Big Brother resumes watch in Oxfordshire

On Friday, The Register reported

Oxfordshire police have turned speed cameras back on as others throughout England switch theirs off, prompting questions as to whether senior police and county council figures are playing politics.

Last August, following the withdrawal of central government funds, Oxfordshire made motoring history by being the first county to switch off its speed cameras. This move is reported to have saved some £600,000 per year.

What was the effect of this switch-off, and why were the police so keen to have the cameras back on?

Figures released today by Oxfordshire Police show that for the seven months from August 2010 to January 2011, the total number of casualties across all of Oxfordshire rose from 1171 to 1179: that’s an increase of eight, or just under 0.7 per cent.

At camera sites themselves, the total number of collisions rose from 60 to 62, with injuries increasing from 68 to 83. Sadly for Oxfordshire’s Speed Supremo, Superintendent Rob Povey, in the press this morning with the assertion that we "know" that speed kills, the entirety of this increase of 15 casualties came from non-serious injuries.

Nationwide figures apparently lend some credence to the claims by police, with a study by Professor Richard Allsopp (pdf) suggesting cameras prevent 800 fatalities or serious injuries each year (KSI):

Professor Allsopp, as most experts in this field, does not disaggregate fatalities, since although the general view is that speed increases total KSIs, the question of whether a particular accident will result in a death is far more complex and related to many factors other than speed.

It may well be that speed cameras in Oxfordshire helped reduce incidents, but the figures provided by Oxfordshire Police – without any analysis by those previously employed as experts – are not, by themselves, enough to draw any serious conclusion. The fact that a senior police officer should claim they [do] tells us more about a lack of Police respect for statistical evidence than anything about what is actually happening.

Run the figures backward, and the actual casualty figures for 2010/11 are very much in line with a long-term trend decline running back to 2001, with blip years in different categories across the period. So, 2004/5 reported overall casualties well below trend, while fatalities in 2006/7 were massively up on the previous year.

The article concludes

But then, it seems likely that this debate was never all that much to do with the evidence. As the BBC reported in November last year, plans to turn the cameras back on were already "under way" then. At that point, it is possible that the police were working, at most, on just two months worth of evidence.

For many police officers, or at least Superintendents, I suspect the real issue is not saving lives, or even making money, but enforcing compliance. They couldn't bear the thought of us exercising judgement, and choosing a speed appropriate speed for the conditions. We are to obey the law, no matter how rigid or unreasonable.