Friday, 12 August 2011

It All Depends How You Look at it

Coming back from Belgium after a short holiday with Mrs Lola fast asleep alongside (in the passenger seat, before you ask) I whiled away the time doing some mental sums, spurred on by the generally very good (except French) driving standards.

In the UK we are hectored all the time with factoids like '3500 people die on Britains roads each year - that's nearly 68 each week'. I think that the actual road deaths are about 3000 now, but we'll use 3,500 to be generous.

Now, it seems to me entirely erroneous to take road deaths per week as your measure of 'safety' I mean, we could all sit in our cars on our drives or parked and not drive anywhere and there would be no deaths. Would it not be better to measure road deaths by passenger mile? So let's do some sums.

I am going to take only passenger cars and ignore everything else. There are about 33m road vehicles, of which about 17m are cars.

We each do about 12,000 miles per year.

That's 2.04 X 10 to the eleventh power passenger miles per year.

Divide that by 3500 and you get 52,845,714 car miles per fatality.

Since the average driver does 12,000 miles per year and if we assume a 60 year driving life the total miles travelled would be - 720,000.

Personally I reckon that's pretty low odds that I'll kill someone or be kiled by someone on the roads.

5 comments:

Mark Wadsworth said...

Those Belgians have got lovely motorways, it must be said. The 33 million is the correct number for licensed vehicles, but are there really only 17 million cars? Is that a guess or a real statistic?

DNAse said...

I think road deaths/injuries are best measured on a per hour exposure rate. One mile on a motorway will clearly take much less time than one mile across a busy city. This way you can also make a better comparison to other slower forms of transport such as cycling and walking.

The way the DofT present the data is terrible. All the attention is focused on the headline rates without any attempt to normalise to exposure or changes in usage.

dearieme said...

A few years ago I stumbled across the odd fact that the police and the NHS issue distinctly different figures for road deaths per annum.

Lola said...

MW - A Google search got me to an 'official' site that have the 17m 'passenger cars'. Pesonally I thought it was 20m.

Robin Smith said...

Unless you are cyclist.