A Study on Secular Change of Traffic Performance Using Vehicle Detector Pulse Data on an Interurban Expressway

Abstract

The purpose of this study is to understand the decline in traffic performance on an interurban expressway over time at the micro level and to examine the factors that contribute to this decline. The analysis was conducted by lane and vehicle type based on vehicle detector pulse data from two time points in 2006 and 2019. The results showed the speed had generally decreased during non-congestion flow. Moreover, there was a change in the time headway. This change can be attributed to the change in lane utilization in bins of low-flow rate and to the rising number of drivers who drove with a margin and the overall reduction in speed in bins of high-flow rate. The breakdown flow rate had also declined due to the increasing number of vehicles which have long space clearance and do not follow the car in front during the time immediately before traffic congestion. Even if that kind of vehicles increase, the shock wave is caused and leads to the traffic congestion. The study also found that the space clearance during traffic congestion increased, and it affected the decline of the queue discharge flow rate.