Simulated safety performance of rear-end and angled vehicle interactions at isolated intersections

This paper applies a calibrated microscopic simulation model to assess the safety implications of signalization at a stop-controlled isolated intersection. Safety performance is measured in terms of a crash potential index (CPI) that makes use of time-specific vehicle parameters, such as deceleration rates, spacing, and speed profiles. Four performance measures are obtained: (i) average CPI/vehicle, (ii) CPI 85th percentile, (iii) number of vehicles with CPI > 0 (defined as interacting), and (iv) number of conflicts (defined in terms of a given CPI threshold). Two types of interactions are considered, namely rear end and angled. For rear-end interactions, CPI/vehicle was found to be significantly higher following the introduction of fixed signal controls. For angled interactions, CPI/vehicle was found to decrease with signalization. For both types of interactions, the CPI 85th percentile was found to decrease nonlinearly with signalization, especially for higher assumed volumes on the major approach. Rear-end vehicle interactions increased significantly following signalization and with increasing volume, whereas no such increase was observed for angled interactions. The key observation is that the number of vehicles subject to angled interactions was found to decrease after signalization. Key words: safety performance, microscopic simulation, signalized and stop-controlled intersections. Cet article applique un modele de simulation microscopique etalonne pour evaluer les implications de securite d'une signalisation a un carrefour isole controlee par un arret. Le rendement en matiere de securite est mesure en termes d'indice potentiel de collision (<< CPI >>) qui utilise des parametres temporels des vehicules tels que les taux de deceleration, l'espacement et les profils de vitesse. Quatre mesures du rendement ont ete obtenues : (i) CPI moyen par vehicule, (ii) 85e percentile du CPI, (iii) le nombre de vehicules ayant un CPI > 0 (definis comme interdependants), et (iv) le nombre de conflits (defini en termes d'un CPI seuil donne). Deux genres d'interactions sont consideres : par l'arriere et a angle. Le CPI/veh. pour les interactions par l'arriere s'est grandement accru apres l'introduction de controles de signaux fixes. Le CPI/veh. pour les interactions a angle diminuait avec la signalisation. Pour les deux types d'interactions, le 85e percentile du CPI diminuait de maniere non lineaire avec la signalisation, surtout pour les volumes de trafic presumes plus eleves dans l'approche majeure. Les interactions entre vehicules par l'arriere ont augmente considerablement apres la mise en place de la signalisation et avec un volume de trafic superieur; cette augmentation n'a pas ete observee pour les interactions a angle. L'observation principale est que le nombre de vehicules sujets a des interactions a angle a diminue apres la mise en place de la signalisation. Mots-cles : rendement en securite, simulation microscopique, carrefours signales et controles par un arret. [Traduit par la Redaction]
Introduction A number of recent studies of crashes for North American urban roads suggest that over 50% of these reported crashes take place in proximity to intersections. Intersections present special [...]