In response to the letters that 20mph zones could cause more accidents I don’t believe there is any evidence for this – indeed, all the evidence suggests quite the reverse.
According to the Royal Society for the Prevention of Accidents who gather and collate evidence from numerous Department of Transport and Transport Research Laboratory reports, reductions in speed limits reduce accident rates. If, for example, average speeds are reduced by 1 mph, the accident rate falls by approximately 5%.
There has been extensive research on 20mph zones in both Portsmouth and London (where they are widespread) which has shown dramatic decreases in road accidents – sometimes by as much as 61%. Importantly, the reduction in accidents was particularly significant for the most vulnerable road users such as cyclists, motorcyclists and children.
Yes driver education is an important factor in reducing accidents but so is a reduction in average speeds.
My personal experience of 20mph zones is that they feel safer and much more pleasant to be in as a pedestrian than roads with higher speed limits but they also feel safer as a driver and they do not slow down journeys significantly as the traffic tends to move at a smoother, slower pace.