Abstract
A general speed limit of 70 m.p.h. came into operation at noon on December 22, 1965 on all roads in Great Britain (including motorways). The main reason for the 70 m.p.h. speed limit trial was to discover what effects, if any, such a limit had on the numbers and severity of road accidents. To assess this, the Laboratory studied the numbers of accidents and casualties which occurred on different types of road before and after limit came into operation. Traffic flows and vehicle speeds were measured before and after the introduction of the limit and several sample surveys were made to obtain information about drivers' and non-drivers' attitudes towards the limit and about their knowledge of its application.