I READ in The National (Holyrood set for vote on speed limit of 20mph, December 4) that Scottish Greens MSP Mark Ruskell is pushing for a reduction of the default speed limit in built-up areas from 30mph to 20. His rationale for this proposal is that it will improve road safety and reduce traffic pollution.

I can accept the road safety argument. The cynic would suggest that reducing the speed limit to 0mph would eliminate road safety issues altogether. However, one mustn’t be cynical, and I fully endorse his attempt to improve the unacceptable rate of road traffic accidents.

What I cannot accept, however, is that the reduction will improve levels of pollution. A typical motor vehicle will cruise comfortably at 30mph in fourth gear. However, if the speed is reduced to 20mph it will have to drop to third gear. By definition this means that, for each unit of distance travelled, the engine will fire more often and will therefore emit more pollution, not less. Mr Ruskell’s aim of providing “cleaner, healthier and safer streets” would be likely to produce “dirtier, unhealthier but safer streets”. See compromise? It’s a pure pain!
Ken Gilmour