EFFECTIVE INSTALLATION OF AN AUXILIARY LANE FOR CONGESTION MITIGATION AT MULTI-LANE EXPRESSWAY BOTTLENECKS

Abstract

An auxiliary lane is usually used as an effective measure against traffic congestion to correct lane utilization and increase traffic capacity at the sags of multi-lane expressways. There are three forms of auxiliary lanes that have been installed in Japan, i.e. left-addition left-closure, right-addition right-closure, and right-addition left-closure. In our previous research, we found that the right-addition left-closure configuration is preferable for congestion countermeasures at high flow level, while the right-addition right-closure one is preferable for improving the level of service (LOS) at moderate flow level. In this study, a microscopic traffic flow simulation model was used to investigate the effective installation method of an auxiliary lane as a countermeasure against congestion at a bottleneck of sag. The results showed that it was advantageous to install an auxiliary lane from 400 m upstream of the bottleneck longitudinal curve section and from 800 m to 1.0 km from the downstream end of the longitudinal curve section, with an additional lane length of about 1.5 km to 2.0 km.