What it means: all road casualties reported to the police in Great Britain, divided by the total distance driven by motor vehicles that year. It shows how risky each kilometre of travel is, separately from how much people drive. In 1950 the rate was 277.6. Figures cover casualties reported to the police only; many minor injuries are never reported. A change of 5% or more on the year before counts.

Source: DfT, reported road casualties Great Britain, table RAS0101 (casualties and traffic), converted from miles to kilometres.