Back in May the local Lib Dem manifesto included a committment to introduce 20mph zones where residents want them to improve road safety.

The reasoning behind implementing 20mph zones is really twofold. Firstly it does reduce the average speed of traffic within the zones even when other traffic calming measures are already in place. More importantly, the 20mph zones are a sign and an encouragement to local residents that they own the streets, not the motor cars. The 20mph zones make the streets safer for other users, whether pedestrians of cyclists or even small children wlaking to school or visiting friends.

Lib Dems in Portsmouth were the first major city council to introduce 20mph zones and they did it on a huge scale covering the whole city apart from the main roads which stayed at 30mph. These zones have now been in place for two years and have been shown to reduce overall traffic speeds. The effects on accident figures  are much less clear with little or no reduction. However, the key question of residents’ attitudes to the new regime on their streets is much more difficult to measure but the received wisdom is that if traffic speed is reduced then people will feel safer about walking and cycling and also about allowing children out. I have not yet seen any actual data on this.