Our research shows just 13% of drivers in the UK adhere to 20mph limits, despite these slow zones accounting for more than 10,000 accidents a year. Using Department for Transport (DfT) data, we have built this heatmap to compare how the number of accidents in 20mph zones has changed in each police force across England, Scotland and Wales between 2015 and 2018.

Overall, there were 148% more accidents in 20mph zones in 2018 compared with 2015.

There are a number of forces which have seen large percentage increases during this period, with the biggest being seen by Dyfed-Powys, Metropolitan Police, Suffolk and West Midlands forces.

Some forces have seen a reduction in the number of accidents, although these are largely in areas with a small number of 20mph zones.

London has by far the greatest number of 20mph zones and accidents recorded by the Metropolitan Police account for nearly 57% of the total accidents across the UK. The roll out of London’s additional 20mph zones in recent years has also meant accidents have risen 10-fold between 2015 and 2018.

A number of councils across the UK are continuing to introduce 20mph limits with the aim of reducing accidents and improving road safety in urban areas. However, analysis of Department for Transport speeding figures found 86.88% of drivers in the UK exceed the speed limit on 20mph roads, with the average speed measured at 26mph*. The analysis suggests that, as the number of 20mph zones rises, so do the average speeds of motorists using them.

Since 2017, the average speed of motorcyclists in 20mph zones has increased from 27mph to 30mph, while van drivers’ average speed has also gone up from 25mph to 26mph during the same period. The latest DfT Road Casualty Report shows that there were 10,661 accidents on 20mph roads in the UK in 2018, accounting for nearly 1 in 10 of all road accidents for the year.

BookMyGarage co-founder, Karen Rotberg, said: “It’s been proven that 20mph zones help improve traffic flow and cut down on accidents, with the DfT’s own research suggesting 20mph zones work best when the average speed is below 24mph.

“But the zones have been largely despised by motorists, who find it painfully slow driving through them, which is probably why the limits are being roundly ignored.”