Speed limits of 20mph ‘don’t improve safety’

SPEED limits of 20mph have ‘little impact’ on crashes, casualties and drivers, according to a study.

Schemes to reduce road traffic speed in certain areas have become increasingly popular.

At 30-40mph, the risk of pedestrian fatalities is up to 5.5 times greater than at speeds of 20-30mph. But a three-year study of a 20mph project across Belfast suggests the measure did not make roads safer. Researchers from Queen’s University Belfast, Edinburgh University and the University of Cambridge studied 76 city centre streets before and after the new limit.

When compared with nearby streets, a 20mph limit made little difference for collisions, casualties or speed. In fact, drivers hardly slowed down at all – which could explain why crashes and casualties did not improve. Collisions dropped by just 3 per cent and 15 per cent respectively one and three years later, while casualties fell by just 16 per cent and 22 per cent respectively. None of these reductions was deemed statistically significant.

Average traffic speed fell by only 0.2mph one year later, and 0.8mph three years later. The only significant decrease was in traffic volume, with 166 fewer vehicles per week in the morning rush hour. Writing in the Journal of Epidemiology and Community Health, the team said that the policy may only work alongside ‘other interventions such as driver training, CCTV, community speed watch and police communication’.

In 2017, Manchester council halted funding for a 20mph limit, as it made ‘no difference

‘Problem with compliance’

to speed or accidents’. Yet trials in Bristol and Edinburgh saw collisions fall significantly.

RAC spokesman Simon Williams said there seemed to be ‘a serious problem with compliance’, adding that chicanes and speed bumps may help.

Mary Williams, of safety charity Brake, described 20mph limits as ‘life-saving’, adding: ‘ The difference between a 20mph and a 30mph limit is a doubled stopping distance.’