Length of Auxiliary Lanes at Dual-Lane Highway Entrances Based on Gap Acceptance Theory

Abstract:

To investigate the appropriate length of the auxiliary lane at a two-lane highway entrance， this study utilizes roadside LiDAR to collect data on vehicle operating speeds and headway distributions within the auxiliary lane area and analyzes their distribution characteristics. Additionally， UAV aerial videos combined with Tracker vehicle tracking software are employed to obtain accepted and rejected gaps at the entrance auxiliary lane section. Using the Raff critical gap estimation method， the critical gap for this section is determined to be 2.475 s. Based on driver behavior in the entrance auxiliary lane section， as well as vehicle operation characteristics and microscopic lane-changing behaviors， a length calculation model for the two-lane entrance auxiliary lane is established. The auxiliary lane is divided into two components： waiting distance and left lane-changing distance. The model parameters are calibrated based on the critical gap， vehicle speed， and headway distribution characteristics， and a recommended length for the two-lane entrance auxiliary lane is proposed. The results indicate that the length of the entrance auxiliary lane is positively correlated with vehicle speed. Moreover， the recommended auxiliary lane length proposed in this study is shorter than the value specified in the Design Specification for Highway Alignment， suggesting that the existing standard provides a certain length margin. In land-constrained areas， vehicle operating speed can be regulated to appropriately shorten the auxiliary lane length， optimizing land use efficiency.