Smeed's law

Smeed's formula is expressed as: or, weighted per capita, where D is annual road deaths, n is number of registered vehicles, and p is population.

Smeed became deputy director of the Road Research Laboratory and, later, Professor at University College London.

Smeed claimed his law expresses a hypothesis of group psychology: people take advantage of improvements in automobiles or infrastructure to drive ever more recklessly in the interests of speed until deaths rise to a socially unacceptable level, at which point, safety becomes more important, and recklessness less tolerated.

The Australian state of Victoria experienced deaths in excess of the Smeed formula until about 1970, but subsequently adopted a range of interventions which took it from being a poor performer in terms of road safety to one of the best.

(see Andreassen,[4] Broughton,[5] Oppe,[6] and Ameen & Naji[7]) However, John Adams of University College London argued in 1995 that Smeed's law linking deaths, vehicle-miles and population was still valid for a variety of countries over time, claiming that the relationship held for 62 countries.

[citation needed] Other researchers have tried to find a way to describe the trends in countries with a higher vehicle per person ratio.

[10] One study suggested that at higher ratios, a collective psychology is formed where people are more aware of the risk of motor vehicle related deaths and are inherently more careful in their driving.

Education on motor vehicles and safe driving habits are more common, but are not considered in Smeed's Law.