How Do Traffic Signals Work?

[@stephen_l1474]

Simple! They show red light when I am near, they show green when I am not.

[@uncle_cezar]

This! 😂

[@GamingWithNikolas]

True

[@antonirajasa7260]

Hahaha correct 😅

[@mojo6385]

you need to get a job driving a firetruck

[@astromec6303]

Well in France, I have almost the opposite feeling (at least in the town I live, which doesn’t have a that large population). The traffic light is often green, and when it’s not, the red phase is relatively short.

[@Kezenmacher]

Here in germany the amber light also turns on for a brief moment, when it goes from red to green. This allows the drivers to engage the clutch early, and start driving as soon as the light turns green.

[@phyphor]

In the UK, too, we have Red -> Red + Amber -> Green -> Amber -> Red www.gov.uk/guidance/the-highway-code/light-signals-controlling-traffic

[@operator8014]

We need that here in the U.S. so bad.

[@PatricioHondagneuRoig]

*THIS IS HOW IT SHOULD BE* In Argentina the lights go from red to green and as a pedestrian you can end up trapped in the middle of the road. As always, Germany's three steps ahead.

[@RealCadde]

No, what "we" (as in anywhere) needs is countdown timers telling you how many seconds are left on that particular stage so drivers who will be arriving at a red knows how long they'd have to wait so they can just slow down enough to never come to a complete stop at the lights.

[@ABaumstumpf]

There are many things that could be improved in many countries, but changing traffic laws is not easy cause that would require everybody to learn about those laws and train them. Things like the US were turning right despite red light is allowed in many cities can really help on some streets. There are also traffic-lights that tell the time till they switch again, and some where the light extends all over the pole to make it easier to see (i know some intersections where the ONLY light is like 7m high up and right above the stop-line. You have to keep 2-3 m distance and it is still hard to see)

[@Ian-jq4zg]

Light: *turns yellow to warn drivers to slow down because it's turning red* Drivers: *speeds up because it's turning red*

[@tyllisxu5774]

Now we know if we can get there on time since he said how long yellow lights last :)

[@nenblom]

AMEN and then they could wind up blocking the intersection. 😡😡😡😡👎👎😡😡👎👎

[@hummusgaming3884]

The stupid reason why people do this is because of drag races, look at how the lights light up, they remind one to punch the gas lmaooo

[@Palestineexists]

When it turns red there’s a delay before the opposing light turns from red to green. When you’re caught at a yellow>red light, it’s been my experience that all the lights following it will also catch you on yellow>red just before you get to the intersection. Making a small trip into a long one, so next time you see yellow, punch the gas.

[@AndrooUK]

Unless you're in other countries that you actually must stop for an amber (yellow) light, unless doing so would cause a serious collision or accident. The UK, and other nations such as Australia, require stopping at an amber/yellow light as if it's red, unless doing so would be dangerous or impossible.

[@Raaaahhhhbbbie]

When I was a kid I thought traffic lights were operated by people in offices under the intersection

[@abbysapples1225]

that's a pretty good imagination you have there. And it made me laugh reading it. Cuz it's something that I thought why didn't I think of that when I was young. Have a nice day and stay safe and healthy. God bless.

[@quillmaurer6563]

Look at 8:19, we see a photo of exactly that - an early traffic light manually controlled by a guy in a box under it. Of course the box is above the ground on a post with the light, not buried under the street. But imagine how expensive it would be to pay someone to do that at every intersection.

[@liamwelsh5565]

I thought when the wind was blowing the traffic lights up and down that they were dancing.

[@yourethinkingtoomuchstopit717]

L 😞

[@gurusatyadattatreya242]

Here in India we still have many areas were the traffic lights will be controlled manually

[@albertbatfinder5240]

Many countries have a countdown indicating the number of seconds to green. It’s good for stress. If you just miss the green light and immediately the red light starts counting down from 45 or whatever, it doesn’t seem so bad. Red light wait time is often perceived to be three or four times longer than it really is. There’s also a sense that the light has made a “contract” with the driver.

[@jovetj]

I imagine these will eventually filter into the USA.

[@immigrantgaming420epic]

in my country's capital its only for pedestrians

[@HowardDPVT]

I would friggin' love if this came to the USA. That, and lights being timed (during peak, or normal traffic hours) so that as long as you went the speed limit, or just below, you would clear all the intersections in a sequence. punishing speedsters, and allowing for slower driving.

[@thatguyfromthere1168]

Yeah, in Poland for example!

[@canilogin1730]

Yes, but the problem with this is people will start accelerating when it's at >5 seconds of red and that's a recipe for disaster.

[@lovelybooff3939]

In my home town, the timing between several lights (roughly a mile apart) is set up so if you were to drive the speed limit, you could hit all green lights. Only when you would go over or under the speed limit would you have to brake for a light.

[@SamnissArandeen]

I wish my town would bother to synchronize its lights. Downtown, the lights seem to be synced to always go red as the signal before discharges traffic towards it.

[@fPonias1]

... and in my hometown you only hit them all green if you drive 10 over. I swear it's just so they can hand out more citations.

[@skippyhd3180]

The roads around me couldn't give a fuck about logic and just go off whenever they want to

[@elbersed]

In NYC the major Avenues are synchronized so you can go through many of them in a pack. However, this can only work in one direction, the other direction becomes an exercise in frustration.

[@Khorne_of_the_Hill]

the problem with that system is that if you hit one red light, then you pretty much get all red lights

[@philipberthiaume2314]

Where I am from in Canada, we are beginning to use roundabouts more and more, even in residential areas. These permit a continual flow of traffic, even at the heaviest part of rush hour while naturally slowing traffic down through intersections. The stats show a significant decrease in vehicle to vehicle and vehicle to pedestrian collisions.

[@pyro-millie5533]

I live somewhere that relies on a lot of roundabouts as well, but only in fairly residential areas or slow-moving areas such as the roadways into a shopping center. They were confusing to get used to at first, but man, now, I’d take a roundabout over a traffic signal any day. However the giant ones in Europe on major roads with no defined lanes are so terrifying to me lol.

[@elbersed]

Perhaps it’s a bit of a stereotype, but people in Canada are simply better behaved. In parts of the US, people ignore the basic principles of yielding at the roundabout and think yield is a four letter word.

[@muthukumarannm398]

@@elbersed the higher the population the worse they behave in traffic. I'm from India. I can tell.

[@davidburgess741]

They're brilliant until a certain critical mass is reached. Then they are dysfunctional.

[@SeaWasp]

@@muthukumarannm398 I spent a month in the South of India. People seem to just do what they want regardless of traffic signals haha, and the horn is the insurance policy! Also, on my end of Canada, there are people who have been driving for decades that have no clue how to use a traffic circle to the point where there have been newspaper articles published reminding drivers of how to use them

[@byronrideaux]

If roadways ways are like veins, then Los Angeles has a bad heart and has daily heart attacks

[@xdgaming70]

ATLANTA Delete that shit right now

[@tylerb1483]

Atlanta as well

[@xdgaming70]

Alex Haughton The joke was how bad Atl has bad traffic as well. I grew up in the city and I hated taking the interstate.

[@gimmerqueen]

the M5 is a heart failure

[@byronrideaux]

@@gimmerqueen The 405 freeway is a blood clot

[@billrussell6643]

I have a 52 year career involving design, fabrication, installation, timing and manufacturing vehicle traffic control systems. I applaud you for an excellent summary of these very complex systems. You even got then lingo correct that, in my experience, is rare except for actual practitioners of the art.

[@0rnery0verwatch]

Seems like fascinating work... how does one get involved?

[@astumout]

​@orneryoverwatch7031 traffic design engineering - but video said with technology advancing, the jobs going to become computer based

[@el.blanco552]

There's a light near where I live where for a busy intersection that literally gives 3 seconds of green light and causes the most frustrating traffic imaginable

[@brandonsavitski]

Sounds about the same as the traffic light on my street. It gives about enough time for 1 vehicle to pass through before it turns Red again right after it just turned Green a few seconds earlier. Your lucky to get one vehicle threw the intercection before the light changes back to yellow and then Red.

[@NotSoCrazyNinja]

There's an intersection between a seldom-used side street and a main street in my town. They have the lights default to red on the main street and green on the side street and the sensors take a good 30 seconds to go from detecting a car on the main street wanting to go (with zero traffic on the side street) to changing the light so the main street traffic can go. Nine times out of ten, you're getting stopped at that intersection if you take the main street. It causes so much traffic right in downtown. I kind of think they designed it like that on purpose. The only reasoning I can figure is to force people to stop and see the downtown businesses and tempt them to make a turn down the side street instead of continuing on the main street.

[@jacobcamenzind6365]

There’s one T-intersection near my home that has like 5 seconds of green and 1-2 minutes of red. 🤯

[@kojak8403]

@@NotSoCrazyNinja - I once spoke with a guy who works in the traffic control business and he said that such limits - nonsensical to the naked eye of most drivers - are often implemented on the territorial boundaries of legal entities, e.g. counties. They block or push traffic onto the other, to have less problems within.

[@Stettafire]

There is one road I must take to go to my homeland. On the way back, you go from a 70 m/h road and there is a bend then there is a set of lights that change from green to red spending almost no time on amber. People either slam on, or skip the red. But the road crossing is also a 70 with the same problem. That road is dangerous

[@grindarius661]

Thailand's traffic light. Green : go Amber : go faster Red : go when nobody is around I'm sick of it lol

[@dleivam]

Where I live most drivers do this (I don't) : Yellow: accelerate Red: go anyways Green: wait for the cars that passed with red

[@jamesisaac7684]

If you have money. All signals are green in India.

[@grindarius661]

@Jadandlud Thailand police have their checkpoint placed 20 meters from the intersection. Who take the free lane on the left will be scanned and fined automatically. Nowhere to escape

[@grindarius661]

@Jadandlud That's just sad. I always got caught with loose chain and not cleaning my car. for 200 THB. I cannot blame them. If I do i would lose another 200 for blaming cops. lol damn

[@mwbgaming28]

@@grindarius661 trolling to the max

[@TheAssassin409]

As a Traffic Engineer, I think he did a good job with this video.

[@420sakura1]

Is that a JOB?

[@schievel6047]

As a city skyline player I think so, too

[@tobe.moemeka]

im gonna have to call bluff on that one

[@TheAssassin409]

@@tobe.moemeka ?? ok? dont really have any reason to lie. i work for my states department of transportation. I primarily do traffic signal design, signing, pavement markings, as well as in depth reviews on a bunch of different permits and certifications coming from private developers. dont be fooled by some 6+ year old minecraft stuff. then again, id still play it if i could find the motivation to sit down and place blocks for a few hundred hours like I use to.

[@magead]

@@TheAssassin409 he was joking though

[@robhelenflaherty9083]

You took a mundane topic like traffic signals and made it interesting! Some of the photography was spectacular, all in all a very slick production.

[@RubixB0y]

Nothing is mundane if you put your curiosity to work!

[@ebouwman034]

I think all that real world video was stock footage, just like stock photos.

[@1997saltydog]

Honestly I thought it was boring and not straight to the point.

[@jovetj]

Nerds don't know the meaning of the word "mundane."

[@robloxguy9246]

Eric B flippin hell the lonely chair video was cool

[@you_just]

“You can’t put a high-five interchange on every block” My cities in Cities: Skylines would beg to differ

[@abatall]

No replies and 150 likes? Wow

[@Blues9]

Cities Skylines is the best game

[@avaaznfan8952]

I'm a traffic engineer and I do a lot of work with traffic signals from design, programming, and retiming. Very challenging but enjoyable work. This video is very well explained

[@TGears314]

I am a mechanical engineer, and I have noticed many of the techniques you pointed out in the video just in my everyday driving. However, what you said at 10:45 is something I never really thought about. Traffic IS self limiting, I live in a large urban area (1.25+ million people) so I know how bad traffic can be during peak times and I know MANY people who wait for traffic to “die down”. Thanks for such a thorough discussion of this topic. It’s what brings me back over and over again!

[@kwayy9787]

Engineers: Traffic management is hard Cities Skylines players: Watch this bish

[@RealCadde]

Give a Cities Skylines player a realistic city and tell them to fix traffic without leveling that, this or those buildings and they cannot build there because that's a environmentally protected area. And they can't build a road there because there's a politically active group opposing it for some reason. Oh and you only have X amount of money to spend and you don't make it back just by plopping down some profitable zoning someplace. Engineers have it way worse than Skylines players have it. In many cases they can't even change streets to one way because people will actually complain.

[@RealCadde]

Oh and Americans really hate roundabouts.

[@thedankside2552]

Cadde great point, but I’m sure he was just being sarcastic

[@muramustudio6023]

@@thedankside2552 can i r/wooosh him already?

[@RealCadde]

@@muramustudio6023 Nope.avi, because i already know he's sarcastic but most people won't and will take it to heart.

[@zmanjace1364]

I like roundabouts but apparently so does one of the city engineers in a town by mine. They keep putting the in everywhere. There is a spot with 3 roundabouts that aren't even 50 yards for each other and go nowhere. They then decided to put a stoplight at the busiest intersection that occurs AFTER the roundabouts so if it turns red, traffic backs up into the roundabout completely defeting the purpose of the roundabouts. No idea why they didnt just move the roundabouts 25 yards over and not use a light.

[@angolin9352]

I used to think roundabouts were a good idea until one was actually along a route I travel. I dread the damn thing and avoid it whenever I can.

[@laurencefraser]

@@angolin9352 outside/at the edge of the city I live in, on one of the major routs out of town, there are two roundabouts. They're great. There are two reasons for this: 1 they're pretty big, basically barely different from a one way road. 2 they've been put in a place where the roads that join up have about equal amounts of traffic, and are sized appropriately to handle that traffic. If the traffic flow gets too great, they'd need to be made bigger to keep working, and if it only increased on one set of roads the others would get choked out and it would be useless. Tiny roundabouts are Terrible. The town I used to live in was reasonably sized, strung out along a main road and a bit to either side. A motorway had been built that meant a lot of traffic bypassed the center of town, but that main road still had big freight trucks drive down it pretty regularly. Some genius decided that this was unacceptable (it had been the state of things and an utter non-issue for decades, mind you. If anything, it had reduced), and those trucks must be forced to use the motorway.... So tiny roundabouts were installed at a couple of the intersections. Of course, there wasn't really room for them, all they could do was shave some of the footpath off the corners so cars could go around the obstruction, but the turn was too tight, and the island too tall, for trucks to get through. This stopped the trucks, but also did the following: Made turning across oncoming traffic stupidly awkward Forced you to Break the Law every time you tried to go straight through or turn across opposing traffic, because it was a round about, but there was literally no Time to indicate accordingly due to the whole thing being too small (in practice people just ended up indicating as if it were a regular intersection) Meant that traffic coming from opposite directions turning across each other interacted, rather than not Killed the yearly Christmas Parade (and any other such events) because the Floats couldn't pass Blocked Fire Engine Access to the town's main commercial area, And blocked fire engine access to the road bridge over the river, oh, And blocked fire engine access to the local government buildings and houses on the opposite side of the commercial area on the Other axis too! (the fire engines had to go around the block to miss the round about coming out of the fire station, then drive a quarter of the town's length, then get on the motor way, drive about half the town's length (crossing the river), get off the motor way, then come Back just to get to places on the opposite river bank)... This was Partially fixed by banking the road such that one roundabout was only half as far above the surface so the fire engine could drive Over it (the one blocking the bridge was not corrected when I last had reason to look, now many years ago, and a later development meant that, if willing to drive most of the length of town twice, the other bit would not have been cut off any more even without the fix). So, yeah, well designed roundabouts in the right place are great and really easy to deal with. Stupidly designed roundabouts or those put in the wrong place range from the annoying to the murderous. (The city I live in also has an opposing pair of one way roads cutting through it on each of the four sides of the city centre. Their traffic lights are synced up (have been for decades) such that on a trip down one of them you'll hit a red light once between getting on them and hitting the end (unless you're super lucky, then not at all)... They're functionally an enormous roundabout... And that's actually the point, because the pull a Lot of traffic out of the city centre (enough to cause problems for businesses there), because the roads there can't handle it (and the city centre Still gets choked up some times.) So, yeah... Pick the right tool for the right job and its great, force it into the wrong place and you break things.

[@elijah4606]

There's a roundabout near my school that probably reduced idle time by 85-90%, easily. In the right situation, they're fantastic.

[@metro3041]

@@angolin9352 In my town, so many people died daily at a single intersection, they put a round-a-bout to keep the town from getting sued. It's much faster to go through the intersection, and after a year of it being installed, not a single person has died in the round-a-bout. I'd say they work pretty well.

[@michaelpugh2617]

morrowvision was that not a part of drivers ed for u

[@rencheple]

I had not discovered your channel before today, but I am loving the Public Works series. Incredibly interesting and it really helps understand some of the challenges that our municipalities face in the most invisible and ubiquitous tasks. Keep them up!

[@theultimatereductionist7592]

8:18 Man, THAT'S the job I want: sitting up on a pole in all kinds of blazing hot and frigid cold temperatures, manually directing the traffic. Where can I sign up?

[@merc-svt9701]

if im not mistaken, i believe usually that job is an police officers job.

[@viswasubramanian4738]

Come to India. You can do it in rain as well

[@IncognitoPotat0]

One additional point about inductive actuated control; This system can sometimes not detect motorcycles and bicycles, which is why red dead laws exist in certain states, which allow motorcyclists to run a red light after a certain amount of time or cycles.

[@brothyr]

time to re-play Cities: Skylines.

[@anse7288]

Unless cars remain stuck in one lane even if there are more ones.

[@ginglyst]

@@anse7288 traffic manager plugin helps alot :-)

[@berys76]

@@anse7288 *8 lane road exists * Sims : one lane time

[@james2042]

@@anse7288 usually means you have bad pathing

[@KX36]

I came across this game only about 3 weeks ago. Perfect timing, I feel this video was released just for me!

[@FlymanMS]

Good but not perfect, needs more pretty colored flowing water.

[@ayden3133]

These videos are honestly awesome, as a civil engineering student, it's great to have concept overviews. While not a substitute, these videos help explain the concept in an understandable way.

[@antonahill1750]

I’m a service tech for traffic signal equipment and I found this to be cool, would like to see a more in depth video off vehicle detection systems, loops, video and radar. Well done.

[@SkyboxMonster]

This video should be shown in highschool to new drivers. many people do not know these features of traffic control.

[@wayvirgo]

City Traffic Engineers should be forced to watch this, and then if they can't pass a test afterward, they should be barred from working on city works projects!!!

[@Stettafire]

Well, highschoolers cannot be new drivers in my country. I still think our kids should learn about these things though

[@stevepowsinger733]

With a test afterwards.

[@donkey7921]

Why? This explains how the things work not how to drive.

[@Anonymous-pm7jf]

@@donkey7921 Simple..because it affects your driving.

[@magiman1988]

0:50 areal footage is from Stožice roundabout, Ljubljana, Slovenia. Fun to give it a go, if you are in the area!

[@ec1628]

magiman1988 3:01 areal footage of the 110 - 105 interchange. Maddening and aggravating from 5:30 - 11:00 AM & 2:00 - 7:00 PM Monday - Saturday. I advise you to avoid.

[@Leon_Schuit]

It's actually not a true roundabout, but rather a traffic circle because of the traffic lights on it (at least by the look of the stopping vehicles)

[@notquality3471]

Location: Texas Yee haw

[@fritzpacson1785]

wait a second... this aint texas, i dont see horses and gunslingers

[@theburningtoastmonsterofur7028]

Yet*

[@SuperAWaC]

THE STARS AT NIGHT ARE BIG AND BRIGHT

[@HankHill4]

Finally a state where I’m from I will drink a beer to that

[@HankHill4]

Yep

[@hedgehog3180]

In Denmark we also often have seperate lights for bikes which work completely differently and have different rules. Biking is so common here that in major cities at peak hours you can often get congestion with bikes but of course it takes up so much less space that it's less of a problem. There is an intersection near me where they made it so that the bikes actually get the entire road area in front of the cars so that the bikes can get going faster at peak hours.

[@georgigobg]

Cool video! 1:27 This is where I live on the other side of the planet. Our city has like three traffic lights total. Quite remarkable it made it in this video!

[@Broockle]

When will they finally use my idea and implement a complex system of catapults...

[@Taladar2003]

Foolish, everyone knows trebuchets are the superior car hurling device.

[@nateyoumans6059]

@@Taladar2003 put me in the screenshot pls

[@--_--IMP--_--]

Ballistas > Catapults/Trebuchets. Better aim and accuracy. I personally would like to see them implement a complex series of trampolines and giant, upward-facing fans. Perfect for most modes of transportation!

[@theburningtoastmonsterofur7028]

Na those all are old school, we gotta use cannons

[@piranha031091]

With trampolines as relays!

[@LazerLord10]

That example of a self-driving intersection is why I think adoption fully autonomous passenger vehicles will take way longer than people will think. As far as I'm aware, an intersection like that can't work if there is one human involved in those quick exchanges. Maybe there could be autonomous-only roadways made, but that seems unlikely.

[@mi4johns]

At the beginning of the 20th century, they had a similar problem: Half the traffic was cars & the other half was slow-moving horses, so a lot of places had dedicated lanes for each.

[@namlehai2737]

It is technically possible, as autonomous vehicles are independant distributed systems. They can identify objects and humans themselves, without needing signals from that object (although in this case there can be errors)

[@GraveUypo]

not to mention a single failure from one of the vehicles and the accident will pile up for miles.

[@peytonbock3375]

The boring tunnel basically. Just wish they would be smaller roads involved not just SF to LA. It would also create a company monopoly.

[@crazyperson5222]

Autonomous would be cool, I could go anywhere in the country and sleep eat and be on my phone then the car has a software glitch and bam I'm dead because stupid car crashes into a wall it didn't detect on its sensors because of a software glitch or malfunction! So I say F Autonomous vehicles because AI could kill a majority of the population in one day in Autonomous driving vehicles.

[@bmxican1023]

I'm an engineer doing water treatment plants and I love your channel, especially the new "public works" theme you've got! Would love to see a video on water treatment plants as well (loved the weir/water tower videos as I've installed those as well)

[@agustinusyosef2157]

You give more information about traffic in lesser time than my teacher in class. Thanks man.

[@seagie382]

WHEN YOU STOP BEFORE THE SENSOR AND WONDER WHY EVERYONE BEHIND YOU IS ANNOYED AND THE RED IS TAKING TOO LONG, AHAHHAHAHHHHHH

[@JackFlashTech]

I used to get stuck because my motorcycle wouldn’t trigger the sensor. I’d try to wave up the car behind me onto the sensor, but they never understood what I was saying.

[@weldonyoung1013]

@@JackFlashTech , absolutely. I do the same on a bicycle. Jack, you ever heard the term '4-wheeler'.

[@Admiral_Ali]

I'm a Transportation Engineer, and I approve this video.

[@mch2359]

Have you ever heard of a traffic engineer being fired for out of sequence lights? It will never happen, the first thing traffic engineers learn is the excuses. The fool taxpayers are simply not spending enough money on traffic signals. Because really, who are the real fools? Those having more and more of their assets confiscated by the government to pay for more traffic engineers and light fixtures, or those collecting the funds with a built in excuse to justify no appreciable results?

[@Admiral_Ali]

@@mch2359 calm down bud, I said I approved this video, didn't say I approve the technicality in each and every aspect of traffic engineering explained in every other second of the video. Overall, his tone and explanation is correct, for layman viewers and learners. I'm sure professionals like you have lots to add into this topic and I would be glad to learn from you.

[@mch2359]

@@Admiral_Ali Sorry for the rant. Go to any Road Commission web site and get your fill of them complaining about being under funded. All the while they are wasting money. For example 2 fixtures can stop 4 lanes just fine, no need to replace perfectly functional signals with one for each lane.

[@andersenzheng]

lol, unexpected triggering.

[@WingKLok]

Mark H. Depending on design standards for electrical items (how many items allowed on pole, ways to mount certain items) and any new developments (planned widening, planned system modifications/upgrades, or additional traffic for anticipated growth) there may be a need to replace poles. That however is within purview of electrical engineers. Unfortunately some work in the schematic world, not fully realizing that what they plan have consequences (are they "break away" i.e. designed to be break off under certain assumed circumstances; do I need to add protection if they must be located within "clear recovery zone") The latest hot topics are "vision zero" where stakeholders work toward zero roadway fatalities in varieties of way- engineering, education (i add engagement), and enforcement; and "Complete Streets"- life cycle of transportation planning, engineering and maintenance should consider usage by all modes (and all user ages) of transportation, depending on functional class of facilities. Listen to staff reports and ask questions at your local jurisdiction's planning meetings/public focus meetings. It may not be sexy but sure as heck easier to correct/change at 65% design than when you see it being done. But do ask as we- consultants or city employees- are supposed to explain to you, the taxpayers, so you can understand. Speaking from experience in US private and public sectors :)

[@thrownchance]

FYI in big parts of europe a red + yellow traffic light signals that it is about to go green. Therefore you always know if you are going to have to stop or can just go and not slow down at all. And there is also a blinking green light, which shows that it is about to go red and therefore you can adjust your speed to keep the traffic flowing and avoid sudden stopping.

[@Liggliluff]

More than half of Europe, but there are still places like France, Spain, Italy that don't do that and does the same as USA.

[@jutah]

Great info! Good broad topic to cover!

[@nonami_066xswqoqowiwl]

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[@KAMZA.]

I LOVE your channel!

[@khagemann7462]

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[@Wejims]

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[@man_on_wheelz]

This "platoon" coordination mentioned around the 9:00 mark is used on Michigan Ave. in Chicago, IL. Seems to work pretty well actually, as any traffic backup on Michigan Ave. typically gets cleared by the time the light changes. Hold ups are the cars on the sidelines sitting still by a building.

[@RichTCS]

This was most of my semester-long graduate course in traffic engineering - in a 12 minute video! 👍🏼👍🏼👍🏼

[@kings5223]

This video does a fantastic job laying out the basics of traffic engineering. You are doing a real service with these videos.

[@Sam-lr9oi]

Cannot wait for a video (or sub-series) about public transport infrastructure, my preferred form of traffic congestion relief. Also walkability, but that's probably less immediately fun to talk about.

[@davedee6745]

"Red light--stop. Green light--go. Yellow light--go very fast" --Robin Williams as Mork

[@d1oftwins]

Hmm, I thought it was Jeff Bridges as Starman.

[@josephclegg3562]

Nanu Nanu. Lol!

[@ghostman52621]

Dave Dee people use a yellow to advantage that means to start slowing down

[@diegosa1530]

Very good video! I watched it from Spain and I have the impression, that roundabouts should be more used in other countries. In places where the traffic is not very very high they are pretty efficient and act as a form of self-regulating traffic.

[@Icg199424]

PE, I just want to say after months of viewing and liking your videos, you are exceptional. Maybe epoxy coated rebar has a limited audience but some of us liked it! This one was good too. I built a lot of roads and bridges and always thought Traffic Engineering was a laugh, probably non-existent. This one helped. Keep it up!

[@isaackuppens1427]

Please make more videos. I love how you explain engineering concepts so everyone can understand. Keep up the great work.

[@gregoryclark8217]

I realised after watching this, that I have never been through a 4-way intersection as we just don't have them in the UK. Something that may help the UK with congestion at traffic lights is the flashing orange we get after red and before green as it warns drivers to prepare to move instead of the light suddenly turning green, allowing a quicker start.

[@mrcoiganable2988]

We dont have the 4 way junction here as its pointless and slows traffic, I never understand why americans have these junctions, make no sense at all. What is the point in slowing all traffic down? Just do what we do and slow two of them down and let the other two free flow, makes much more sense.

[@TessHKM]

I think the biggest think that helps with congestion in the UK is your network of buses and trains.

[@patrick_test123]

9:00 👏don't👏enter👏an👏intersection👏unless👏you're👏able👏to👏clear👏it.

[@JaidenJimenez86]

In London (and probably other places), there are cameras which can detect if you do this (as well as other things such as make an illegal turn), and issue fines automatically.

[@Sir_Uncle_Ned]

Self-driving cars understand this rule. Most humans do not.

[@Ledfndr]

intentional box-blockers are a pet peeve for me as well.

[@SgtLion]

Have you ever heard the tale of the Yellow Box Junction? I thought not, it's not a tale many UK drivers would tell you..

[@CoryMck]

@@JaidenJimenez86 $300USD fine in my city

[@TestingPyros]

I have a series of signals that are near my house. I grew up here, so I have had the chance to watch these lights not only get added, but get manipulated into their current system. The biggest pain is a pair of lights that handle somewhere around 2 miles worth of cars during rush hour. Seriously, the line of cars can start around a mile before one of the lights. It is on a 2-lane road, and the other option is only a 4-lane road. Look up Mills Gap Road and Highway 25 in Asheville, NC. It is AMAZING to see what has been done with these two lights and the rest of the run from Fletcher to Asheville on those roads!

[@menguardingtheirownwallets6791]

In Kitchener-Waterloo, Ontario, Canada, we had an intersection near our house that was a nightmare each morning and evening as it got clogged up with traffic. The city replaced the lights at the intersection with a roundabout and presto, no more traffic jams there. There are other stoplights nearby that don't seem to have any problems, but that one intersection was a mess and it is those few intersections that are best served with roundabout traffic circles.

[@ThaumaturgistGuard]

1:27 - footage from Bulgaria, and, to be specific - Veliko Tarnovo. I wouldn't notice if it wasn't for the wall painting showing a scene from the times before our freedom

[@darkmoonbg]

Намерих Българина

[@mndkv2747]

ей този коментар и аз търсих 😀

[@extrastuff9463]

Watching these roads makes me realise how happy I am with the bicycle roads in my country, if there's any serious amount of traffic there tends to be a physical separation between the main road and bicycle paths to the sides. On roads with less traffic it tends to be shared but with a coloured indication what is reserved for cyclists. Many of our traffic signals also have both ground loops and a button on a post to press for people with fancy modern bicycles that don't trigger the detection system. I've noticed in some of the newer ones they even include a light indication which turns on the moment a bicycle is detected or the button is pressed. I also like the "countdown circles" that some pedestrian and bicycle traffic signs use nowadays, basically an indicator that has a full circle which gradually shrinks to nothing. When it turns off entirely the green light is expected to come on, the result is usually that everybody starts moving at the same time instead of a few slowly reacting people here and there.

[@kleinereisbar591]

Netherlands?

[@extrastuff9463]

@@kleinereisbar591 Correct, bicycles are quite useful over here with our fairly flat terrain and good road infrastructure for it. It may take me longer to get to the city compared to a car or bus, but while doing my shopping there I can get to the right place in the city much faster. And I've got two large bags at the back of my bicycle and a backpack to fill with stuff instead of having to carry it. Works out great for all but the largest objects that really need a car/trailer.

[@kleinereisbar591]

@@extrastuff9463 i'm from Cologne and my mom loves to travel to your country to go on a bicycle trip 😂

[@belladonnaRoot]

@@kleinereisbar591 Sometimes I dream of moving to a place where cycling is a common mode of transportation. Cycling in Nashville Tennessee is suicide. Even if there are bike lanes, there are driveways and side streets every 10 meters, debris/potholes galore, and most roads don't have any space for bikes in the first place.

[@LucarioBoricua]

I find it so weird that the USA forbids countdown displays for vehicular traffic signals, even if it uses them for pedestrian signals.

[@MrCBroz]

I would've loved to hear your thoughts on roundabouts and why they differ in prevalence in Europe vs. the US.

[@Holland1994D]

They even differ a lot in Europe themselves. We have some turboroundabutes here in the Netherlands for handling more volume (asymmetrical roundabouts). That are roundabouts with more lanes, but you shouldn't be able to change lanes on the roundabout it self to prevent accidents and increase flow. This explains is better: from the Technical University of Delft: kzbin.info/www/bejne/n368mpVpfrdnaas

[@havocmaverick]

In Wisconsin there are many roundabouts, and many more to be made.

[@jimstanley_49]

Roundabouts are becoming more prevalent in Montana, and you would not believe uproar. The number of people who have been issued licenses, but can't comprehend a yield sign is astounding.

[@edwardsmith7131]

As Americans we have been taught that we all individually OWN the road and this is antithetical to the concept of yielding which is critical to the safe operation of a roundabout. Our car culture has promoted competitive and adversarial driving habits and combined with a subconscious ignorance of what YIELD means that enough American drivers will simply bully their way through a roundabout endangering everyone around them.

[@jovetj]

Maybe you were taught that you own the road, but I wasn't.

[@poetnathan26]

you have one of the best channels on KZbin seriously like I watch your videos all the time they are so informative and you don’t ever ramble on too much, while yet packing each video with tons of interesting information thats very accessible- even when complex. you do an extraordinary job! I commend you. thank you for all your efforts & time.

[@moogthedog2816]

Ex-traffic software engineer from the UK here. I worked on ASCT (Called Urban Traffic Control or UTC here) systems for 12 years as my first job our of University. I started purely in the communications realm, getting bits and bytes from the controllers on street to the each other and to the control rooms (via dedicated systems and then using the internet), and eventually moved up to working on the actual adaptive systems, producing prototype systems from requirements and simulations presented to us by city councils, working on interoperability between our equipment and those of our competitors, and producing a series of sub-systems whereby the health of the whole traffic network equipment may be monitored and maintained. This video is a great starting point, but there's a LOT more going on under the hoods of the equipment out on street. There are adaptive functions that will deal sensibly with failing sensors, local timed control where controllers on a route are able to stay in absolute sync even if there's no link between them, along with safety routines and equipment that *guarantee* that a junction never displays an unsafe or silly series of signals on a phase (telling two conflicting streams of vehicles that they can go, or leaving everything stopped for ages) - even if the ASCT systems tell them to. Sorry - those films where people hack the city hall and turn all the junctions green or red? Ain't gonna happen. :) There's a lot going on in the anonymous grey cabinets along the street, and a lot of work goes in to them. Thanks for highlighting us :) For everyone else - the absolute *absolute* rules that any traffic engineer would like you to follow are: 1) Leave distance between you and the car in front to allow people to merge 2) Do not enter a junction unless your exit is completely clear for you. Loads of delays and plenty of accidents are caused simply because people are too impatient, too close or too fast.

[@vladick]

Hello! Could you please explore the topic of the dedicated bus (public transport in general) lanes and their influence on traffic? In my opinion, this kind of lane discourages driving and improve the traffic situation.

[@TS6815]

I don't know if there's a lot of formal writing on the subject, but the phenomenon of small urban municipalities aggressively building traffic out of their thoroughfares and creating a tragedy of the commons is an all too real fight I see in metro Detroit. It's all well and good for a city or two (each only a few square miles in footprint) to riddle their roads with bike lanes, bus lanes, 15mph speed limits and pedestrian yields every few hundred feet but the entire metro area is at risk of gridlock cascades when big arteries like Woodward get cut down to 10% of their throughput because Ferndale wants peds to be able to cross at 5:15pm unencumbered

[@TS6815]

@@ivandiaz5791 nice bad-faith argument? it certainly makes sense in city centers but the particular road I'm talking about alternates from 6 to 8 lanes, 45 and 50mph. it's a major trunkline for commuter traffic and more so for events (four sports/concert venues at its terminus) yet one town that controls about 3/4 mile has slowed traffic down to 30 and placed down pedestrian yields. forget the pragmatic traffic flow issues, it's straight up dangerous at off-peak hours when drivers aren't watching closely enough

[@danhard8440]

no matter how well you plan the flow of traffic your still going to have someone in the pack on their cell and not realize everyone has already went and they are just sitting there

[@wushushorty1]

You raise your fist in frustration and they curse you. lol

[@VadimR4]

In Chicago, the yellow lights are shorter to get more revenue from the red-light cameras.

[@hkhjg1734]

Larry John if the city doesn’t provide adequate warning for motorists to stop thats the city’s fault not motorist’s fault.

[@nomadben]

@Wxlfman_773 Chicago is fucked.

[@brentboswell1294]

Da machine!

[@yournextdoorneighbo1]

Literally just idling in a left turn lane in Chicago, lightly layed off the brakes and moved forward a couple inches and a red light camera went off. Like seriously wtf

[@ckvon9644]

Those cameras have been banned in many places.

[@mickeyb492]

KZbin's algorithm has blessed me with the information I subconsciously always wanted to know!! Great video

[@ExTexan]

Even back in the 70s, Houston had timed their signals in the downtown area for 27mph, such that, traveling at that speed, you’d see the light(s) ahead of you turn green in sequence so you would never have to use your brakes. The thing that made that so amazing to me was the fact that two major cross streets were two-way, while all others were one-way, with each consecutive street alternating directions. The engineering required to make the signal timing work for all downtown streets is mind boggling. Of course, I’d inevitably end up driving behind someone who was clueless about the timing. They’d accelerate hard off the line when a light turned green, and then have to brake hard at the next light, coming to a complete stop, requiring them to be starting from a dead stop when the light turned green. Other drivers behind them wouldn’t be able to keep the steady speed dictated by the signal timing.

[@renerpho]

3:50 I wasn't aware that the traffic light phases are different here in Europe. Between red and green, we have a "red+orange" phase that means "don't cross, but prepare for green".

[@jovetj]

The Red+Amber phase is common across Europe and some other parts of the world, but unheard of in North America.

[@tjur]

There's also blinking green for car traffic in some of the european countries, because, it's actually forbidden to jump on yellow, unless you're so close to the intersection that braking is impossible. Another difference in euro is that often left-turns doesn't have separate phases, it's just they need to yield to oncoming traffic (both cars and pedestrians).

[@stevepowsinger733]

Interesting idea

[@Leon_Schuit]

@@tjur The left-turn can be protected, it just depends on the size of the road and the amount of trafic it's likely to experience. If there are two lanes going in either direction it often is, or if it's a busier intersection extra lanes are added to accomodate a protected left-turn.

[@rachelt2415]

I think this is because America has far fewer manual transmissions. We don't need to prep the car in anyway to go and accelerate quickly.

[@ancbi]

0:31 stockfootage of traffic, shows Thailand. Yes, Thank you for reminding me... Grady.

[@locabal8354]

Malaysia and Korea too

[@SuperAWaC]

could be showing india where traffic lasts for days and people take breaks driving and leave their cars to go get food, and you can have food delivered to your car in traffic

[@DosAussieThai]

That traffic isn't too bad. It's actually considered "Flowing traffic" by Bangkok standard.

[@WaterShowsProd]

It’s Ratchaprasong intersection (Central World on the right-hand side); during non-peak traffic time to be sure.

[@Ice_Karma]

2:46 "Intersections also need to be rigidly standardized, so that, when you come to an unfamiliar one, you already know your role in the careful and chaotic dance of vehicles and pedestrians." Halifax, Nova Scotia could really do with learning that lesson.

[@FireByTrial1]

I swear that city designed their traffic systems to be the exact opposite to what it should be. Especially downtown near the fort

[@liamwelsh5565]

I get lost every time I go there. It's so confusing. Hello from PEI where there are almost more roundabouts then traffic lights now!

[@Ice_Karma]

@@liamwelsh5565 Hah. I'm originally from Charlottetown!

[@liamwelsh5565]

@@Ice_Karma I'm from Stratford and a lot has been built over the last 10 years or so. If you haven't been here in a while, there's a lot of new buildings and things.

[@Ice_Karma]

@@liamwelsh5565 I haven't lived in Charlottetown since 1990, and since 1992 I've been back only four times, in 1995, 1998, 2006, and 2010... and every time I do visit, it's just weirder and weirder... =/

[@gregchurch]

Thank you for raising awareness of how traffic signals work. These signals are common areas of frustration for communities. Local leaders rarely prioritize solving these problems, or reprogramming to adjust to changes in traffic patterns, nor updating the technology. I live and work in the area of the US and Texas with the fastest population growth (for the past 40 years). Local Government Engineers have not considered technology frequently enough to solve traffic flow problems. (And the technology is not advancing fast enough). Actually I regularly see new roadways and highways that are designed in a manner that actually causes the problems. Which leads me to think they don't possess the intellectual capacity to be making these decisions. It would be great if you could create more in depth content on new, basic, advanced solutions to solving traffic.

[@gyrojomo]

Thanks!

[@ehow5678]

There is an intersection on my way to college the is green for just enough time to get about three cars through. I'm convinced that whoever programmed it forgot a zero

[@FrozenBusChannel]

I remember seeing a video about a Chinese intersection having just 0.9 second of green light

[@stevepowsinger733]

You can complain. If you can figure out to who.

[@weldonyoung1013]

@@stevepowsinger733 , it does not do any good in my city. Every traffic light is on a very short phase here. When I stated it was a problem, I had to limit the problem to ONE intersection. Maybe in the next 120 years or so I can get back to them about the rest of the traffic lights.

[@WeepingAngels91]

Bicycle infrastructure is something I'd love to hear your opinion on Grady. If perhaps you're doing a series of videos on traffic flow like you did with water, I think it'd be an interesting topic to cover.

[@satriaamiluhur622]

This was much more educative than entire semester of urban planning class in college

[@LucarioBoricua]

This is taught either in transportation engineering (especially at a graduate level) or in transportation planning. Source: am graduate civil engineering student specializing in transportation.

[@stevend.bennett427]

In So-Cal my main peves are lights that change when no car is near the intersection, and lights at an intersection that trip with one or two vehicles and then cycle through to allow for vehicles that aren't there.

[@augiegirl1]

5:46 I believe that the length of the painted white line on the passenger side of a left turn lane (indicating the entrance to the turn lane) corresponds to the amount of time that a yellow light will stay yellow before changing to red. IOW, if my speed is the same as the speed limit, & I pass the left-turn lane entrance before the light turns yellow, I will have enough time to cross the intersection before the light turns red. For example, if the light turned yellow at 3:31 of the video, the silver minivan coming toward the camera would be able to get through before the light turned red, since it was past the entrance to the left turn lane.

[@stump1897]

As a civil I love your channel. I may start having my interns watching it as part of their homework

[@rubenyoranpc]

A nearby city just went like "Light? Nah fam we Dutch so roundabout it is" and replaced all the lights for turbo roundabouts, except for 2. Another city uses the "green wave" format, as long as you drive the speed limit you will only be held up at the first light. All the lights are timed so there is a wave of cars going between lights.

[@6yjjk]

A few years back, when they brought in live bus schedules at all the bus stops here, they claimed that the system would be integrated with the city traffic lights. The idea was that a bus running late would get green lights until it was back on schedule. A genius idea... but I spoke to a bus driver recently and she said it never happened.

[@robertpierce1981]

Thank you Grady. I work with traffic loops and detectors in my job with garage doors. Typically it’s parking garage and forklift access.

[@KatTheFoxtaur]

Very nicely edited video! Though I'm almost surprised you didn't mention the conflict monitor. It's a piece of hardware that most people don't even know exists, and hopefully never needs to intervene. If the monitor detects voltage on conflicting green signals which could cause an accident, it will send the entire intersection into flashing mode. It can often be noticed in videos where a car crashes into a traffic signal pole, causing a momentary wiring short, and suddenly the entire intersection is flashing instead of sequencing. Also a fun fact: Signal cabinets generally have an access panel on the outside, which allows a police officer to manually put the intersection into flashing mode, especially when they are directing traffic themselves. But they can also set it to manual sequence mode, in which the officer temporarily takes over the timing of the phase changes, using a wired remote control button, known as a "pickle"!

[@skiingbronconut7876]

CONGRATULATIONS ON 1M SUBSRIBERS GRADY. !!!! Your hard work is very appreciated. ! 🎉🎉🎉

[@DosAussieThai]

0:20 That traffic isn't too bad. It's actually considered "Flowing traffic" by Bangkok standard.

[@jmalmsten]

My opinion? Switch all intersections governed by red lights to roundabouts. They are basically maintenance free. They have almost no idle time where noone can be in it. Their function is standardised so practically anyone should be able to navigate them safely... Etc etc... I just prefer roundabouts in general because of their simplicity and efficiency.

[@daverhodes382]

Wtf you smoking? What about small, city centre junctions or pedestrians?

[@RRansomSmith]

Big cities with congested roads don't have enough space for those

[@edwardsmith7131]

@@daverhodes382 this works even better in small towns and city centers because it mirrors the slow speed "California Stop" intersection negotiation that has been occurring all along. The 4-way stop and traffic light are best at STOPPING traffic, not allowing it to flow. A traffic light WILL be superior to a roundabout in a situation where side road traffic must attempt to merge into a continuous stream of vehicles from a major arterial highway; when there is no gap in the roundabout you can't merge in. In this case traffic lights force the issue by stopping arterial traffic flow. A roundabout is not by any means a panacea for traffic flow management but when intersecting roads have comparable traffic levels it can increase Level of Service by removing the stop-start traffic jam waves generated by traffic lights.

[@KingBobXVI]

The traffic engineers in Seattle saw the part at 8:30 and decided to do the exact opposite. On Mercer Ave, which cuts through a major section of the city and ends with a freeway onramp, the lights are clearly synchronized, but in a way that guarantees the smallest possible platoon of vehicles. The group furthest from the freeway gets blocked between two lights for an extended duration while incoming traffic from both sides get blocked for multiple cycles, but all 6 or so of the lights further up the road are green. As soon as the blocking light turns green, the rest of the lights all turn red. The end result is that that section of road between the two furthest lights sets the maximum size of the platoon, which eventually gets to go all the way to the freeway, but that the side streets trying to empty into the same space are completely unable to ever feed into it.

[@katherinegrice4415]

As a example of set lights, go to Downtown Orlando, Florida and look at Orange Avenue. It's between Colonial Drive and East-West Expressway. This is a good example of set lights. There are several lights (block after block after block). When getting off the expressway, if you pace yourself and catch the first Green Light, you can keep going (without stopping) until you get to Colonial Drive. You should add this street to your video as an example of your explanation.

[@saxmastergq]

Can you do a video about different kinds of roundabouts? like dumbbell roundabouts and turbo roundabouts

[@Ghaz002]

oddly enough moving to the big city relieved my traffic problems, because now I can take public transit

[@robbie6625]

Bicycles... I can get most anywhere in the downtown area in less time than it would take me to drive there.

[@Stettafire]

0:58 fun fact, the US favors traffic lights over roundabouts, but the UK favors roundabouts over traffic lights.

[@stevepowsinger733]

Its changing fast in my Florida city. Roundabouts everywhere now

[@leytonnoerenberg8917]

The US is actually starting to implement roundabouts rapidly now. The reason why you don’t see them as often is because they’re are more expensive to construct then you think.

[@Stettafire]

@@leytonnoerenberg8917 I think it's more expensive to retrofit then to build it from scratch

[@zouzouuu]

I'm watching this for a project. A HARD PROJECT. And I think Practical Engineering did a pretty good job on explaining how traffic light work. This video was very useful! Thank you!

[@williamford9564]

Excellent presentation. On the discussion actuated systems, I moved to North Carolina six years ago and it annoys me the number of intersections with left turn lights that are not actuated and therefore we sit for minutes when there is no traffic coming through from the other direction.

[@bololollek9245]

The best solution we have right here and now is basically public transport. There is nothing in traffic that is as inefficient as 1 person in a car.

[@SubtlyAggressive]

When you're running late, you get all red lights, lol

[@crazyrobots6565]

In most cities, they're timed to eachother. So if you go the speed limit, you should hit all greens. But when you're in a rush (and speed) you hit all reds lol

[@crazyrobots6565]

@Tom R not if you drive the speed limit. Most people don't. You probably don't. And that's why you hit every red. Try it some time, odds are that your city has it times so that IF YOU DRIVE THE SPEED LIMIT, you will only hit one red on a straight road.

[@Palestineexists]

Or your not driving fast enough, Sunday drivers and pace cars feel entitled to slow everyone down.

[@GraveUypo]

@@crazyrobots6565 we call that a "green wave" here, but it's a myth. in my city i know of only two real green wave enabled streets and it only works for the full lenght if you go slightly above the speed limit. for the rest of the city, it's red waves. you literally have to stop every fucking time for pretty much the full length of the red signal because it usually turns red 5 seconds before you have the chance to cross. maybe if you floor it with a ferrari you could make it.

[@andodide]

Obligatory "I can relate with this so much as a Cities Skylines player". But tbh I do relate to it, it's pretty cool that a game can take many challenges of traffic management and turn it into an actually fun (but frustrating sometimes) experience. Shout outs to all traffic engineers out there, you guys go through so much shit to try and contain traffic lol

[@SerunaXI]

Cities Skylines feels like something that was made to torture traffic engineers.

[@AndrooUK]

Yes, because Cities Skylines allows realistic lane design and traffic behaviour without any mods...

[@DSB1234567890]

"intersections need to be standardized so that when you come to an unfamiliar one, you already know your role" *Laughs in Boston*

[@benahrens2006]

In Dubuque, Iowa, United States, the entire city is nearly a grid, and if you hit one green light, every subsequent light is green on that road. They are timed so that if you go the speed limit, you will hit no more than one red light until you turn. It’s freaking amazing!🥳

[@ninjanerdstudent6937]

This is the longest driver's ed ad I have ever watched.

[@adarshyadav340]

Being a civil engineering I can understand your hard work behind this video. Really appreciate your efforts. You made it quite easier for everyone

[@treeforface]

You should also do a video on modern, entry-deflected roundabouts. Particularly in how efficient they are as a replacement for traffic lights in many places, and how they differ from earlier designs.

[@jimincal]

This is a decent video. I would have been overjoyed if there had been an explanation as to why pedestrians don't have to push the ped button 30 times prior to getting served. This drives traffic engineers nuts, but every day we see peds pounding on that button ("Why doesn't the signal let me cross? ... Oh, finally!") A few glitches + comments: * At 2:30 the horizontal signals are shown in the wrong configuration (in the U.S. the red indication should be on the left); this happens at other points in the video. * BTW, the aerial image shown at 2:57 is the interchange between the Harbor Freeway (I-110) and the Century Freeway (I-105) in Los Angeles (south of downtown). North is to the left. I can't imagine when that video was shot because there's almost no traffic! The Harbor Freeway at that location carries about 300,000 vehicles per day. * At 3:45, the narrator is technically incorrect by saying "the amber light warns that the signal is about to change from green to red." That would mean an amber light would appear before the green turns off, which we know doesn't happen. [Picky comment, I know] * At 7:00, note the inductive loops for the bike lane. Such a lane is not available at the majority of intersections. The narrator says "too small to trigger the loop," but it's not really the size of the vehicle that matters. Rather, it's the amount of metal in the vehicle (motorcycles usually have enough metal, but many bikes are made from non-metallic composites), the positioning of the detector loop, the positioning of a two-wheeled vehicle in the lane (sometimes bikers like to come to a stop next to the lane line) and the sensitivity setting of the detector. * Huge goof at 8:53: the intersection on the left is showing green indications for all four approaches simultaneously. Disaster scenario(!) which technically can't happen if there's a Conflict Monitor in the controller cabinet, which would send all the signals in the intersection into flash mode.

[@dandregills5356]

This is one of the most informative and eye opening videos I've ever seen. Thanks to you and to Google for making this the first result when I searched "how do traffic lights work". You made a new subscriber today

[@thevoteman]

This all sounds nice and dandy but everybody knows there's a group of gnomes under each intersection that control the light with gears and pulleys and rope

[@nokompass]

Do a video on Train Signals and crossings. I mean, I know how they work but I think it would make an interesting video for everyone else.

[@jovetj]

The train sends its love out down along the track and the signals all in love and get turned on. We all know how it works already.

[@jaysmith1408]

Problem is the differences in railways. There’s the straight forward B&O and PRR signals, the simple CN and BNSF traffic signals, and the German signals, that make no sense whatsoever.

[@kelley4493]

Thank you!! I always look forward to ur vids :)

[@abbysapples1225]

I really enjoy the video, it was really good. I was surprised that you didn't mention about how traffic signals work in situations where there's a malfunction or loss of power.in America definitely in Pennsylvania where I live if the major arteries traffic lights go out they flash an amber light every so many seconds to allow the traffic or the drivers I should say it's a know that they can go through but with caution the other people in the side streets get a flashing red light let them know they have to stop and they're pretty much treating it as a stop sign. And speaking of stop signs here in Pennsylvania it passed a law last year that if you're sitting at one of those traffic lights in the middle of the night and 15 minutes later you're still sitting there you can go. Now it's probably more like 5 minutes later. as a child and even to this day in my early forties I am still fascinated with the function of traffic lights and their complexity over the years. I also enjoy the signals and studying the signals for a railroad they have the same color scheme but have a different functionality.

[@Liggliluff]

(9:30) That is why you aren't allowed to enter an intersection if you can't leave it. Accidentally entering the intersecion does happen; but most people should be aware of it.