Empirical Analysis of Traffic Performance Improvement Mechanisms by Audible Speed Recovery Information Provision

Abstract

This paper explores the improvement mechanisms of traffic performance such as the traffic capacity before congestion and the queue discharge flow rate by the audible speed recovery information provision introduced as a congestion measure at the Kobotoke tunnel of Chuo Expressway, Japan. Specifically, we apply the recent advanced traffic flow theory for endogenously describing the capacity drop phenomenon at sag and tunnel bottlenecks (Jin, 2018; Wada et al., 2020) to data measured before and after the introduction of the system and compare results. We then show that (i) the improvements in traffic capacity before congestion and the queue discharge flow rate can be explained by a common mechanism “reduction of safety time gap” within the bottleneck section; (ii) the improvement in acceleration during the congestion at the end of the bottleneck section does not result in that in queue discharge flow rate, and thereby there is room for further improvement.