title: 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.
authors.affiliation: a Griffith School of Engineering , Griffith University , Gold Coast , Queensland , Australia.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Qu
authors.forename: Yan
authors.initials: Y
authors.lastname: Kuang
authors.forename: Erwin
authors.initials: E
authors.lastname: Oh
authors.forename: Sheng
authors.initials: S
authors.lastname: Jin
mesh_terms: D000054:Acceleration; D000063:Accidents, Traffic / Q000517:prevention & control*; D001334:Automobile Driving / Q000706:statistics & numerical data*; D002681:China; D003654:Deceleration; D004779:Environment Design; D006801:Humans; D018570:Risk Assessment; D012449:Safety; D013997:Time Factors