In 2017, The Royal Society for the Prevention of Accidents issued a detailed report regarding speed limit reduction to 20mph using speed limits alone and speed limits combined with traffic calming.
To evaluate the success of the 20mph limit pilot, 48 ‘before’ speed surveys were taken across a sample of street locations in the pilot area before the implementation of a 20mph limit. Speed surveys were taken again after the 20mph limit was enforced. Of these locations, 20 locations remained at a 30mph limit for the pilot period and 28 of the locations were changed to the new 20mph limit.
For the 28 locations that had their speed limit changed to 20mph, average ‘before’ speeds were 22.8mph, while ‘after’ speeds fell to 20.9mph, an average fall of 1.9mph. In the locations that remained at a 30mph limit, the average fall in speed between the ‘before’ and ‘after’ speed was 0.8mph. 12 ‘before’ locations also had an average speed that exceeded 24mph, an average of 25.8mph. The average ‘after’ speed at these locations was 22.4mph, an average fall of 3.3mph.
However, there were some slight increases in the average speed in 4 of the ‘before’ locations. 4 locations also continued to have average speeds of over 24mph. To ensure that these speeds fall towards 20mph; it was proposed that permanent engineering changes were made to these streets, including physical traffic calming measures, additional signage and road narrowing, as with a traditional 20mph zone.
Overall, the speed surveys have demonstrated that the 20mph speed limit has resulted in an overall positive drop in speeds in the majority of cases. Although 75% of the locations still have a speed average in excess of 20mph, in all but 4 of the locations, speeds are below 24mph, which is the DfT threshold recommended for the effective operation of 20mph limits.
Benefits evidenced through this pilot scheme were lower vehicle speeds, and strong residential support for 20mph limits. Surveyed residents also mentioned benefits of 20mph limits such as safety for children walking
around the area and playing in the street, and better walking and cycling conditions.In the year following the launch of the scheme, data also showed a 7% increase in journeys by foot, a 5% increase in journeys by bicycle and a 3% fall in journeys by car.
[In Birmingham,] Under the banner of ‘slower is safer’, a city-wide publicity campaign is underway to show road users the benefits of driving at 20mph on residential roads. There are also a number of other activities to encourage drivers to stick to the 20mph limits currently taking place. These activities include ‘kid’s court’, an educational activity, which gives speeding drivers the opportunity to face a panel of school children or receive penalty points on their license and a £100 fine. A video featuring local school children has also been produced and is being used to deliver a message to speeding drivers when the police are out on location delivering roadside education and enforcement activities.