one slice has been removed. 0:05:40.440 --> 0:05:43.400 When that slice comes round towards the switch, the switch 0:05:43.440 --> 0:05:45.839 is actually able to move out and the the switch 0:05:46.440 --> 0:05:50.320 uh completes a circuit. All right, So there's a circuit 0:05:50.400 --> 0:05:53.640 for every single light at the intersection, for the red light, 0:05:53.680 --> 0:05:56.000 for the yellow light, green light, for each of the 0:05:56.040 --> 0:06:00.720 directions that are involved. Okay, this is a four wast yes, 0:06:00.920 --> 0:06:03.279 so four away stop. You know you've gotta you've gotta 0:06:03.360 --> 0:06:08.160 switch for every single light. Uh So these these the 0:06:08.320 --> 0:06:12.479 series of wheels are on a rod and they turn 0:06:13.080 --> 0:06:17.640 um in time with a solenoid. The solenoid activates, it 0:06:17.680 --> 0:06:21.120 turns the wheels and then that's what actually completes the 0:06:21.160 --> 0:06:25.479 circuits and make the different lights switch from red to 0:06:25.640 --> 0:06:30.640 green to yellow. Makes sense. Um, these solenoids on a ratchet, 0:06:30.839 --> 0:06:32.920 so it can move down, but it can't move back 0:06:33.000 --> 0:06:37.880 up right, So it's not it doesn't justn't go from say, 0:06:38.120 --> 0:06:41.000 yellow to green. It has to go from green to 0:06:41.080 --> 0:06:43.400 yellow exactly. And you also don't have to worry about 0:06:43.440 --> 0:06:45.440 it switching from green to red and then back to 0:06:45.480 --> 0:06:48.320 green immediately, because that would happen if if if it 0:06:48.320 --> 0:06:50.120 didn't have the ratchet, if it didn't have that breake 0:06:50.240 --> 0:06:53.400 stop there. Um, a light could change and then change 0:06:53.520 --> 0:06:55.800 right back, and then you've got traffic accidents all over 0:06:55.839 --> 0:06:59.560 the place. Uh So we got enough of those with 0:06:59.600 --> 0:07:03.159 it work properly. Right. So, the solenoid is connected to 0:07:03.200 --> 0:07:07.560 a motorized timer, and the timer is this little round drum. 0:07:07.600 --> 0:07:11.360 It's got a hundred grooves carved into the side of 0:07:11.360 --> 0:07:15.000 this drum. Right within those grooves, you can place these 0:07:15.040 --> 0:07:17.680 little metal tabs, and the metal tabs also hit a 0:07:17.680 --> 0:07:21.160 little switch. When the tabs hit the switch, that's what 0:07:21.240 --> 0:07:24.240 activates the solenoid. Okay, so the drum is attached to 0:07:24.280 --> 0:07:28.360 a gear. The gear turns at a certain frequency, certain 0:07:28.440 --> 0:07:32.440 number of revolutions per minted. That's what dictates how fast 0:07:32.480 --> 0:07:35.320 the drum turns. That's what dictates how how often the 0:07:35.320 --> 0:07:39.040 solenoid is activated, which in turn dictates how the little 0:07:39.040 --> 0:07:43.480 wheels connected to the circuits turn. That is the timing 0:07:43.520 --> 0:07:47.160 mechanism on the old UH traffic lights. And if you 0:07:47.200 --> 0:07:50.120 were actually standing next to a controller box and you 0:07:50.120 --> 0:07:53.320 were listening, you could probably hear the clicks as those 0:07:53.320 --> 0:07:58.760 wheels turned into place. Um and UH. You could even 0:07:58.840 --> 0:08:02.240 install multiple drms within a single control box, so you 0:08:02.240 --> 0:08:04.600 could have it switch at different times of the day. 0:08:04.640 --> 0:08:07.960 So let's say during rush hour traffic you need one 0:08:08.040 --> 0:08:10.560 section of the road to be green more often than not. 0:08:11.400 --> 0:08:13.280 But then in the middle of the day the traffic 0:08:13.280 --> 0:08:16.280 patterns change, so you would want the light behavior to 0:08:16.360 --> 0:08:19.960 change as well, and then maybe overnight it changes again. Um. 0:08:20.040 --> 0:08:22.280 You could actually do that by having multiple gears in 0:08:22.320 --> 0:08:24.800 there and have it switch automatically from one to the 0:08:24.840 --> 0:08:28.120 other based upon the time of day. Today, all of 0:08:28.120 --> 0:08:31.320 that is kind of it's it's antiquated. I mean, you 0:08:31.800 --> 0:08:33.840 don't find that in most systems today because now we 0:08:33.880 --> 0:08:37.120 have solid state electronics. Everything's on circuit boards. We don't 0:08:37.120 --> 0:08:39.960 have to worry about all those uh those actual mechanical 0:08:40.040 --> 0:08:44.680 switches right right, But some of them are still on timers. Yeah, 0:08:44.840 --> 0:08:48.120 that's true. That's true. You know when you describe things 0:08:48.160 --> 0:08:50.760 that run on gears like that, I'm trying to picture 0:08:51.080 --> 0:08:54.080 exactly how this hardware goes together. I can't help singing 0:08:54.240 --> 0:08:58.480 Powerhouse in my head when I imagine the gears turning right. Uh. 0:09:00.080 --> 0:09:04.839 That okay, so and and Marshall actually wrote a blog 0:09:04.880 --> 0:09:06.920 post about this where he links to a video where 0:09:06.920 --> 0:09:08.280 you can see. If you want to go to the 0:09:08.480 --> 0:09:12.400 to the blogs how Stuff Works and search marshall brains 0:09:12.520 --> 0:09:16.000 blog posts, you can find a post that links back 0:09:16.000 --> 0:09:20.520 to a video that shows these elements, these mechanical elements. Yep, yep, 0:09:20.960 --> 0:09:22.959 I remember that one. Actually I saw that as I 0:09:23.000 --> 0:09:27.320 was doing some some research. Um. Now, of course, uh, 0:09:27.400 --> 0:09:29.480 you know there are timers, and there are the uh, 0:09:29.840 --> 0:09:32.280 the lights that work on a sensor system as well. 0:09:33.080 --> 0:09:36.920 Um and the timers seem like they're fairly self explanatory. Yeah, 0:09:36.920 --> 0:09:40.840 it's it's a state timer instead of mechanical same same 0:09:40.840 --> 0:09:46.000 philosophy as the mechanical ones. But yeah, different different methodology, 0:09:46.040 --> 0:09:48.880 but same effect. And that, Um, what happens. You've got 0:09:48.920 --> 0:09:52.880 some civil engineers who who observed the traffic patterns, who 0:09:52.920 --> 0:09:56.240 come up with the the pattern that should be used 0:09:56.280 --> 0:09:59.600 for any particular intersection, the amount of time that each 0:10:00.040 --> 0:10:02.679 lane of traffic should have to be able to pass 0:10:02.720 --> 0:10:06.160 through that intersection. And um, you know, normally they will 0:10:06.280 --> 0:10:10.360 visit an intersection multiple times throughout different days to really 0:10:10.360 --> 0:10:12.640 get a good idea of what the traffic patterns are, because, 0:10:12.640 --> 0:10:15.600 like I said, they changed throughout the day, right, So 0:10:15.679 --> 0:10:17.760 in the evening it may be that, you know, one 0:10:17.880 --> 0:10:20.880 particular road is hardly a used all while another one 0:10:20.960 --> 0:10:23.480 is is really heavily used. You would want, of course, 0:10:23.559 --> 0:10:28.280 the traffic light to favor the heavy use one. Um. 0:10:28.320 --> 0:10:31.200 And again this is it sounds kind of simple, except 0:10:31.200 --> 0:10:33.800 that when you take into account that you need to 0:10:33.840 --> 0:10:37.440 also look at the intersections that are essentially directly adjacent 0:10:37.480 --> 0:10:41.120 to that first intersection, like go in in every direction 0:10:41.120 --> 0:10:45.240 of that intersection to the next light and see what 0:10:45.360 --> 0:10:49.400 that timing is, because that's gonna affect the traffic as well. Well. 0:10:49.440 --> 0:10:51.960 Then you have to go one further out from those, 0:10:52.800 --> 0:10:55.640 and before long you're looking at a huge net that 0:10:55.720 --> 0:11:01.560 incorporates the entire area, which is why it gets so complicated. Um, 0:11:01.600 --> 0:11:04.360 but not all of them are timers. Some of them 0:11:04.440 --> 0:11:07.479 use sensors, and these are the ones that I find fascinating. 0:11:07.559 --> 0:11:09.320 You can you can tell whether or not they have 0:11:09.400 --> 0:11:13.480 a sensor generally by looking at the uh not up 0:11:13.520 --> 0:11:16.679 where the traffic lights are, but down on the road. Yeah. Um, 0:11:16.760 --> 0:11:19.840 there are different kinds of sensors. There are some intersections 0:11:19.840 --> 0:11:24.160 they'll use light based sensors like lasers or well, but 0:11:24.160 --> 0:11:26.560 but most, in fact, I would I would go so 0:11:26.600 --> 0:11:30.240 far as to say the majority of all sensor sensors 0:11:30.320 --> 0:11:34.160 used in traffic lights are inductive loop sensors. Yes, that's 0:11:34.160 --> 0:11:36.400 the ones that you see, uh, the little grooves in 0:11:36.400 --> 0:11:40.400 the pavement directly underneath, like the white stripe where you're 0:11:40.400 --> 0:11:43.720 supposed to stop your car generally or or immediately before 0:11:43.800 --> 0:11:46.160 in some cases immediately after, which I think is kind 0:11:46.160 --> 0:11:48.800 of dangerous if that's the sensor that you're supposed to 0:11:48.800 --> 0:11:51.800 be on to trigger the light. But that has to 0:11:51.800 --> 0:11:54.280 do with the civil engineers, or perhaps they were painted 0:11:54.280 --> 0:11:58.720 by uncivil engineers. Could be UM, but we wonder why 0:11:58.800 --> 0:12:00.840 is the Civil War even called that because they were 0:12:00.880 --> 0:12:10.760 not UM. So the sensors that are implanted underneath the 0:12:10.840 --> 0:12:15.040 roadway act very much like an electromagnet. Yeah, that's essentially 0:12:15.040 --> 0:12:18.280 what they are. They You've got a coil of wire 0:12:18.600 --> 0:12:23.920 that is underneath the pavement and m and what it's 0:12:23.960 --> 0:12:28.040 it's generating a magnetic field and when something really large 0:12:28.080 --> 0:12:31.400 and metal passes over it, it acts as an inductor. 0:12:32.120 --> 0:12:37.559 And when the system uh can detect that that increase 0:12:37.600 --> 0:12:39.720 in the magnetic field. Because once you have the inductor there, 0:12:39.720 --> 0:12:43.480 that really boosts the magnetic field. Wants the system detects that, 0:12:43.640 --> 0:12:46.400 it's the indicator to say, hey, there's a car waiting 0:12:46.440 --> 0:12:50.680 at this intersection, so at the earliest opportunity we should 0:12:50.679 --> 0:12:56.440 look at switching the light so that the car can move. Um. 0:12:56.600 --> 0:12:59.960 There's some problems with this system though, Yes. The big 0:13:00.000 --> 0:13:02.319 this problem being that if you are not in a 0:13:02.400 --> 0:13:06.200 fairly you know, like a medium to too larger sized vehicle, 0:13:06.760 --> 0:13:10.880 you may not have enough of metal in the mass 0:13:10.880 --> 0:13:15.040 of whatever vehicle you're in to to activate the inductor loop. 0:13:15.360 --> 0:13:19.600 So what you're saying is, if you were in our writing, 0:13:19.640 --> 0:13:24.560 say a motor scooter, motor scooter, bicycle, motorcycle, even even 0:13:24.559 --> 0:13:27.160 a small car like a smart car. Smart cars are 0:13:27.200 --> 0:13:31.600 tiny and may not even be enough of a mass 0:13:31.600 --> 0:13:34.560 in order to get the inductor loop to activate. It 0:13:34.559 --> 0:13:37.680 may not generate enough of a magnetic field for the 0:13:37.679 --> 0:13:39.920 sensor to be tripped, which means you're sitting at a 0:13:39.920 --> 0:13:44.280 traffic light forever waiting for that thing to change, and 0:13:44.320 --> 0:13:47.840 it may take until another car or other vehicle pulls 0:13:47.920 --> 0:13:51.720 up behind you and perhaps if they're close enough, complete 0:13:51.720 --> 0:13:55.760 that that inductor loop so that you can actually trigger 0:13:55.840 --> 0:14:02.240 that light. UM and another or of Marshall's brains posts 0:14:02.240 --> 0:14:05.040 that that I saw when I was looking at UM 0:14:05.080 --> 0:14:08.800 looking at some information for this podcast. UM. Some cities 0:14:09.160 --> 0:14:14.400 do have special infrared controllers too for emergency vehicles like 0:14:14.440 --> 0:14:17.600 fire engines and police cars, UM, that will allow them 0:14:17.640 --> 0:14:21.560 to trip the signals before they get there. It's it's 0:14:21.680 --> 0:14:25.080 essentially a remote control of sorts that allow them to 0:14:25.280 --> 0:14:27.760 UH to affect the signals and that that keeps them 0:14:27.800 --> 0:14:30.400 from having to of course, they're going to go to 0:14:30.480 --> 0:14:32.320 the light anyway if they feel like it's safe. But 0:14:33.160 --> 0:14:36.040 if they can go ahead and change the traffic lights 0:14:36.120 --> 0:14:39.880 rather than having to go through the intersection without affecting 0:14:39.880 --> 0:14:42.200 those at all, that that helps them control the flow 0:14:42.440 --> 0:14:45.080 of traffic too to some extent. I have a hint 0:14:45.160 --> 0:14:48.720 for people who do drive motorcycle, scooters, bicycles, that kind 0:14:48.720 --> 0:14:52.680 of thing, if they want to activate those loops. Uh. 0:14:52.760 --> 0:14:54.440 This is not the same thing that Chris was just 0:14:54.480 --> 0:14:57.840 talking about. Chris was talking about actually changing the light 0:14:57.880 --> 0:15:02.600 signals in an official way. Just activating yeah, to let 0:15:02.640 --> 0:15:04.960 to let essentially to let the system know, Hey, I'm 0:15:05.040 --> 0:15:07.000 here and I would very much like it if I 0:15:07.000 --> 0:15:10.320 could get across the street please. Um. What you can 0:15:10.360 --> 0:15:12.760 do is you can install a couple of magnets on 0:15:12.800 --> 0:15:16.360 the bottom of your vehicle. Uh. And by installed it 0:15:16.480 --> 0:15:19.440 just means stick because that's the one thing about magnets. 0:15:19.480 --> 0:15:23.000 They stick to metal. Uh some metal, so, yes, well 0:15:23.040 --> 0:15:26.720 the metal that you typically find in vehicles. Yes. Uh. 0:15:26.800 --> 0:15:29.600 So you get a couple of powerful magnets and you 0:15:29.920 --> 0:15:31.800 attach them to the base of the vehicle, and then 0:15:31.840 --> 0:15:35.120 when you when you drive over the loop, the magnets 0:15:35.200 --> 0:15:38.400 in there, they usually generate a strong enough magnetic field 0:15:38.400 --> 0:15:40.720 that that will be enough to trip the sensor and 0:15:40.800 --> 0:15:43.000 let it know, hey, there's a vehicle here. So even 0:15:43.040 --> 0:15:45.040 if you're just writing in a little scooter that normally 0:15:45.080 --> 0:15:51.080 wouldn't activate it, you'll get a signal. Now, these systems 0:15:51.120 --> 0:15:56.160 are connected, as we said earlier, to a master control system, 0:15:56.200 --> 0:15:59.720 and the master control system's job is to maintain an 0:16:00.240 --> 0:16:04.280 on everything that's going on across the the whole uh well, 0:16:04.400 --> 0:16:07.720 whatever the area is that it that they oversee, whether 0:16:07.760 --> 0:16:11.840 it's a local like thing or a citywide thing, um, 0:16:11.840 --> 0:16:14.720 but it usually it monitors traffic twenty four hours a day. 0:16:15.400 --> 0:16:19.440 Often these systems can be manipulated remotely so that, let's 0:16:19.440 --> 0:16:22.680 say that that the the operator knows there's a fire 0:16:23.200 --> 0:16:26.840 uh a fire alarm that's gone off in a building downtown, 0:16:26.920 --> 0:16:29.800 and they know where the the fire engine is going 0:16:29.840 --> 0:16:35.040 to come from. They can actually proactively uh uh set 0:16:35.120 --> 0:16:37.760 up the system so that it stops traffic so that 0:16:37.800 --> 0:16:40.640 the fire engine can get through without any dangers of 0:16:40.920 --> 0:16:44.520 or reducing danger of collision. I can't ever say without 0:16:44.560 --> 0:16:48.080 any because there's always gonna be some something that falls 0:16:48.120 --> 0:16:52.840 outside the extremes, right um. And they can also just 0:16:53.040 --> 0:16:55.800 keep an eye on how signals are behaving and if 0:16:55.840 --> 0:16:58.200 they if there's a signal oiled edge or anything like that, 0:16:58.520 --> 0:17:01.040 they can arrange for an electrician in or or you know, 0:17:01.120 --> 0:17:03.520 repair unit to go out there and take a look 0:17:03.560 --> 0:17:07.199 at it. Um. And they have to consider a lot 0:17:07.240 --> 0:17:09.000 of things when they're putting light. As we said, when 0:17:09.000 --> 0:17:11.439 they're putting these traffic lights in, it's everything from the 0:17:11.480 --> 0:17:15.960 spacing between the traffic signals along the street. Um. They 0:17:16.000 --> 0:17:19.160 have to look at the different timing aspects of each 0:17:19.160 --> 0:17:21.639 of those. They have to look at just the traffic volume. 0:17:21.720 --> 0:17:24.560 How many lanes of traffic are there. Is it going 0:17:24.640 --> 0:17:28.399 to to handle the traffic volume well enough so that 0:17:28.440 --> 0:17:30.639 you don't have to worry about fiddling with the timer 0:17:30.720 --> 0:17:34.719 so much? Um, even the driver behavior on that street. 0:17:35.080 --> 0:17:38.680 Because of course, Chris and I know from living in Atlanta, 0:17:39.000 --> 0:17:42.080 there are different parts of Atlanta where people drive in 0:17:42.080 --> 0:17:46.439 incredibly different ways. Let's say, like to eight five. If 0:17:46.480 --> 0:17:48.439 you're not going to eighty miles per hour, you've just 0:17:48.480 --> 0:17:52.240 been run over. Now, granted to also does not have 0:17:52.280 --> 0:17:55.720 any traffic lights on it, but um, yeah, there's surface streets, 0:17:55.760 --> 0:17:58.359 Like there's certain areas of Atlanta where you know, people 0:17:58.440 --> 0:18:01.840 drive nice and leisurely and and everyone's kind of you know, 0:18:01.920 --> 0:18:04.040 laid back and relax in other parts of Atlanta where 0:18:04.080 --> 0:18:06.440 you feel that, you know, you've just entered the road 0:18:06.480 --> 0:18:09.320 warrior and two men will enter and one man will leave, 0:18:09.400 --> 0:18:11.800 and you know, Mel Gibson's right behind you and burying 0:18:11.800 --> 0:18:15.320 it down. And Okay, I've had some really really weird 0:18:15.400 --> 0:18:17.600 dreams lately. As all I'm trying to say, I understand 0:18:17.600 --> 0:18:21.919 which so yeah, the driver behavior actually does play a 0:18:21.960 --> 0:18:25.640 part in how traffic managers look at at setting out 0:18:25.640 --> 0:18:29.800 traffic lights and timing them out properly. Um. And it 0:18:29.840 --> 0:18:33.160 seems to me that that, um, if you've got lasers 0:18:33.320 --> 0:18:36.720 or inductive loops or uh you know, even those rubber 0:18:37.040 --> 0:18:39.840 air filled rubbered hoses I guess they're pneumatic hoses of 0:18:39.920 --> 0:18:42.919 some kind that uh tell the box that their cars waiting, 0:18:43.240 --> 0:18:46.560 it seems like including those would sort of wreck the 0:18:46.680 --> 0:18:50.600 plan of trying to manage traffic I mean other than 0:18:51.359 --> 0:18:55.760 I mean and by by a master control program. M. 0:18:56.359 --> 0:19:01.600 Wait a minute, I'm beginning to understand everything and of line. Um, 0:19:01.640 --> 0:19:05.480 but no, yeah, having a master computerized program, uh, it 0:19:05.520 --> 0:19:08.119 seems like it wouldn't work. It wouldn't be compatible with 0:19:08.160 --> 0:19:11.880 having sensors at individual intersections that allowed cars to trip 0:19:11.920 --> 0:19:14.160 the lights as soon as they arrived and we're sitting 0:19:14.160 --> 0:19:16.080 there at the stoplight. It seems like it would be 0:19:16.080 --> 0:19:19.399 more it's more sort of a if you will, lazy 0:19:19.480 --> 0:19:24.440 fair version of traffic. I think they'll make the lights work. 0:19:24.440 --> 0:19:25.639 I think part of it. I think part of this 0:19:25.760 --> 0:19:28.440 that when that detects that there's a car there, um, 0:19:28.480 --> 0:19:30.560 it doesn't necessarily say okay, well we need to change 0:19:30.560 --> 0:19:32.840 the lights now. It's it's saying, okay, we need to 0:19:32.920 --> 0:19:36.040 change the lights at some point when it's safe to 0:19:36.040 --> 0:19:38.600 do so. Keep in mind that if they're steady traffic 0:19:38.640 --> 0:19:42.320 going over an intersection, that and that inductor loop, actually 0:19:42.440 --> 0:19:44.720 it's picking it up because of course you're still having 0:19:44.800 --> 0:19:49.480 cars going through. So these systems are are fairly intelligence 0:19:49.480 --> 0:19:52.159 probably the wrong word to use, but they're they're able 0:19:52.400 --> 0:19:57.640 to detect traffic at uh if it's if everything's working properly, 0:19:57.920 --> 0:20:00.040 they're able to detect traffic and a fairly rely I 0:20:00.119 --> 0:20:05.040 will rate. So it's still it's not as planned out 0:20:05.080 --> 0:20:07.520 as maybe the timed ones are in the sense of 0:20:07.520 --> 0:20:11.080 it doesn't take as much human intervention. But there's still 0:20:11.280 --> 0:20:13.120 you know, it's kind of it is kind of adjusting 0:20:13.119 --> 0:20:15.320 traffic on the fly. But as I should point out that, 0:20:15.359 --> 0:20:17.639 I realized that as soon as you pull up, it 0:20:17.640 --> 0:20:21.640 wouldn't necessarily trigger the sensor and automatically turn the light, 0:20:21.720 --> 0:20:25.800 because if the box can tell that there are there's 0:20:25.800 --> 0:20:29.320 a steady flow of traffic going over the inductors in 0:20:29.560 --> 0:20:33.960 the other lanes perpendicular to the ones that you're in, um, 0:20:34.000 --> 0:20:35.760 obviously it's not gonna go, oh, well, hey, you know, 0:20:35.760 --> 0:20:38.160 I'm just gonna go ahead and stop them. This one 0:20:38.200 --> 0:20:41.160 guy really needs to go, so we're gonna stop everybody else. 0:20:41.280 --> 0:20:44.280 I sort of always figured that it was a situation 0:20:44.280 --> 0:20:46.800 where they go, okay, well it's been ten seconds since 0:20:46.840 --> 0:20:49.119 the last car, it's been fifteen seconds since last car. 0:20:49.240 --> 0:20:52.320 Traffic is slowing down, there's less of it there. It's 0:20:52.520 --> 0:20:54.160 safe to go ahead and give them a yellow light 0:20:54.200 --> 0:20:55.960 to prepare them for a red light. And some of 0:20:55.960 --> 0:20:58.199 them work on a on a combination of the timer 0:20:58.280 --> 0:21:01.400 and the sensor, so some of them have like even 0:21:01.720 --> 0:21:04.680 in some cases you'll you'll come up to traffic lights 0:21:04.680 --> 0:21:07.040 that you know have the sensors in them, and yet 0:21:07.040 --> 0:21:10.040 the traffic lights occasionally change on their own because that 0:21:10.119 --> 0:21:14.120 they do ultimately rely on a timer system. Um. And 0:21:14.160 --> 0:21:16.320 the anat thing about those timer systems you can actually 0:21:16.359 --> 0:21:20.240 program them so that they behave differently on different days 0:21:20.280 --> 0:21:23.280 of the year. So if you know, for example, that 0:21:23.359 --> 0:21:26.320 say on fourth of July, that a particular stretch of 0:21:26.440 --> 0:21:29.120 road is going to be really heavily used, you can 0:21:29.160 --> 0:21:32.680 program the system ahead of time to compensate for that 0:21:33.440 --> 0:21:35.760 before you know, like you know, back in June you 0:21:35.760 --> 0:21:37.800 could you could program it in and then fourth of 0:21:37.880 --> 0:21:40.119 July comes around and the system behaves just as you 0:21:40.240 --> 0:21:44.960 told it to, so that everything's working properly. Um. Cool, Well, 0:21:45.720 --> 0:21:50.040 I'm trafficked out. Well, I think it's a it's one 0:21:50.040 --> 0:21:52.040 of those things that we sort of take take for granted. 0:21:52.080 --> 0:21:56.560 But the the systems that they've put in to make 0:21:56.640 --> 0:21:59.920 this work, um, and try to be sort of intell 0:22:00.040 --> 0:22:01.959 gin about the way you manage traffic flow. I mean, 0:22:01.960 --> 0:22:04.080 it's obvious anytime there's been a bad storm and the 0:22:04.160 --> 0:22:07.040 and the lights are out, how much work actually goes 0:22:07.119 --> 0:22:11.840 into planning out the traffic patterns of a city. And uh, 0:22:11.880 --> 0:22:15.680 the effect that having those sensors tripping the lights and 0:22:15.680 --> 0:22:18.720 and letting the boxes, the controller boxes know what's going 0:22:18.720 --> 0:22:21.480 on in an intersection. It's it's obvious how much difference 0:22:21.520 --> 0:22:25.160 that makes having that technology available to us, particularly in Atlanta, 0:22:25.240 --> 0:22:27.560 where people seem to forget that if the traffic light 0:22:27.680 --> 0:22:30.480 is out, you treat it as a four way stop. Yeah, so, 0:22:30.560 --> 0:22:32.399 Or when they're flashing yellow on one side and you're 0:22:32.400 --> 0:22:34.919 supposed to proceed with caution versus flashing red, which means 0:22:34.960 --> 0:22:36.760 you're supposed to come to a complete stop, right and 0:22:36.880 --> 0:22:40.879 everybody stops regardless, or if it's flashing yellow, people don't 0:22:41.560 --> 0:22:43.520 slow down at all. They're just like that means go, 0:22:44.119 --> 0:22:46.919