How Do Traffic Light Sensors Work? | Did the lights fail?

In this video, we look at a situation that developed when my viewer was leaving a car park behind a police vehicle. Were these lights broken, or were there things that the motorists could've done to help the lights change?
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[@deetee5861]

The policeman was very good to not just jump the lights and to attempt to sort the issue. Then, by getting community support officers involved and moving his car too. Props to that officer for not being selfish! ❤

[@butikimbo9595]

Shelfishness sould not be part of police dictionary. If so it should be reported as such. Here in this case with dashcam evidence that, could be a matter do it or not and officers acted by the members of the public side, what is also good to share at least to also show the positive and expected actions from our Police Officers.

[@kdmq]

If the police car had flipped on the emergency lights and jumped the lights, it might have actually caused the light to turn green. Especially considering that the cammer would have pulled forward a few feet.

[@steffenscheibler5849]

I worked for a company supplying road-telemetry and traffic management systems systems (global supplier, also to the UK). There are many different types of sensors but the UK predominantly uses motion detectors on small junctions such as this one because they are very cost-effective and work (mostly) rather well for those types of junctions. Larger or more complex junctions typically have better systems which will trigger on more than just motion and often also combine magnetic loops in the tarmac to detect if a vehicle is standing at the line (which is why you always should drive up to the line, not stop ~5 meters before it!).

[@andyalder7910]

There is an induction loop on this set but it's between the two cars, clearly visible on StreetView.

[@Ep1cure]

Your knowledge is very much appreciated, but the reason I prefer a gap is that I can shuffle to help through emergency vehicles. I normally stop about when I no longer see the line approaching slow, which I know is a before the line (about 3 metres). I haven't had issues with the sensor, but if so, might consider going forward then, maybe nudging to the left a bit (UK traffic from driving on the left, meaning opposite plan if I were from right hand road systems).

[@TestGearJunkie.]

Showing my age here, but I remember the old pneumatic rubber strips sunk into the road. You could get out and go and jump up and down on them..!

[@prekatori]

@@andyalder7910 (51.285841, -2.482382 - if anyone wants to check) I think the dashcams engine should be on top of the loop. The road markings changed between street view in 2016 and this video, but you can see that the loop is pointing away from that white spot on the pavement at 45°.

[@khalidacosta7133]

Siemens? Dynniq? Go on spill the beans then! lol It's often why I end up straddling both lanes when the road is quiet... to get the lights to change quicker at the junction ahead... I am not drunk.. I swear!!

[@davidhaslam1056]

Hands up if you would of simply reversed a few feet and moved forward to see if that worked. 🙋‍♂️

[@jimmysandhu9586]

1000% yes, I done it just yesterday 😂

[@EZ-D-FIANT]

Yea I've also done it in the past....👍👌👍

[@grahambiggs2017]

Or the car behind could have moved forward. Or you could wave your hand in front of the sensor on top of left-hand traffic light. I wonder why so much crime goes unsolved in this country. 🤔

[@lariwoo]

Can't reverse in a one way system unless you are parking though?

[@EZ-D-FIANT]

@@lariwoo If your gonna be pedantic I will too, you sure that car Park exit qualifies as road....

[@SGz_Eliminated]

I think Ashley was spot on, the traffic just doesn't move after its cycled back to red. The chances of the sensors breaking at that exact moment is extremely slim.

[@Djnffnoeosmfasjjd]

This is not a red light camera.

[@tarnmonath]

@@Djnffnoeosmfasjjd No-one said it was.

[@markhorton8578]

The default fail would be red, for safety purposes.

[@JB9000x]

It is probably a Microwave Vehicle Detector which works on doppler reflection

[@JB9000x]

​@markhorton8578 if it stays red for long enough it will suspect a fault and revert to forced stage demand

[@antm2296]

This happened a few months ago with temporary traffic lights for construction work, the lights were situated at a blind bend, I had a copper behind me along with around 20 cars. After 8 minutes on red and no change or other traffic oncoming, I started to creep forward and went straight through with all the cars following, long behold they were manually put onto red purposefully as when we got around the corner there was a construction HGV blocking the road and using its crane to drop off materials. So we all put our tails between our legs and reversed like proper idiots 😂

[@kiradotee]

That is stupid from the workers. They should have sent someone with high viz to be next to the red light. Ideally with a stop sign. If the temporary light is red for like 5 minutes people will jump them, they'll assume they're broken which is fair.

[@ianl1052]

​@@kiradotee It would have been safer for all of you to stay where you were, as so many people had committed to this maneuver, until the lorry had finished its dump and then carry on. While everyone was waiting, the police officer could have got out and informed everyone behind the lights of the issue and tell them not to follow.

[@annabelholland]

In that case, the road should have either been closed or have an authorized personnel (traffic management officer, police, Highways England) stop traffic and give reasons why. Remember that having traffic stopped longer than 60 seconds without reason may cause impatience

[@kinkaito5433]

@@ianl1052 With so much roadworks in the UK people will only wait so long, as alot of the time, traffic lights are either not set up correctly, or are broken, people aren't going to wait for a end-less amount of time, if the road was "Closed" for that long, There should be a Road closed sign, or a person to direct traffic/and explain whats taking so long, People will not, and should not, have to wait and Pray the lights are working,

[@kinkaito5433]

@@annabelholland Cannot agree more.

[@PedroConejo1939]

At least the Highway Code (checks notes) allows you to make a judgement call if you have good reason to believe the lights have stopped working: "If the traffic lights are not working, treat the situation as you would an unmarked junction and proceed with great care." - Rule 176. Given the dashcam evidence, if there was no possibility of trying to reset them by reversing, I'd follow the advice given. Another reason to have a dashcam. It is a good reason for auto-cycling the lights every few minutes, but that's for the engineers to implement. I don't listen to the radio these days, but I used to hear 'stuck on red' quite a lot in the traffic updates on my way to work.

[@smilerbob]

100% agree and going through on red would be last resort for me if all other options do not work. As for the traffic reports, I always used to think someone phoned that in as an excuse to jump red lights and if caught refer them back to the traffic reports on local radio. One of many stories I used to make up to help alleviate the dullness of the daily drive to and from work

[@PedroConejo1939]

@@smilerbob That made me chuckle. It was the kind of thing I might do.

[@allanhook]

The highway code says if the lights had stopped working. I would say that this means they are not showing any lights. The lights were working, just not working properly.

[@markwalton8644]

​@@allanhook Not Necessarily. If the computer which controls them freezes then they no longer work as they should, so I don't see why you can't proceed with great care.

[@smilerbob]

@markwalton8644 I think the key phrase is “if the traffic lights are not working” rather than “if the traffic lights are not illuminated” thus covering for all types of failure modes as you describe 👍

[@CraigNiel]

I've been in this exact situation (without the Police though) where the red light just stayed on and would not change. I tried reversing and driving forward but nothing happened. After about 5 minutes I just had to go through the light as it seemed broken. I just treated it like any other junction and gave way to any traffic as you normally would. Luckily it was quite quiet and I just took it really slow and all was well. It's so ingrained in us not to go through a red light (and rightly so) that it really does feel so strange to do it, even under such necessary circumstances.

[@klausbinn777]

More accurately, it's ingrained in MOST of us. 🙂

[@CraigNiel]

@@klausbinn777 haha yeah that's true!

[@InviolateTree]

In that seituration you can go thorught a red as you have a good reason to cut the red then only time you can't do this is if there a cameras

[@stevezodiac491]

​@@klausbinn777yes, there are a lot of car and particularly taxi drivers who drive through red lights.

[@Peer_Review]

Something I found really interesting going to the US is that apparently you’re allowed to turn right through a red traffic light (equivalent to a left turn here in the uk) when at a junction, basically treating it as a stop sign. It felt super wrong every time

[@craigstevenson6565]

I'm just dropping a wee message to say thank you. I just passed my test, first time one minor with my dad as my only instructor. Your videos helped me in many situations!!!

[@ashley_neal]

Great job! Congratulations!!

[@1988dgs]

Backing away and approaching again would have fixed this. Also on the ground loop system with a motorbike stopping and starting again gives the system a bigger jolt

[@learigg]

The lights in Ayrshire are mostly controlled by induction loops buried in the road. A common issue is cars turning right not pulling forward on green light. There is a loop in the road where you wait to turn right, if you're not on top of this then the filter light will never activate. I've sat through 4 or 5 light sequences when the driver in front refuses to pull forward. We could definitely use some general training on how lights work and also reinforce thats its ok to pull forward when right exit is busy, assuming we're not on box junction.

[@alex291190]

Sainsburys in Prestwick is bloody awful for that.

[@DaveHines1]

As a motorcyclist , I’ve often found traffic lights don’t pick up my motorbike , and have to wait several minutes til they cycle . I recently got stopped for about 5 minutes at temporary traffic lights which kept on letting cars thru periodically from the other direction , they eventually changed to green when a police motorcyclist approached the lights passing the stop here sign .

[@RichardBeds]

As a cyclist I often find that traffic lights don’t trigger. I wonder whether it’s because I’m not a big enough object to trigger them? I also find that some traffic lights with induction loops don’t work in the rain.

[@clickrick]

@@RichardBeds Big enough, heavy enough, contain enough metal ... all of those things, depending on the precise sensors.

[@insoft_uk]

As a cyclist they don’t pick up cyclists and have no option to just ignore and continue through if safe t do so, so much for Highway Code telling cyclists to stop at reds as in some situations we be waiting for hours One set I know that’s like this and learned to just ignore them.

[@andrewnorris5415]

Same on a cycle. My tips that I found work are - 1) temp lights, usually a small extra LED red light comes on when it has picked you up. Move about a bit or go closer, these are motion sensor based. 2) look out for the sensor tracks in the road. When your front wheel goes over it, push down very hard on the wheel at low speed. This nearly always works on lights that would otherwise not pick me up.

[@C0baltBlueJ]

I had this on my motorbike a few years ago. I must have waited a good 5 minutes with zero traffic in any direction before I decided to *carefully* pull out on the red. I assumed it was because it was dark and it hadn't seen me, even though I had my lights on.

[@johnlochness]

One thing I've noticed with temporary traffic lights in recent years is that if the road is quiet they will turn to red for both directions, then when a car approaches they can instantly turn green for that direction.

[@Lysimachus]

This happened to me on my first ever day of driving on my own... I decided to just proceed anyway after five minutes of waiting and on the other end luckily all incoming traffic had come to a stop.

[@joefarr3304]

Often with temporary lights if you flash your high beam at them they will have changed by the time you get there. I was always told it was so they could detect emergency services vehicles with their flashing high-beam lights.

[@Kromaatikse]

This junction has both motion and inductive sensors. You can see the grooves for the latter pass under where the camera car stops the first time (diagonal, third car back) and also, crucially, *between* where the police car stops (halfway across the stop line) and where the camera car stops. This latter set of grooves go straight across the road, and are most easily seen where they interrupt the double-yellow painted lines. I think the lights changed for the first time, not because there was a gap in the traffic, but because it sensed at least three cars waiting (both the first-car and third-car sensors active). Then it was confused, not by a lack of movement per se, but because the remaining cars stopped in positions where the installed sensors couldn't detect them. If the police car had reversed back so that it covered the first-car sensor, this would have prompted the lights to insert this road into the normal cycle sequence; the third-car sensor allows for a priority system, and I think the motion sensor is mostly used to judge when to revert to red.

[@thedave7760]

Or if our driver had just pulled forward to the police car just a little it would probably have sensed something.

[@RoamingAdhocrat]

Reversing back off a junction towards queueing traffic with pedestrians crossing is dangerous. Police driver had already crossed the stop line - after that point he should've ignored the lights and proceeded over the junction cautiously at his own discretion (same as any other motorist). Instead he got two colleagues to make a bit of a meal of things!

[@spac20]

Perfectly said 💯👌🏽

[@robhunt8682]

I cannot see any grooves in the road. I think what you are seeing is the reflection from the windscreen of the air vents. I thought they were sensors in the road at first but if you look carefully they are actually the vents' reflection

[@Kromaatikse]

@@robhunt8682 There are diagonal grooves visible just before the camera car stops for the first time, and it stops directly over them. This is the "third car waiting" sensor. The grooves for the "first car waiting" sensor are not easily visible on the road itself, but there are corresponding "cuts" in the double yellow lines which are easier to see. This sensor falls between the two cars when they stop for the second time, but is also out of view while stationary. These two inductive sensors are used in conjunction with the one on top of the lights, which is motion sensitive (so can detect approaching or flowing traffic) but cannot detect a stationary vehicle.

[@dr_dr]

Was the buried induction loop between the cammer and the Police car? It looked like it, in which case the Police cars poor positioning over the white line meant the system couldn't "see" it, and the car behind hadn't come forward enough to trigger it either.

[@grahambullman]

These lights are 400 yds away from my house, and this happens a lot with them. They don’t recognise me when I’m on my bike. Normally two lanes of traffic line up, depending which lane is required around the bend which I think helps to keep things flowing and ensure there is generally some movement. 🙂

[@andyalder7910]

Sit on top of the induction loop just behind the turn right arrow; on a motorbike have your engine over the loop, on a push bike try the front wheel over the loop and keep turning the handlebars so the metal wheel makes the induced current fluctuate. You can clearly see where the loop is cut into the tarmac, if you are in front of this you won't trigger the lights so move aside and wave a car forwards over the sensor. You can also ask the council to adjust the sensitivity.

[@andrewnorris5415]

My tips that I found work are - 1) temp lights, usually a small extra LED red light comes on when it has picked you up. Move about a bit or go closer, these are motion sensor based. 2) look out for the sensor tracks in the road. When your front wheel goes over it, push down very hard on the wheel at low speed. This nearly always works on lights that would otherwise not pick me up.

[@davidkane4652]

Im very sorry you have to live in Midsomer Norton

[@grahambullman]

@@davidkane4652 I'm not. Pubs, supermarket, post office and restaurants all within 5 minutes walk of home, and greenway cycle track on my doorstep.

[@clickrick]

My late father worked in traffic management until he retired some 25+ years ago. There are many variants of traffic light control, with sensors visible above (as here) and buried in the road (as you said), with time of day also a factor, but most have a default "error" mode that they will fall back to if they fail to sense anything for a set period of time. As with everything, that period can vary, with times of 15 minutes not being uncommon in a city. In other words, if it doesn't sense traffic approaching for 15 minutes, the controller will assume there's a fault with the sensors and go to standard timed intervals. Whether it then goes back to sensor-driven is another variable, but you might see a small red light visible on the equipment somewhere which will indicate that it's in this error state.

[@pugsterjosh7925]

Does the UK have anything similar to the US, whereby an engineer can initiate a “flash” state for the whole junction where all the lights will flash amber?

[@clickrick]

@@pugsterjosh7925 Flashing amber in particular is used in the UK at pedestrian light controlled crossings to indicate "proceed with caution". It follows the red phase. I don't believe there's anything equivalent to what you say, though. Not that we couldn't, and the same "proceed with caution" message would be entirely applicable, but I think the traffic engineers have long since learned that the driving public cannot be trusted to exercise "caution". Ever.

[@mattwoolford]

Hi, software engineer 👋🏼 I don’t pretend to have worked on traffic light systems but I spend a good chunk of my time observing technologies in our every day (and maybe getting a bit frustrated with the build of some traffic light systems in particular)! TL;DR don’t flash your lights at traffic lights. It does nothing and so you look silly. Sensors you see on top of traffic lights are used to detect MOVING traffic as the video points out. However, the under road sensors (induction loops) detect traffic that has moved over it or is stationary above it. The best traffic lights have under road sensors 200m or so back, which means the traffic lights are green by the time you reach them. The worst traffic lights keep the major road waiting on a red light, and the empty-of-traffic minor road on green. The sensors on top of traffic lights are generally infrared or microwave. For simplicity, let’s just call it radar. Radar can detect stationary or moving objects, but how would it know if it is detecting a stationary car or a rogue pigeon eating someone’s McDonald’s fries? Instead the radar sensors measure speed to solve this, with a prefixed speed to determine a car. A pigeon is unlikely to be consistently moving towards the traffic light above 5mph (birds fly erratically, for example). Induction loops measure, you guessed it, induction, thanks to the metallic build of cars. This can be used as a switch. It doesn’t require constant induction to know that a car is there, if the induction changed over the threshold and then disappeared, this would be a sign that a car has passed over it. Here’s the general basis of the algorithm I’ve observed with some made-up numbers, and some brief research would seem to confirm (please bear in mind every traffic light system is different, but in a general sense the following is likely to apply). A basic set of traffic lights should have a fixed timer for an interchange. For example RED_TIME = 120 //Seconds GREEN_TIME = 30 //Seconds WHILE (TRUE): //Repeat indefinitely WAIT(RED_TIME) CHANGE("GREEN") WAIT(GREEN_TIME) CHANGE("RED") A good traffic light system should build on this by adding vehicle actuation (sensors). A separate process will run: SENSOR.ON("Vehicle Detected", REDUCE_RED_TIME(RED_TIME * 0.1) // Fast forward the red time by 10% of the remaining time to reduce waiting time ) This means that when a sensor detects a vehicle (or vehicles depending on build), that traffic will get prioritised, but in the case the sensor hasn’t detected anything, there will still be an opportunity every 120 seconds for vehicles to pass through which is a failsafe. Most traffic lights will do this. On complex junctions though, there are obviously other considerations such as traffic directions and sequencing.

[@drcl7429]

This is not really how it works in embedded systems.

[@mattwoolford]

@@drcl7429correct by my own admission, but for the sake of concept, this is how it works to the everyday person 😄

[@rogerknight8092]

You need to multiply by 0.9 to get a 10% reduction.

[@mattwoolford]

@@rogerknight8092 not in my example when I’m using it as an argument to a pseudo function “reduce_red_time” as I am reducing the red time by a specified 10%. But yes, that is the calculation for finding 90% of a value in any other circumstance

[@JB9000x]

I did software engineering at university and I've been a traffic engineer for 20 years. 😊

[@geko7844]

One big issue I see is people not driving right up to the stop line - they often stop about a car-length back. This is a problem for lights with just one magnetic sensor - it doesn’t detect a car there and so the light stays on red for longer (until the lights cycle themselves). Interestingly, I remember an old Kipkay video years ago which recommended putting a strong magnet under your car - especially for small vehicles like mopeds - to make sure you trigger the lights 😅

[@captafrica]

Oddly enough, I had exactly this situation a few months ago, in a major city at night trying to join from a two lane, one way side road to a main road. I waited at the lights for around 6 minutes in the left lane, realised something wasn't right when private hires blew through the lights while the rest of us waited. Once a gap in the traffic developed, I proceeded through the lights treating it as an unmarked junction (As Rule 176 in the Highway Code states). Bad luck for me that an undercover police car had joined the queue around 30s before this and pulled me over once I'd passed the junction. 3 points and a fine with a solicitor advising me not to fight the FPN as technically there is no official guidance on how long a light needs to be out before we can consider it broken, and losing the fight in court could result in a much larger fine and a charge for driving without due care and attention. I tried explaining to the officer that pulled me over that the light clearly was not working and I had several minutes of evidence of this on my dashcam. He wasn't interested and "kindly" let me know that I don't have the authority to determine that a light is broken and that I should wait at the red light for as long as it takes.

[@russell5791]

Rule 176 of the highway code Only go forward when the traffic lights are green if there is room for you to clear the junction safely or you are taking up a position to turn right. If the traffic lights are not working, treat the situation as you would an unmarked junction and proceed with great care. - It does not say who or what is defined as a traffic light not working, neither does it give guidance on how long you should wait before determining the traffic lights are not working. It also does not define whether a light stuck on red is a traffic light not working. It does not say that you can't define when the lights are not working, in fact the highway code is suggesting you decide. Vague at best, probably worth fighting in court. (I woiuld have)

[@mda5003]

Difficult without police being there but I've always assumed that after waiting around 4 minutes the lights must be stuck and to proceed with caution always remembering that in the event of an accident/collision you would be at fault for crossing a red light. However, I would be concerned though if there was a possibility of there being a red-light camera in operation.

[@pocky1scot1]

You would only be at fault for not being safe not because of the broken red light. Rule 176 "if the traffic light is not working, treat the situation as you would an unmarked junction and proceed with great care"

[@kenbrown2808]

I have no experience with UK red light cameras, but my understanding of how US red light cameras work, is that the trigger for the camera is defeated if a car stops at the stop line and then proceeds through the junction. of course, this should not be taken as instruction on how to run red lights.

[@mda5003]

@@kenbrown2808 I've never heard of how that would defeat a red-light camera in the UK simply by stopping and then moving off. The cameras we have can even see what you've had for breakfast!

[@kenbrown2808]

@@mda5003 it's why I clarified that I have no knowledge of the logic UK red light cameras work on. in the US, a red light camera will see a car approaching a red light, and wake up, and watch for it to cross the line. if the car stops at the line, it says, "aw shucks, it stopped" and then looks for other moving cars. I'm guessing part of that is because in most places, motorists are allowed to make a right turn on red, after stopping, if it is safe to do so. I know we have the rule that the camera must produce photographs of the car approaching the line, and then completely crossing it, before a citation can be issued, though.

[@pugsterjosh7925]

⁠​⁠@@kenbrown2808 I believe in the UK red light cameras utilise the induction loops that are already embedded in the tarmac. If the light is red and the control system registers a temporary change in magnetic field, it must “assume” that a vehicle has ran a red light and snap a picture.

[@ihateunicorns867]

This happens to me all the time when I'm on my bike. There's this one spot where I always get stuck. If it was just a junction, I'd dismount and wheel my bike through, but it's an alternating one-way system.

[@NckBrktt]

I have noticed not all traffic lights can detect 2 wheeled vehicles. This can be an issue at quiet times early in the morning. At some lights I sometimes have to wave madly and flash headlamps even though there is absolutely no other traffic coming. Even then sometimes nothing works and I have to "proceed with caution" (usually 6am and deserted). Other times a car or van will approach from behind and rescue me by triggering the lights.

[@thomaselliot2257]

That happened to me over 30 years ago trying to come out of a side street at Paisley Road Toll , Glasgow, to be exact. My traffic lights seemed permantly on red. I waited for about 3 cycles of lights on the main roads . It was early evening , I think , and it WAS quiet, so I emerged against my red light. Of course, there a was a police car from nowhere, and stopped me , but they let me go when I explained. Phew 🙄

[@lyndsnevircs3745]

I was required to wait at these lights yesterday. Even when we were stationary, the lights changed to green within 2 minutes. I would say they were faulty, they changed red very quickly aswell from my past experience.

[@JaneAustenAteMyCat]

So they work better when you're paper, or perhaps a pen? Interesting 🤔

[@johnkeepin7527]

While this is an exit from a public car park, there are some places where the exit only works for buses fitted with traffic signal priority (TSP) kit, which is used to detect them and sets the route for them. Also used to give them priority over certain junctions, in which case the sequencing of routes varies, rather than a standard one.

[@mrsulzer66]

Another function of sensor would appear to be speed control. I commute (at night) through a set on a main road which as you state in the video, remain at green until traffic from the junction triggers them. Although, if you approach these lights (on the main route) even 5-10 mph faster than the speed limit, will trigger the lights to go to red regardless of the fact there is No other traffic anywhere.

[@pauleff3312]

AS A CYCLIST - I *hate* jumping red lights.... But if they don't know I'm there because I'm not big enough / heavy enough / wide enough to "trip" the sensors, and it's 1 AM or so and there is absolutely no-one about WHAT DO YOU EXPECT ME TO DO? Sit there and freeze to death? I always, always stop for red lights but I won't wait longer than 20 seconds where and when the roads really are deserted. I listen, listen, listen and then set off again - usually cussing whilst doing so into the video camera about the traffic lights needing to work for me too!!!! I HATE jumping the lights and would just prefer that they work!

[@ibs5080]

One nice option in North America if traffic lights ever get stuck on red: The fact that it's legal to turn right on a red light over there, with a few caveats to be obeyed. You can also turn left on a red light over there, providing the street you are turning into is one way. Again, a few caveats exist but it's a useful option to have in case of lights stuck on red...or indeed to get out of the way of an emergency vehicle. Oh and over there, red light cameras can distinguish a legal turn on red, as long as you come to a complete stop behind the line first. They even have signs at such intersections to remind you to come to a full stop first.

[@jaycee330]

Unfortunately, in this example it wouldn't work, as the cammer is approaching a right-turn only lane (which in the US would be left-turn), so even if the option to turn left on red was available, it would not help here, as you would have to cross opposing traffic.

[@neiltill]

I think if i had no police assistance and it was safe for me to do so after that long waiting I'd of carefully gone through the red light and hopefully the sensor (if it wasn't broken) was triggered by traffic behind me to get things working again. I do know at work as a bus driver if I had a situation like this, I can report to our control that a set of traffic lights appear to be stuck on red, on said road, and they can report it to the local council.

[@juddy_1997]

Wouldn’t work in Australia we have red light cameras at every intersection

[@neiltill]

@@juddy_1997 you could be sat there a long time in Australia then?

[@juddy_1997]

@@neiltill possibly but this isn’t very common.

[@Eelesy02]

Hi there, I work as a traffic signal engineer. You’re correct in fact that the ‘sensor’ is looking for moving cars which is why it’s stuck on red. It’s called an MVD - Moving vehicle detector. Usually smaller side roads also have a stop line detector whether that’s a physical in road induction ‘loop’ or an above ground sensor/camera. This would detect a car that is waiting at the stop line even if it’s stationary. It looks as if there isn’t one here because usually they have a failsafe and get stuck on rather than off. If you report to your local council they are usually pretty good when it comes to traffic light issues and they might have one installed. Cheers 👍

[@blueish4]

you'll sometimes get the ground detection loops on smart junctions with cycle lanes - obviously since bikes are smaller (and sometimes not made up of enough metal) they'll never detect you. in these cases i normally cross the junction with care in the pedestrian phase after pushing the button you can also treat a broken sensor traffic light as a stop sign if and only if its cycled through the same phase twice and ignored you, just be very careful

[@oxonomy2372]

You can try leaning your bike over, works on some

[@andrewnorris5415]

Not heard of these that pic up metal! One of my bikes is full carbon so would have no chance. My tips that I found work are - 1) temp lights, usually a small extra LED red light comes on when it has picked you up. Move about a bit or go closer, these are motion sensor based. 2) look out for the sensor tracks in the road. When your front wheel goes over it, push down very hard on the wheel at low speed. This nearly always works on lights that would otherwise not pick me up.

[@alexanderbabington5270]

I had a similar situation where the traffic light was not changing on my driving test. Observed multiple full cycles where it did change to let traffic out from the opposite road but not mine on a cross roads. I made the decision it had failed told the examiner and said I was going to procede with caution provided there was no traffic. The examiner didn't say much at the time but afterwards said he agreed with my assessment. I passed the test

[@vator_rs]

Hi Ashley, I just wanted to say big thank you for all your videos all the way here from Serbia! This past Monday, I passed my drivers test on 2nd attempt with 5 minors! Your videos have helped me learn a lot about traffic flow and how to deal with certain situations. I will keep watching but now I don't have to stress about passing the test 😂

[@ashley_neal]

Congratulations!

[@vator_rs]

@@ashley_neal Thank you!

[@bryansmith1920]

Thank you Ashley for trying to get out there the knowledge about road sensors, I honestly wonder what motorist think, when they see the geometric pattern in the road surface at a T/L controlled junction, I'm an ex HGV driver also a Qualified driving instructor from back in the 1980's, I feel sad for the lack of knowledge of young drivers

[@ChrispyNut]

There's a set near me that defaults to red on main road, green on side. Even though you didn't explicitly get me started on it, traffic light irritations always bring my mind to those which are incapable of detecting cyclists.

[@rampak1]

Lights near me default to red on all roads if no traffic is detected for a while. This is great because it means that when you do approach from any direction at a quiet time the lights will immediately go green for you.

[@ChrispyNut]

@@rampak1 That is the more sensible way, until Syke, someone coming from the adjacent at the same time 😆 These lights are just badly set up. I tried to get them changed, but, nope. Most annoying are the trucks that have to (almost) stop, so much wasted fuel and extra pollution. Oh and they also don't detect cyclists. So bad!.

[@StevenGreenGuz]

I once came across the opposite problem. The lights were going green in both directions, I almost got knocked off my bike. A friend and I decided to play traffic cop and directed traffic and tried to explain to drivers what the problem was. Eventually some police officers came along and took over. They just told us to bugger off, no other discussion. I guess a good deed is its own reward.

[@1harryrobert]

The Conflict Monitor prevents this from happening.

[@ibs5080]

When on a relatively free flowing road with multiple traffic lights, I like to have a few vehicles ahead of me in the hope they will trip the sensor for me. I've managed to get quite a long uninterrupted "green wave" using this technique, having the other vehicles do all the work of slowing and then accelerating to the next set of lights. In the meantime, I've been able to maintain a relatively constant speed.

[@frogsplorer]

Cool!

[@PedroConejo1939]

In Nottingham back in the late 70s (I think), there was a green wave on several roads with multiple sets of lights. Stick to the speed limit and you could get through most times. Automatic Grüne Welle is, I believe a German implementation (like many traffic improvements) and I can remember learning about it when I lived there in the 80s. It was far from new, even then; there were even signs telling you the optimum speed.

[@johnnymichael1804]

Atta boy, Ibbadeeb.

[@Shaun137]

Glad I found this again, Happened outside Asda in Stafford. Someone blocked the exit route on the Box Junction and the lights cycled twice and then got stuck as nothing was moving and the sensors must have decided there was no need to change. The roads in Stafford were chock-o-block again due to an accident on the M6. Decided that when said car had moved out the way to pull forward slowly on Red and when it was safe to proceed off, the car behind followed too. Hopefully that got the lights going again. Box Junctions are there for a reason, no real excuse getting caught on one unless there's exceptional circumstances.

[@QuentinStephens]

One thing this shows is that traffic lights need two sensors: cameras and ground loop, in case one of them fails.

[@em0_tion]

💲👀😂

[@averyboringusername]

The two principal sensors used on traffic signals are microwave detectors (usually a small box on top of the signal) and inductive loops (wire embedded in the road surface). The microwave detector has a microwave transmitter and the reflected transmission is picked up by the detector. A moving object will create a Doppler shift with the reflected signal. If the detector observes a change in the reflected signal it assumes a vehicle is approaching. Microwave detectors usually have a minimum trigger speed for approaching vehicles to stop false positives. Inductive loops generate an electromagnetic field, a metal object within the field changes the properties of the field which is detected by the field circuitry. A few observations: When a signal is controlled by an induction loop at the traffic light there is sometimes an earlier loop to detect queue length. If a vehicle is waiting at the lights on the induction loop if you stop your car on the earlier loop you can trick the system into thinking the queue is longer than it actually is therefore reducing the time of your red phase. Puffin crossings (pedestrian user-friendly intelligent) have a microwave detector to sense if people are still on the crossing. Impatient drivers who keep creeping forward can sometimes be detected by the crossing occasionally confusing the system into thinking a pedestrian is still crossing therefore making the driver wait for longer. The microwave detectors on temporary signals often have a small led which illuminates when the sensor detects movement, you can watch for that led to make sure the lights have detected you.

[@ShedTV]

I agree with the theory that the sensor isn't being triggered. I think it's pointing at the bit of road between the Police car and your viewer. The Police driver got caught out as the lights changed quite quickly, because they're probably timed in favour of the main road. He couldn't clear the junction, leaving him stranded across the line. The other car is too far back to catch the sensor. I'm pretty sure if the Police officer had reversed up to the camera car it would have triggered the lights.

[@andyalder7910]

There is an induction loop in the road but it's between the two cars, clearly visible on Streetview.

[@ShedTV]

@@andyalder7910 Thanks, I just had a look. I wonder if the sensor on the top of the lights is there to detect cyclists who might not trigger the loop. Even with the entire Somerset constabulary wandering around nobody walks in between the two cars!

[@Real_Venture_Out]

I worked for a company years ago that used to to use temporary traffic lights for road works, and the sensors on the traffic lights that we used were positioned on the top and wouldn’t detect traffic travelling towards them at less than 5mph. The flashing of headlights is a complete myth, it’s the physical movement that they detect.

[@StefanVeenstra]

“Smart lights” as they're sometimes called here in NL. Though no mounted sensors, usually just loops in the ground that detect cars and even cyclists approaching or waiting. Do think people shouldn't take these for granted though, I've had seen plenty red light jumpers going for it, because they expected green and didn't bother to slow down. Just because these systems aides traffic flow, we shouldn't give up on paying attention.

[@itIsI988]

Can't stand the ground loop ones. Given how most bikes are aluminium these days it's no wonder why cyclists generally run red lights.

[@JamesTombs]

Have lights near us that you need to have the front of the car on or slightly beyond the white line to get picked up otherwise traffic going right gets skipped in the light cycle. Many cars, especially learner drivers it must be said, stop a good 5-6ft before the line and end up sitting for a prolonged period through multiple cycles before they get impatient and start creeping forward at which point they'll hit the line and the lights will pick the traffic up. This can cause quite a lot of traffic to build up and someone put up a cardboard sign on the traffic island telling people to make sure there car was forward of the line to stop this happening.

[@WhiteEagleTube]

There is actually a magnetic sensor on these lights, you can just about see the wire buried below the white arrow. There just wasn't enough of the police car over it.

[@aspuzling]

What is a magnetic sensor exactly? Can it detect the steel frame of a car or something? If that's the case then it shouldn't matter whether the car is stationary or not. But if it is a radar sensor like Ashley is suggesting then it will matter.

[@andyalder7910]

See the induction loop cutout better on StreetView on the exit of Sainsbury's carpark in Midsomer Norton.

[@WhiteEagleTube]

@@aspuzling I think it creates a low magnetic field. So anything with sufficient mass in that area will trigger the sensor. I think they are always paired with a camera as well.

[@garyt123]

Not magnetic at all, but an induction loop as @andyalder7910 has mentioned. They work literally thanks to "mass" of metal.

[@jaycee330]

Agreed. If the police car had reversed back and moved forward again, it would have probably triggered it.

[@martinbatley9512]

Over the 40 years I've been riding motorcycles I've been stuck at red lights plenty of times due to the underground sensor failing to register my bike. I usually move the bike around trying to trigger the sensor. Failing this I go through on red taking due care. I have actually been caught 4 times by the police going through on red. Fortunately each time I respectfully explained the situation and they recognised I'd taken good care going through. I should mention that each time it's been late at night with little danger .

[@brendanhegarty6792]

The sensors are built into the roads in Australia. Some drivers stop so far forward that I worry they won't trigger the sensor so I drive right up behind them so my car covers the sensor. I can remember years ago being stuck behind a truck waiting to turn out of a shopping centre. He was the first in line but too far back to trigger the sensor. I had to get out of my car and tell him to drive forward or the lights would never have turned.

[@ianl1052]

Respect to the police officer for staying patient and calling for assistance to cure the problem.

[@123MondayTuesday]

These traffic lights detect cops and hold them up

[@ashley_neal]

I love your comments 😂

[@IseiNabuka]

Thank you Ash for this, most drivers in my area do not or not aware that most traffic lights nowadays have sensors on them. In a shopping complex where I work, we have to tell drivers who are stuck at a traffic light is that they need to drive up towards the white lines as the sensors cannot detect any vehicle

[@1harryrobert]

Oh dear, lol.

[@lozyoung4110]

Pet hate - sensors that don't detect me on my bike!

[@simoneast757]

I work at Headway Traffic Management and I'm fully qualified in all traffic lights, the simple answer is. On top of the traffic lights is a radar vehicle activation which detects movement, if no movement then the lights will stay red giving the main road green as a priority. In this situation I would of reserved back if I could and drove up to the lights to activate the radar or driven up to the police car, in this video tho the radar seems to be abit dodgy or just simply dirty as dirt can affect the sensor. Theses vehicle activation radars are on all Temporary Lights which I personally put on the road for the last 6 years now, I'm glad that the council are putting these radars on Permanent lights now BUT...the council need to clean them to avoid this problem but they don't. Hope this helps 👍

[@laceandwhisky]

Been in this circumstance before and after waiting so long called 101 to let the cops know so they could relay the issue and then I edged out and used it like a normal T junction. Always a gap at some stage 😊

[@ironlungthe3rd]

Worked in traffic management in the UK and currently in Australia for many years, the traffic light changing is called 'phasing', this is when a light changes from green then amber to red or vice versa, the grooves cut out and cable layed in are generally referred to as 'loops', they detect any vehicle by electro magnetic interference above the circuit, The sensors that are on the lights themselves are very temperamental, and by the situation at hand definitely means there is a fault with the system, this can occur due to many different things, it may be that the phasing is incorrectly set, or they work off of cars needing to be places with a certain tolerance, unless that is detected it will not trigger the phase.

[@ibs5080]

Interestingly, in Canada and the USA, the sensors are often loop detectors set in the road surface itself. They detect the metal of a vehicle above them and often there are two or more loop detectors in each lane to give the traffic lights a sense of how long the queue of waiting vehicles is. They can cause issues detecting cyclists and motorcycles but to aid this, they also have an X to mark the spot where a two wheeler should tilt their vehicle to be picked up by the loop detector. Question: Does the UK ever have loop detectors or only the type of sensors as in this video, namely mounted on the traffic lights?

[@thomaselliot2257]

I remember vaguely that Ashley covered those sort of sensors many videos ago . I wonder if he would be able to provide a link . Ashley DID mention it in this video 🙂

[@signaltheway]

That detector on top of the signal is a Microwave Vehicle Detector, and due to the way it works, only detects moving vehicles. Typically, where there isn't a revertive demand (i.e., when the 'side road' is clear, it automatically reverts to the 'main road'), an MVD would be paired with something that can detect a stationary vehicle at the stop line for just this eventuality. This may be something which looks similar to the MVD or it might be something in the carriageway such as an inductive loop. Another thing worth noting is that in coordinated networks, the timings might not be quite as responsive as you're expecting them to be, because there's an external influence in control of the signals which is looking at a bigger picture. This could be something local (i.e. one set of signals at green holding another set of signals just down the road at green), or they could be under the control of a central control system. There will often still be detection like in the video as a fall-back control method, which might be used say overnight when there is no need for coordination, or when a fault condition means the signals are not under the control of the coordinating system.

[@Rich-CV]

I work in traffic management ( temporary traffic management) includes temporary lights, road closures etc. Usually the sensors are motion sensors especially on temp lights, but I have seen more recently lights set to timings which makes a much longer wait time on RED, if you are driving towards a set of temporary lights the (When red light shows wait here) board is supposed to be 15 metres back if you go by the traffic management Red book, but you soon realise at that distance the lights sometimes struggle to trigger so need to just slowly move forwards and the red light will trigger on the sensor just above the red light.

[@chrispayne523]

I seem to remember being told somewhere, might have been during my PSV training that if lights don't change after 5 minutes carefully move through them.

[@rickiecheese36]

I agree with some other comments. I worked for a Hire company supplying temporary lights for roadworks. The sensor work by detecting the movement of approaching vehicles. The viewers car should of moved back (if possible) and forwards again to create movement to wake the lights up. They usually have a small red light on the front that flickers to indicate that movement has been detected.

[@pajownik]

Happens a lot when you are on a motorcycle. Sensors often don't detect bikes. In many countries The Highway Code allows motorcyclists to proceed with caution. In UK there is no problem, as really important people don't ride motorcycles.

[@rondameier8168]

I preface this with I live in the states..... Here I would say almost all have the sensors in the ground, or under the tarmac as you called it... And if you know where that area is, then drive onto it. I have a signal near me that is a left turn off the freeway exit, but the right hand turn is not with it at the same set of lights, it's also on a steep incline and it's a strange kind of left hook if you will. Well it also doesn't like to change if you aren't on the plate under the tarmac, a very specific way. You also can't flash your highbeams at the signal because of the angle they sit at, because a lot of lights here have a sensor on the top of the light as well. So what I learned a long time ago was to reverse back and roll forward again. And to do this as many times as you need, or if traffic allows. Motorcycles here are notorious for not being heavy enough to set the sensor off. And will at times get stuck at the lights till a heavier vehicle pulls up. So with the light near me that does this, I just roll back and forward again, but I've also learned to stop on the sensor in a little bit of a different way, and it seems to work... I also think in some places here that if you've sat at a light for over 3 minutes (don't know what the exact time would be), and if there is no traffic you are allowed to treat it as a 4 way stop, 2 way stop, etc....

[@nabilomar4631]

Motorcycle rider - This happens to me all the time with these sensors. Luckily I'm in London so a car is not far behind usually, I normally just pull forward into the cycle box or beyond the white line a little and tell the car behind me to come forward. Lights always change within 10 seconds of this.

[@davet2555]

Used to have this a lot on my old bike and a particular junction. Gave it some time and then treated it as a give way

[@_.Madness._]

Had the same thing happen at a similar junction last month. The main road lights would go red for pedestrians several times, but our side road light was stuck on red. No one in front had the sense to move their car back and forth to activate the sensors. After a 10-minute standoff, the guy in front had enough and started to make a U-turn and just like that, our light turned green. Next time, I might as well bring a tent and camp out if no one moves.

[@benchilcott6908]

I've noticed that in my area, traffic lights on main roads will default to red, while emerging traffic from side roads has green lights. I think this has a similar effect to speed bumps to stop cars absolutely sending it when the roads are empty.

[@adewhite3921]

I've just came across this video and recognised that this is in my local town of Midsomer Norton.These traffic lights and the lights around the corner have always been a problem. On a busy day you have 2 lanes of traffic coming from the left which then have to stop just 10/15 yards past these lights at another set of lights. You only need someone to end up stopping in the box junction in front of these lights to mess everything up as nobody can then pull out when these change to green. By the time the other lights have changed , these will have gone back to red.

[@stephenhill8790]

With temporary lights often a wave of your hand will work, if it has not changed, the others you need a long branch, but don't stand too close, flashing lights will not work as it's an infrared system, some can use ultra sonic but rare

[@bikes_camera_more]

Traffic light sensors are a frustration as a cyclist, too. Many times I have waited at a red traffic light, for the lights to only change upon a car or other larger vehicle pulling up behind me.

[@pgsm15]

Been in this exact situation a light close to home, especially at night behaves this way...so if I there's little traffic I avoid it. How I handle them: 1. Move back and forth if there's space to do so (if this doesn't work) 2. Go through the red light when the otherside has also got a red light, still proceeding slowly and giving them priority at all times

[@brantnuttall]

I was caught in a similar situation last year. I was coming up a very major road in Blackpool when the traffic lights didn't work. And despite cars and buses queueing up behind me, I sat at the red lights for 3 revolutions (4 way junction). On the 4 revolution though I carefully jumped the red lights and all the following traffic did the same. They were fixed later on that day though.

[@isaacplaysbass8568]

I have encountered a similar issue whilst commuting by bicycle late at night, when stopped at traffic lights with the (magnetic) induction sensors embedded in the road (you can usually see the lines in the road where the sensors have been set into the asphalt). I discovered that to "tell" the traffic light controller that I was there, I could lie my steel bicycle frame down onto the ground, which would immediately trigger the light-change sequence so that I could proceed with my journey

[@skypirate4806]

I’ve been in this situation before, it usually ends up either the person at the lights skipping the red light carefully, or if there’s space behind them, they reverse so the sensor picks them up.

[@user-gt4og5le1k]

Hello Neal, you are right the sensor relies on movement passing over the magnetic triggers in the road, motorcycles have this problem when they don,t activate the trigger and holds traffic up behind, provide camera evidence from camera activity and the police/DVLA or the CPS won't action the event.

[@megajohntopunishenslave427]

I’m a bus driver in London ATO temp lights are always messing up. Thus there default aspect is red. We are taught that if suspected or not changed for over 5 mins pass the red light under extreme care and caution with hazards on.

[@chrisddr3]

Motorcyclist in NL here. My longest wait was 7 minutes at a light in an eerily empty intersection, ended up running the red. It is quite a common situation, on a bike you need to approach the intersections in the central position of the lane, otherwise the sensor is likely to miss you.

[@catthompson9444]

Had an experience in Drighlington where 3 horse riders were stuck at traffic lights unable to trigger the lights. We assumed that they were triggered by weight rather than movement,. They stood aside, we moved the car forward to the front, and everything started flowing again.

[@lesliejefferies4814]

A good reason for leaving a gap between stationary vehicles in a queue - remember the old phrase "tyres on tarmac"? This would allow vehicles to move slightly backwards or forwards to kick the sensor into life - if not broken, that is.

[@wintersun398]

I recall an article from the late 90’s saying the traffic light phases in London were modified to make flows less efficient. To purposely slow to flow of traffic. Also induction loops in the roads can be used to calculate traffic speed! If you drive above the speed limit on the approach to some lights they’d turn to red.

[@abdirisakaliabdi2655]

It is obstacles I go through as a delivery rider using a motorcycle, especially at night! So I always try to communicate the sensor by reversing or coming near the sensor, and most of times it works

[@kempo_95]

In the Netherlands for big junctions, there are often 3 magnetic loops per side. One for warning the system a car is coming, one queue loop that lets the system know how big the queue is, and one loop at the stop line. Magnetic loops can be problematic for motor drivers because they can park in between the lines.

[@imranw4221]

I have this problem in my town in Essex. Best thing to do is if no is behind you then reverse and drive towards the white line to trigger the sensor. Usually works. If that doesn’t work then, I would creep forward if it’s clear in front then go. Better have a dash cam recording just in case you get a ticket. That way you can argue your case.

[@gordslater]

Radio and radar guy here (though for bigger/faster vehicles than this haha) If it's a doppler radar sensor, which it looks like it is, it would not detect (or, in another mode/design) only just barely detect stationary vehicles. So yep - you were right - reversing back and foward again would probably have triggered the doppler gate. Hard to see, but it seems the radar head is pointed almost directly at the camera vehicle, so moving forward into the space behind the cop car should have worked. Also of note is that the cop car was well forward and probably under the beamwidth of the antenna at that point. This is one of the reasons why it's important never to stop beyond the "when red light shows wait here" sign on TTLs. In that happens, the radar antenna which is meant to detect traffic approaching cannot see you, so you could be sitting there for 10 minutes or more. Hilarious if you're in a pub on a quite road watching it. Traffic lights are designed to fail safe and have extra watchdog circuits to ensure that even if the main controller fails. So it's possible that there was an actual failure (not user failure or corner-case failure) on the car- park/side road sensors or lights and it failed safe by forcing that side road to red.

[@gordslater]

just realised the ironic pun of the electronics systems definition of corner-case failure on a traffic light junction vid. I really should try harder, sorry

[@klapiroska4714]

The traffic light sensors should have some way of detecting traffic waiting at the stop line. I mean, you cannot always guarantee that everyone gets through in one light cycle. I'm not sure how this particular senor exactly works, or how it is programmed, but it could be "watching" the area right behind the stop line. If that is the case, it wouldn't really detect the police car as it is almost completely over the stop line, and it wouldn't detect the viewer as they are still quite far from the stop line. Notice how the pedestrian signal turns red as the viewer crosses the stop line indicating that the traffic light is about to turn green. What might help? Police reversing a bit or the viewer creeping forward a bit might have helped, especially if the sensor is trying to detect if there is something waiting behind the line. Walking between the vehicles might be able to do the trick too. Now the police walked near the pavement, and the system is probably adjusted in a way that it won't confuse someone walking on/near the pavement to an approaching/waiting vehicle. I bet this hadn't happened if the police had not continued past the stop line as their exit was blocked.

[@seanwilson471]

You are correct Neil. If both car had reversed up and re approached the sensor picks up the movement. It depends on what is behind our viewers car if was able to reverse. Just like any other PIR sensor. It's sensitivity is quite low so people don't set it off but sufficient to see a bicycle. Approaching this sort of sensor is best if you approach at nice even steady movement it will pick up and cycle the lights. On a cold day the sensor is more sensitive than in hot sunshine as it can see the difference in the infrared signal. Also if the engine of the vehicle is hot it picks it up quicker. Coming out if the car park the vehicle engine could be cold so less infrared signal.

[@Masher8559]

This is a very common thing for me in Plymouth as a motorbike rider. Many of the lights will not pick me up if i am riding home alone past 12am when there is no traffic. I've moved my bike all over the area by the white line trying to get these certain lights to pick me up but they never change from red. If i am lucky a car will come and then they change. I've reported it a few times to Plymouth city council but nothing is ever done, so now i have to either go the longer way home where i know the lights detect me or carefully run the red light when there is no traffic.

[@Spongeblunt]

You get this quite a lot when riding round on a bike as the sensors don't pick you up, asked a South Wales police officer about this when he saw me stuck at a junction and he said if it happens again at any junction to give it a minute and if it doesn't change when it's clear to emerge carefully with clear observations as if the lights were marked as out of action.

[@WingNuts2010]

This is a common problem in Edinburgh. Too often I will come to a side junction, the two or three vehicles in front will have time to go through before the amber light comes on and because I or the car in front are only creeping up to the lights, I have sat there as the lights go through two or three cycles for the other roads before the one we are waiting at change. It might help the 'main' volume of traffic, but I see so many other vehicles that are wise to this problem and will risk going through on the amber.

[@garyt123]

Ashley, they don't actually detect _movement._ They detect the presence of metal. This occurred because the cop car had passed the "loop" buried in the tarmac. If the cop car had reversed about a metre and a half, the lights would have changed. When a vehicle passes over the "loop" or is stopped within the "loop", any reasonable mass of metal induces low voltage eddy currents in the wire loop. This decreases their inductance, and this is what the circuit detects. It is very, very, often, that lights don't change for small capacity motorcycles, which _literally_ don't have enough mass to induce a current in the "loop", so the light stays red. Car park barriers use the same principal - remember that episode of Mr. Bean trying to exit a car park without paying? He thought it was weight, or pressure.....

[@phire0]

As a motorcyclist, occasionally the sensors built into the road do not detect motorbikes so we need to wait there for quite some time for the lights to cycle, but if they don't cycle after some time, then we need to treat it as the lights not working, and according to the highway code, treat it like an unmarked junction and proceed with great care. That would be all well and fine in a situation like in this video, and personally as the police car, I would assume the lights to be not working after some time and would proceed when the road is completely clear, but I have no idea what I'd do at a much busier junction with traffic flowing from different directions.

[@CakeFine]

There are plates/strips installed 50-75 yards from the traffic light stop line and another just before it, you can see where they are as they are covered by hardened black resin. If neither vehicle goes over it, it won't cycle. Police car should have reversed to fix the issue. Thats why when vehicles stop beyond a filter light, it won't change properly.

[@bellshooter]

It's a sensor that senses the movement of arriving traffic, Ashley is correct, reverse and re-approach , that will work. We have a set of lights with a right turn filter and road subsurface sensors, if nobody moves forward of the stop line on forward green the filter will not work...

[@richcolour]

Thanks for highlighting the issue. Too many people here in Edinburgh stop before the magnetic coil sensor, or after it in the bicycle area. I often get out and ask them to move over the sensor. I sent Edinburgh Council a very detailed description of the problem at my local junction. No reply or action taken. Considering putting my own sign up saying "Stop here to trigger the green light"

[@joespittle1]

I had an experience similar to this a few weeks ago, it was just me waiting to turn onto a main road, there was traffic coming out of the road I was on but most of them were turning right on the red and looping around to eventually "turn left" (presumable because they knew the light was a bit rubbish). After 5 minutes of waiting I just reversed back a bit and carefully moved over to the right turn lane and copied the other cars. Also made note of the time and reported it to the traffic division of the local counsil

[@wavydavy9816]

I live in the countryside nea Gloucester. There's a busy crossroads by me and the traffic is always a nightmare. Over the past year different workmen have carried out works at least 6 times (which involves days of temporary lights which make the problem even worse). I think they've been trying different sensors and timings but what they fail to take into account is the huge number of old people drriving vehicles all of whom are lucky if they can manage to get their _own_ car into gear and moving before the lights change, leaving everyone else to sit in the queue for another try, 6 minutes later. It would be quicker to take a 10 mile diversion but you'd only get stuck behind a tractor instead 🤷‍♂

[@NC750X]

Every day, I find myself stuck at lights designed to detect larger vehicles that are moving, leaving me waiting for a change that never comes. As a motorbike rider, these sensors often fail to register my presence, prompting me to cautiously navigate through after a minute of futile waiting, ensuring the way is clear.

[@thefiestaguy8831]

Near where I live there's a set of traffic lights that ALWAYS get stuck on red for ages. Traffic will be stopped in all three directions and yet the lights stay red for a good 25-30 seconds, the pedestrian crosswalks aren't active either as the red man is shown. I once got stuck at these in a marked police vehicle with a member of the public in front of me. I pulled up next to them and told them to follow me through slowly. Blues on, slowly went through checking to the left and straight ahead for oncoming traffic. We had sat there for literally 2 minutes on a red light, no car queuing opposite on the other side of the road coming towards us at the same lights and nothing to the left either. It was around 1AM and myself and the other car were the only vehicles on the road at those set of lights, no pedestrians around either. Sometimes they really do just break or get glitched out.

[@ImranOO7]

This has happened to me many times. I used to work as a private hire driver and working nights the lights used to hang on red. I blamed how some roads come out towards the lights, especially a side road so close to the lights and when you come out, it never picked you up. The only best way I found was to reverse back up and drive up to the lights. Another thing I found was if you were over the white line or far from it, the lights won’t change because it will not pick you up.

[@GreboGent]

Back when I was riding on small motorbikes (50/125) I had a couple of instances like this. no one else was around in any direction, after 5-10 minutes I would shut my engine off, walk the bike round the junction and away from the traffic lights, then get back on and carry on -I’ve found bigger motorbikes don’t have this trouble as often. if there’s a car behind me I’ll roll forward a little and encourage them forward to where I suspect the magnetic sensor is, it’s the same reason that I usually filter to be the second vehicle in the queue

[@petecollins4925]

You may also find a relatively long wait at some junctions with a right turn controlled by lights. There can be up to 3 induction loops for queue detection and your filter light will not turn green until the furthest loop from the stop line detects a vehicle. If it's a right turn from a particularly busy road this timing may be extended so that a certain amount of extra time will pass before you get the green depending on how much traffic is on the main.

[@ConquerDriving]

There is a junction near me that suffers from this problem. Reversing and going forwards again seems to solve the problem.

[@mrddb4328]

Those sensors are called MVDs moving vehicle detectors (micro radar detection technology). You are correct they need to see movement to activate the green light, they should be set to slow moving vehicle detection. They need to add stop line detection to activate the gree when traffic stops at the stop line.