Estimating the Safety Performance of Urban Intersections in Lisbon, Portugal

According to official statistics, a large percentage of crashes are reported in Portuguese urban areas. For instance, from 2004 to 2007, about 70% of all injury accidents and 43% of the fatalities occurred inside urban agglomerations. This important safety problem has also been observed on the urban network located in and around Lisbon. Understanding this significant problem, the Government of the Portuguese Republic via its research grant agency – The Foundation for Science and Technology – funded a project whose primary objective consists of developing tools that would help estimating the safety performance of various components of the urban highway system in Lisbon. This paper documents one component of the safety tools that are currently under development. More specifically, this paper describes the steps that were taken to develop predictive models for estimating the safety performance of signalized and unsignalized intersections located in Lisbon. Several crash predictive models (CPMs) were developed using the Poissongamma modeling framework. Two types of models were estimated: flow-only and models with covariates. They were estimated using crash and other related data collected at 44 three-legged and 50 four-legged intersections for the years 2004-2007, inclusively. It was found that some highway geometric design characteristics were associated with the crashes occurring at urban threeand four-legged intersections in Lisbon. Vieira Gomes et al. 1