New analyses to understand injury risk
Last year I looked at cycling injuries, and cycling risk, in different London boroughs. Often policy-makers and the media focus on Central and Inner London, because that’s where we see clusters of serious injuries and deaths. But if we normalise the figures based on the amount of cycling, we find many Outer boroughs are riskier. Looking only at injuries, and not risk, gives only part of the story. Measuring how many injuries there are per-mile walked or per-hour cycled helps us to take account of differences or changes in the amount of walking or cycling.
Looking at levels of risk experienced by road users (like cyclists or pedestrians) helps us separate out the effect of activity levels. This is important for policy. We shouldn’t celebrate a reduction in pedestrian injuries if that’s only happened because people have stopped walking. The policy goal should be to increase walking while reducing the risk each pedestrian experiences; likewise for cycling.
New research and metrics are starting to reflect this approach.
Methods shed light on who and what causes injury risk
Looking at National Travel Survey data, I found that for pedestrians and cyclists, riskis mostly caused by motor-vehicles, and risk per-kilometre walked is much higher for disabled and lower-income people.
Per-mile or per-hour injury risk is important and is measured andanalysed more than it used to be. But even that isn’t the full story about risk. We shouldn’t look only at risk experienced by the vulnerable, but also risk posed by those most likely to cause injury; who are predominantly in motor-vehicles.
Measuring and reducing the risk each driver poses to other people is an important aspect of road danger reduction. So often, people walking or cycling are told to plan their routes, to consider detouring to avoid injury risk, or to “dress for urban warfare”, as Peter Walker puts it. All of which make walking and cycling harder, when we should be making them easier.
What about driving? Are drivers expected to consider the risk they pose to others and plan routes accordingly? Quite the reverse: apps increasingly encourage drivers to plan routes based on small time savings. So I wanted to consider what effect this might have on road danger.
Are new technologies increasing risk?
Increasingly drivers are using in-car apps, such as Waze and Google Maps, that provide directions based on real-time traffic information. These apps may be fundamentally reshaping how drivers use the road network.
Is the main road busier than usual? Why not leave it to cut through a parallel residential street? No need to worry about getting lost if you are being directed at every turn.
Researchers have started to warn about the negative impacts of enabling drivers to use unexpected routes in the hope of reaching a destination quicker.
I worry that these services may be taking cars off busier roads where people expect them, and moving drivers onto side streets that aren’t designed for through-traffic. And the impact on pedestrians, especially children, does indeed look significant.
Do motor-vehicles pose greater risk on minor or major roads?
Earlier this year I published a paper which compared the risks posed by people driving on urban main and minor roads. Each mile driven on a minor urban road, results in 17% more killed or seriously injured pedestrians than a mile driven on an urban A road. For slight injuries, there are 66% more pedestrians injured per-mile driven on minor urban roads, compared to each mile driven on urban A roads.
If a residential, back-street route is longer in distance than the main road, the risk of injury grows further.
Why would driving along minor roads be more likely to injure pedestrians?
Many reasons exist. For example, it might simply be that there are more pedestrians on those residential streets. Other reasons might be to do with street design: for instance, on minor roads there are rarely formal crossing points, so people must cross informally. People walking on residential streets may feel more at home and pay less attention to the lower levels of motor traffic on those streets. Or conversely one may pay insufficient attention when driving on residential streets, especially when following an app.
It’s probably a combination of factors. But the result is that if the proportion of driving distance on minor roads grows, we may see more pedestrians injured.
Gauging the risks posed to child pedestrians
I conducted some new analysis for this blog, inspired by Dr Audrey de Nazelle asking about the impact on child injuries. This new analysis focuses on children and covers both urban and rural areas.
In both types of area, and for slight and more serious injuries, we see substantially more child pedestrian casualties per-mile driven on minor roads compared to A roads. The same is true for child cyclists (whereas considering cyclists from all age groups, risks posed by drivers on A and minor roads are similar).
Specifically, on urban roads, driving a mile on a minor urban road is twice as likely to kill or seriously injure a child pedestrian, and three times more likely to kill or seriously injure a child cyclist, compared to driving a mile on an urban A road.
The gaps in rural areas are even bigger, which may be related to the high default speed limit and lack of footways on minor rural roads. Each mile driven along a rural minor road is nearly five times more likely to kill or seriously injure a child pedestrian than each mile driven along a rural A road.
Perhaps this is not surprising. Children are more likely to be allowed out on minor roads unsupervised – particularly on their own street or streets close by. Given the ongoing reduction in children’s independent mobility, a small patch of streets around their home may be all that’s left to them (if anything).
But drivers today are armed with knowledge about how best to save a minute or two or avoid a traffic jam by cutting through these apparently quiet streets. Unfortunately, this means putting people walking and cycling, especially children, at greater risk of injury.
We need to weigh up whether our children’s safety, health, and ultimately, freedom are acceptable prices to pay for a minor convenience for drivers. I would argue that we adults (most of us are drivers, unlike children) have made the wrong choice.
So what policy recommendations can we draw from this new analysis?
First, Highway Authorities should do more to restrict through-traffic from minor streets. For instance, by using bollards or planters which allow access but cut off ‘rat-running’. This will help counter the tendency for motorists to cut through side streets and put children at increased risk of injury. At the same time, we need to make main roads safer too, for instance by reducing speed limits and improving crossings.
Second, app providers need to reconsider their routing systems, to put more weight on child safety and less on driver time savings. They are unlikely to make the change of their own accord, so as a first step, governments and transport authorities should be calling on them to do so.
Third, there is a strong case for reducing rural as well as urban speed limits. The default urban speed limit is 30mph and increasing numbers of urban streets are 20mph. Yet speed limits on single carriageway rural roads – usually, without footway provision, often narrow and with poor sight lines - are generally set at 60mph. While drivers encounter relatively few pedestrians and cyclists on such roads, collision severity tends to be worse given the higher speeds. Even a 20mph reduction on minor rural roads from 60mph to 40mph could make a big difference to injury risk in the countryside.
But in the meantime, do you drive? Walking or cycling is the best way to keep our streets safe and healthy. But for journeys that you still need to make by car, please if possible choose the main road route, helping reduce the risk that you will injure a child.