OT traffic lights

So, you are driving along at night and you reach traffic lights which are red for you. Nobody else has been through the intersection for 10 minutes or more. Why do traffic engineers make you wait at the red light for 10 or more seconds before the green light for the cross road changes to orange? I've spoken to a traffic light engineer and he has no good reason for the delay, which can easily be set to 0 seconds. But they don't do that, just because they have always had a delay. Are they stupid, or is there a good reason for the delay? I'm not actually that impatient, but there is a situation where public transport has a tight schedule to keep, and the extra 10 or 20 seconds on every trip does make a difference, and is a waste of time anyway.

Reply to
Matty F
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The whole point of traffic lights is to introduce delays, so that congestion builds up enough to justify turning the town into a congestion charged or cyclist and pedestrians only zone.

I have on bored trips counted the amount of time spend waiting at empty clear traffic lights. In light traffic in a major town, it tends to 50% of the time.

Reply to
The Natural Philosopher

I guess it's so that people get accustomed to stopping at the red light and not running through it on the expectation that it will change to green as they approach.

Public transport vehicles can be fitted with transponders so they get priority at lights.

Owain

Reply to
Owain

I find this strange, I often go through lights where in quiet times both ways are red, then as soon as a car triggers the sensors it goes green for that vehicle. No delays.

Reply to
Broadback

'Cause they have old dumb timed only lights, not ones that sense traffic and change to let that traffic flow (if safe/possible to do so). The ones on the narrow bridges here are timed (they cycle the direction of flow not just sit in one state) but also sense the traffic. I've approached them and had them started to change to red to instantly reverse that change and let me through, only having to slow a little. If there is something waiting the other side they let that go first, only fair.

I'm not sure I understand that. A lot of the delay is down to letting slow traffic clear the junction (horse 'n cart, cyclists, tractors etc) and letting stuff that tries to beat the red light clear as well. On a fast road the you need quite a few seconds to let some who has decided to race the forth coming red light to blat through the junction at 60mph...

Reply to
Dave Liquorice

My guess would be that traffic flow sensors don't pick up cyclists very well, that junctions need some time to clear of slower cyclists, and at night and side on, some cyclists may not be that visible.

(It was certainly my most scary accident when a driver ploughed into the side of my bike from a side-street in Cambridge, despite me being loaded up with all the visibility stuff)

Reply to
dom

Similarily here, some years ago on a main route out of town, at an intersection with a minor road, late at night and in the absence of traffic the lights defaulted to red for the main route.

At the time I formed the conspiracy theory that this was quite intentional at the behest of police. The idea being that any suspect driver being 'followed' would be stopped at the lights, and then more easily questioned without the neccesity of a blue light job that might otherwise take a dramtic turn, or jump the lights which would create a sufficiently serious offence for the police to have good case against the driver even if their other suspicions turned out to be unfounded.

Now I am inclined to think the reason was more simple, as has been mentioned, that traffic engineers have a built in philosophy of delay and congestion, and simply thought 'that'l slow them down'.

Roger R

Reply to
Roger R

For the amber gamblers - AKA people not in charge of their vehicle. Of whom there are many.

Reply to
Lino expert

More than that, it avoids the racing the lights senario, where, if the normal expectation is green, and the driver will keep up speed expecting nothing to change. If unexpectedly, a vehicle on the side road causes the lights to change, because the driver did not expect to stop, driver then increases speed to race the lights. Sometimes this senario has fatal consequences.

Roger R

Reply to
Roger R

Traffic lights in Bulgaria (and probably elsewhere, Russia?[*]) have countdown red/green digital displays in seconds that show how much is left on the the green, and how much wait is left on the red. This is for road users, not pedestrians as in the US.

Great excuse for accelerating up to junctions.

[*] - underpants moment,
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Reply to
Adrian C

In the case I'm concerned about, the main road has a green light most of the time. The side road is only for buses who have well-trained drivers. There's no way they would run a red light. There are lots of passengers who would notice and complain.

In this case the bus company has paid for the traffic lights to be installed. The traffic light controller knows perfectly well when a bus has arrived. The traffic light engineer simply refuses to program the lights correctly. Let's say that there is supposed to be a bus exactly every 10 minutes, and the trip actually takes nearly 10 minutes. An extra 10 or 20 seconds of wasted time on each trip can make the buses late all day.

Reply to
Matty F

There was a set of lights I used to go through daily, about 10 years ago. One day, the time sequencing on the lights was adjusted, and this resulted in massive tailbacks. After 3 or 4 days of this, I got to the lights, and someone had painted a sign under every traffic light which read: "Any complaints? Call head of traffic planning on 077....." They were fixed when I went through again at lunchtime;-) I don't suppose his mobile stopped ringing until they were.

Reply to
Andrew Gabriel

Personally I've generally thought that at night, in many locations, it would make a lot of sense to have a green light permanently on for the main road, with a flashing red on the side road meaning Stop and procede when safe. A bit like France's flashing amber, but there you still have to slow on the main road, as the side road can also be flashing amber and traffic may emerge without stopping.

SteveW

Reply to
Steve Walker

I think it varies by country and region, TBH - there doesn't seem to be much consistency. Maybe you're just in an area where they happen to like long delays; I've seen some setups where it really is 0.

One possibility is that it's just to give time for anyone already within the junction (e.g. a slow cyclist) to clear it without seeing that the lights are about to change and worrying that they'll get flattened.

Maybe it's also a delay to allow any emergency services vehicles chance to muscle through for setups that don't give automatic priority to transponder-fitted emergency vehicles (not sure if they have those in NZ?)

There's also the chance that approaching traffic will run the orange / red light, so the planners want as much delay as possible before a change to green just in case (I remember one set of lights on a fast road coming into Wellington where the change from green to red was *extremely* quick - there were probably quite a few incidents of vehicles sailing through on a red/orange at that particular junction)

cheers

Jules

Reply to
Jules

Where I am in the US some of the major intersections have flashing amber warning lights before the junction so that drivers know the light's likely to have changed to red by the time they get to it; it's really handy to have given how US traffic planners often prefer traffic lights to slip-roads, so you do a lot of 65 -> 0 -> 65 driving...

Reply to
Jules

US version has flashing amber on main road with priority, and flashing red on side road, basically meaning give way. Switches to this mode when traffic congestion level no longer requires controlling by lights (or on a timer with older sets).

We could definately do with something like that, or more traffic lights which were peak hours only. There's a series of about 6 lights I go through driving back from my parents, and when it's 11pm or later, I get stopped at usually 4 or 5 of them for a couple of minutes each, and there's not another vehicle to be seen anywhere!

I've had several US colleagues complain to me about UK traffic lights being confusing. This caused me to think about them more critically and compare with the US traffic lights, and on reflection, the US traffic light control is very much better. Not something I noticed being familiar with the UK scheme until it was drawn to my attention though.

Reply to
Andrew Gabriel

There is also an issue of petrol wasted in stopping and then re-starting for

10 seconds.

Near me is a bridge controlled by lights and they are excellent. If nothing is coming the other way they always change as you approach - unless you are going fast!

Reply to
John

Depends where you are - the US can be quite variable in junction setups. I've never seen those up here, just flashing amber on all routes (for "proceed with caution") for major roads with crossing minor ones, or on some freeways they have the flashing red on the on-ramp (but no flashing amber on the freeway side). At busy times the freeway ramp ones continously cycle green-red and only one vehicle is supposed to go through on green if they can (but they still have to give way to freeway traffic once past the light)

Thankfully just about all of them here have sensors to detect vehicles, so change nicely late at night.

I agree; I was surprised at how good it is when I first moved here. Being able* to run a red light when turning without crossing traffic is awesome for keeping things moving, and the US lights failsafe to flashing red if there's a problem (rather than just cocking up as I've seen UK ones do), and I particularly like the way they give priority to emergency services vehicles (although maybe they do that in the UK now too?)

  • although I think that's another variable thing, and some states don't allow it.

'course they make up for it in the US by having some of the most shitty road markings and lighting that I've ever seen in any country :-) Knowing where to place yourself on the road can be quite an art, particularly when it's dark / wet / snowy.

cheers

Jules

Reply to
Jules

If the light is "always" green for them then they may even get out of the habit of looking for the light, not to mention checking whether their way is clear.

Owain

Reply to
Owain

Do the French still have the "priority to traffic joining a road" rule?

How much is that down to most of their junctions being simple cross roads, with generally fairly equal traffic on all 4 ways, rather than our fairly common 5 or more ways with very different traffic levels on each way?

They do have nice things though like "turn right on red" I didn't see any flashing versions but I do like the french flashing system, I think that is better than our "peak time only" set ups.

The fun thing is the states is a round about or "traffic circle" the number of warning signs and instructions on how to negociate it are quite a sight to behold. Wonder how they'd cope with a "magic round about" like those in Swindon or Hemel(?)... B-)

Reply to
Dave Liquorice

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