The researchers compared bicycle collision rates in areas before and after introducing an e-scooter scheme, to areas without such a scheme. This ‘natural experiment’ looked at routinely collected police data on road collisions in the UK, between 2015 and 2023.

The e-scooter schemes were all introduced following the start of the COVID-19 pandemic. Overall rates of collisions for all vehicles went down during the COVID-19 pandemic, likely due to the lockdowns and restrictions on travel and socialising. When the restrictions lifted, overall traffic collision rates went back to pre-pandemic levels for all areas, regardless of whether they had an e-scooter scheme. 

However, the rate of bicycle collisions was about 20% lower in the e-scooter scheme areas after they were introduced, compared to the pre-pandemic period. Even after COVID-19 pandemic restrictions were lifted, all bicycle collision rates in e-scooter scheme areas stayed at least 10% lower than expected compared to control areas. And for the most serious and fatal bicycle collisions, rates stayed 20% lower than expected in e-scooter scheme areas.

Combining cycle and e-scooter collisions together did not change the results. This suggests that the reduction in bicycle collisions did not come at the cost of more e-scooter collisions. 

These findings support the ‘safety in numbers’ hypothesis. This argues that the more people use ‘micromobility’ forms of transport such as bicycles and e-scooters the safer they become, possibly because car drivers take more care.

Although there have been similar findings from previous studies, this is the first natural experiment to look at micromobility ‘safety in numbers’. It gives stronger evidence than we have had before.

Yoav Ben-Shlomo, Professor of Clinical Epidemiology at the University of Bristol and Theme Lead at the NIHR Applied Research Collaboration West (ARC West), said: “We were delighted to confirm the safety in numbers hypothesis but we need further data to be sure this is a real effect.

“If more people are encouraged to cycle, because the roads are safer, there are potentially even larger positive effects. Not just from fewer accidents, but because of the health benefits of being more physically active.”

Zoe Banks Gross, cycling instructor and founder of East Bristol Kidical Mass, added: “This research showing a decrease in cycling collisions alongside the increased use of e-scooters is positive. Increasing actual and perceived safety is important to encourage more people to cycle.

“Even with a decrease in collisions, our streets still need more space for active travel and micromobility.”

Brian O'Kelly, Manager of Bristol Road Club cycling club, said: “The safety in numbers hypothesis is true in that it changes the way a motorist views cyclists and other vulnerable road users. When you see a lot of the same thing, such as a slow cyclist, you get less triggered and so use better judgement in passing them."

Paper 

‘Risk of bicycle collisions and “safety in numbers”: a natural experiment using the local introduction of e-scooters in England’ by Hannah B Edwards, Frank de Vocht, Russ Jago, Miranda Armstrong, Edward Carlton, Yoav Ben-Shlomo in Injury Prevention [open access]