Green Traffic Lights?

[Jocko]

The local traffic lights have variable timings. And then there are lights you have never encountered before.
My question is, what is the best way to approach a green light?
If a light is red I hang back, hoping it will change, but I keep getting caught out on green lights, especially if they are already green when they first come into view. I never know whether to keep my speed up, hoping to reach them before they change, or slow down, expecting them to go red before I get there. I seem to make the wrong guess more often than I make the right one. I slow down, expecting them to change but they don't. But just before I reach them they do! If I had just kept going, when first I saw them, I'd have breezed through. Or I don't slow, then have to brake, wasting inertia and wasting fuel. Short of blowing off red lights I have no option.
Is there a technique for green lights? What do you guys do?

[JazzyB]

Well the one's I have an anxiety over are the one's with a camera, because if you cross them when red you will be flashed etc.

I would just drive 'normally' as driving oddly tends to change the lights as most have sensors in the road to control them.

[peteo48]

It's an interesting one because you, like me, will have read various hypermiling or eco driving websites and they keep stressing this maintenance of momentum rather than stop start.

Obviously you don't want to keep a highish speed then slam the anchors on if it changes. My own approach is to ease off the throttle on approach so I'm able to carry on or stop relatively smoothly.

[Jocko]

Well the one's I have an anxiety over are the one's with a camera, because if you cross them when red you will be flashed etc.

I would just drive 'normally' as driving oddly tends to change the lights as most have sensors in the road to control them.

We are lucky here in that there are no camera mounted traffic light around here. The traffic flows don't warrant them. There are a few in Edinburgh and I am ultra careful with them! We do have a number of lights, between the main trunk road and our hospital A&E, that have aerials mounted on them. I believe it is so that emergency ambulances can set them to green as the approach. The few lights with filter lights are sometimes a good indication, though there use is variable as well.
The lights here are set for time, depending on the time of day, with sensors on the side roads, but only right at the junction. There are no advance sensors to check traffic approaching, unfortunately. So the main road gets two minutes green, unless a vehicle triggers the sensor on the side road, which then reduces the main road's green time.
I try moderate hypermiling techniques (I don't coast with the engine off or pump my tyres up brick hard), so maintaining inertia with minimum fuel use is fairly high on my agenda.
What I do do is switch the engine off, if I have to stop at a light which has just turned red. There is one light which, at 06:30, takes 3 minutes to change, irrespective of traffic flows. You can arrive as it turns to red, sit for your 3 minutes, and not another vehicle passes. We also have a few sets of four way lights that only allow one stream at a time to move. They are a nightmare, and best avoided all together.

[peteo48]

Round my way a lot of the lights seem to be on sensors because the time they stay on Red varies enormously. What I have done is identify certain sets where, once they turn red, you know they are going to stay on red for at least a few minutes. I turn off at those sets of lights if they have just gone red.

On idling more generally, I am still astounded at the number of people who leave the car idling even when there is no climate reason for doing so. I know some local parents are getting very agitated near a local primary school at other parents doing this. I walk past this school occasionally and the stink of diesel and petrol is chronic at pick up time.

[VicW]

A lot of sets of traffic lights have movement sensors on them  so that traffic flow is always smooth without unwanted delays. Nearly all temporary traffic lights have movement sensors for the same reason.

Vic.

[Geoffers]

The local traffic lights have variable timings. And then there are lights you have never encountered before.
My question is, what is the best way to approach a green light?

It's quite simple - approach and expect it to change!

[Jocko]

It's quite simple - approach and expect it to change!

That is how you have to do it, but how you handle that and still try to save fuel is the issue.

[culzean]

There is quite a complicated interchange by where I live, about 8 years ago they fitted the island (which rarely had any queues)  with old tech traffic lights and there were quite long queues and a lot of local protest, after 8 years or so of queues due to lights they took 8 months or more to redesign the interchange and during that time they just had temporary give way signs held down with sandbags,  there were no queues,  now they have switched on the 'state of the art, computer controlled lights that change sequence in response to traffic flows' - yes you guessed it - the queues are back, not as bad as the old tech lights,  but much worse than when the temporary give way signs were in use.  So they have gone from a simple island with no lights (and no queues) to an island with low tech lights and long queues to temporary give way signs and no queues,  spent a fortune on New lights and a redesign oh the roads and now we have queues again - this is just one reason I doubt autonomous cars will be any better than human controlled ones.

[Jocko]

The difference is autonomous cars won't get frustrated.
There is a large interchange at the Sheriffhall roundabout just south of Edinburgh. Six feeder roads including two dual carriageways (which actually fan out into four lanes).
The main problem for the jams are motorists continuing to enter the roundabout on Amber, some even as the lights change to Red. They then fail to clear the next set of lights before they change. This restricts how many vehicles can enter from the Green light. As a result queues build, drivers get more frustrated, they drive onto the roundabout well into the Red and the problem just gets worse.

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[culzean]

That is exactly what happens with traffic lights,  especially ones actually on the islands, when they change they can cause traffic build ups that block other entrances and exits.  Funny thing is, as our planners in Britain (surely the home of the traffic island) destroy traffic flow on our islands with traffic lights other countries are removing lights from islands.   On another island by me with about 7 roads coming on and off I used to get stopped by every set of lights actually on the island  at 5am and 11pm (depending on shift) when there was no other traffic around.  Lights actually on the island  means the cars are indexed around the island between junctions and the space available between some junctions is only enough for about 20 cars so it is horrible in rush hour,  and the fact that cars were getting bunched up meant that getting in the wrong lane made it impossible to swap lanes and maybe another trip around the island,  and tightly packed cars made it impossible to read the directions marked on the road.  Traffic sorts itself out much better without lights,  but lights are fitted for health and safety reasons.

[Jocko]

Another gem of road planning is the light controlled crossing right at a roundabout. It either causes the traffic to back up on the roundabout (preventing traffic who are not even going that way from progressing), or as you join the roundabout (where checking right is your priority), you suddenly find the road blocked by stopped traffic or a pedestrian in the middle of your carriageway!

[richardfrost]

In the film 'Starman' Jeff Bridges' alien learns ti drive by reading the car handbook and observing others. He then declares the rule for traffic lights, based on observation:

Red: Stop
Green: Go
Amber: Go very fast