Whilst combing through the Government’s road casualty statistics for a recent post, we were struck by a startling change. The number of casualties on roads with a 20mph speed limit has almost trebled over the past five years, from 1,827 in 2010 to 5,079 in 2015.
That 178 per cent increase – shown in the graph above – is in stark contrast to the trend on other roads, where casualties have fallen by 12 per cent in the same period.
But this doesn’t mean 20mph zones have become more dangerous over the last five years. It just means there are a lot more of them now, thanks to road safety campaigns like ‘20’s Plenty’ and ‘GO 20’. A survey of local councils by the charity Brake in 2015 found that 21 per cent of those who replied had introduced or are planning to introduce 20mph zones, and a further 36 per cent are conducting limited trials.
The aim, of course, is to make roads safer, and the statistics suggest it’s working. We can see this by looking at 20mph and 30mph roads together – as we do in the graph below. This helps to account for the fact that many roads have seen their speed limit reduced from 30mph to 20. On all these roads, casualties have fallen by 9.4 per cent over the last five years.
As well as helping to reduce the overall number of casualties, 20mph speed limits also make our roads safer because accidents on them are less likely to kill. Our third graph, below, shows the proportion of accidents on each type of road that resulted in at least one fatality.
In the last five years, just 0.4 per cent of reported accidents on 20mph roads result in a fatality, compared to 0.6 per cent of those on 30mph roads and 1.3 per cent of those on 40mph roads.
Of course these statistics don’t tell the full story. We can’t know how many more people would have died had speed limits not been reduced, nor how many lives could be saved be reducing them on more roads. But evidence-based efforts to improve road safety such as these are certainly very welcome.