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If you are perfectly on the ball (0.75 seconds reaction), and you don't plan to do full panic braking, but allow yourself firm braking at 0.45g the MAXIMUM safe approach speed to a set of traffic lights that may change to red with a standard 3 second amber is 44mph.

So a reduced speed limit where there are traffic lights is sensible. Putting traffic lights on 'fast roads' in NOT sensible.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

SS is right - it HAS come up before, but the fact remains that there ARE roads with 60mph speed limits that have traffic lights.

And Lum - I know that A580 road quite well. It is as you described, and a friend of mine who lives not too far from it tells me that it's one of the most dangerous roads in the country - possibly for the reasons being discussed.

Yes - There are red light cams on some of these lights on the A580. Think the worst one is at Ather Leigh Way. Cycle is way to short. Changes before a car clears (or it did the last time I drove that way about a year ago now.) My sisters live in the Worsley area - they know that road very well and are always telling me that the traffic lights along the set from what they call "Critchley's Corner to The Common" are "lethally" short and have a camera and all still have fatal pedestrian collisions as well. Have checked it out - floral tributes at alll three lights within a mile of each other.

Road also suffers from subsidence (was a mining area) as it runs westwards in direction of St Helens.

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Mad Mog! You're right ^ it's the A580, not the A570. I'm sure we're talking about the same road. I've edited my post.

Press the button marked edit! Top right of each message you posted. You do need to be logged on for the system to be able to associate you with your posts and make the button appear.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Thanks SS! For some reason, the edit button wasn't being displayed - done now.

Back on topic, in parts of Spain, the change from GREEN to RED involved the green and yellow lights being on together, followed by red. So, you had the yellow telling you to stop if you could, but the green telling you to go... I think this has been changed now. I've not noticed this combination in more recent visits to Spain.

There must surely be a warning that there are traffic lights ahead on the A580..?

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I'm sure there are, but that's beside the point. The point is that at 60mph, which I believe is the limit on the A580, a vehicle covers 264ft/sec and the stopping distance from 60 is given as 240ft in the Highway Code, assuming ideal conditions, ie dry road, daylight, alert driver. In less than ideal conditions, at night on a damp road with a tired driver, a car might be three seconds away from the traffic light (eg. 270-280ft) but still be unable to stop before the light changes to red.

That's 60mph = 264 feet in THREE seconds.

Comfortable braking (0.45g) from 60mph, including 0.75 seconds thinking time gives an overall stopping distance of 333 feet.

We can do a full emergency stop in good conditions (0.9g) and expect to stop from 60mph in 200 feet overall, but who wants to emergency stop for a traffic light? And even more to the point, if conditions are less than ideal - and it only takes a wet road or a downhill slope - it will become impossible to stop from 60mph in the distance available.

Braking distance calculator spreadsheet available from http://www.safespeed.org.uk/braking.html

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

It varies, but certain sections of it are NSL/70mph for cars. Its more commonly referred to as the "East Lancs" road.

In my Legacy, I reckon I could do an emergency stop in the 3 seconds just. It would require a split second decision as to whether to stop or continue, as just slowing down for a second would result in you passing through a redlight whether you then tried to stop or not.

In my Passat, there is no way I could stop in the 3 seconds. The brakes aren't as good, the tyres are narrower and have less grip and the car is heavier. I would have to slow down well before the traffic lights change if I were in that car.

So, what happens if I'm in the Legacy doing 70, and someone is tailgating me in a car similar to my Passat. Then the lights change when I'm 3 and a bit seconds away.

Do I:

a) do the emergency stop. I wont break any laws and as a bonus i'll get a new rear bumper, bootlid, exhaust and a few weeks off work.

b) continue at 70, potentially setting off a red light camera. Then have to take a day off work to explain my actions to some unpaid busybody

c) speed up to 90 to ensure that I pass through on amber, and hope there's no mobile cameras around.

Of course, if the road is clear, I could move into the other lane whilst doing my emergency stop, assuming I can keep control of the vehicle whilst doing so. But for the purposes of this exercise, assume that the other lane has traffic in it.

d) think ahead more and reduce your speed before it becomes an emergency.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

A traffic signal engineer tells me that the red-amber phase actually serves to increase capacity through junctions. If you didn't have it, that phase would need to be part of the red phase, and therefore the preparation time currently in the red-amber phase would be transferred to within the green phase. Unless drivers at the front were mega-alert, this could mean two cars less going through on each cycle.

In practice, while drivers often start moving during the red-amber phase, IME they rarely get very far beyond the stop line before the lights go green.

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Any views expressed in this post are personal opinions and may not represent the views of Safe Speed