Updated estimates of the relationship between speed and road safety at the aggregate and individual levels

•Studies of the relationship between speed and road safety are reviewed.•The focus is on studies published after 2000.•Two mathematical models are supported.•Individual driver speed has the same relationship to safety as the mean speed of traffic. Recent studies of the relationship between the speed of traffic and road safety, stated as the number of fatalities and the number of injury accidents, are reviewed and their results synthesised by means of meta-analysis. All studies were based on data fully or partly for years after 2000. Previously proposed models of the relationship between the speed of traffic and road safety, including the Power Model and an Exponential Model, are supported. Summary estimates of coefficients show that the relationship between speed and road safety remains strong. The Power Model and the Exponential Model both fit the data very well. The relationship between speed and road safety is the same at the individual driver level as at the aggregate level referring to the mean speed of traffic.