Citation

Nicholson AJ. Traffic Eng. Control 1989; 30(5): 241-246.

Affiliation

Univ of Canterbury, Canterbury, NZ

Copyright

(Copyright © 1989, Hemming Group)

DOI

unavailable

PMID

unavailable

Abstract

This paper describes some simple measures of the extent of accident clustering in a network. It is argued that such measures could be used to assist both the identification of the most appropriate form of accident reduction programme and the assessment of the effect of an accident reduction programme. While the various pictorial representations indicate the existence and degree of any accidents clustering, there is felt to be a need for a simple numerical index of clustering. Both the coefficient of variation and the coefficient of concentration are suitable, in that their values will change in accordance with expectations based on commonsense. The coefficient of variation is a well-known statistical descriptor, and it appears to be a more sensitive indicator of changes in the level of clustering. The relatively little-known coefficient of concentration appears to highlight any inequality in accident occurrence more than does the coefficient of variation, and it is therefore concluded that both indices should be used.