WEBVTT - How Railroad Crossing Signals Work 0:00:00.320 --> 0:00:02.880 Brought to you by the reinvented two thousand twelve camera. 0:00:03.240 --> 0:00:08.959 It's ready. Are you get in touch with technology with 0:00:09.039 --> 0:00:17.720 tech stuff from how stuff works dot com. Hello, everyone, 0:00:17.760 --> 0:00:20.479 welcome to tech stuff. My name is Chris Poulette and 0:00:20.520 --> 0:00:23.080 I am an editor at how stuff works dot com. 0:00:23.079 --> 0:00:26.800 Sitting across from me is senior writer Jonathan Strickland. I 0:00:26.880 --> 0:00:30.040 hear that train of coming. It's coming around the bend. 0:00:31.680 --> 0:00:35.440 So did you engineer that quote? No, actually I did 0:00:35.440 --> 0:00:39.120 not engineer that. That was That was something conducted by 0:00:39.159 --> 0:00:42.479 someone else. That was such a terrible stretch. But you 0:00:42.520 --> 0:00:45.040 know what, I'm gonna save myself here by going into 0:00:45.080 --> 0:00:53.320 a little listener mail. This listener mail comes from Weston, 0:00:53.360 --> 0:00:56.280 who says, Hi, my name is Weston. Well I know Weston. 0:00:56.320 --> 0:00:59.360 I just said that I'm from South Carolina and looking 0:00:59.400 --> 0:01:02.279 through your white extensive list of podcasts, I could not 0:01:02.400 --> 0:01:06.039 find one that involved how railroad crossing signals work. So 0:01:06.080 --> 0:01:07.959 I was wondering if you could explain that, and if 0:01:07.959 --> 0:01:10.760 you could explain how railroad crossing systems tie into traffic 0:01:10.760 --> 0:01:13.960 signals in more urban districts. Thanks a lot, keep doing 0:01:14.000 --> 0:01:17.560 your thing. Well, thanks Weston. Yes it is true. We 0:01:17.680 --> 0:01:21.920 had not done a podcast on railroad crossing signals. Uh, 0:01:22.800 --> 0:01:25.760 it just never honestly occurred to me, and in fact, 0:01:25.880 --> 0:01:29.759 until I started researching this, I had no idea how 0:01:29.800 --> 0:01:33.959 complicated it really was. That's true, although they have changed 0:01:34.000 --> 0:01:36.480 over the years too to some degree. Yeah, it used 0:01:36.480 --> 0:01:39.360 to be that the railroad crossing signal was that the 0:01:39.480 --> 0:01:42.319 train in very busy areas, the train would come to 0:01:42.360 --> 0:01:45.920 a stop. A flag man would go to the crossing 0:01:45.959 --> 0:01:49.640 area and and manually stop traffic for the train to 0:01:49.640 --> 0:01:53.360 pass through, and then would go jog get back on 0:01:53.400 --> 0:01:55.520 the train and then everything would start up again. So 0:01:55.560 --> 0:02:00.120 that's about you know, that's pretty simple technology. Yeah, have 0:02:00.160 --> 0:02:02.440 to agree that that's uh well, there's not a lot 0:02:02.480 --> 0:02:05.840 of electronic technology involved in that. At night, sometimes they'd 0:02:05.880 --> 0:02:10.079 use flares. I've actually seen that. I've there was a 0:02:10.160 --> 0:02:14.280 rural crossing, a railroad crossing in northern Georgia, which is 0:02:14.320 --> 0:02:16.720 where I grew up. What you can tell because of 0:02:16.760 --> 0:02:21.160 my deep Southern accent, But in in rural Georgia there 0:02:21.240 --> 0:02:23.920 was a crossing at one point. I remember as a 0:02:24.000 --> 0:02:25.760 kid we came up to it, and I think the 0:02:25.800 --> 0:02:30.040 reason for using the flares was not because there was 0:02:30.080 --> 0:02:34.120 no modern crossing signal there. I think the modern crossing 0:02:34.120 --> 0:02:37.919 signal was unfortunately out of order, and so they were 0:02:38.000 --> 0:02:41.320 using the flares as a backup system and UH, and 0:02:41.440 --> 0:02:43.720 that's exactly what they did. They stopped the train, a 0:02:43.760 --> 0:02:47.320 guy got out and lit some flares along the side 0:02:47.400 --> 0:02:51.200 of the tracks, and then the train went through and 0:02:51.240 --> 0:02:54.359 we had to wait, and then we drove on by. 0:02:54.680 --> 0:02:57.359 Well then it actually seems like it could be a 0:02:57.400 --> 0:02:59.720 little bit more reliable than some of the technology that 0:02:59.800 --> 0:03:03.720 we we're researching. UM. I have to have to give 0:03:03.760 --> 0:03:09.000 any shout out actually to uh matt Enus who has 0:03:09.040 --> 0:03:15.000 a really awesome website about the electronics behind railroad crossing 0:03:15.120 --> 0:03:18.280 signal technology and it's it's very very through. Apparently he 0:03:18.360 --> 0:03:21.239 really likes electronics and trains, so this was sort of 0:03:21.240 --> 0:03:23.600 a natural for him. Yeah, you can find his his 0:03:24.440 --> 0:03:28.160 website at Matt dot z o n T dot org. 0:03:28.960 --> 0:03:31.160 I thought i'd give a shout out because I also 0:03:31.200 --> 0:03:34.200 found it really helpful. He has lots of of of 0:03:34.200 --> 0:03:39.080 technical drawings for for circuitry as well as some great animations. 0:03:39.400 --> 0:03:43.240 It really makes understanding this UH a lot easier, although 0:03:43.280 --> 0:03:46.560 again it's still a very when you get if you 0:03:46.600 --> 0:03:50.640 really dig down, it's still really complicated. Well A said it. 0:03:50.680 --> 0:03:53.320 As it turns out, just about every type of signal 0:03:54.080 --> 0:03:59.320 UH crossing signal uses some form of an electronic relay 0:03:59.880 --> 0:04:02.880 or I should say electrical relay. Um. And a lot 0:04:02.880 --> 0:04:06.520 of it has to do with basically detecting that a 0:04:06.600 --> 0:04:10.480 train is coming. Now it's not necessarily from a distance. 0:04:10.840 --> 0:04:13.119 In a lot of cases, it's basically when it's right 0:04:13.200 --> 0:04:16.599 on top of the crossing, not literally right now, when 0:04:16.760 --> 0:04:19.520 when it's right there at the crossing before it gets 0:04:19.560 --> 0:04:22.600 to the uh for it actually gets to the intersection 0:04:22.640 --> 0:04:26.480 with a roadway. Yeah. Yeah, so there are some there 0:04:26.480 --> 0:04:29.200 are lots of different types of these these systems, we 0:04:29.240 --> 0:04:32.640 should say, because first of all, uh, it's it's easy 0:04:32.720 --> 0:04:37.880 to forget that the railroad system is not a unified 0:04:38.120 --> 0:04:41.960 thing overseen by a single entity. No, that's correct. There 0:04:42.000 --> 0:04:46.320 are several railroad systems throughout the United States alone, and 0:04:46.360 --> 0:04:47.960 you know that's just the United States where you know, 0:04:48.240 --> 0:04:50.640 it gets way more complicated when you're looking at things 0:04:50.680 --> 0:04:54.039 like international railroad systems that go through most of Europe 0:04:54.160 --> 0:04:57.960 for example. UM. So, because there are all these different 0:04:58.040 --> 0:05:00.000 entities that are running the railroads, I mean there are 0:05:00.000 --> 0:05:04.560 are certain standards, like railroads are railroad rails are at 0:05:04.600 --> 0:05:08.640 a standard with where else your trains cannot go from 0:05:08.640 --> 0:05:13.599 one system to another. But things like the signaling systems 0:05:13.640 --> 0:05:17.840 the electronics they use are not necessarily standard across the board. 0:05:17.839 --> 0:05:20.200 They're all supposed to operate in a standard way, but 0:05:20.640 --> 0:05:23.760 the way you get there is not necessarily standard. If 0:05:23.760 --> 0:05:26.560 that makes sense. Well, what I thought we might do 0:05:26.680 --> 0:05:29.520 is actually talk about the signals themselves, and then we 0:05:29.520 --> 0:05:33.440 could talk about the way that they're triggered me because um, 0:05:33.720 --> 0:05:37.160 you know, and at a given intersection. Actually, that's that's 0:05:37.240 --> 0:05:39.599 another good point back to what you just said, was 0:05:40.200 --> 0:05:45.160 um that not every signal, uh, not every crossing has 0:05:45.200 --> 0:05:49.200 the same types of signals either, even on the same uh, 0:05:49.279 --> 0:05:52.280 even on the same railroad. So you know a lot 0:05:52.320 --> 0:05:54.840 of times you'll see you know, the signal mast, which 0:05:54.880 --> 0:05:57.479 is that poll with the lights on either side of it. Hum. 0:05:57.520 --> 0:06:01.680 And basically this is just a current flowing through, just 0:06:01.760 --> 0:06:04.560 like you would with a typical light bulb. Um, but 0:06:04.760 --> 0:06:09.080 it's it's got a relay, a flasher relay between that 0:06:09.240 --> 0:06:12.000 basically alternates the circuits. So one light goes on the 0:06:12.040 --> 0:06:14.200 other one goes off. Then they switch back and forth, 0:06:14.240 --> 0:06:15.960 back and forth. Yeah, I think it pretty easy. Think 0:06:15.960 --> 0:06:18.279 of the flasher relay is kind of like a switch 0:06:18.960 --> 0:06:21.360 that opens and closes, but when it when it when 0:06:21.400 --> 0:06:24.040 it opens for one side, it's closed for the other 0:06:24.120 --> 0:06:27.240 and vice versa. So as long as power is running 0:06:27.240 --> 0:06:29.720 through this, one side of the lights will light up 0:06:29.760 --> 0:06:32.640 and the other side will remain dark. And it alternates, 0:06:32.640 --> 0:06:36.120 and that's what creates the flashing pattern. And they alternated. 0:06:36.360 --> 0:06:39.480 There's one way that it can be alternated. Again. There 0:06:39.480 --> 0:06:42.560 are lots of systems, but one way that they can 0:06:42.600 --> 0:06:47.120 alternate is through using electromagnets. Our old friend, the electromagnets, right, 0:06:47.200 --> 0:06:51.680 So the electro magnets will have a set of coils 0:06:51.680 --> 0:06:54.320 on either side, and when one set of coils gets power, 0:06:54.760 --> 0:06:57.960 that pulls the switch to that side and creates a 0:06:58.000 --> 0:07:01.159 magnetic field which pulls the switch her. That's what lights 0:07:01.240 --> 0:07:04.640 up the lights on one side, and then the other 0:07:04.680 --> 0:07:06.760 set of coils will get power. The first set will 0:07:06.760 --> 0:07:09.679 lose power, so now the switch will be pulled back 0:07:09.760 --> 0:07:11.720 to the other side, which will light up the other 0:07:11.760 --> 0:07:14.400 side of the lights. And alternating this back and forth 0:07:14.520 --> 0:07:17.160 is what gives you that click click click click as 0:07:17.200 --> 0:07:21.360 the as the flashers go on and off. Uh. I 0:07:21.400 --> 0:07:26.080 will have to say, though, that this behavior changes dramatically 0:07:26.200 --> 0:07:30.360 if you happen to be within a certain distance of UFOs, 0:07:31.160 --> 0:07:36.720 as seen in the documentary but nothing but Close Encounters 0:07:36.720 --> 0:07:38.560 of the Third Kind? Man, did you not watch it? 0:07:38.600 --> 0:07:42.080 I mean those lights went crazy. This means something, This 0:07:42.160 --> 0:07:45.680 is important. Okay, that was That was clearly a joke. 0:07:45.720 --> 0:07:48.960 I was referencing a Spielberg movie, Close Encounters of the 0:07:48.960 --> 0:07:52.080 Third Kind. I do not, in fact believe that aliens 0:07:52.120 --> 0:07:55.680 affect our railroad crossings at some too busy messine with 0:07:55.720 --> 0:07:59.280 our fast food restaurants. At some point we should uh 0:07:59.600 --> 0:08:03.720 do a podcast on why every time aliens come down 0:08:04.120 --> 0:08:09.720 your radio dial changes and the rail road You're always 0:08:09.760 --> 0:08:13.120 near a railroad. You know what drives me stuff podcast? 0:08:13.120 --> 0:08:15.520 I'm listening to the radio and next thing, you know, 0:08:15.600 --> 0:08:18.160 aliens come down and it switches the golden oldies. I 0:08:18.200 --> 0:08:21.720 just hate that. Um And we got a little off 0:08:21.880 --> 0:08:27.560 track on our railroad podcast speaking speaking of electromagnets, so 0:08:27.640 --> 0:08:31.400 that the same the same uh things sort of applies 0:08:31.440 --> 0:08:34.640 to the bell. The bell that goes clian client client clang, 0:08:34.679 --> 0:08:37.840 that tells you that's going on, except, um, what's going 0:08:37.920 --> 0:08:41.680 on there is the electromagnet is pushing the clapper to 0:08:41.760 --> 0:08:43.400 the bell. The clapper is the thing. If you're not 0:08:43.400 --> 0:08:46.959 familiar with bell technology, and I'm not talking about mob bell, 0:08:47.920 --> 0:08:51.960 it's got the il communication. Um, you got the clapper 0:08:52.040 --> 0:08:54.800 being pushed to the side of the bell by an electromagnet. 0:08:55.040 --> 0:08:56.880 But the thing is the thing. I thought it was 0:08:56.920 --> 0:08:59.560 cool about this at least according to to Matt's page. 0:09:00.120 --> 0:09:02.720 Is what happens is once the clapper reaches the bell, 0:09:02.920 --> 0:09:07.040 it's breaking the connection uh to the electrone, so it 0:09:07.120 --> 0:09:09.760 pulls it back and it pushes it back again. So 0:09:09.800 --> 0:09:12.560 it's just snapping back and forth. It's the momentum that 0:09:12.600 --> 0:09:15.080 carries it forward so that it actually makes contact with 0:09:15.120 --> 0:09:17.560 the bell. Yes, and then it gets pulled back to 0:09:17.600 --> 0:09:20.800 its original position where again where and then it gets 0:09:20.800 --> 0:09:23.680 pushed again. Yeah and yeah, that's kind of that's pretty neat. 0:09:24.240 --> 0:09:26.360 And of course it's happening at a regular interval because 0:09:26.400 --> 0:09:29.240 of the the length I guess of the piece, the 0:09:29.280 --> 0:09:33.480 physical clapper piece. It's it's a centrical same same principle 0:09:33.559 --> 0:09:36.480 that you'll find on other alarm bells, things like you 0:09:36.520 --> 0:09:39.480 know the classic fire station alarm bell works on the 0:09:39.520 --> 0:09:42.840 same principle. I'm sorry that kind of alarms me. Yeah, 0:09:42.920 --> 0:09:44.680 well I live right next to a fire station, so 0:09:45.720 --> 0:09:51.120 really familiar with the fire station bell. Okay. So the 0:09:51.160 --> 0:09:55.240 gates that drop down in front of the uh the crossing, 0:09:55.280 --> 0:09:58.160 you know, the red and white bars basically if that, 0:09:58.360 --> 0:10:01.520 sometimes have lights on them. Sometimes I don't. UM, they 0:10:01.640 --> 0:10:04.440 use a different kind of technology. They actually use a 0:10:04.440 --> 0:10:07.600 motor UM and there's a relay called the motor control 0:10:07.600 --> 0:10:12.679 relay that basically allows the the motor to operate in 0:10:12.679 --> 0:10:15.400 one direction as the gate comes down. So basically it 0:10:15.559 --> 0:10:17.600 is starting to push the gate down and at a 0:10:17.600 --> 0:10:19.640 certain point, of course, you know, there's a weight on 0:10:19.640 --> 0:10:22.920 the other end to counterbalance and um, at a certain 0:10:22.920 --> 0:10:26.000 point the gate would come crashing down, so about midway 0:10:26.040 --> 0:10:30.080 down or so, the relay switches the motor to prevent 0:10:30.160 --> 0:10:33.720 it from the gate from crashing down too quickly. So 0:10:33.760 --> 0:10:35.680 on what you know, at the beginning, it's starting it 0:10:35.760 --> 0:10:37.959 down and then the bottom is like oh okay, okay, okay, 0:10:38.000 --> 0:10:40.040 not too fast, not too fast, all right, there you go. 0:10:40.280 --> 0:10:42.920 So yeah, so in one case it's actually pushing it downward, 0:10:42.960 --> 0:10:45.120 and in the other case, it's pushing upward, but not 0:10:45.360 --> 0:10:47.439 so hard that it makes the gate go right back 0:10:47.520 --> 0:10:50.959 up again, right, and just slows the gates decent. Yeah. 0:10:51.160 --> 0:10:53.760 And and of course there are many ways to achieve 0:10:53.840 --> 0:10:56.720 this effect. Apparently it has to do with the manufacturer 0:10:56.760 --> 0:11:00.440 of the gear. Um, at least according to Matt, it's 0:11:00.440 --> 0:11:04.560 really useful railroad signal technology page. Yeah. And and the 0:11:04.600 --> 0:11:07.120 reason you don't want those gates coming down too quickly, 0:11:07.200 --> 0:11:08.920 I mean, apart from the fact that it's gonna cause 0:11:09.000 --> 0:11:11.360 way too much wear and tear in your equipment, is 0:11:11.400 --> 0:11:15.600 that you don't want to whack cars that are in 0:11:15.679 --> 0:11:21.040 the the the railroad area when the signal is activated. 0:11:21.080 --> 0:11:22.400 You know, you have to have enough time for the 0:11:22.440 --> 0:11:26.280 car to clear. Um. That's also that's really the chief 0:11:26.320 --> 0:11:29.240 reason for the bell. The bell is really there to 0:11:29.320 --> 0:11:32.280 let people know people who are on the tracks at 0:11:32.320 --> 0:11:34.640 that moment as they're crossing over, that hey, there's a 0:11:34.679 --> 0:11:38.719 train in coming, your best get some moving. But that 0:11:38.840 --> 0:11:40.720 they use the bell ringing noise because they found that 0:11:40.800 --> 0:11:42.960 having an old guy send and they're yelling that out 0:11:43.040 --> 0:11:47.760 just wasn't nearly as effective. Yeah. Yeah, it's um one 0:11:47.800 --> 0:11:51.240 of those things that people still try to circumvent quite 0:11:51.240 --> 0:11:55.079 frequently terrible, terrible idea. It's a very very bad idea 0:11:55.120 --> 0:11:58.880 to try to drive around the gates um or you know, 0:11:59.520 --> 0:12:01.960 if you have to be any crossing, like there is 0:12:02.040 --> 0:12:06.840 one near my house, Um, people often go through and 0:12:06.880 --> 0:12:09.560 sit there on the track waiting for the light change. 0:12:10.440 --> 0:12:13.360 And that's just a bad idea. Yeah, you don't want 0:12:13.360 --> 0:12:15.480 to be there. There are stories I could tell, but 0:12:15.520 --> 0:12:19.160 I won't, but yeah, it's just a bad idea. So 0:12:19.200 --> 0:12:22.080 that got that. That covers the UH the basics of 0:12:22.120 --> 0:12:26.439 the arms and the mast, yeah, and the lights that 0:12:27.520 --> 0:12:30.880 in the so and the these this system. By the way, 0:12:30.960 --> 0:12:35.040 you asked Weston specifically about how that works within urban areas. 0:12:35.559 --> 0:12:42.760 The system can be keyed into any adjacent UH traffic signal. Essentially, 0:12:42.760 --> 0:12:46.559 it's just part of that traffic signals cycle. So if 0:12:46.600 --> 0:12:52.319 the traffic signal receives UM signal from the railroad crossing 0:12:52.400 --> 0:12:57.160 its superseds, anything else on that intersection, so instead of 0:12:57.160 --> 0:12:59.760 the lights cycling through as they normally would, it'll be 0:13:00.080 --> 0:13:04.440 stuck on a particular setting. So maybe like the parallel 0:13:04.520 --> 0:13:08.120 road would still get green, but the road that would 0:13:08.120 --> 0:13:12.160 intersect would have a red until the until the signal 0:13:12.280 --> 0:13:15.720 from the railroad crossing gave the all clear. Yes, that's 0:13:15.720 --> 0:13:18.559 that's exactly how it works. At the crossing near my house. 0:13:18.679 --> 0:13:22.400 It blocks out all the traffic that would necessarily cross. 0:13:22.440 --> 0:13:26.520 And the thing is, I've I've seen cars unfortunately who 0:13:26.679 --> 0:13:30.080 uh not unfortunately in the other sense we were speaking 0:13:30.080 --> 0:13:32.199 of earlier, the ones who get there at the red 0:13:32.320 --> 0:13:35.600 light waiting to cross. There's there are basically two sets 0:13:35.600 --> 0:13:38.319 of there's two roads, one on either side of the 0:13:38.360 --> 0:13:41.040 tracks parallel to it, and they'll go and they'll wait 0:13:41.040 --> 0:13:43.840 on that red light and then the gates will come down. 0:13:43.840 --> 0:13:46.160 They're going, Ah, you gotta be kidding me. I mean, 0:13:46.240 --> 0:13:48.040 there's a train coming and now I have to wait 0:13:48.040 --> 0:13:50.040 through this. Yeah, this was gonna be maybe a min 0:13:50.080 --> 0:13:52.440 and a half way, and now I'm looking at upwards 0:13:52.440 --> 0:13:54.880 of three to ten minutes just fitting on the train. 0:13:55.080 --> 0:13:57.160 I gotta say, though, I did have that happen to 0:13:57.160 --> 0:13:59.360 me not that long ago, but it ended up being 0:13:59.480 --> 0:14:02.400 a thing as opposed to a bad thing, because it 0:14:02.480 --> 0:14:07.120 was a circus train. It was actually really cool. That's yeah, 0:14:07.559 --> 0:14:13.240 um Dumbo waved, Okay, Well, actually that's that. This is 0:14:13.280 --> 0:14:17.120 where it stops being quite so simple to explain, because 0:14:17.440 --> 0:14:21.480 those are the signals. But triggering the signals, that's that's 0:14:21.520 --> 0:14:24.480 a little more more tricky. Let's let's talk in a 0:14:24.560 --> 0:14:27.360 really high level way, because if you dig down, it 0:14:27.400 --> 0:14:29.840 just gets to the point where you really need a 0:14:29.920 --> 0:14:35.000 good I was about, say, grounding a good understanding of 0:14:35.280 --> 0:14:39.840 electrical engineering in order to uh, to really follow and 0:14:39.920 --> 0:14:43.760 because probably I would guess most of our audience doesn't 0:14:43.800 --> 0:14:46.120 have that necessarily. I'm sure there's some of you who do, 0:14:46.880 --> 0:14:49.400 but I think the general audience probably doesn't. It would 0:14:49.400 --> 0:14:51.920 just be it would be torturous for us to try 0:14:51.960 --> 0:14:53.880 and walk through it. Yeah, I'm not sure that I 0:14:53.920 --> 0:14:58.880 have the the basics down enough. Sure I don't have 0:14:58.920 --> 0:15:01.200 the basics down, but we can talk a little bit 0:15:01.200 --> 0:15:05.720 about it from a high level. Um that virtually any 0:15:05.760 --> 0:15:08.960 of the crossings that have electronic signals, you're gonna see 0:15:09.120 --> 0:15:11.520 one of those boxes like you would see at a 0:15:11.520 --> 0:15:14.720 at an intersection in an urban environment that has a 0:15:14.720 --> 0:15:18.280 series of relays and basically a couple of batteries in it. 0:15:18.720 --> 0:15:22.440 You might say, why does it need the batteries? Well, Um, 0:15:22.560 --> 0:15:27.400 the tracks around the railroad crossing have a circuit in 0:15:27.440 --> 0:15:32.760 them that helps control the railroad crossing signals. Yeah, let's 0:15:33.400 --> 0:15:35.520 to kind of give it a basic set, all right. 0:15:35.600 --> 0:15:39.600 Imagine that you have a stretch of railroad track, okay, 0:15:40.040 --> 0:15:43.440 and that you are approaching You're you're walking along the 0:15:43.520 --> 0:15:46.200 railroad track, and you're you're gradually getting to a point 0:15:46.200 --> 0:15:51.800 where the railroad is going to intersect with a road. Now, 0:15:52.080 --> 0:15:54.920 as you're walking along that track, you will eventually come 0:15:54.920 --> 0:15:58.280 to a point where there will be a special insulator 0:15:58.480 --> 0:16:03.840 block that is on each rail. Now, this insulator block, 0:16:03.920 --> 0:16:06.440 the whole reason for this is to allow there to 0:16:06.520 --> 0:16:09.640 be a circuit along a stretch of track. If you 0:16:09.680 --> 0:16:12.440 didn't have that insulator block there, the the electricity would 0:16:12.480 --> 0:16:16.120 just flow through the entire track and just disperse essentially 0:16:16.720 --> 0:16:20.480 because you would have like the world's biggest circuit. So 0:16:20.520 --> 0:16:22.560 you have to block it off. Yeah, and this is 0:16:22.600 --> 0:16:26.560 not the kind of charge like you'd see on light rail, um, 0:16:26.600 --> 0:16:28.480 you know the third rail. Yeah, this is not to 0:16:28.680 --> 0:16:31.240 provide power to the train at all. No, No, it's 0:16:31.280 --> 0:16:35.640 just detection system. Yeah exactly. So you've got you've got 0:16:35.680 --> 0:16:39.840 these insulators, that's what blocks the electric signal from continuing through. Uh, 0:16:40.120 --> 0:16:44.280 You've got and you have relays connecting the two tracks together, 0:16:44.520 --> 0:16:47.840 and you constantly have a low level of power going 0:16:47.920 --> 0:16:53.800 through this this basic circuit all right. Now, Uh, there's 0:16:53.840 --> 0:16:59.720 usually another insulator block somewhere near where the actual road intersects, 0:17:00.040 --> 0:17:03.040 and then you have a second set of circuits on 0:17:03.080 --> 0:17:06.199 the other side and in its most basic form. And 0:17:06.240 --> 0:17:08.439 the reason for that is so that you can detect 0:17:08.480 --> 0:17:11.399 when the train passes from one one part of the 0:17:11.440 --> 0:17:14.560 track to another part. And that's important because eventually you're 0:17:14.600 --> 0:17:18.000 gonna have to have these signals stop signaling. You have 0:17:18.040 --> 0:17:21.280 to have something that tells the electronics, Hey, the train's gone, 0:17:21.560 --> 0:17:23.640 turn off the flashers, turn off the bell, and lift 0:17:23.680 --> 0:17:26.520 the gates. Yes. He As a matter of fact, the 0:17:26.520 --> 0:17:29.399 the part of the track approaching an intersection is called 0:17:29.480 --> 0:17:34.360 the approach yes, which by the way, is not always 0:17:34.400 --> 0:17:38.280 the same side because trains, because some tracks will allow 0:17:38.359 --> 0:17:42.640 trains that travel in either direction, So the approach is 0:17:42.680 --> 0:17:46.520 completely dependent upon the direction the train is coming from 0:17:46.560 --> 0:17:49.800 at any particular time. So the approach side will change 0:17:49.840 --> 0:17:53.720 depending on the where the trains coming from. Um. Now, 0:17:54.160 --> 0:17:58.800 when a train crosses over the insulator and hits the 0:17:58.840 --> 0:18:02.480 section of track where you've got that circuit, the trains 0:18:02.520 --> 0:18:06.679 wheels are steel. The axle connecting the wheels are steel. 0:18:07.920 --> 0:18:11.000 This massive amount of steel when it makes contact with 0:18:11.080 --> 0:18:15.520 the tracks creates a short circuit, which means that it's 0:18:15.560 --> 0:18:17.600 it's it's pulling the power, so it's no longer going 0:18:17.640 --> 0:18:19.800 through the relay like it normally what it's going through 0:18:19.800 --> 0:18:24.879 the axle instead, and that's what is That's what creates 0:18:24.960 --> 0:18:28.360 the the alert for the signaling system that hey, there's 0:18:28.359 --> 0:18:32.680 a train coming. Now. There are other problems with this, yes, 0:18:33.080 --> 0:18:34.800 one of the big ones is that this does not 0:18:34.960 --> 0:18:39.199 tell we're acting like this is all like you know, 0:18:39.240 --> 0:18:42.560 they're all coherent and cognitive. It's not. But this does 0:18:42.600 --> 0:18:45.919 not indicate how fast that train is moving, just that 0:18:46.000 --> 0:18:48.600 there is a short circuit, and therefore the signal should 0:18:48.640 --> 0:18:51.240 go off right. So you have a couple of different 0:18:51.520 --> 0:18:53.960 things you have to take into consideration there. One is, 0:18:55.000 --> 0:18:57.520 are all the trains that are traveling on this track 0:18:57.960 --> 0:19:00.680 generally going to be moving at the same speed. If 0:19:00.680 --> 0:19:03.639 they are, that makes this problem way easier to solve, 0:19:03.680 --> 0:19:05.960 because what the problem is you need to figure out 0:19:06.359 --> 0:19:09.920 how long from the moment that this short circuit happens, 0:19:10.240 --> 0:19:14.879 should the signals. What's the time delay between when the 0:19:14.880 --> 0:19:18.760 short circuit happens and when the signals activate, right, because 0:19:18.880 --> 0:19:21.640 if the train is too far back and the signals activate, 0:19:21.680 --> 0:19:24.639 you you take everybody off because they're like, well, look, 0:19:24.680 --> 0:19:27.600 the gate came down and I've been waiting here for 0:19:27.600 --> 0:19:30.160 for fifteen seconds and I still don't see a train. 0:19:30.240 --> 0:19:33.720 I'm just gonna go, and that's going to cause a problem. Um. 0:19:33.760 --> 0:19:35.480 In other cases, you may have a train this moving 0:19:35.640 --> 0:19:39.159 so quickly that when it triggers the short circuit, it 0:19:39.200 --> 0:19:44.200 actually reaches the intersection before the signals go off, so 0:19:44.320 --> 0:19:46.760 you have to take that into account. Now, if all 0:19:46.800 --> 0:19:48.760 the trains are moving at the same speed, you just 0:19:48.880 --> 0:19:54.680 figure the right distance from the crossing and you install 0:19:54.760 --> 0:19:58.760 everything that way, and then there's no problem relatively speaking, 0:19:58.800 --> 0:20:01.520 because the trains are always going to hit the intersection 0:20:01.560 --> 0:20:03.359 at around the same time, so you can time it 0:20:03.400 --> 0:20:06.320 out that way. If the trains are gonna be moving 0:20:06.320 --> 0:20:08.680 at different speeds, then you have to figure out, okay, well, 0:20:09.280 --> 0:20:12.840 how do I indicate how fast this train is going. 0:20:13.080 --> 0:20:15.520 You can either fudget where you kind of take an 0:20:15.560 --> 0:20:17.879 average speed of all the trains that tend to go 0:20:17.960 --> 0:20:21.639 across that track, or you can pick the trains that 0:20:21.680 --> 0:20:25.280 are the most common, like the ones that are are 0:20:25.400 --> 0:20:27.720 usually on that track or that travel through there during 0:20:27.760 --> 0:20:31.439 high traffic areas and use that speed. Or you can 0:20:31.520 --> 0:20:36.320 install sensors that actually do indicate you know how fast 0:20:36.400 --> 0:20:39.159 the train is going and then send that information to 0:20:39.680 --> 0:20:44.120 the control system to alert it when it should initiate 0:20:44.200 --> 0:20:49.320 the warning. So those are your various options. But yeah, 0:20:49.400 --> 0:20:51.960 that's it's all about short circuiting, which is kind of 0:20:51.960 --> 0:20:54.000 cool because when you think about it, you know, the 0:20:54.320 --> 0:20:59.800 connotation of the term short circuit has usually a fairly 0:21:00.000 --> 0:21:03.000 negative feel to it, right, you know, you know, you 0:21:03.080 --> 0:21:06.240 normally don't want things to short circuit unless you're Johnny 0:21:06.280 --> 0:21:11.000 five nice. Yeah, I like that. I figured I had 0:21:11.040 --> 0:21:15.080 to work that in there. Well, he was alive, he 0:21:15.160 --> 0:21:20.280 was theoretically, Um, So the thing is you have so 0:21:20.320 --> 0:21:23.000 that that's basically how it knows it's coming. The question 0:21:23.080 --> 0:21:27.879 is how the crossing signal UH is notified when the 0:21:27.880 --> 0:21:31.520 train is gone. And so basically there are are two 0:21:31.560 --> 0:21:36.040 sets of tracks there too, since there are two approaches, 0:21:36.080 --> 0:21:38.639 because theoretically, if a train could come from either direction, 0:21:38.640 --> 0:21:41.199 you would want that anyway, but you also need the 0:21:41.240 --> 0:21:46.320 other approach to to notify it too. Because um, as 0:21:46.400 --> 0:21:49.199 the train passes from one side of the crossing to 0:21:49.280 --> 0:21:53.439 the other, there is another uh, there's another circuit too short. 0:21:54.160 --> 0:21:59.320 And when both sets of circuits are therefore untriggered anymore, 0:21:59.359 --> 0:22:01.919 that means, well, the train has come and gone, and 0:22:01.960 --> 0:22:04.440 those signals can you know, the the arms go back 0:22:04.520 --> 0:22:06.320 up and the lights go back off, and the bell 0:22:06.400 --> 0:22:10.880 stops clanging most of the time, but there are problems 0:22:10.960 --> 0:22:13.600 with it it you know, those of you who live 0:22:13.680 --> 0:22:18.240 near railroad tracks and have seen trains do this annoying behavior. 0:22:18.600 --> 0:22:21.040 Um because of course they probably have to. There are 0:22:21.080 --> 0:22:23.080 reasons why they have to. But for the driver it's 0:22:23.119 --> 0:22:25.080 kind of annoying to sit there and watch a train 0:22:25.840 --> 0:22:30.160 stop and then back up a little bit, and you're going, 0:22:30.200 --> 0:22:32.280 how long do I have to wait? Well, that does 0:22:32.359 --> 0:22:35.400 happen from time to time. They're there, you know, traffic 0:22:35.440 --> 0:22:38.520 issues to be considered. And the thing is the relays 0:22:38.720 --> 0:22:43.040 aren't exactly endowed with a lot of artificial intelligence. They 0:22:43.160 --> 0:22:45.840 they're either on or they're off right, And there are 0:22:45.840 --> 0:22:48.639 times when a track, a train can pass through an 0:22:48.680 --> 0:22:52.120 intersection and then it has to back up for traffic 0:22:52.119 --> 0:22:54.960 reasons a little bit, and that triggers the signal again, 0:22:55.080 --> 0:22:58.560 and then when it leaves, it's you know, there, there's 0:22:58.680 --> 0:23:00.440 it can it can trip the signal to a point 0:23:00.440 --> 0:23:04.159 where the next train that comes from from uh, you know, 0:23:04.520 --> 0:23:06.479 I'm not sure if it comes from that direction from 0:23:06.520 --> 0:23:10.080