Bayesian Analysis of Road Accidents: A General Framework for The Multinomial Case

An important aspect in road safety research concerns the development of analytical tools to identify road sites with high risk. Within a context of optimization subject to financial constraints, decisions have to be taken as to which sites should be considered for treatment or safety improvement. The most economically reasonable selection criterion is to select those sites which had the highest accident rate in the preceding year. This is a bad procedure because of the well known regression to the mean problem. Even if no remedial treatment is made, the number of accidents recorded at the same site in the following year will naturally decrease toward its temporal mean. In other word, very high accident rates should be viewed as outliers.