ASSESSING THE SAFETY IMPACTS OF OVERTAKING ON RURAL TWO-LANE HIGHWAYS FOR DIFFERENTIAL CARS AND TRUCKS SPEED LIMITS USING MICROSCOPIC SIMULATION

摘要

Recently a number of jurisdictions in North America have implemented legislation to limittruck speeds on two-lane highways, through differential speed limits. This safety strategymay affect the overtaking behaviour on these highways and the implications of thisstrategy for accidents during overtaking are not well understood. Arguably the overtakingbehaviour is the most complex and important component of driving on two-lane highways,and plays an important role in traffic safety. The most important factor in overtakingmodelling is the gap acceptance which is correlated with safety. The presence of a largetruck in the traffic stream can have a significant effect on the gap acceptance behaviour.This paper presents a micro- simulation platform for modelling overtaking gap acceptancebehaviour and applies the model to rural two-lane highways subject to reduced truckspeed limits. The safety implications of differential truck speed limits for two-lanehighways for different traffic volumes were evaluated based on changes in number ofovertaking manoeuvres and risk of gap acceptance behaviour. It was found that theimposition of reduced speed limits for trucks increases the number of car-truck overtakingmanoeuvres and hence compromises safety while it does not significantly decrease orincrease gap acceptance risk. The two-lane highway microscopic framework was shownas a viable road safety assessment alternative.