An empirical study on heterogeneous traffic car-following safety indicators considering vehicle types

Considering different car-following characteristics of trucks and cars, this study verifies the heterogeneity of steady car-following behavior of four leader-follower vehicle-type combinations based on the naturalistic driving dataset. The best-fit distribution model of surrogate safety indicators (i.e., distance headway (DHW), time headway (THW), time to collision (TTC) and safety margin (SM)) of four combinations are identified. Then, the performance of surrogate safety indicators in various speed ranges is compared to select a homeostatic risk perception indicator. After that, the longitudinal control model is calibrated for four combinations. Results show that the heterogeneity of different leader-follower vehicle-type combinations has been confirmed by surrogate safety indicators and calibrated parameters of the longitudinal control model. SM is suitable as the homeostatic risk perception indicator for four combinations when the speed is less than 90 km/h, and the advised safety warning SM value of is 0.9 or 0.95 for four combinations.