Link between more active travel and lower VRU casualties

[David Swift]

I have had good discussions with colleagues in Public Health and have seen some good cross working opportunities. They are putting together an Active Wellbeing Strategy. The registrar has added a line in the draft strategy that states ‘enabling active modes of transport can contribute to a reduction in road injuries’. This seems to lean heavily on a 2022 WHO publication, which highlighted that ‘the magnitude of crash rates for walking and cycling are not inherently linked to these modes, but depend heavily on local circumstances, such as traffic conditions and quality of infrastructure’. Importantly, a strong relationship between higher walking and cycling levels and safety has been consistently observed. Does anyone know if there is any research that supports the link between more active travel and lower VRU casualties? I have always heard the theoretical link between increasing pedestrians/cyclists will lead to less risk, but have always had concerns about the initial increased exposure to those modes prior to getting to the ‘safe’ level, whereby other road users are more aware.

[William Cubbin]

David,
There is a fair amount of evidence on this topic, and is usually referred to as the “safety in numbers effect”. As far as I am aware it is more well-researched for cycling than walking. An important thing to bear in mind is that the effect is often measured as a reduction-in-risk-per-user-mile-travelled rather than a reduction in total number of VRU injuries. So more active travel tends to result in less risk for each individual person who walks or cycles, but does not necessarily reduce total VRU injuries across the population. However, since active travel modes have less kinetic energy than motor traffic, if an increase in active travel results in a corresponding decrease in motor traffic, there is the potential for a reduction in total risk to all road users.
Some studies worth looking at:
1. https://www.sciencedirect.com/science/article/pii/S0001457516301555 – The study itself has quite a narrow scope, but the literature review covers a good range of other studies.
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC1731007/ – Tests the theory with a range of datasets.
3. https://www.sciencedirect.com/science/article/abs/pii/S0022437522001402 – Looks at the effect on injury severity, rather than injury rates that most studies cover.
4. http://www.cyclinguk.org/sites/default/files/file_downloads_widget/0912_rg_rss-conf_safety-in-numbers_pres.pdf – This is a good non-academic summary but cites some of the academic evidence.

[Andrew Fraser]

Dear David,

I have found it rather difficult to find what you actually want, rather the reverse.

I suggest that you contact Marcus Jone of TRL, directly, as he may be more up to date than any of us. He is mentioned here:

https://www.itsinternational.com/feature/trl-cities-must-do-more-help-vrus

Some background data (for London) can be found here:

https://content.tfl.gov.uk/road-risk-and-vulnerable-road-user-working-paper.pdf

and I have a feeling that a download of this might be useful – it has plenty of references to explore:

https://www.who.int/europe/publications/i/item/9789289057882

I would advise the registrar to be careful about confusing accident rates, which may well fall during your interim period with accident numbers, which may well rise (although the London experience seems not to confirm that).

I suspect that much will depend on the quality and (practicability) of whatever measures are taken. In my own area, I am currently contesting the removal of mini-roundabouts (!) as part of the local authority’s somewhat scrappy cycling strategy. I think Plowden and Hillman warned against a half-hearted approach decades ago, so we need to be careful …

Sorry I can’t be of more assistance.

Andrew.

[William Cubbin]

Further to my previous reply, as luck would have it I cam across this paper today (trying to write my thesis!): https://www.sciencedirect.com/science/article/pii/S0001457509000876
It explores what can make a safety in numbers effect strong enough to reduce net casualties over the population, rather than merely reducing the risk per user mile.

[Rebecca James]

Hi,
It’s not quite what you’re asking, but in West Yorkshire, our data analysts have started looking at ‘road users injured vs vehicles involved’ in relation to our road traffic collisions. This was primarily to help us look at ‘who’ we needed to target with our road safety / behaviour change campaigns. As you would expect (because there are so many of them on the roads, making so many journeys) the vehicles involved are mostly cars. So I think the extrapolation would be that if you can reduce the number of cars on the roads, but shifting those journeys to public transport or walking/scooting/ cycling journeys then then you’d expect to see a reduction in collisions. Even assuming that the number of (for example) pedestrian / cycle conflicts increased (which you might expect if you suddenly increased the numbers of people walking or cycling), you’d expect to see a reduction in casualty severity? I’d be happy to link you to the data analysts in our area if you think this would help?

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