20 mph limits are a much debated topic in cycling circles. Here, York Cycle Campaign Committee member and science journalist Dr Kate Ravilious explains why the York Cycle Campaign has decided to remain neutral on the issue
Intuitively it seems to make sense. Introduce 20mph speed limits on our roads; vehicles slow down; pedestrians and cyclists are safer; more people decide to walk or cycle. At least that is the chain of consequences that I imagined would happen if more areas imposed 20mph speed limits, but being the nerd I am I thought I’d take a look at the evidence. Sadly 20mph limits don’t appear to be the magic bullet I hoped they might be.
Back in 2014 the Department for Transport commissioned a 20mph impact study. The resulting 68 page report was published in 2018, and presents extensive evidence from 12 case study areas across England, plus a number of 30mph comparison areas. Crucially this is the only study to have proper controls (comparing with similar 30mph zones) against the 20mph intervention, enabling a true comparison of the effect of the 20mph zone. Other studies have sometimes shown benefits of 20mph zones, but they fail to take account of other factors that may have influenced the outcome, such as increased traffic congestion, gentrification of the neighbourhood, planting more trees alongside the road, changes to the road layout such as adding pedestrian crossings and cycle lanes and so on. By comparing with equivalent 30mph zones over the same time period this study is able to determine whether it is the introduction of the 20mph zone that has brought about the changes, or whether other factors are at play.
So what impact do 20mph speed limits have? The first question I wanted to ask was whether 20mph limits actually made drivers slow down. My personal experience of driver behaviour in the 20mph zone outside Fishergate School (see photo) has been one of disappointment, with drivers regularly whizzing over the pedestrian crossing at speeds far in excess of 20mph. This 20mph zone was installed back in 2011, at a cost of £85,000 (equivalent to around £100,000 today), amidst huge controversy and against the advice of North Yorkshire Police, who said they wouldn’t be enforcing the speed limit. The evidence from the DfT report suggests that my Fishergate experience is far from an outlier. On average the introduction of a 20mph limit resulted in speeds falling by just 0.7mph in residential areas and 0.9mph in city centres.
A Department for Transport Statistical Analysis, published in June 2019, reveals that an eye-watering 87% of car drivers travel at over 20mph in a 20mph zone. Buses and lorries are little better, and 92% of motorcyclists seem to think the signs don’t apply to them. More than one fifth of vehicles travel at over 30mph in a 20mph zone. See pages 11 and 12 of the report for full breakdown of the results.
Disappointing. But nonetheless, even a small reduction in speed can make all the difference when it comes to accidents. The most recent estimates suggest that pedestrians have an 8% risk of being fatally injured when hit by a car travelling at 30mph, versus a 1.5% risk when the car is travelling at 20mph. So even a reduction in average speed of 1mph should make a big difference – right?
Wrong. The evidence from the 12 case studies showed no significant change in collisions and casualties. Any reductions that were observed were mirrored in the 30mph comparator areas, suggesting that it was other variables (such as greater traffic congestion) that were causing the reduction.
One location – Brighton – bucked the trend. In this case the benefit to pedestrians was clear, but interestingly the 20mph limits still didn’t lessen the risk for cyclists at all. Here is the relevant paragraph from page 46 of the report:
Brighton Phase 1 is the only case study area where we have been able to estimate a statistically significant change in collisions and casualties, relative to the 30mph comparator area. The results show a significant reduction in overall collisions (-18%), overall casualties (-19%), pedestrian casualties (-29%), and casualties aged 75 or over (-51%). However, there is no evidence to indicate a real change in casualties involving cyclists and under 16s, at this time.
The report authors speculate that the 20mph limits were more effective at reducing accidents involving pedestrians in Brighton because they were applied on roads that were busier in the first place. But for cyclists the benefits still failed to emerge.
So it seems that slower traffic brings no benefit for cyclists. Something I would concur with based upon my own experiences. Cycling along Fulford Road during rush hour is something I try to avoid. Usually the traffic is moving but slow. In these circumstances drivers seem more likely to stop in front of junctions and give way to traffic wanting to turn into the junction. This happens in front of Aldi all the time. It seems like a friendly gesture on the driver’s behalf, but for the poor cyclist pedalling up the inside of the traffic, it is potentially lethal. Meanwhile, it also seems that at slower speeds drivers think it is okay to skim past cyclists more closely than they might when driving faster. Too often I’ve nearly been knocked off my bike by a bus wing-mirror whipping past my head, or someone pulling a trailer that is wider than their car. And those pesky left turns across the cycle lane, without checking mirrors to see if anyone is cycling up the inside, seem to happen more frequently in slow-moving traffic. From my personal experience I feel safer cycling along Fulford Road when traffic is moving at 30mph, than when the road is congested and traffic is moving slowly.
The final question I wanted to ask was whether having 20mph limits in place encourages people to cycle more? In this case the data showed a very small upward tick in walking and cycling – 5% of residents self-reported that they walked more and 2% said they cycled more. But crucially it wasn’t clear that this small increase could be credited to the 20mph speed limits, or whether other factors were at play.
All in all the current evidence indicates that 20mph speed limits offer few, if any, benefits to cyclists. This certainly wasn’t what I wanted to hear, and it is disappointing. To put it another way cyclist safety is often framed in terms of willingness of a parent to allow a 12 year child to cycle independently on a cycle route. The DfT report indicates that imposing 20mph speed limits on a road like Fulford road (“A major strategic road”), would result in 46% of vehicles travelling at less than 20mph – a mere 3% more than when the road had 30mph limits. That means out of every thirty cars that pass the child, only one extra vehicle would be persuaded to travel at less than 20mph (a rise from 13 to 14). Sixteen vehicles would still whizz by at over 20mph. Hardly much of a change from the 17 vehicles travelling at over 20mph when the road had 30mph speed limits. As I parent, these statistics don’t persuade me that 20mph speed limits make it safe enough for my 12 year old to cycle unsupervised on this kind of road.
This is my take on the evidence, and it don’t necessarily reflect the views of everyone in the York Cycle Campaign. However, it is because 20mph zones have no proven benefit for cyclists that York Cycle Campaign remains neutral on 20mph speed limits. The focus instead is on campaigning on the measures that have been proven to increase cyclist safety and participation.