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Commuter heading back home on Westminster Bridge.

Cyclists make cities safer for everyone

Encouraging commuting by bike and improving cycling infrastructure can benefit all road users, including motorists and pedestrians.

There is power in numbers and perception of our safety increases when we are part of a large group, all performing the same activity, rather than as an isolated individual. When it comes to cycling there is a broad amount of evidence that shows that this is not just a perception, but that risk is actually reduced where more people are on bikes. However, whilst the understanding that an increased number of cyclists on the roads makes it safer for everyone is widely supported, recent research unpicks the reasons and suggests it is not numbers alone that create the reduction in incidents, injuries and fatalities.


In the largest study of road safety to date researchers at the University of Colorado, Denver, and the University of New Mexico looked through 13 years of data from 12 large cities in the United States with a lot of cycling, including Oklahoma City, Memphis, Kansas City, Dallas, Houston, Austin, Chicago, Denver, Seattle, San Francisco, Minneapolis, and Portland and investigated over 17,000 fatalities and 77,000 severe injuries. During those years, the U.S. saw a 51 % increase in bicycling to work and the number of protected bike lanes double each year starting in 2009.

The study, published in the Journal of Transport & Health 2019, found that bike facilities act as “calming” mechanisms on traffic, slowing cars and reducing fatalities. Between 1990 and 2010, Portland’s bicycle share increased from 1.2 % to 6 % and the road fatality rate dropped by 75 % over the same period. With added bike lanes, fatal crash rates dropped in Seattle by 60.6 %, San Francisco by 49.3 %, Denver by 40.3 %, and Chicago by 38.2 %.

Originally, it was believed that an increase in cyclists would lead to a “safety-in-numbers” effect which would make drivers more likely to slow down and be aware of their surroundings. However, this research found that it’s not the number of cyclists, but rather the infrastructure built for them, such as separated and protected bike lanes, that create this effect.


In the UK, a review by the University College London’s Centre for Transport Studies, reported in the journal Injury Prevention that the apparent risk reduction in popular cycling areas is not explained simply by there being more cyclists on the road, “it is unlikely that the effect of SIN (safety in numbers)  is an emergent property of the sheer numbers of cyclists or pedestrians, but more likely to be an effect of significant investments in measures that make cyclists and pedestrians feel safe, such as dedicated infrastructure and the enforcement of laws that regulate how pedestrians, cyclists and motorists behave on the roads.”

Whilst this was written in 2015 it applies very strongly to our current situation and the increased appetite from government to support cycling. The paper goes on to say “ These kinds of investments are expressions of a country’s political will to improve safety for pedestrians and cyclists, and as such, the SIN effect may be a reward for this, or the effect may in fact be in the opposite direction. That is, those places less risky for pedestrians and cyclists may be the places where more people walk and cycle.”

Motorists having less accidents and driving more safely in places of high cycling use is very interesting and an area that demands much further research, as the authors acknowledge saying, “assuming a causal direction from increased numbers of pedestrians and cyclists to improved motorist behaviour merits further research.” However, the final message is that creating safer environments remains the key to improving the experience and safety of pedestrians and cyclists  “dedicated infrastructure and separation from motor traffic, is likely to achieve the desired effect to reduce pedestrian and cycling collisions, fatalities and disabilities.”

Regardless of the reasons why ‘safety in numbers’ reduces risk, the positive effect of more people cycling is something we all stand to benefit from. Let us hope that the current feelings towards cycling is not short lived and that the Prime Minister’s promise of a ‘golden age of cycling’ comes to fruition. More cyclists, more cycling infrastructure, and a broader acceptance of cycling as a means of transport could transform many aspects of our cities, including making them safer places to live and work.



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Wesley E. Marshall, Nicholas N. Ferenchak. Why cities with high bicycling rates are safer for all road users. Journal of Transport & Health, 2019; DOI: 10.1016/j.jth.2019.03.004

Christie N, Pike I. Is it safe in numbers? Injury Prevention 2015;21:276-277.

Written By:

Cycle SOS
Cycle SOS only deal with cycle accident claims. We understand cyclists, and believe that cyclists have the right to be safe on the roads. Cycle SOS The Cyclists National Helpline is made up of a highly trained team of specialist personal injury cycling lawyers that have recovered millions of pounds for people making bicycle accident claims.