20mph safety benefits not undermined by pandemic comparison, says TfL

Transport for London has rejected accusations that claimed success in reducing causalities from death or serious injury collisions by 25% due to new 20mph limits was based on erroneous comparisons between pre-pandemic data and data covering pandemic lockdowns, when traffic levels were significantly lower.

In a news release TfL said that monitoring of the 20mph schemes in the capital revealed that collisions fell by 25% (from 406 to 304) between 2020 and 2022, and collisions resulting in death or serious injury reduced by 25% (from 94 to 71), “demonstrating the huge impact of lowering speeds across London”.

Since 20mph speed limits have been introduced, collisions involving vulnerable road users have decreased by 36% (from 453 to 290), while collisions involving people walking have decreased by 63% (from 124 to 46), said TfL.

But website Transport Network claimed an internal TfL document showed that officials knew that a 24.9% fall in collisions resulting in someone being killed or seriously injured (KSI) should be seen against a ‘background’ reduction of around 16.5% due to less traffic.

In March 2020, TfL introduced a 20mph speed limit on all of its roads within the central London Congestion Charging zone as part of its Vision Zero commitment to eliminate death and serious injury on the capital’s roads by 2041.

TfL said the data referred to runs from 1 May 2020 to 30 June 2022. “The KSI reduction of 24.9% on roads where 20mph has been introduced should be seen in the context of a GLA-wide reduction in KSIs of around 16.5% over the same period, demonstrating that reducing speeds leads to greater benefits than on roads where speeds have not been reduced”, a spokesperson told LTT.

“Post-implementation speeds in scheme areas have exceeded expectations, showing reductions of between 1.7 and 5mph (between 15 and 20% reduction), in spite of reduced traffic levels as a result of Covid.”

Penny Rees, TfL Head of Healthy Streets Investment, said: “The data shows that there was a clear reduction in the number of casualties on roads with 20mph limits, even when accounting for the impact of the pandemic.

“Lowering speeds is crucial to eliminating deaths and serious injuries from London’s roads. People hit by a vehicle at 20mph are around five times less likely to be killed than at 30mph.”