Review of 20mph Zone and Limit Implementation in England

This work was commissioned to undertake a review of the implementation of 20mph zones and limits in England. It was part of the wider Local Road User Safety evaluation and Action Learning commission to consider where and when zones and limits are being implemented, the rationale for their use and the characteristics of supporting traffic calming measures. The findings have enhanced the understanding of the different approaches to 20mph zone and limit use and implementation.

The review and research study focused on two areas of 20 mph scheme development and use; the rationale for their use; and the quantity/variability of scheme designs and coverage. The study findings were derived using a combination of Department for Transport databases and primary data collated from a selection of case study Local Highway Authorities (LHA). The findings should therefore be considered within this context.

The main findings of the review are:
• There are an estimated 2,150 20 mph zones in operation in England.
• Case study evidence indicates that 96% of 20 mph zones take the form of vertical traffic calming/deflection measures, such as road humps. 1% of zones utilise horizontal measures, such as chicanes, and 3% contain a mix of vertical and horizontal measures.
• 10% of 20 mph measures in case study authorities are speed limit controlled areas, using signing only.
• The average case study LHA road network length incorporated within zones and limits is 2.7 km, with a range from less than 1 km to 25 km.
• In case study areas the percentage of the total LHA road network covered with 20 mph zones and limits varies from less than 1% to 44%.
• In forming the decision to introduce 20 mph zones and limits implementation in the vicinity of schools provided by far the strongest rationale. This rationale was not always supported by historic evidence from recorded casualties in the 20 mph zones and limits areas.
• The location of zones and limits did not appear to be linked to levels of social deprivation or the proximity to hospitals.