Determination if VISSIM and SSAM could estimate pedestrian-vehicle conflicts at signalized intersections

Abstract

ABSTRACTThis article examines the optimum values of postencroachment time (PET) and time-to-collision (TTC) parameters that would define a pedestrian-to-vehicle conflict at signalized intersections using a simulation model (VISSIM) and a surrogate safety assessment model (SSAM). A total of 42 video hours were recorded at seven signalized intersections for field data collection. The observed conflicts from the field were used to calibrate VISSIM and replicate the conflicts. The calibrated and validated VISSIM model generated the pedestrian–vehicle conflicts from SSAM software using the vehicle trajectory data in VISSIM. The mean absolute percent error (MAPE) was used to determine the optimum TTC and PET thresholds for pedestrian–vehicle conflicts and linear regression analysis was used to study the correlation between the observed and simulated conflicts at the established thresholds. The results of the regression analysis indicated the highest correlation between the simulated and observed conflicts when the TTC parameter was set at 2.7 and the PET was set at 8. It was also found that the VISSIM model might underestimate the number of pedestrian–vehicle conflicts at specific intersections that would involve illegal pedestrian behavior such as jay walking or pedestrian signal violation that would occur in the real world.