Road safety impact of higher levels of walking and cycling “safety in numbers”

In this, my final blog on the link between road safety and our transport response to climate change, I want to focus on the safety impacts of moving people out of vehicles and onto bikes, buses and their feet.  We can look at this impact on safety from multiple angles.  Firstly, with minimum safety improvements to the road network and secondly, if we make changes like lower speed limits and installing supporting streetscape designs (a more desired outcome, better aligned to the Safe System Approach).

Research shows, the safety of travel by different modes varies. While motorcycles are the least safe, buses and trains are recorded as being the safest.  Walking (including to and from the bus) and biking is generally less safe than being a car occupant.  However, these high-level statistics do not show the full picture. 

In the Waka Kotahi research report 289, I examine safety benefits associated with moving people out of their cars onto the footpath (walking) and into cycling. I discuss the significant “safety in number effect” for both these modes (i.e. risk decreasing per road user with an increase in their volumes). The two figures below show how the crash (accident) risk for cyclists and pedestrians drops as their volume increases (at signalised intersections). 



Safety improves with more people walking and cycling

The research indicates that the most safety benefits (per person crash risk) for cyclists and pedestrians were associated with doubling the current volumes (100% increase). The graph (above) shows that safety benefits continue to increase as the number of cyclists increases (300% increase). This also assumes that people in cars shift to walking and cycling as the numbers of pedestrians and cyclists increase.  The crash risk of cyclists and pedestrians is many times (4 to 8 times) that of a car driver at low volumes, but just under double if there is a 300% increase in these modes.  This research is based on average pedestrians and cycle volume at traffic signals in 2005/6.  Cyclist numbers, in particular, have increased a lot since then.

Reducing the risk further with lower speeds and supporting infrastructure 

Vulnerable Road User (VRU) risk (i.e. risk for pedestrians, cyclists, e-scooter, mopeds, etc) can be lowered further by applying lower speed limits, further reducing traffic volumes and adding new cycling and pedestrian infrastructure.  Research shows, VRU risk reduces dramatically when operating speeds reduce from 50km/h to 30km/h; the latter being the safe system speeds for pedestrians and cyclists. 

Safer speeds can be achieved by applying lower speed limits and installing supporting infrastructure in busy pedestrian and biking areas (eg. town centres and commercial areas) while managing speed at high conflict points across the rest of the network. For example, put in raised and painted crossings where pedestrians and cyclists cross busy roads. 

Lowering traffic volumes can also reduce crash risk.  If the transport response to climate change does lower traffic volumes in the median to long-term, this will also make our streets safer for walking, cycling and using other forms of personal transport.   

This is my final blog exploring the relationship between our climate change and road safety future goals.  My other three blogs can be found at the links below:

Climate friendly bus priority measures and safe mobility

Safer people, safer vehicles and climate change

Achieving vision zero while saving the planet.


The Australian Road Safety Conference in Christchurch, New Zealand will also be exploring the link between climate change and road safety.  Hope to see you there!