Powerful new long-term TfL research shows 20mph speed limits save lives on London’s roads

Compelling new TfL research that the number of people killed and seriously injured on borough roads in London reduced by 34 per cent following the implementation of the 20mph speed limit between 1989 and 2013. The report, the first of its scale in London, analyses more than 150 20mph schemes between 1989 and 2013, examining the three-year periods surrounding the implementation of each 20mph scheme.

The evidence in this new report will be instrumental in TfL’s work toward achieving the Mayor's Vision Zero goal to eliminate death and serious injury from London's transport network and to enable more walking and cycling in the capital.

TfL carried out this new extensive analysis to fully understand the impact of road safety measures across the city over a longer time span. The report shows that, with the exception of motorcycle fatalities, which did not change, 20mph schemes led to fewer fatalities and less severe injuries across every mode of travel.

The report shows that 20mph schemes significantly reduced the number of deaths and serious injury, including:

•   A 40 per cent reduction in the number of people killed (from 15 to 9), compared against the background trend of 7 per cent fewer fatalities across borough roads
•  A 34 per cent reduction in the number of people killed or seriously injured (from 395 to 260), compared against the background trend of a 15 per cent fall in people killed or seriously injured across borough roads
•  A 75 per cent reduction in the number of children killed (from 4 to 1), compared with no change across the control group. Additionally, a 50% reduction in children’s casualties (from 517 to 280), against the background trend within the control group of 20%.
•  A 35 per cent reduction in collisions and 36 per cent reduction in casualties on borough roads, against a background trend of 12 per cent fewer collisions and casualties across all borough roads 

The report acknowledges other road safety improvement measures implemented between 1989-2013 and recognises that the implementation of 20mph schemes on borough roads is not the sole cause of improved road safety in this time. For this reason, the report compares against the background trend seen across all borough roads in this period to provide compelling evidence that 20mph schemes reduce the number of casualties regardless of all other road improvement.

The report demonstrates the positive impact of slower speeds on safety and supports the importance of similar measures in future plans to further improve safety in the capital. London boroughs have made excellent progress reducing the default speed limit on their roads to 20mph, with 21 out of 33 boroughs now having a default 20mph speed limit. TfL expects this number to grow in light of the positive impact these schemes are having on collisions. TfL also provides sustained support to London Boroughs though the £87.6m Local Implementation Planning (LIP) funding that was confirmed for 2025-26, which works towards introduction of further 20mph zones and other road safety measures.  

London has been leading the way in implementing lower speed limits to cut death and injury on its roads. Since 2018, TfL has introduced more than 264km of 20mph speed limits, and over half of London's roads now have 20mph speed limits. Not only do 20mph schemes reduce the number of fatalities and casualties on the road, they also support more people to walk, wheel and cycle and reduce noise pollution, without impacting air quality or journey times.

TfL is committed to lowering speed limits across London, with plans to continue to roll out 20mph on its road network next year. TfL will also be publishing further research on the impact of 20mph schemes across London.

Speed is the single most important factor in the likelihood and severity of a collision, with collision data showing that the faster a vehicle is travelling, the more likely a collision will occur and the more severe any injury resulting from the collision will be. In 2023, speed was a contributory factor in around half of fatal collisions and over a third of all injury collisions in London. [2]

Walking and Cycling Commissioner Will Norman, said: “This compelling new analysis shows clearly that lowering speeds is saving lives. Every death or serious injury on our roads is one too many. Slower speeds not only protect the most vulnerable, they also help create safer, more welcoming streets, and are a vital part of building a safer London for everyone
“The Mayor and I are proud that London is leading the way with bold, evidence-led action to reduce danger on our roads, and we will continue working to eliminate death and serious injury on the transport network as part of our Vision Zero goal.”

 Lilli Matson, TfL’s Chief Safety Health and Environment Officer said: “It is brilliant to see the long-term analysis in this report. It contains hugely important findings which show the difference that 20mph speed limits have made to road safety in London, and we are able to fully understand the impact of road safety measures across the city over a longer time span. Lower speed limits save lives. We’re committed to eliminating unsafe speeds across London, and the analysis in this report reinforces our approach. No death or serious injury on London’s streets is acceptable or inevitable, and we are determined that London continues to be at the forefront of making real and lasting change.”

Jeremy Leach from 20's Plenty for Us said, "Over the past 30 years London’s boroughs have pioneered the widespread use of 20mph speed limits making streets feel safer and be safer for residents and visitors alike. This latest research from TfL backs up other studies that show streets are safer with 20mph speed limits and more people able to walk, wheel and cycle and to be active. We hope that the small number of London’s boroughs that have yet to make widespread use of lower speed limits will not miss this chance to bring in 20mph limits on many of their streets and roads.

 Newham Councillor Sarah Ruiz, Cabinet member for Environment, Sustainable Transport, Children’s Services and Education said: “Reducing the speed of traffic on our roads is essential for making the borough safer for all our residents and encourages our residents to take up the many advantages of switching from cars to sustainable transport, like cycling or walking.

“The statistics are clear the 20 mile an hour limits are saving lives and serious injury and make it safer and more attractive to get about the borough.”