The secret law governing London's traffic

I sometimes wonder why on earth I stay a member of the AA.  Their breakdown service is usually very good, but they take my membership and use it to imply that I agree with their rather dysfunctional views on motoring - which seems to me that there should be no restraints to it.

They claim rather disingenuously that they are not against the London congestion charge, but this is the story they generated yesterday pouring scorn on the whole idea - arguing that it has extracted £2.6 billion from motorists over the past decade without actually reducing congestion.

Well, I have to reveal to them what clearly remains a secret - congestion was always going to stay the same if it means average journey times.  It always has been the same, for the past century - an average of around 12 mph.  Because there is a reason why that should be.  There is another 'hidden hand', but not an economic one, and the man who helped uncover what it was and helped to popularise the answer was one of the most unusual transport planners of the century.  

Martin Mogridge was originally a physicist who wore long hair and leather trousers, with a cultivated air of exoticism.  His interests included science fiction and Victorian eroticism, and just before his untimely death in 1999 at the age of only 59, he began studying Hebrew.  

Over the previous three decades, while the major cities of the world enthusiastically demolished their slums and built massive urban highways, transport experts had been puzzling over the phenomenon of how new roads – even widened roads – seemed to increase traffic.  Economists had noticed that, if there is more road space, then people find it worthwhile to pay to use their cars, if they had one.  Then public transport attracts fewer paying passengers and the fares go up or services reduce, and even more people go by car.  Even in the 1930s, they had noticed that new roads released what they called ‘suppressed demand’.  Worse, then the traffic goes faster and the buses find it more difficult to negotiate traffic streams or cross big highways.  

That was a vital clue: the speed of road transport and public transport are linked, and the journey times door to door for both are often very similar.  Mogridge realised that, in London, everything depended on the speed of the underground system.  If you build more roads, people go back to their cars because it is then quicker than going by underground – until the point when the speed is so slow that underground travel is faster.  Then they leave their cars behind and go by tube.  

The solution to speeding up the traffic is therefore to speed up the main public transport infrastructure.  What’s more, said Mogridge, this works even if you take space away from cars to make room for public transport.  It was the thinking that led to Zurich’s successful strategy to reduce car use based on better pedestrian access and investment in trams.  By the end of his life, Mogridge reckoned that traffic speed could be doubled just by reducing space for cars, though it remains difficult for public officials – at least in the UK – to act on this new law of traffic management.

If Mogridge was right, the likely effect of the congestion charge zone in London would have been to cut traffic a little, but leave journey times exactly the same - and so it proved.  Now we can move onto the next conundrum: why do these bone-headed types at the AA think that my only interests are those of a motorist - and not as a father, a citizen and an asthmatic?

Find out more in my book The New Economics.