Sir – For lack of £300,000 the county council has closed down Oxfordshire’s speed cameras, however much this may cost us in increased accidents.

But a year ago, £300,000 was spent on installing “20 mph” speed limit signs on the residential roads in Oxford, to cut down accidents. How effective has that been? You report that there has been a 6.7 per cent drop in accidents in the first nine months of this scheme, compared with the preceding three years, and you quote the “cabinet member for transport” as saying how pleasing this fall in accidents is.

Unfortunately, it is not at all clear that there has been a fall in accidents since elsewhere, under the headline Drivers desert the city, you report that city centre car park usage is down by 11 per cent.

If this reflects a similar overall decrease in traffic in the city, then accidents should have fallen 11 per cent too, just to be level pegging. In this case, a fall of only 6.7 per cent would imply that the speed limit signs have actually made Oxford more dangerous!

So could you tell us how much traffic at the centre was reduced, in the same nine-month period, as compared with the preceding three years?

Michel Treisman, Oxford