Ecological studies hypothesise a ‘safety in numbers’ (SiN) effect whereby road safety for cyclists and other micromobility users improves as their numbers increase. But causal interpretation of these studies is difficult due to confounding and reverse causation.

The introduction of e-scooter rental schemes in selected districts in England meant an increase in micromobility users in these areas, which presented an opportunity to test the SiN hypothesis using a ‘natural experiment’.

This presentation will report the results of this natural experiment study, which found that road collisions for cyclists did appear to reduce in districts with an e-scooter rental scheme, compared to districts without one. The effect was specific to bicycle collisions and strongest in the subgroup of serious/fatal collisions. This is a positive, but preliminary finding, and should be verified in further work.

Hannah Edwards, Senior Research Associate in Medical Science, University of Bristol

Hannah Edwards is an epidemiologist and public health researcher at the University of Bristol and the NIHR Applied Research Collaboration West.

Her research is mainly in the field of maternal and child health, working with large-scale routine datasets as well as primary data from trials and cohort studies. More recently she has also been dabbling in road safety research, in collaboration with the physical activity and public health research team at the University of Bristol and road safety experts at the Department for Transport.