Sunday 8 February 2009

Ben Goldacre’s bad statistic

I always enjoy Ben Goldacre’s ‘Bad Science’ column in The Guardian. It mostly dedicates itself to demolishing health stories in the press, demonstrating that lazy journalists uncritically recycle PR releases put out by businesses, quack health outfits, etcetera. Taking three cod liver oil capsules a day increases your chances of obtaining a first class degree in astro-physics by 80%, experts say sort of thing.

This week Ben puts his boot into the insurance company LV’s claims of a sudden surge in cycling injury crashes (not ‘accidents’ if you wouldn’t mind, Ben). Read his analysis here. If you interpret the statistics soundly, Goldacre argues, “bicycle accidents have fallen by 33%”.

I’ll reserve judgement on this, I think. His argument seems reasonable. The problem with these kinds of debate is that crash statistics about fatalities and injuries in themselves are not an index of danger. A road can appear safe because it has no recorded deaths or injuries but this may simply be because cyclists have been terrorized from using the road and pedestrians never attempt to cross it because of the extreme danger.

What bothers me is stuff like this:

the Cyclists Touring Club, which certainly sounds like a dapper bunch, has collected data that shows a 91% increase in cycling in London since 2000.

No, Ben, there has NOT been 'a 91% increase in cycling in London since 2000'. This statistic emanates not from the CTC but from Transport for London. And what was measured was not ‘cycling in London’ but cycling on certain key commuter routes. It's a questionable statistic, and Ben Goldacre's inadvertent mis-use of it is a fairly common one. A better way of measuring something as broad as 'cycling in London' is to look at how people make their journeys. And on average two per cent or less of journeys in Greater London are cycled.

Commuter cycling into central London has plainly increased over the past decade. But it is far from clear if there has really been a dramatic increase in cycling on other routes. I suspect there hasn’t been but no one is interested in failure. Everyone involved in cycling is keen to quote the TfL figure because it offers what appears to be a scientific justification for what they do. TfL can pat itself on the back for a job well done. So can the LCC. So can everyone. The London Borough of Waltham Forest is equally keen to assert that everything is rosy for cycling. But if I want to cycle from Waltham Forest into central London I basically have the choice of just three routes across the Lea Valley. The fact that cyclists use them proves nothing about the merits of the cycling facilities, since they would use those routes whether there were cycle lanes there or not. Nor does a rise in use indicate inbuilt enthusiasm for the London Cycle Network. People cycle for all kinds of reasons. There was apparently a surge in cycling after 7/7, driven by fear of using tube trains and buses. In a recession some people may choose to cycle to save money.

Even Waltham Forest’s cherry-picked routes sometimes contradict the picture of an explosion in cycling. The figures for daily use by cyclists of the Crooked Billet underpass indicate not success but stagnation: 1998: 335, 2002: 312, 2006: 309, 2007: 324.

I would contend that cycling in London is becoming more unpleasant and more dangerous. The rapid decline in traffic policing has resulted in a massive flouting of road traffic regulations by drivers. The invention of the mobile phone and the reluctance of the government to criminalise use of a mobile while driving with an instant ban has created a greatly increased risk for all road users, especially the most vulnerable. Lastly, road design is becoming progressively more hostile to cycling. One way streets are proliferating, aimed at managing parking and vehicle flow, with total disregard for the convenience of cyclists. In Waltham Forest the disastrous policy of installing rubber speed cushions on residential streets has not calmed traffic but on the contrary promoted erratic and aggressive driving.

I know four people who have given up cycling. One because of having her bike stolen, one because of being hit by a reckless driver, and two because they no longer felt safe cycling to work. These last two cyclists now drive to work.

Me, I don’t know how much longer I want to go on cycling. Not after experiences like today, when a 4X4 came at me on my side of the road, headlights blazing. I was waiting for it to lurch back on to its side of the road, and it didn’t. As it thundered past half an inch from my right handlebar I saw why. The male driver was engrossed in chatting into his handheld mobile phone, while steering with one hand on auto-pilot. I managed to get the reg: M341 URX. Call the cops? The Met is no more interested in cracking down on mobile phone using drivers than the government.

I’m getting more and more tired of this crap, and more and more tired of the everything-is-fabulous-for-cycling-in-London message. Not where I live and cycle it isn’t.