Empirical Analysis of Capacity Drop Phenomenon at Multiple Sag and Tunnel Bottlenecks on Expressway in Japan

Abstract

This study conducts an empirical analysis of "capacity drop (CD)" phenomenon at multiple sag and tunnel bottlenecks on expressway in Japan based on the recent advanced continuum traffic flow theory. Specifically, jam sections (and jam events) were selected with reference to jam event data compiled by expressway companies in Japan during the year 2019, and the model was calibrated using ETC2.0 probe data and vehicle detector data. Then we estimate the safe time gap, acceleration parameter at the downstream end of the bottleneck, and other parameters. We then show the following two results with confirmation the generality of the theory and the trends of the estimated parameters. Firstly, where in the sag the bottleneck section appears is various. Secondly, the safety time gap between vehicles determines the absolute level of the Queue Discharge Flow rate (QDF).