Safety Evaluations of Aggressive Driving on Motorways Through Microscopic Traffic Simulation and Surrogate Measures

The majority of road accidents, 75-90%, are related to driver errors of one form or another. Aggressive driving is the most common driver error which results into unnecessary fatalities, injuries and frustrations. This paper addresses the safety evaluations of aggressive driving through use of microscopic traffic simulation and safety surrogate measures. A motorway was simulated and calibrated in VISSIM with vehicle classes of normal. The proportion of aggressive drivers was made to increase from a base model of all normal vehicles to a maximum of 15% with an increment of 3% at a time. Four different scenarios of driving aggression were investigated, namely: (1) Close following or tailgating, (2) Weaving in and out through traffic, (3) Speeding or driving too fast for condition, and (4) Combined aggression of close following, weaving through traffic and speeding practiced all at the same time. Surrogate Safety Assessment Model (SSAM) was used to evaluate the safety of each scenario by comparing them against a base model of all normal drivers. Quantitative results on the measures of safety performance of the scenarios were presented in terms of percentage increase in simulated vehicle conflicts of probable crashes or near crashes. The severity of the resulting crashes and also crash risk involvement of aggressive drivers was also discussed separately for each form. Drivers who speed, follow closely, weave through traffic and their combination were found to be involved in vehicle conflicts by much as 2.36, 6.16, 7.02 and 10.36 times more than normal drivers respectively.