Does The Crash Rate Really Double For Each 5 km/h above 60 km/h
The ?Travelling Speed and Risk of Crash Involvement? research report of November 1997 found that ?the risk of involvement in a casualty crash doubled with each 5 km/h increase in free travelling speed above 60 km/h.? This report was undertaken by an excellent team, but the findings were was at apparent odds with previous research which showed a crash rates increasing for speeds above and below speeds in excess of the speed limit. This paper reviews the data in this report in a different manner, and other factors, to give a different view of what the information can be shown to prove. It concludes that the data supports that risk of crashes is best represented by a U shaped curve around mean speeds, with crash risk rising for very low speeds, and for high speeds. It further suggest that the current speed enforcement tolerances are probably appropriate, but that the penalties at 15 km/h or more above the speed limit should be more severe.