Assessing the Risk of Road Traffic Fatalities Across Sub-Populations of a Given Geographical Zone, Using a Modified Smeed’s Model

Abstract

Smeed (1949) provided a regression model for estimating road traffic fatalities (RTFs). In this paper, a modified form of Smeed’s (1949) model is proposed for which it is shown that the multiplicative error term is less than that of Smeed’s original model for most situations. Based on this Modified Smeed’s model, Bayesian and multilevel methods are developed to assess the risk of road traffic fatalities across sub populations of a given geographical zone. These methods consider the parameters of the Smeed’s model to be random variables and therefore make it possible to compute variances across space provided there is significant intercept variation of the regression equation across such regions. Using data from Ghana, the robustness of the Bayesian estimates was indicated at low sample sizes with respect to the Normal, Laplace and Cauchy prior distributions. Thus the Bayesian and Multilevel methods performed at least as well as the traditional method of estimating parameters and beyond this were able to assess risk differences through variability of these parameters in space.