On the causal effect of proximity to school on pedestrian safety at signalized intersections: A heterogeneous endogenous econometric model

Abstract Pedestrian safety in proximity to schools is a major concern of transportation authorities, local governments, and residents. In fact, several countermeasures (e.g., school-zone speed limits) are usually in place around schools to provide a safer environment, especially for school-age children. Two questions arise here: (i) are transportation facilities in proximity to schools truly safer than other facilities given a variety of implemented road safety interventions around schools? and (ii) how can we answer the previous question properly using a reliable approach that accounts for possible confounding? While previous literature has mixed results and does not provide clear methodological/empirical guidelines in this regard, we propose an approach that answers the above questions. We illustrate our method on a sample of intersections in Montreal, Canada. Specifically, to underpin a causal interpretation, for the first time in the extent of transportation literature, we develop a heterogeneous endogenous econometric model that estimates the causal effect of proximity to school on pedestrian safety, addressing a complex endogenous relationship between the two. Various built environment, traffic exposure, and road geometric/operational characteristics are considered. The results indicate that if endogeneity is not accounted for, the effect of proximity to school is underestimated, while not being significant at a 5% level of significance. However, after accounting for confounding factors, the proposed endogenous model indicates that proximity to school deteriorates pedestrian safety. Therefore, traffic safety countermeasures and policies in place (if any) during the study period have not been sufficient and/or effective in improving pedestrian safety at intersections near schools. Our heterogeneity in mean and variance formulation provided more insights. For example, we found that, interestingly, as pedestrian volume increases at intersections around schools, the adverse effect of proximity to school on pedestrian safety decreases, a possibility not previously explored in the extent of road safety literature, confirming a strong safety-in-numbers effect.