For much of the time on London’s roads, 30mph is a theoretical rather than practical speed limit. As of 2021, average speeds during the central London evening peak were 9.6mph, rising to 19.4mph in outer regions.
Consequently, TfL’s decision to reduce the speed limit on ‘red route’ main roads across five boroughs is unlikely to have an outsized impact on journey times. What the evidence suggests it will do is save lives. The Transport for London Road Network found that at sites it monitored, collisions resulting in death or serious injury fell by a quarter after speed limits were reduced to 20mph.
