4th January 2018

Surprising findings point to 20mph zones perhaps not increasing safety as much as anticipated

Along with speedbumps, mini roundabouts, potholes and vehicles sat idling outside public buildings, 20mph zones are something that today’s motorists have come to accept when driving through urban areas.

They were first documented by the DfT in 1990, with early adopter regions including Sheffield, Kingston upon Thames and Norwich in the nineties1. Through a mix of simplistic speed limit changes, self-enforcing zones and areas with variable and part time limits, in conjunction with road islands, deflections, narrowing, humps, plateaus, cushions and uneven ‘rumble strip’ road surfaces, 20mph zones have proliferated across the UK.

Safety was a key factor driving their introduction and while some earlier studies and statistics have now been discredited somewhat, a review by E. Rosen2 concluded that, compared to 30mph zones with a fatality risk of 8%, this could be realistically reduced to 1.5% if the speed limit was lowered by 10mph.

RoSPA’s excellent factsheet on 20mph zones highlights that 2016 saw 789 people killed on built-up roads in Great Britain, while almost 16,000 were seriously hurt and just over 113,000 were injured, the majority of incidents occurring on residential roads.

The road safety charity Brake3 has passionately championed 20mph speed limits, with a particular focus on keeping children safer. They say that research has identified that children are unable to judge the speed of an approaching vehicle if it’s travelling at a speed greater than 20mph.

As part of their GO 20 campaign, Brake’s resources highlight that a car travelling at 20mph would be able to brake to a stop without hitting a child who runs out into the road around 12m or three car lengths in front, whereas the same vehicle traveling at 30mph would still be doing 27mph even if the driver braked immediately5. This is certainly a sobering thought and one we’ve publicised online through our young driver brand, Carrot Insurance5. The organisation 20’s Plenty for Us has also ardently fought for 20mph zones to be widely introduced6.

Just before Christmas, though, the ‘no-brainer’ perception of 20mph zones had cold water poured on it to an extent. Around a year ago, Bath and North East Somerset Council introduced thirteen new 20mph zones to the tune of £871,000, but surprisingly found that the rate of people killed or seriously injured actually rose in over half of the areas7.

Somewhat perplexed, the Council’s report stated: “There is no simple explanation for this adverse trend but it could be that local people perceive the area to be safer due to the presence of the 20mph restrictions and thus are less diligent when walking and crossing roads, cycling or otherwise travelling.” This theory certainly sounds like one plausible explanation, as it’s not uncommon to see pedestrians nonchalantly walking out into the road in urban areas.

Seemingly admitting defeat, the Council concluded that there is “little in the way of persuasive argument for continuing the programme in the future” but frankly conceded that it doesn’t have the funds to reverse the region’s 20mph zones – a process which would likely cost the same as the initial implementation.

This isn’t actually the first time that 20mph zones have been touted as potentially more dangerous. Back in 2010, the DfT reviewed Portsmouth’s scheme and identified that fatalities and injuries increased after its introduction8.

Despite these deflating statistics, many road safety voices like UK mobility charity Sustrans believe that 20mph zones do “make our streets safer, more inclusive and attractive for all”, to quote its CEO, Xavier Brice. He points to various studies including one by the British Medical Journal that have found that fatalities and injuries involving children have halved over the last twenty years thanks to the introduction of 20mph zones9.

Bath and North East Somerset Council’s views10 sound entirely logical, that a year isn’t long enough to properly assess the effectiveness of such measures, and that 20mph zones should be enforced  more robustly nationwide to combat the trend for motorists to ignore such signage, the DfT having found that 81% of cars recorded during 2016 exceeded 20mph limits quite blatantly11.

Augmenting low-speed roads with functioning speed cameras may sound punitive but would surely result in 20mph proving as effective as it was once hailed, and perhaps increased education aimed at adult pedestrians and cyclists would also prove beneficial. At all times of the year and especially until the clocks go forwards again in March, all motorists from private to fleet drivers need to be particularly vigilant in built-up areas to protect children and others, regardless of whether the limit is 20mph or not.


1. https://www.rospa.com/rospaweb/docs/advice-services/road-safety/drivers/20-mph-zone-factsheet.pdf
2. https://www.aaafoundation.org/sites/default/files/2011PedestrianRiskVsSpeed.pdf
3. http://www.brake.org.uk/facts-resources/15-facts/1256-speed-communities
4. http://www.brake.org.uk/assets/docs/DropChart.pdf
5. http://blog.carrotinsurance.com/cyclists-and-school-runs-stay-alert-on-the-road-this-week/
6. http://www.20splenty.org/
7. http://www.telegraph.co.uk/news/2017/12/17/20mph-limit-dangerous-costly-reverse-council-admits/
8. http://www.dailymail.co.uk/news/article-1317430/20mph-zone-increases-death-rates-switching-cameras-reduces-accidents.html
9. https://www.express.co.uk/life-style/cars/893770/20mph-speed-limit-increase-road-deaths-crash
10. http://www.bathchronicle.co.uk/news/bath-news/editorial-give-20mph-zones-more-973262
11. http://www.telegraph.co.uk/news/2017/07/03/drivers-ignore-20mph-speed-limits-official-figures-show/