Traffic Lights

Introduction

Apart from Bhutan, every country in the world has traffic lights. (Although I must admit that in 2003, I spent a couple of days driving around Cairo, one of the world’s largest cities, and didn’t see any – nor any lane markings – traffic in Cairo seemed to work on a free-for-all basis, a bit like a dodgem track. I suspect that things might be different now, though.)

Anyway, the UK currently has 33 000 sets of traffic lights, and it is estimated that drivers spend 8 minutes a day sitting at red lights. That’s 2 whole days (48 hours) each year. Multiply that by 40 million drivers in the UK, and that’s a lot of time. Of course, if we consider the whole world, we would probably have to multiply again by something like 50 . That would make 4 billion days spent waiting at traffic lights each year.

Peak and Off-Peak Modes

When road junctions reach a certain critical busy-ness, installing traffic lights can reduce delays. Below that critical business, they increase delays. Lights tend to be installed if the junction reaches that critical busy-ness at any time. Often this is just a couple of hours per day, five days a week, at peak times.

Once installed, though, the lights generally operate 24 hours per day. For most of those hours, the junction is at less than the critical busy-ness, and the delays are then longer than they would be without the lights. Most people have sat waiting at a red light late at night at a junction with no other traffic, when it would have been perfectly safe to proceed.

There is a way, though, to get the best of both worlds: traffic control during peak times and free movement at times when the control is not needed. All that is required is to change the light mode during off-peak times. A suggestion is to have a flashing green light for the traffic that has right of way and a flashing red light for the traffic that needs to give way. Flashing amber can be reserved for when the lights are out of order.

The flashing should be at a calming rate, maybe 1 second on, 1.5 seconds off.

This could be achieved world-wide (except in Bhutan) with a minor change to the programming of lights. And it would be something that drivers would get used to very easily – and be grateful for.

AI can control lights

In the old days, police would stand at busy intersections and control the traffic. This has the advantage that the whole queue going one way can be let through, then, as soon as it has passed, the whole queue the other way can be let through.

Nowadays with traffic lights, often the whole queue doesn’t get through, or the lights stay green long after the queue has passed, holding up traffic going the other way unnecessarily.

AI is sufficiently advanced now that with a camera pointing in each direction from an intersection, a program could handle the traffic as efficiently as a policeman used to do it. The program would be relatively simple (compared to that say for self-driving cars), and the same program could be used on all traffic lights world-wide.

Red and amber

One final change could make a small but significant improvement. In the UK, lights change from red to red and amber together for a couple of seconds before turning green.

This allows drivers to put the car back into gear and to be ready to take off the moment the lights go green. Relative to other countries where the lights go from red to green without any warning, this saves a second or so at each light cycle, something that results in significantly improved traffic flow in busy times, especially when the whole traffic queue doesn’t get through in one light cycle.