20mph Zones and Speed Limits

In December 1990 the Department of Transport issued Circular Roads 4/90 which set
out guidelines for the introduction of 20mph speed limits; local authorities had to
apply for consent from the Secretary of State to introduce a 20mph zone.

The Department for Transport’s current guidance is set out in DfT Circular 01/2006
which encourages and supports local authorities to implement 20mph limits and
zones in situations where there is a particular risk to vulnerable road users. The
guidance sets out that the purpose of 20mph areas is to create conditions in which
drivers naturally drive at around 20mph as a result of traffic calming measures or the
general nature of the location.

Early evidence indicates that 20mph limits are less effective than 20mph zones, and
rely on visual and environmental cues to encourage drivers to adopt lower speeds.

This factsheet explains the different types of 20mph zones and limits, the evidence for them and their purpose, and contains RoSPA’s policy statements on 20mph zones and limits.