Safety Evaluation for Expressways: A Comparative Study for Macroscopic and Microscopic Indicators

Abstract

Objective: This article is to assess the performance of 3 macroscopic safety indicators (speed, speed dispersion, and volume) and two microscopic potential crash risks (time to collision and deceleration rate to avoid crash) on safety evaluation for expressways. Methods: Field data were collected at 3 locations for 4 different time periods on an expressway in Beijing, China. The speed of each vehicle, headway time, and vehicle length were recorded by a traffic management system. The 5 safety indicators were thus calibrated on the basis of the collected data. Further, consistency and comparative analyses were applied to assess the performance of indicators. Results: According to the analyses, speed dispersion was a better predictor of the two microscopic potential risks compared to the two macroscopic indicators. Conclusions: Speed dispersion is recommended to proactively assess road safety because (1) it provides consistent risk evaluation with microscopic potential risks and (2) it makes data collection easier.