Seat belts again

Yesterday when I showed Mayer Hillman the graphs in my last blog on this subject he complained that they displayed the statistics for all road user deaths and not the statistics for those affected by the seatbelt law, i.e. people in the front seats of cars.

My excuse was that at the time I produced the graphs, almost 20 years ago, I was focused on total numbers because of the evidence that the law coincided, in Britain and elsewhere, with increases in the numbers of pedestrians and cyclists killed. Also, at that time no one was claiming that the law had saved anything remotely approaching the recent claim by the Government, RoSPA and PACTS of 2400 lives saved per year.

But stung by Mayers insistence that the claimed saving of 2400 lives per year was more than the total number of car occupants killed, I went back to the numbers.

The graph below shows the data for the same period for car occupants only. I asked the computer to fit a line to the data up to and including 1982 (the year before the law came into effect, small red arrow) and it produced the downward sloping trend displayed. When asked to fit a line to the statistics after the seatbelt law the computer replied with an upward trend. When the claimed 2400 lives saved is displayed on the graph it shows that the law should have brought impressive numbers back from the dead. The claim would appear to be based on the work of creationist statisticians.

picture-8Source: Road Accidents Great Britain: 1982 & 1989, Table 5,  HMSO.