This report here which I have to admit does not appear entirely unbiassed, suggests that cameras cost £50k each to install and the same to run annually. Even if the real figures are half of these, they don't come cheap. I seem to recall Lewisham Council quoting £500 as the cost of installing a road hump so it is easy to see why they are an attractive solution for the Highways Department, even if they are hated by drivers.

Presumably the 'running cost' of a speed camera includes the cost of processing the offenders, handling their driving licences, chasing the non-payers etc, but it would only seem financially viable to use speed cameras where they are going to catch a lot of people. Clearly there are diminishing returns. If there is one instead of every road hump, they are going to cost a lot and catch almost no-one!

Even in areas where there are lots of cameras - think the A23 Brixton Road or the A20 Sidcup Road - drivers accelerate and brake between cameras with consequent adverse effects. And, as the article suggests, speed in excess of the speed limit (as distinct from excessive speed for the conditions), is a factor in only about 10% of accidents.

Personally, I think the answer is driver education. Some drivers may only be 'educated' by traffic police who can issue tickets for all types of bad driving, not just speeding, and can confiscate cars, and perhaps other assets from repeat offenders as well as disqualification.