1 00:00:20,792 --> 00:00:24,377 Jane: This is But Why: a Podcast for Curious Kids. I'm Jane 2 00:00:24,377 --> 00:00:28,637 Lindholm, and right now I am actually standing on an overpass 3 00:00:28,637 --> 00:00:32,237 in Los Angeles, California. Maybe you can hear the traffic 4 00:00:32,237 --> 00:00:35,537 behind me. I'm here in Los Angeles talking about traffic, 5 00:00:35,597 --> 00:00:40,037 partly because Los Angeles is known for traffic. There are 6 00:00:40,097 --> 00:00:45,977 almost 8 million cars registered in Los Angeles County, which 7 00:00:45,977 --> 00:00:49,142 includes more than just the city. There are only about 10 8 00:00:49,142 --> 00:00:52,502 million people who live here, so that's a lot of cars. And when 9 00:00:52,502 --> 00:00:55,622 you think about all the miles that people drive around this 10 00:00:55,622 --> 00:00:59,342 city and around this county every day, it's astronomical. In 11 00:00:59,342 --> 00:01:04,262 fact, one of the most crowded highways in the whole world is 12 00:01:04,262 --> 00:01:10,607 here, the 405 freeway. Close to 400,000 vehicles go on it every 13 00:01:10,607 --> 00:01:14,267 single day, and its congestion problems are pretty legendary. 14 00:01:14,627 --> 00:01:17,927 Some people call it Carmageddon, when the cars are just stopped 15 00:01:17,927 --> 00:01:21,887 on the freeway. Other times people say it's called the 405, 16 00:01:21,887 --> 00:01:27,287 because people can only go about four or five miles per hour. Los 17 00:01:27,287 --> 00:01:30,707 Angeles has a lot of cars and a lot of drivers, and it's a good 18 00:01:30,707 --> 00:01:34,352 place to start our conversation today, which is all about 19 00:01:34,772 --> 00:01:38,972 traffic, but not just about lots of cars on the road. You want to 20 00:01:38,972 --> 00:01:42,152 know about things like how traffic lights work, and we're 21 00:01:42,152 --> 00:01:45,992 also going to tell you things like how they make highways and 22 00:01:45,992 --> 00:01:49,352 traffic lights the most efficient to try to ease the 23 00:01:49,352 --> 00:01:53,972 congestion that I'm seeing right now here at five o'clock on a 24 00:01:53,972 --> 00:02:01,097 Friday, which is called rush hour. Hey, it's Jane back in the 25 00:02:01,097 --> 00:02:04,577 studio now, it was way too loud to do the whole episode there. 26 00:02:04,637 --> 00:02:09,197 And actually that was like seven years ago that I recorded that 27 00:02:09,197 --> 00:02:11,657 while I was visiting Los Angeles, where I used to live. 28 00:02:12,377 --> 00:02:15,497 We've been wanting to make an episode about traffic and roads 29 00:02:15,497 --> 00:02:19,142 and traffic lights for a long time, even before I went and 30 00:02:19,142 --> 00:02:23,402 recorded that. And today, finally, we found someone who's 31 00:02:23,402 --> 00:02:26,762 excited and ready to answer all of your traffic related 32 00:02:26,762 --> 00:02:27,542 questions. 33 00:02:27,740 --> 00:02:30,620 Mike Knodler: My name is Mike Knodler, and I'm the director of 34 00:02:30,620 --> 00:02:33,920 the Transportation Center at the University of Massachusetts, and 35 00:02:33,920 --> 00:02:36,920 I'm a Professor of Civil and Environmental Engineering at 36 00:02:36,920 --> 00:02:37,580 UMass. 37 00:02:37,639 --> 00:02:41,299 Jane: Mike's job is all about helping people and things get 38 00:02:41,299 --> 00:02:45,199 from one place to another safely and efficiently. When he was 39 00:02:45,199 --> 00:02:48,259 little, Mike wanted to be a math teacher, but as he grew up, he 40 00:02:48,259 --> 00:02:51,439 realized he wanted to focus more on applying mathematical 41 00:02:51,439 --> 00:02:55,099 concepts to the real world to solve problems, and he still 42 00:02:55,099 --> 00:02:55,759 teaches too. 43 00:02:56,140 --> 00:02:59,260 Mike Knodler: So that was the switch to engineering, and then 44 00:02:59,260 --> 00:03:02,200 within engineering, that's when I found transportation. I really 45 00:03:02,245 --> 00:03:07,525 love it when we teach things in our classes and then see our 46 00:03:07,525 --> 00:03:12,025 students go on and design or build that same thing, maybe in 47 00:03:12,025 --> 00:03:14,905 other places, or if we're working on a design, and then 48 00:03:14,905 --> 00:03:18,865 you see it get built. That's really, really rewarding. And if 49 00:03:18,865 --> 00:03:22,105 it works as you intended, and you've potentially saved 50 00:03:22,105 --> 00:03:24,850 someone's life, or you've made their life better because 51 00:03:24,850 --> 00:03:27,730 they're able to get where they need to go. That's really, 52 00:03:27,730 --> 00:03:28,570 really rewarding. 53 00:03:28,300 --> 00:03:30,700 Jane: Of course, when we're talking about transportation, 54 00:03:30,700 --> 00:03:34,660 it's way more than just cars on the road. We've made episodes 55 00:03:34,660 --> 00:03:38,080 about trains and boats and bikes, and we'll link to all of 56 00:03:38,080 --> 00:03:41,500 those in our show notes, but our episode today is going to be 57 00:03:41,500 --> 00:03:44,680 about how we've developed the systems that help us know when 58 00:03:44,680 --> 00:03:48,220 to go, when to stop, when to walk across a crosswalk, whether 59 00:03:48,220 --> 00:03:50,740 you're a pedestrian or in a car, these things are really 60 00:03:50,740 --> 00:03:55,105 important, and the systems are what help us be able to move 61 00:03:55,165 --> 00:03:59,725 efficiently and safely. Now, speaking of moving, have you 62 00:03:59,725 --> 00:04:03,925 ever been stuck in traffic in a car? I know lots of you have, 63 00:04:03,925 --> 00:04:06,985 and maybe that's when you get your good But Why listening in 64 00:04:07,465 --> 00:04:11,005 you've sent us a lot of questions about why we get stuck 65 00:04:11,005 --> 00:04:11,845 in traffic. 66 00:04:12,080 --> 00:04:17,060 Ben: My name is Ben. I'm five years old. I live in Rockville 67 00:04:17,060 --> 00:04:20,660 Center, New York. Why is there traffic? 68 00:04:20,660 --> 00:04:24,980 Lainey: Hi. My name is Lainey, and I'm six years old. I live in 69 00:04:24,980 --> 00:04:30,380 Nashville, traffic? 70 00:04:31,040 --> 00:04:34,768 Wallace: My name is Wallace. I live in Montreal. I'm seven 71 00:04:34,844 --> 00:04:39,562 years old. And my question is, how does congestion get made on 72 00:04:39,639 --> 00:04:40,400 the roads? 73 00:04:40,399 --> 00:04:43,309 Mike Knodler: Yeah, so traffic, in terms of, you know, the build 74 00:04:43,367 --> 00:04:46,511 up of cars, let's say, or, you know, creating a bit of 75 00:04:46,569 --> 00:04:50,062 congestion, is when there's a lot of people that want to use 76 00:04:50,120 --> 00:04:53,845 the same space at the same time. That's really the basic sort of 77 00:04:53,904 --> 00:04:57,571 underlying cause of traffic. You know, it gets it gets a little 78 00:04:57,629 --> 00:05:01,122 bit more complicated when we start talking about people that 79 00:05:01,180 --> 00:05:04,382 might be in a car, versus walking versus on a bike, and 80 00:05:04,440 --> 00:05:07,700 now you've got what we call mode, so we've got all these 81 00:05:07,758 --> 00:05:11,367 different modes trying to use the same space at the same time, 82 00:05:11,425 --> 00:05:14,220 and that causes that disruption in that traffic. 83 00:05:15,380 --> 00:05:18,320 Jane: I live in a town that doesn't have any traffic lights. 84 00:05:19,100 --> 00:05:23,540 We don't have any stores. We are a very small town, but we still 85 00:05:23,540 --> 00:05:28,820 have stop signs, and we have some intersections where the 86 00:05:28,820 --> 00:05:32,300 roads cross or a driveway comes in, where you have to know the 87 00:05:32,300 --> 00:05:36,200 rules, even without a sign. So even for people who live in 88 00:05:36,200 --> 00:05:40,265 rural places, there is usually some sort of infrastructure that 89 00:05:40,265 --> 00:05:44,885 helps us be safe, or know who's going to go when, and some sort 90 00:05:44,885 --> 00:05:50,345 of rules or ideas around how we can move around on the roads in 91 00:05:50,345 --> 00:05:54,065 a way that allows all of us to go as efficiently as possible, 92 00:05:54,065 --> 00:05:57,305 right? When did that kind of system start to develop? 93 00:05:57,600 --> 00:06:00,180 Mike Knodler: Yeah, no, that's been that's been in existence 94 00:06:00,180 --> 00:06:03,240 since people started navigating, a lot of even predates, you 95 00:06:03,240 --> 00:06:09,120 know, cars in many, in many ways. And so it's all the signs, 96 00:06:09,300 --> 00:06:12,840 the traffic signals, all the pavement markings that you see. 97 00:06:13,020 --> 00:06:17,100 All of those are intended to help keep drivers and other 98 00:06:17,100 --> 00:06:21,000 users of the system informed as to what they're supposed to do. 99 00:06:21,225 --> 00:06:23,625 But more importantly, we're really talking about trying to 100 00:06:23,625 --> 00:06:27,525 keep it orderly. And by keeping it orderly, we hopefully keep it 101 00:06:27,525 --> 00:06:29,925 safe and then also keep it efficient. 102 00:06:29,925 --> 00:06:33,285 Jane: What did those systems look like before we had cars? 103 00:06:33,560 --> 00:06:35,900 Mike Knodler: Some of it goes back to horse and buggy days, 104 00:06:35,900 --> 00:06:39,680 right? So when we used to have people navigating, and so some 105 00:06:39,680 --> 00:06:42,400 of the early signage was referring to where you could and 106 00:06:42,400 --> 00:06:44,740 couldn't ride, and what you couldn't couldn't do. And then, 107 00:06:44,740 --> 00:06:49,480 obviously, with the introduction of the cars, we started to add 108 00:06:49,480 --> 00:06:52,420 in things. But we had speed limits before we had cars as an 109 00:06:52,420 --> 00:06:55,960 example, so people were limited in terms of how fast they were 110 00:06:55,960 --> 00:06:59,740 allowed to go. And then as we've added more and more technology, 111 00:06:59,980 --> 00:07:04,320 we've added more and more of the rules and the markings and the 112 00:07:04,320 --> 00:07:07,020 devices that are intended to help keep the system orderly. 113 00:07:07,620 --> 00:07:11,220 Jane: So were the speed limits for things like trains, or were 114 00:07:11,220 --> 00:07:13,440 they even for how fast you could go on your horse? 115 00:07:13,439 --> 00:07:16,259 Mike Knodler: Yeah, so I think you had some horse related ones. 116 00:07:16,259 --> 00:07:18,899 And then obviously the early days of automobiles had speed 117 00:07:18,899 --> 00:07:22,159 limits as well, and so there was definitely trying to keep 118 00:07:22,219 --> 00:07:25,819 speeds, particularly in areas where same things we see now, 119 00:07:25,939 --> 00:07:28,579 but in areas where you're likely to see somebody walking a 120 00:07:28,579 --> 00:07:31,219 pedestrian, interact with somebody that might have been on 121 00:07:31,219 --> 00:07:34,159 a horse or in a vehicle, you know, we know that that 122 00:07:34,159 --> 00:07:38,239 difference in speed causes a safety concern. So how do we 123 00:07:38,299 --> 00:07:41,019 control the speeds to make everybody safer in that 124 00:07:41,019 --> 00:07:41,619 situation. 125 00:07:42,320 --> 00:07:45,260 Jane: And eventually we got to traffic lights, and a lot of 126 00:07:45,260 --> 00:07:47,780 kids have questions about traffic lights. 127 00:07:47,900 --> 00:07:53,540 Ishan: Hi, my name is Ishan. I live in San Jose, California. I 128 00:07:53,540 --> 00:07:57,440 am five years old. How do traffic lights work? 129 00:07:57,600 --> 00:08:01,020 Evie: Hi, my name is Evie. I'm seven years old, and I live in 130 00:08:01,020 --> 00:08:04,620 Rockville Center, New York. And my question is, why do we have 131 00:08:04,620 --> 00:08:05,400 traffic lights? 132 00:08:05,400 --> 00:08:08,100 Isadore: I'm Isadore. How do traffic lights work? 133 00:08:08,000 --> 00:08:12,920 Alice: I am Alice. I am seven years old. I live in Salt Lake 134 00:08:12,920 --> 00:08:16,400 City, Utah. How do traffic lights work? 135 00:08:16,400 --> 00:08:22,880 Jackson: Hi. My name is Jackson. I live in Orlando, Florida. I'm 136 00:08:22,880 --> 00:08:26,420 seven years old. How does a traffic light work? 137 00:08:26,420 --> 00:08:31,445 Emily: Hello. My name is Emily. I'm six years old. I come from 138 00:08:31,445 --> 00:08:34,625 London, UK. How the traffic lights work? 139 00:08:34,625 --> 00:08:42,005 Sarah: Hi. My name is Sarah, and I'm from St Paul, Minnesota, and 140 00:08:42,005 --> 00:08:45,365 I'm six years old. And my question is, how are traffic 141 00:08:45,365 --> 00:08:46,205 lights made? 142 00:08:46,000 --> 00:08:47,800 Mike Knodler: So the traffic lights are actually more than 143 00:08:47,800 --> 00:08:52,420 100 years old now. So the patent goes back to the early 1900s, 144 00:08:52,420 --> 00:08:56,800 1920 right around there. And again, they were all created 145 00:08:56,800 --> 00:09:00,760 with the idea of keeping orderly flow. And so primarily the idea 146 00:09:00,760 --> 00:09:04,000 of stopping one stream of traffic so that another stream 147 00:09:04,000 --> 00:09:06,760 of traffic going in an opposite direction would be able to go. 148 00:09:07,060 --> 00:09:09,925 And so some of the early traffic signals, if you look at them, 149 00:09:10,045 --> 00:09:13,045 they're actually kind of unique. They were arms, and the arm 150 00:09:13,045 --> 00:09:15,325 would go up and say, go, and then another arm would come up 151 00:09:15,325 --> 00:09:18,565 and say, stop. And that was sort of the way that they work. 152 00:09:18,565 --> 00:09:20,665 Jane: Not like a train arm, but smaller. 153 00:09:20,960 --> 00:09:23,600 Mike Knodler: Yeah, no. So it was on a mast arm, so it would 154 00:09:23,600 --> 00:09:26,420 be up on a regular pole, and then at the top of the pole 155 00:09:26,420 --> 00:09:29,780 would be an arm that would raise up and say, stop, or an arm that 156 00:09:29,780 --> 00:09:30,980 would raise up and say, go. 157 00:09:31,100 --> 00:09:34,400 Jane: So that was before we had electricity, yeah, that we could 158 00:09:34,400 --> 00:09:35,060 have on poles. 159 00:09:35,060 --> 00:09:38,420 Mike Knodler: Yeah. And then now, now we have a lot more 160 00:09:38,780 --> 00:09:41,840 technology and a lot more capability. And so we switched 161 00:09:41,840 --> 00:09:45,605 to lights being sort of the primary measure by which we do 162 00:09:45,605 --> 00:09:49,205 that. And then now we have a lot more complexity as well in terms 163 00:09:49,205 --> 00:09:52,805 of what we've designed at intersections and some of the 164 00:09:52,805 --> 00:09:55,385 different we call it the signal phasing. So what are some of the 165 00:09:55,385 --> 00:09:58,565 different phasing things we can do where we maybe tell this 166 00:09:58,565 --> 00:10:01,325 group of vehicles they can go, and hold another group back, or 167 00:10:01,325 --> 00:10:03,905 maybe we tell the pedestrians they can go and stop all the 168 00:10:03,905 --> 00:10:06,725 other traffic. And so there's a lot that goes into what we can 169 00:10:06,725 --> 00:10:09,770 actually do to make them operate again with the idea of trying to 170 00:10:09,770 --> 00:10:10,610 keep everybody safe. 171 00:10:10,610 --> 00:10:14,510 Layelle: Hello. My name is Layelle. I'm five years old. I'm 172 00:10:14,510 --> 00:10:21,170 from Phoenix, Arizona. Why does traffic lights always works by 173 00:10:21,170 --> 00:10:22,130 themselves. 174 00:10:22,130 --> 00:10:27,470 Alex: Hi, I'm Alex, and I'm seven years old, and I live in 175 00:10:27,470 --> 00:10:32,555 Iowa. Why do traffic lights know when to go and to stop? 176 00:10:33,020 --> 00:10:36,380 Elliot: Hi, my name is Elliot. I'm 11 years old. I live in 177 00:10:36,380 --> 00:10:40,400 Great Falls, Virginia, and I would like to know how big is a 178 00:10:40,400 --> 00:10:43,640 traffic light. How does it know when to go from red to yellow to 179 00:10:43,640 --> 00:10:47,300 green and keep in sequence with all intersecting roads? 180 00:10:47,780 --> 00:10:50,480 Isla: Hi, my name is Isla, and I'm four years old, and I live 181 00:10:50,480 --> 00:10:55,760 in Vermont. My question is, how do stoplights know when to turn 182 00:10:55,760 --> 00:10:56,360 green or red? 183 00:10:56,360 --> 00:11:03,500 Max: My name is Max, and I'm five, and I live in Michigan and 184 00:11:03,800 --> 00:11:07,640 and I want to know, why are traffic lights smart? 185 00:11:07,919 --> 00:11:10,679 Jane: How do traffic lights know when to turn from green to 186 00:11:10,679 --> 00:11:15,239 yellow to red and back to green by themselves, and how do the 187 00:11:15,239 --> 00:11:18,959 traffic light patterns change depending on the amount of 188 00:11:18,959 --> 00:11:20,899 traffic on the road or the time of day. 189 00:11:21,080 --> 00:11:24,920 Mike Knodler: Yeah, yeah. No, that's so true. So on some 190 00:11:24,920 --> 00:11:27,980 level, we actually can just make them what we call pre timed, 191 00:11:28,100 --> 00:11:31,700 where the timing is just fixed, and no matter what, it's always 192 00:11:31,700 --> 00:11:34,700 30 seconds of green for this street followed by 30 seconds of 193 00:11:34,700 --> 00:11:37,700 green in the opposite direction. Perhaps that's, that's, that's 194 00:11:37,700 --> 00:11:40,880 pretty basic. You know, there are some where we don't have the 195 00:11:40,880 --> 00:11:43,400 technology in place to sense the traffic that's there, and they 196 00:11:43,400 --> 00:11:46,265 might operate on that, that pre timed schedule. So that's that's 197 00:11:46,565 --> 00:11:49,505 sort of basic, that might be in smaller locations where you 198 00:11:49,505 --> 00:11:53,885 don't worry about sort of traffic flows building up, but, 199 00:11:53,885 --> 00:11:57,965 but what's more likely now, a lot of the intersections that 200 00:11:57,965 --> 00:12:02,165 you come up to have sensors. The easiest way to think about this 201 00:12:02,345 --> 00:12:06,005 is that each of the legs of the intersection typically has some 202 00:12:06,050 --> 00:12:09,110 relationship to the different sensing technology that's there. 203 00:12:09,350 --> 00:12:12,950 And so if we, for example, for using an overhead camera, we 204 00:12:12,950 --> 00:12:16,850 might be able to look and say, Hey, there's a car over here. As 205 00:12:16,850 --> 00:12:19,310 soon as you get a chance, we need to bring the green back 206 00:12:19,310 --> 00:12:22,070 over here, because there's a car waiting to go. That's that's 207 00:12:22,070 --> 00:12:24,530 sort of the basic of how it works. But some of the sensing 208 00:12:24,530 --> 00:12:27,890 technologies in the ground, sometimes we put it on some of 209 00:12:27,890 --> 00:12:30,395 the legs of the intersection. Sometimes we put it on all the 210 00:12:30,395 --> 00:12:34,595 legs. It's really a function of how much data we really need to 211 00:12:34,595 --> 00:12:38,135 be able to make the best decisions for that, that traffic 212 00:12:38,135 --> 00:12:42,875 signal, and how to make it work, and then not to add too, too 213 00:12:42,875 --> 00:12:46,595 much, but now we actually go even further than that. We 214 00:12:46,595 --> 00:12:50,675 actually can operate multiple traffic signals all together. 215 00:12:51,035 --> 00:12:54,860 And so the traffic signals are talking to each other and saying 216 00:12:54,860 --> 00:12:59,240 things like, Hey, I'm going to release a group of vehicles on 217 00:12:59,240 --> 00:13:02,900 green, and they're coming your way. So you probably want to be 218 00:13:02,900 --> 00:13:06,020 ready to turn on a green as soon as they get there in, you know, 219 00:13:06,020 --> 00:13:08,900 and then we calculate out what the time is so, so the traffic 220 00:13:08,900 --> 00:13:12,980 signals can coordinate in that way to be able to, again, try to 221 00:13:12,980 --> 00:13:13,520 optimize it. 222 00:13:14,020 --> 00:13:17,800 Jane: Now, when you describe it in my head, it makes me think 223 00:13:17,800 --> 00:13:22,660 that there's like some person in either a building who can see 224 00:13:22,660 --> 00:13:25,540 the cameras, or, you know, it sounds like there's some little 225 00:13:25,540 --> 00:13:28,960 person in the traffic signal itself, saying, okay, now is the 226 00:13:28,960 --> 00:13:31,660 time I'm going to release all those cars. But this is it's 227 00:13:31,660 --> 00:13:33,820 not, there's not a person doing this. 228 00:13:34,300 --> 00:13:38,065 Mike Knodler: No, not in real time. So in fact, you probably 229 00:13:38,065 --> 00:13:41,905 drive by them hundreds of times and maybe never notice it, but 230 00:13:41,905 --> 00:13:44,245 most of these signalized intersections that you would 231 00:13:44,245 --> 00:13:48,025 drive by, if you look to one of the corners, there's probably a 232 00:13:48,025 --> 00:13:52,105 cabinet, a metal box, on the side of the road, and in that 233 00:13:52,105 --> 00:13:55,645 metal box, easiest way to think about it is there's a mini 234 00:13:55,645 --> 00:13:58,825 computer, and that mini computer is really the brain of the 235 00:13:58,825 --> 00:14:01,810 traffic signal. We call it a controller, and that's the 236 00:14:01,810 --> 00:14:05,110 that's what's taking in all the input from the detectors and 237 00:14:05,110 --> 00:14:07,570 anything else that might be operating at that intersection. 238 00:14:07,750 --> 00:14:11,710 And then that's what makes the decisions that that the traffic 239 00:14:11,710 --> 00:14:14,410 engineers would have programmed into the logic, saying, like, 240 00:14:14,410 --> 00:14:16,570 Okay, here's here's what you can and can't do. Here's how you 241 00:14:16,570 --> 00:14:19,630 should be thinking about it. And then that controller actually 242 00:14:19,630 --> 00:14:21,130 implements it and runs it. 243 00:14:21,240 --> 00:14:24,120 Jane: So in some ways, it's, you can think of it like it's all 244 00:14:24,120 --> 00:14:27,480 kind of computer programming, and the computer programming 245 00:14:27,600 --> 00:14:33,300 might have in its code something that says, If this happens, then 246 00:14:33,300 --> 00:14:37,980 you do this. If this other thing happens, then you do this. So 247 00:14:37,980 --> 00:14:41,100 it's, it's an automated system, but it is all coded for 248 00:14:41,280 --> 00:14:44,565 different, what we would call variables, different things that 249 00:14:44,565 --> 00:14:46,065 could happen in an intersection. 250 00:14:46,065 --> 00:14:48,825 Mike Knodler: Yep, yeah, not all intersections have that, but, 251 00:14:48,825 --> 00:14:51,345 but by and large, I'd say most of the intersections do indeed 252 00:14:51,345 --> 00:14:54,765 have that. Where it'll it'll be able to go through, for example, 253 00:14:55,605 --> 00:14:57,945 we're not going to put on a pedestrian phase at some 254 00:14:57,945 --> 00:15:00,705 intersections if there's never a pedestrian that's there. But 255 00:15:00,705 --> 00:15:03,465 then as soon as a pedestrian walks up and hits the pedestrian 256 00:15:03,465 --> 00:15:06,285 push button, we'll turn on that pedestrian interval to give the 257 00:15:06,285 --> 00:15:09,270 pedestrian some time to cross the street. So yeah, so the 258 00:15:09,270 --> 00:15:12,750 traffic engineers are the ones that have a lot of that control 259 00:15:12,750 --> 00:15:15,630 to be able to sort of program in the rules, and then the 260 00:15:15,630 --> 00:15:17,130 controller actually makes it happen. 261 00:15:17,960 --> 00:15:21,020 Jane: And you mentioned that one of the most important things is 262 00:15:21,020 --> 00:15:25,040 to think about the different types of transportation, or 263 00:15:25,040 --> 00:15:28,760 modes of transportation that might be using the same road or 264 00:15:28,760 --> 00:15:32,480 the same intersection. And so when we think about that, there 265 00:15:32,480 --> 00:15:36,440 are cars, there are trucks, sometimes there are trains that 266 00:15:36,440 --> 00:15:40,805 cross roads. Lots of times there are people walking. We call them 267 00:15:40,805 --> 00:15:44,645 pedestrians. There are bikes that use the same lanes as 268 00:15:44,645 --> 00:15:48,365 traffic, but go at different speeds. Where I live, there are 269 00:15:48,365 --> 00:15:52,505 sometimes horses that are using the roads, or people who are 270 00:15:52,505 --> 00:15:56,525 using vehicles like tractors that are also allowed to use the 271 00:15:56,525 --> 00:15:59,765 roads, but go at very different speeds. And so part of the job 272 00:15:59,765 --> 00:16:02,585 of somebody who is a traffic engineer is to think about all 273 00:16:02,585 --> 00:16:05,450 of the different types of vehicles and people on the 274 00:16:05,450 --> 00:16:09,650 roads, and how to allow them all to use that road safely. That 275 00:16:09,650 --> 00:16:12,170 must be something that you have to think really hard about. 276 00:16:12,600 --> 00:16:14,760 Mike Knodler: Yeah, no, that's probably one of the more 277 00:16:14,760 --> 00:16:18,360 challenging things, because, as you were hinting at, they all 278 00:16:18,360 --> 00:16:20,940 have very different characteristics, you know. So, 279 00:16:20,940 --> 00:16:24,600 for example, people walking, you know, might walk at one speed, 280 00:16:24,600 --> 00:16:27,060 and that's much, much slower than somebody has the ability to 281 00:16:27,060 --> 00:16:31,080 drive in a car. And a bike is probably somewhere in between 282 00:16:31,080 --> 00:16:33,840 those two, obviously, in terms of the spin. So, so we're trying 283 00:16:33,840 --> 00:16:37,065 to manage, you know, the amount of space they take up, coupled 284 00:16:37,065 --> 00:16:41,085 with the speeds that they travel looking, coupled with where 285 00:16:41,085 --> 00:16:44,205 they're looking to go at the same time and and managing what 286 00:16:44,205 --> 00:16:47,565 we call those those conflicts is indeed one of the more 287 00:16:47,565 --> 00:16:50,925 challenging things to think about from a transportation big 288 00:16:50,925 --> 00:16:52,545 picture system perspective. 289 00:16:52,840 --> 00:16:55,180 Jane: Transportation professionals like Mike think a 290 00:16:55,180 --> 00:16:59,080 lot about human behavior when they design systems to keep us 291 00:16:59,080 --> 00:17:02,260 safe, because whether we're talking about pedestrians, 292 00:17:02,260 --> 00:17:06,940 people on bikes or drivers, it's the humans who are making 293 00:17:06,940 --> 00:17:10,480 decisions and interacting with these traffic systems and 294 00:17:10,480 --> 00:17:14,980 driving these big vehicles, and we humans sometimes get confused 295 00:17:15,325 --> 00:17:19,765 or fail to follow directions or drive over the speed limit. So 296 00:17:19,765 --> 00:17:22,825 it's Mike's job to take all of those possibilities into 297 00:17:22,825 --> 00:17:26,425 consideration when designing a system to keep people safe. 298 00:17:27,745 --> 00:17:31,525 After the break, we ask Mike, why does green mean go and red 299 00:17:31,525 --> 00:17:34,645 mean stop, and why do we drive on the right side of the road, 300 00:17:34,705 --> 00:17:37,465 at least in the United States? Stay with us. 301 00:17:38,860 --> 00:17:42,760 This is But Why: a Podcast for Curious Kids. I'm Jane Lindholm. 302 00:17:42,820 --> 00:17:46,780 Today we're learning about transportation systems with Mike 303 00:17:46,780 --> 00:17:49,300 Knoedler, director of the Transportation Center at the 304 00:17:49,300 --> 00:17:52,600 University of Massachusetts. Let's jump right back in with 305 00:17:52,600 --> 00:17:53,500 your questions. 306 00:17:53,960 --> 00:17:59,540 Josephine: My name is Josephine. I am seven years old, and I live 307 00:17:59,540 --> 00:18:05,240 in New York. Why does green mean go and red mean stop. 308 00:18:05,480 --> 00:18:10,700 Alonzo: My name is Alonzo. I'm four year old. I am from 309 00:18:10,700 --> 00:18:18,380 Richardson, Texas. Why does green mean go? 310 00:18:18,380 --> 00:18:22,700 Colette: Hi. My name is Colette. I am seven years old. I am from 311 00:18:22,700 --> 00:18:28,865 Maryland. Why are traffic lights green, red and yellow? Why do 312 00:18:28,865 --> 00:18:30,545 they choose those colors? 313 00:18:30,600 --> 00:18:33,780 Mike Knodler: Yeah, so there's a lot that actually goes into the 314 00:18:33,780 --> 00:18:36,780 actual design of traffic signals and the colors, and it's very 315 00:18:36,780 --> 00:18:42,600 precise, in fact, but one of the reasons that red is associated 316 00:18:42,600 --> 00:18:46,500 with stop is really two reasons. One, we tend to think of red 317 00:18:46,500 --> 00:18:49,620 just being that, that damage, that danger, sort of, you know, 318 00:18:49,620 --> 00:18:52,080 if somebody was bleeding, they're concerned, right? So, so 319 00:18:52,080 --> 00:18:55,005 it has that, that already alarming message, which is, you 320 00:18:55,005 --> 00:18:57,585 know, potentially good when it comes to thinking about traffic 321 00:18:57,585 --> 00:19:01,065 signals. But the other, and the more important reason, is it's 322 00:19:01,065 --> 00:19:05,445 more visible from further away. And so given how important red 323 00:19:05,445 --> 00:19:10,785 is in a traffic signal, we want that to be the most visible. And 324 00:19:10,785 --> 00:19:13,365 so as a result of that, that's one of the reasons that we ended 325 00:19:13,365 --> 00:19:17,205 up with red. Now the other colors that ended up on there. A 326 00:19:17,250 --> 00:19:20,850 lot of what we're actually thinking about is, how are 327 00:19:20,850 --> 00:19:24,210 colors going to appear to people that might have color 328 00:19:24,210 --> 00:19:27,390 deficiencies? So people that might be color blind. And so if 329 00:19:27,390 --> 00:19:31,470 we think about some of the more common color blindness patterns, 330 00:19:31,770 --> 00:19:35,850 we're trying to make sure that we're we're using colors that 331 00:19:35,850 --> 00:19:38,610 are going to show up differently to people that might have 332 00:19:38,610 --> 00:19:42,135 different color deficiencies. And so that's one of the 333 00:19:42,135 --> 00:19:45,375 reasons, as an example, that red is always on the top. So even if 334 00:19:45,375 --> 00:19:48,615 somebody can't distinguish between red and green, they can 335 00:19:48,615 --> 00:19:51,675 see that the top section of the traffic signal is illuminated. 336 00:19:51,675 --> 00:19:54,375 So they know that that's red. Or if they see that the bottom 337 00:19:54,375 --> 00:20:00,015 section of the traffic signal is illuminated, they're going to 338 00:20:00,015 --> 00:20:01,780 know that that's, you know, sort of the green. And so that's 339 00:20:01,780 --> 00:20:02,009 another one of those human factor, there's things that we 340 00:20:02,009 --> 00:20:03,960 take into consideration in the design of traffic signal 341 00:20:03,960 --> 00:20:04,500 displays. 342 00:20:04,540 --> 00:20:09,040 Arlo: I'm Arlo, and I'm from Durham, North Carolina. Why is 343 00:20:09,040 --> 00:20:10,420 stop signs red? 344 00:20:10,540 --> 00:20:13,120 Jane: And stop signs are red, and you talked about that color, 345 00:20:13,120 --> 00:20:16,960 but stop signs, at least in the United States, are also always 346 00:20:17,080 --> 00:20:18,700 one specific shape. 347 00:20:18,780 --> 00:20:21,360 Mike Knodler: Yeah, so that's a really, really awesome question. 348 00:20:21,360 --> 00:20:24,420 So the red, the cautionary message and being visible from 349 00:20:24,420 --> 00:20:28,860 greater distances. But one of the reasons so that we we make 350 00:20:28,860 --> 00:20:33,300 stop signs octagons, is so that they're really recognizable to 351 00:20:33,300 --> 00:20:36,240 people. They know, whether they're in Massachusetts or 352 00:20:36,240 --> 00:20:40,440 Florida or California, when they see an octagon, they know that 353 00:20:40,440 --> 00:20:44,085 it's going to be a stop sign. The other reason that we use 354 00:20:44,085 --> 00:20:49,005 that particular shape is, let's say that I'm on a roadway and I 355 00:20:49,005 --> 00:20:53,385 look to the side street next to me. I can tell from the I can 356 00:20:53,385 --> 00:20:56,745 tell from the back of the sign, that that driver has a stop 357 00:20:56,745 --> 00:20:59,625 sign. So because it's a very recognizable pattern, that 358 00:20:59,625 --> 00:21:03,105 octagon, I can look, if I'm on the main street, I can look and 359 00:21:03,105 --> 00:21:05,730 say, Oh, the driver on the side streets going to stop, because I 360 00:21:05,730 --> 00:21:08,910 know they have a stop sign. And so that's another reason that we 361 00:21:09,030 --> 00:21:13,110 we use. So we use combinations of the letters or the symbols on 362 00:21:13,110 --> 00:21:17,190 the sign as well as the shape of the sign as well as the colors 363 00:21:17,190 --> 00:21:20,370 that are on the sign to communicate messages to people. 364 00:21:20,550 --> 00:21:22,530 And each of them has an intended purpose. 365 00:21:22,530 --> 00:21:26,430 Jane: Okay, but then what about the color yellow or amber? 366 00:21:27,075 --> 00:21:30,315 Sometimes it seems like the adults around us think that an 367 00:21:30,435 --> 00:21:34,155 amber light at a traffic signal means speed up really fast so 368 00:21:34,155 --> 00:21:36,855 you don't get caught at a red that's not what it's supposed to 369 00:21:36,855 --> 00:21:37,035 mean. 370 00:21:37,215 --> 00:21:41,115 Mike Knodler: Yeah, so by nature, the yellow is intended 371 00:21:41,115 --> 00:21:44,355 to imply a cautionary message. So when you see it, for example, 372 00:21:44,355 --> 00:21:47,775 on a sign, it's usually warning you about some, you know, a 373 00:21:47,775 --> 00:21:50,760 curve coming up, or some hazard that might be there on the 374 00:21:50,760 --> 00:21:53,880 roadway. In a traffic signal when we see yellow, it tells you 375 00:21:53,880 --> 00:21:56,820 that whatever was previously on is coming to an end. That's the 376 00:21:56,820 --> 00:21:59,160 other meaning of that. That steady yellow is to tell you 377 00:21:59,160 --> 00:22:02,100 what's happening. And you're right. Some people do say, I 378 00:22:02,100 --> 00:22:04,260 know this means it's ending. I better speed up and go. And 379 00:22:04,260 --> 00:22:07,560 that's that's not the way that we're intending it. But we do 380 00:22:07,560 --> 00:22:10,260 want people to be able to get safely through the intersection. 381 00:22:10,260 --> 00:22:13,080 Jane: Right? So if you're already in the intersection, the 382 00:22:13,080 --> 00:22:13,110 message is, keep going, hustle up. It's going to turn red soon. 383 00:22:13,110 --> 00:22:16,965 You don't want to be caught in the middle of the intersection. 384 00:22:17,145 --> 00:22:21,225 Mike Knodler: Exactly. Yeah. So when we time that yellow in 385 00:22:21,225 --> 00:22:24,225 between, we're really timing it so that if somebody had just 386 00:22:24,225 --> 00:22:26,925 entered, they have enough time to be able to make their way 387 00:22:26,925 --> 00:22:27,165 out. 388 00:22:27,740 --> 00:22:30,320 Jane: And of course, these signals aren't just for drivers 389 00:22:30,440 --> 00:22:34,700 as pedestrians, people who are walking or rolling or strolling. 390 00:22:35,120 --> 00:22:38,060 We need to pay attention to the walk signal that tells us when 391 00:22:38,060 --> 00:22:41,080 it's safe to cross the road and when you need to wait. In the 392 00:22:41,080 --> 00:22:44,680 United States, the walk sign is usually an outline of a person 393 00:22:44,740 --> 00:22:48,940 brightly lit up in white. Once the walk sign turns to flashing, 394 00:22:48,940 --> 00:22:51,640 that's usually saying, if you haven't started crossing, you 395 00:22:51,640 --> 00:22:54,340 should wait for your next turn, because you don't have enough 396 00:22:54,340 --> 00:22:57,100 time to get to the other side before the traffic can start 397 00:22:57,100 --> 00:23:00,780 going again. Sometimes there's even a countdown of numbers, 398 00:23:00,780 --> 00:23:03,660 which is helpful so you know exactly how many seconds you 399 00:23:03,660 --> 00:23:05,040 have left across the road. 400 00:23:05,120 --> 00:23:10,880 Marley: Hi. My name is Marley. I live in Pinole, California, and 401 00:23:10,880 --> 00:23:15,200 I'm eight years old. And my question is, why can cars go 402 00:23:15,200 --> 00:23:17,720 past the speed limit if it's not allowed? 403 00:23:17,840 --> 00:23:20,540 Mike Knodler: Yeah, this, this comes up a lot. Should we be 404 00:23:20,540 --> 00:23:24,020 putting technology on vehicles that limits their speed? Or 405 00:23:24,020 --> 00:23:26,900 should the roadway be able to communicate to the car, take the 406 00:23:26,900 --> 00:23:29,840 human out of it, and tell the car you can't go faster than 407 00:23:29,840 --> 00:23:33,440 this speed on this roadway? One of the reasons that cars have 408 00:23:33,440 --> 00:23:38,420 that ability, though, is because of when, so the probably the 409 00:23:38,420 --> 00:23:41,525 easiest way to think about this is, if you're merging onto a 410 00:23:41,525 --> 00:23:45,425 highway, your car has to be able to get up to speed, or 411 00:23:45,425 --> 00:23:49,265 accelerate up to speed really quickly. Well, that same thing 412 00:23:49,265 --> 00:23:51,725 that allows you to accelerate, you know, if you're coming onto 413 00:23:51,725 --> 00:23:54,245 the highway, to accelerate up to speed, to be able to merge in 414 00:23:54,245 --> 00:23:57,245 with the traffic, and the highway is the same thing that 415 00:23:57,245 --> 00:24:01,265 gives your car the ability to travel faster. And so that that 416 00:24:01,265 --> 00:24:04,205 capability, that horsepower, that acceleration capability, 417 00:24:04,445 --> 00:24:08,210 gives that vehicle, ultimately, that that speed capability. 418 00:24:08,280 --> 00:24:11,400 Nicole: Hi. My name is Nicole, and I'm a mom from Wakefield, 419 00:24:11,400 --> 00:24:15,120 Massachusetts. Why do we drive on the right side of the road? 420 00:24:15,480 --> 00:24:18,360 Jane: And of course, here in the US, that's the side we drive on. 421 00:24:18,000 --> 00:24:20,100 Mike Knodler: Yeah. So, so this one, this is actually goes back 422 00:24:20,100 --> 00:24:24,000 to what we were talking about a little bit ago. Bit ago. So this 423 00:24:24,000 --> 00:24:28,380 actually goes back before cars, back to the horse and buggy 424 00:24:28,380 --> 00:24:34,680 days, and so when somebody was operating a horse, so a group of 425 00:24:34,680 --> 00:24:40,860 horses, they would typically sit on the back left horse, and they 426 00:24:40,860 --> 00:24:44,745 would sit on the back left horse, because it made it easier 427 00:24:44,745 --> 00:24:47,925 for them to be able to, believe it or not, it's going to sound 428 00:24:47,925 --> 00:24:51,465 really, really funny, two things, it kept it easier for 429 00:24:51,465 --> 00:24:55,665 them to be able to navigate and keep the horses on track. But it 430 00:24:55,665 --> 00:24:59,565 also if, back in the olden days, if they had to defend 431 00:24:59,565 --> 00:25:02,265 themselves. Was they would be able to use their right arm to 432 00:25:02,265 --> 00:25:07,530 pull out their their weapon and defend themselves. And so that 433 00:25:07,530 --> 00:25:11,250 capability existed. And so then when somebody was on that left 434 00:25:11,250 --> 00:25:15,570 side, they just made it easier, if the vehicles or the horses 435 00:25:15,570 --> 00:25:18,150 and buggies that were coming at them were on the same so the 436 00:25:18,150 --> 00:25:21,810 drivers were side by side with each other, you know, so left, 437 00:25:22,050 --> 00:25:26,850 you know, left to left. And so that just became what we knew, 438 00:25:26,850 --> 00:25:31,215 and then, and then that became how we we drive, and just became 439 00:25:31,215 --> 00:25:32,655 the rules of the road, and the norm. 440 00:25:33,620 --> 00:25:36,200 Jane: That's the rules of the road in the United States. And 441 00:25:36,200 --> 00:25:39,500 if you drive into Canada or from Canada into the United States, 442 00:25:39,500 --> 00:25:42,280 it's the same. You're probably driving a car that has the 443 00:25:42,280 --> 00:25:44,740 steering wheel on the left side and you're driving on the right. 444 00:25:44,740 --> 00:25:47,620 But if you're driving in some other countries, that is not the 445 00:25:47,620 --> 00:25:50,560 case, and your car might look quite different. You might have 446 00:25:50,560 --> 00:25:52,300 a steering wheel on the opposite side. 447 00:25:53,200 --> 00:25:55,780 Mike Knodler: Yeah, no. And it's really, really such a weird 448 00:25:55,780 --> 00:25:59,260 feeling, and it's a lot of historical carry over at this 449 00:25:59,260 --> 00:26:03,060 point. And so you know you, as you look at country by country 450 00:26:03,060 --> 00:26:06,180 across the world, the majority now drive right side of the 451 00:26:06,180 --> 00:26:09,120 road, similar to what we have, but there are still some that 452 00:26:09,120 --> 00:26:12,180 certainly do and and I don't envision them ever changing, or 453 00:26:12,180 --> 00:26:13,320 at least anytime soon. 454 00:26:13,000 --> 00:26:16,180 Jane: Let's talk a little bit about roads themselves and how 455 00:26:16,180 --> 00:26:19,660 they work. Saoirse lives in Fletcher and wonders: 456 00:26:19,660 --> 00:26:21,820 Saoirse: Why are some roads bigger than others? 457 00:26:21,880 --> 00:26:25,480 Mike Knodler: So it kind of depends, right? So the easiest 458 00:26:25,480 --> 00:26:29,020 way to think about this is every road has a function, or every 459 00:26:29,020 --> 00:26:33,100 road has a purpose. So what's the purpose of that roadway? And 460 00:26:33,100 --> 00:26:37,300 so some roads are maybe they're a really important roadway 461 00:26:37,345 --> 00:26:43,345 because they link a town with a city, but then there's roads in 462 00:26:43,345 --> 00:26:49,105 that city that link that city to a bigger city. And so when we're 463 00:26:49,165 --> 00:26:52,945 expecting that there's going to be a lot of cars wanting to use 464 00:26:52,945 --> 00:26:58,345 that road, we'll design a bigger road to be able to accommodate 465 00:26:58,405 --> 00:27:01,570 more traffic. And then there's some other reasons too. So for 466 00:27:01,570 --> 00:27:04,930 example, you know, we want to make sure that there's access to 467 00:27:04,930 --> 00:27:08,530 all the places that need access. And so sometimes we might design 468 00:27:08,530 --> 00:27:11,710 even though it might be, like you mentioned that you live in a 469 00:27:11,710 --> 00:27:15,010 smaller town, rural area, but we still want to make sure that 470 00:27:15,010 --> 00:27:18,790 there's the ability to get where people need to go. And so we 471 00:27:18,790 --> 00:27:22,030 might design a road that would be able to accommodate that. Now 472 00:27:22,075 --> 00:27:25,195 roads might get bigger if we want to add bike lanes or if we 473 00:27:25,195 --> 00:27:28,375 want to add sidewalks. So those are some of the decisions that 474 00:27:28,375 --> 00:27:31,255 we make with saying, Okay, how much space do we actually have 475 00:27:31,255 --> 00:27:32,095 available to us? 476 00:27:32,000 --> 00:27:36,740 Hazel: My name is Hazel, and I'm six year old, and I come from 477 00:27:36,980 --> 00:27:42,620 Canada, Ontario. Why are there so many cars on the highway? 478 00:27:43,120 --> 00:27:46,120 Mike Knodler: Yeah, that's, I mean, that human decision making 479 00:27:46,120 --> 00:27:50,320 is really at the heart of it all. So when we make it easier 480 00:27:50,320 --> 00:27:55,600 for people to be able to travel in their car, then we, as a 481 00:27:55,600 --> 00:27:59,140 result of that, end up with more cars on the roadway. And so 482 00:27:59,140 --> 00:28:01,440 that's, that's really, so there's, there's obviously we, 483 00:28:01,440 --> 00:28:04,440 as we make it easier for people to travel in their cars, you 484 00:28:04,440 --> 00:28:07,380 know, we get more, but we still see people traveling in their 485 00:28:07,380 --> 00:28:09,780 cars even when they know that they're going to be sitting in 486 00:28:09,780 --> 00:28:13,380 traffic. And part of the reason for that might be that people 487 00:28:13,380 --> 00:28:16,020 want to have their car with them because they maybe they need to 488 00:28:16,020 --> 00:28:18,300 leave, you know, by a certain time it goes somewhere, or they 489 00:28:18,300 --> 00:28:20,480 have to pick somebody else up, or, you know, they might have 490 00:28:20,480 --> 00:28:24,260 some other thing that they have to do, but also, and this is 491 00:28:24,260 --> 00:28:27,680 where, you know, we could debate, sometimes, when we build 492 00:28:27,680 --> 00:28:32,120 up roadways to the extent that we do, we're not necessarily 493 00:28:32,120 --> 00:28:36,500 thinking about, well, what other options that people have? And so 494 00:28:36,500 --> 00:28:40,040 this becomes a really big push to say, well, let's design 495 00:28:40,040 --> 00:28:43,780 better bike infrastructure, let's design better public 496 00:28:43,780 --> 00:28:47,260 transportation if people want to take a bus or a train. If we 497 00:28:47,260 --> 00:28:51,280 design those systems, will we end up with less cars? And 498 00:28:51,280 --> 00:28:54,340 oftentimes the answer is yes. So we're trying to figure out what 499 00:28:54,340 --> 00:28:58,780 the balance is in terms of where to invest the money that we have 500 00:28:58,780 --> 00:29:02,280 building the infrastructure that people need or want to have 501 00:29:02,280 --> 00:29:05,160 based on where they where they live and where they want to go. 502 00:29:05,460 --> 00:29:07,260 Jane: Yeah, it's also interesting, because there are 503 00:29:07,260 --> 00:29:10,920 so many interlocking pieces that need to be in place for people 504 00:29:10,920 --> 00:29:13,740 to be able to live their lives in a way that allows them to do 505 00:29:13,740 --> 00:29:16,680 everything they need to do. And cars, for many of us, are a big 506 00:29:16,680 --> 00:29:20,780 piece of that. But for some of us, we don't have cars, or we 507 00:29:20,780 --> 00:29:24,080 feel like we can't get a get around without a car, like when 508 00:29:24,080 --> 00:29:26,540 I used to live in a big city and I didn't have a car, but the 509 00:29:26,540 --> 00:29:30,080 nearest grocery store was five miles away, and I could only get 510 00:29:30,080 --> 00:29:32,840 a few groceries if I was going to take the bus back home 511 00:29:32,840 --> 00:29:36,140 afterwards. So thinking about how all of these pieces fit 512 00:29:36,140 --> 00:29:41,020 together is a really important part of being an engineer of 513 00:29:41,020 --> 00:29:44,920 certain kind of engineer, or a designer, or thinking about city 514 00:29:44,920 --> 00:29:47,980 and town infrastructure, and if that interests kids, that might 515 00:29:47,980 --> 00:29:49,600 be a great career to go in. 516 00:29:49,000 --> 00:29:52,540 Mike Knodler: Yeah, and what's really and what's even more fun 517 00:29:52,540 --> 00:29:57,100 now is we're starting to see a lot of different modes emerge. 518 00:29:57,100 --> 00:30:01,300 So the example you just gave is you live in a city. And you want 519 00:30:01,300 --> 00:30:05,200 to go to the grocery store, but you can't carry five bags of 520 00:30:05,200 --> 00:30:10,420 groceries on the bus or the subway, for example. But now 521 00:30:10,960 --> 00:30:15,085 there's companies that make electric cargo bikes, and so now 522 00:30:15,085 --> 00:30:17,965 you can actually rent a cargo bike or own a cargo bike for the 523 00:30:17,965 --> 00:30:20,665 day and take the cargo bike to the store and be able to fit 524 00:30:20,665 --> 00:30:23,485 your five bags of groceries and then go home, but not take up 525 00:30:23,485 --> 00:30:26,965 the same amount of space as a car, for example. And so one of 526 00:30:26,965 --> 00:30:30,685 the things that excites me now, and some of the challenges that 527 00:30:30,685 --> 00:30:34,165 the students today might encounter in the near future, is 528 00:30:34,165 --> 00:30:36,670 thinking about what some of those technological innovations 529 00:30:36,670 --> 00:30:39,310 are that solve some of these problems that we're talking 530 00:30:39,310 --> 00:30:39,550 about. 531 00:30:39,550 --> 00:30:42,610 Noah: My name's Noah, and I'm five years old, from Louisville, 532 00:30:42,610 --> 00:30:47,290 Kentucky, and my question is, how do roads carry cars without 533 00:30:47,290 --> 00:30:47,830 breaking. 534 00:30:47,890 --> 00:30:50,770 Mike Knodler: Yeah, that's there's a whole science that 535 00:30:50,770 --> 00:30:53,230 goes into this. You could actually make an entire career 536 00:30:53,230 --> 00:30:56,890 studying roadways. And so, for example, think about airports. 537 00:30:57,190 --> 00:31:00,475 It's kind of the same exact thing, but they're carrying much 538 00:31:00,475 --> 00:31:04,015 heavier vehicles and expectations. So so the design 539 00:31:04,135 --> 00:31:08,515 is really saying how much weight is that roadway going to carry, 540 00:31:08,755 --> 00:31:11,755 and then based on that weight, we'll govern a couple of things. 541 00:31:11,875 --> 00:31:15,715 So what types of materials we might use to build that roadway, 542 00:31:15,895 --> 00:31:20,275 and then oftentimes, how thick it is. So when we put together 543 00:31:20,395 --> 00:31:23,560 the types of materials with the thickness that gives us a 544 00:31:23,560 --> 00:31:27,640 strength. And so we're able to say, based on this anticipated 545 00:31:27,640 --> 00:31:31,000 load of weight, what what strength of roadway do we need? 546 00:31:31,000 --> 00:31:34,540 And then we construct that roadway with that strength so 547 00:31:34,540 --> 00:31:37,900 that we're able to make sure that the road doesn't break. 548 00:31:37,000 --> 00:31:40,600 Jane: It's not something that you would probably look for 549 00:31:40,600 --> 00:31:44,020 unless you're specifically keeping an eye out for it. But 550 00:31:44,080 --> 00:31:48,280 kids, if you're riding in the car or on a bus, and you look at 551 00:31:48,280 --> 00:31:52,000 the road sign, sometimes you will actually see a sign that 552 00:31:52,000 --> 00:31:56,380 tells vehicles how much weight they're allowed to have to be on 553 00:31:56,380 --> 00:32:00,160 that road. There is often a weight limit on a road, and it 554 00:32:00,160 --> 00:32:03,565 will say, you can, you cannot bring your truck on this road if 555 00:32:03,565 --> 00:32:06,985 it weighs more than, you know, 28,000 pounds, or whatever the 556 00:32:06,985 --> 00:32:10,945 road limit is. And in, again, in my town, some of our roads are 557 00:32:10,945 --> 00:32:14,545 dirt, and so at certain times of the year, heavy trucks aren't 558 00:32:14,545 --> 00:32:17,425 allowed on the road, but they are allowed along on the road 559 00:32:17,425 --> 00:32:19,825 when it's dry, or in the winter when it's frozen. 560 00:32:19,825 --> 00:32:22,285 Mike Knodler: Yeah, no, though. So the so a lot of times we 561 00:32:22,285 --> 00:32:24,970 think about bridges is a good example where obviously there's 562 00:32:24,970 --> 00:32:29,050 a weight concern at bridges, roadways themselves, and then on 563 00:32:29,050 --> 00:32:31,210 the highways. Sometimes, when you're driving on the highways, 564 00:32:31,210 --> 00:32:35,770 you'll see weigh stations where the police or similar, will be 565 00:32:35,770 --> 00:32:40,210 out there weighing trucks, because the single fastest way 566 00:32:40,210 --> 00:32:43,330 to destroy a road is to have an overweight truck drive on that 567 00:32:43,330 --> 00:32:47,095 road. It will, it will really break the material and break it 568 00:32:47,095 --> 00:32:49,375 down so that it ruins the roadway. Because once the 569 00:32:49,375 --> 00:32:52,675 roadway gets ruined, it's really, really hard to fix it. 570 00:32:53,035 --> 00:32:55,495 Jane: Well, both Hannah and Evelyn have noticed that 571 00:32:55,495 --> 00:32:59,995 sometimes roadways don't look as good or operate as well as they 572 00:32:59,995 --> 00:33:00,415 should. 573 00:33:00,475 --> 00:33:04,495 Hannah: My name is Hannah. I'm five years old, and I live in 574 00:33:04,495 --> 00:33:08,215 Roswell, Georgia. How does the road get cracks in it? 575 00:33:08,215 --> 00:33:14,860 Evelyn: My name is Evelyn. I live in Philadelphia, and I'm 576 00:33:14,860 --> 00:33:20,980 five years old. And my question is, why are roads sometimes so 577 00:33:20,980 --> 00:33:21,460 bumpy? 578 00:33:22,500 --> 00:33:24,900 Mike Knodler: When lots of cars go over that roadway all the 579 00:33:24,900 --> 00:33:28,440 time, and at the same time that pavement, or that roadway 580 00:33:28,440 --> 00:33:31,260 section, is having to sort of handle the elements of the 581 00:33:31,260 --> 00:33:36,660 weather. So sometimes it gets water on it, then the water goes 582 00:33:36,660 --> 00:33:39,120 into the pavement and then freezes, so it starts to break 583 00:33:39,120 --> 00:33:43,200 the pavement apart a little bit, and you put all these together 584 00:33:43,200 --> 00:33:45,045 and then at the same time, and this is one that people don't 585 00:33:45,045 --> 00:33:48,465 actually see. There's material underneath the ground. So the 586 00:33:48,465 --> 00:33:50,985 when it freezes, it actually starts pushing up on the roadway 587 00:33:50,985 --> 00:33:53,625 from the bottom. So we think about what the traffic is on the 588 00:33:53,625 --> 00:33:56,445 top, but the roads are sort of fighting from the bottom as 589 00:33:56,445 --> 00:33:59,625 well. Because, you know, as the temperature changes, the soil 590 00:33:59,625 --> 00:34:02,805 does some really interesting things as well. So, so that's 591 00:34:02,805 --> 00:34:07,005 what leads to cracks and potholes. And a lot of the 592 00:34:07,005 --> 00:34:10,110 deformations that you see is just the amount of loading that 593 00:34:10,110 --> 00:34:13,350 you'll, you'll, you'll regularly see as part of that. And then, 594 00:34:13,410 --> 00:34:16,350 you know, we can go out and we can do some maintenance to help 595 00:34:16,350 --> 00:34:19,530 sort of make roads last longer. But one of the things is it 596 00:34:19,530 --> 00:34:22,770 costs money, and so, you know, we don't always have the money 597 00:34:22,770 --> 00:34:25,470 available to go out and fix the roadways as soon as there's a 598 00:34:25,470 --> 00:34:29,250 crack. So usually, when you see one crack, you know that there's 599 00:34:29,250 --> 00:34:30,070 going to be another crack before long, and then there'll be 600 00:34:30,070 --> 00:34:32,475 another crack, and then you hope you're able to make the repair 601 00:34:32,475 --> 00:34:35,895 before you have to just fully redo the roadway. And so, so it 602 00:34:35,895 --> 00:34:38,955 becomes a bit of a game, trying to figure out when to do what, 603 00:34:38,955 --> 00:34:40,515 and then what to do specifically. 604 00:34:40,515 --> 00:34:43,335 Jane: Transportation is something that affects every one 605 00:34:43,335 --> 00:34:46,455 of us, and it's thanks to people like Mike that a lot of times we 606 00:34:46,455 --> 00:34:49,815 don't even think about the systems, even though they're all 607 00:34:49,815 --> 00:34:53,955 around us. Mike says one out of every ten jobs in the United 608 00:34:53,955 --> 00:34:57,000 States is related to transportation, which just goes 609 00:34:57,000 --> 00:35:00,480 to show how important these systems are in helping to make 610 00:35:00,480 --> 00:35:04,620 sure people and things get where they need to go safely and as 611 00:35:04,620 --> 00:35:08,940 speedily as is allowed. Thanks to Mike Knoedler for answering 612 00:35:08,940 --> 00:35:12,060 all of our transportation questions. As always, if you 613 00:35:12,060 --> 00:35:15,300 have a question about anything, have an adult record, you asking 614 00:35:15,300 --> 00:35:18,885 it on a smartphone using an app like voice memos, then have them 615 00:35:18,885 --> 00:35:23,385 email the file to questions@butwhykids.org. Uur 616 00:35:23,385 --> 00:35:26,505 show is produced by Sarah Baik, Melody Bodette, and me, Jane 617 00:35:26,505 --> 00:35:31,005 Lindholm at Vermont Public and distributed by PRX. Our video 618 00:35:31,005 --> 00:35:33,825 producer is Joey Palumbo, and our theme music is by Luke 619 00:35:33,825 --> 00:35:37,065 Reynolds. If you like our show, please have your adults help you 620 00:35:37,065 --> 00:35:40,665 give us a thumbs up or a review on whatever podcast platform you 621 00:35:40,710 --> 00:35:45,030 use, it really helps other kids and families find us. We'll be 622 00:35:45,030 --> 00:35:49,350 back in two weeks with an all new episode. Until then, beep, 623 00:35:49,350 --> 00:35:51,690 beep. Stay curious.