Safety Assessment of Auxiliary Lanes in Freeway Interchange Weaving Areas based on Traffic Conflict Technique

Abstract

Auxiliary lanes can provide an improved weaving environment rather than a forced or direct merge or diverse for vehicles entering and departing freeway weaving segments. Considering China's traffic composition and operational status, this paper proposed safety assessment of auxiliary lanes in freeway interchange weaving areas based on traffic conflict technique in order to estimate its safety impacts and related influential factors considered in design. Based on freeway interchange weaving areas data and actual traffic characteristics, simulation models were built with VISSIM. This paper used Surrogate Safety Assessment Model (SSAM) to calculate conflicts by inputting vehicle trajectories from VISSIM, analysed the influence of ramp spacing, lane number of mainline, traffic volume, weaving ratio and percentage of heavy vehicles on safety performance of auxiliary lanes in freeway weaving areas. Finally, Traffic Conflict Modification Factor was presented to evaluate effectiveness of implementing auxiliary lanes. The paper found the safety impacts and related influential factors of auxiliary lanes. T he findings can provide support to effective decision making with regards to constructing future auxiliary lanes in freeway interchange weaving areas.