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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. [ABSTRACT FROM AUTHOR]

Abstract: A systematic procedure is presented for calibrating and validating a microscopic model of safety performance. The context in the model application is the potential for rear-end crashes at signalized intersections. VISSIM® v.4.3 provides the simulation platform for estimating the safety performance for individual vehicles and has been calibrated and validated using separate samples of observed vehicle tracking data extracted from the FHWA/NGSIM program. The calibration exercise involves four sequential steps: (1) heuristic selection of initial model inputs, (2) statistical screening using a Plackett–Burnman design, (3) fractional factorial analysis relating inputs to safety performance, and (4) genetic algorithm procedure for obtaining best estimate input values. Three measures of safety performance were considered: crash potential index, number of vehicles in conflict and total conflict duration per vehicle. Model consistency was assessed by comparing simulated and observed safety performance based on a separate validation sample of vehicle tracking data. The suggested procedure was found to effectively estimate model input parameters that closely matched safety performance measures in the observed validation data. This procedure yields an objective and efficient means for simulation model calibration applied for estimating safety performance at signalized intersections. [Copyright &y& Elsevier]