20mph speed limits encourage more considerate driving, leading to safer streets for all road users, including motorists, cyclists and pedestrians. The lower speeds reduce the risk and severity of road collisions. Detailed analysis over 20 years across London found a reduction in risk and severity of casualties in the roads that had switched to 20 mph.

Reducing traffic speed helps make people feel more confident about being on their local streets and enables children and the elderly to travel independently and safely. Calmer road speeds also help to make walking and cycling more attractive options, leading to less traffic congestion, better health, less noise, more social interaction and stronger communities.