Astounding results in Wales one week after going 20mph

One week to the day after Wales introduced widespread 20mph limits across the country, we have released a report analysing the impact on traffic speeds over hundreds of miles of roads. The headline statistics show a 2.9 mph drop in speeds on the surveyed roads, averaging 19.77 mph compared to 22.67 mph the week before the change. The data and subsequent analysis used traffic information along main routes in ten towns and cities totalling 261 miles in length in the period one week before and one week after the switch.

The drop in average speeds should provide incredible safety benefits to pedestrians and cyclists as well as an expected improvement in air quality to all residents and road users. Sample analysis of two routes has indicated a journey time increase of between 45-63 seconds along the two 2.5km routes in Cardiff and Wrexham.

This independent research has been possible through the use of connected vehicle GPS data provided by TomTom in our Traffic Insights Tool, which allows for a rapid analysis of traffic data within 24 hours. The sample used over 25 million vehicle movements on the Monday-Friday, 6am-6pm periods in the two weeks either side of the change. The full report included figures showing changes in each of the ten towns, the change in speed profiles along all roads, and a sample impact analysis for journey times. 

Richard Owen, Agilysis CEO and the report's author said, "The immediate impact on traffic speeds in Wales has been astonishing, and far greater than many would have predicted. Welsh drivers are, on the whole, accepting lower speed limits and have changed their behaviour accordingly. There will remain some drivers who choose to break the limit by significant amounts but the drop in speeds on the fastest urban roads has been marked."

Speaking about the groundbreaking new data made available for this research he commented, "Advances in data science and the increasing number of connected vehicles on our roads have enabled this analysis and research to take place in a matter of days, where previously we may have had to wait weeks or months. Road authorities and police forces now have access to new data that enables them to understand general patterns of behaviour, and pinpoint roads where further action may be required."