Tuesday 7th December 2004

Research shows traffic detection works

Belgian researcher reckons Brits have known best after all

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A researcher has found that a traffic-sensitive control system, already in use at many UK road junctions, really does work.

Carlos Gershenson, a traffic researcher at the Free University of Brussels, Belgium, is proposing a system which would allow large enough convoy of cars approaching a red light to switch the light to green while the other lights at the junction turned red.

He outlines his theory (see link below) which shows that such a system of traffic lights would be able to adapt to changing traffic conditions, allowing it to find a better switching sequence than one imposed rigidly on all situations.

In most countries, city streets are currently controlled by lights that operate on fixed sequences, resulting in that frustrating middle-of-the-night situation where you wait at a red light in empty streets.

Centralisation a bad idea

Most systems aimed at being more flexible by responding to the state of the traffic usually connect the lights to a central computer which calculates the best light sequence. But not only is this costly, says Gershenson, it's computationally challenging. He reckons that traffic lights should act on their own and respond to local conditions.

In fact, older UK readers may remember the rubber strips across the road at the approach to traffic lights. Pneumatically operated by cars depressing the rubber tube embedded in the road, the system told the control box next to the lights how many cars were approaching the junction.

Gershenson's proposal is in fact an update of this -- although many junctions in the UK already use a traffic-detection camera for just a purpose. He reckons that no-one has dared install them on the dense network of urban junctions because it seems like a recipe for chaos.

Gershenson says it can work. He says he has shown that, with just such local control, the system of lights directing flows on a road grid is able to self-organise so that it typically finds a good global solution to the problem.

The full story is here: www.nature.com/news/2004/041129/full/041129-12.html

Research paper: www.arxiv.org/abs/nlin.AO/0411066

[micky g]

Our traffic management systems are light years ahead of the rest of Europe. I remember there was a traffic sensitive light system to control lane usage in Sheffield back in the eighties. Not sure if they'd take much notice in Paris though.....

[james_j]

Not creating traffic build-ups unnecessarily?

Sounds like common sense or should I say the bleedin' obvious, which our local authorities and highways agency haven't seem to have realised.

However, I often wonder whether the creation of congestion is intentional. There's no other way of explaining some of the traffic management in most of the UK.

[skinny]

maybe i am being a bit thick but surely we already have this at most traffic lights? does the little light sensor on the top not detect activity approaching the lights? Normally when it's quiet and dark, just give them a little flash when you are approaching and they will turn green just as you reach them?

[micky g]

Temporary traffic lights and many permanant lights use radar detectors (like speed cameras - send my detector wappy)! Most use loops set in the road. It's not the systems that generally cause congestion but sheer traffic volumes and antiquated / insufficient road layouts.

[mutant_matt]

I can only speak for London (as that's where I live and work) and the lights here are linked to Ken's clever computers. I even have a friend who works in this department so I know a thing or two about it.

Most lights, certainly in central London can detect a Bus coming (remember, Ken thinks the answer to ALL traffic problems is to get more people on Buses) and changes the lights to green.

The main trouble is, with Ken deliberately setting the phases so as to cause as much congestion for everyone (except the precious Buses of course), the system could work well if some anti-car Muppet wasn't in control of the main computer.

It's obvious when traffic lights you have been using for years, suddenly start having a green phase of about 5-10 seconds and a red phase of several minutes, with long periods of all the sets of lights on red and nothing is moving, that Ken's minions has been dabbling in your area.

You would have thought that with Ken's track record, Londoners would have voted him out when they had the chance but I guess apathy, disinterest and idiocy rule the day, and the ballot box, these days....

Matt