Effect of Supplemental Signal on Start-Up Lost Time at Signalized Intersection

Yongfeng Ma,Jian Lü

doi:10.1051/matecconf/20168102009

Abstract

Supplemental signals have been widely used at intersections to reduce the impact of heavy vehicles. This study aims to measure the effects of supplemental signals on Start-Up Lost Time (SULT). A corrected method of calculating SULT considering heavy vehicles are presented. The method also introduce into basic saturation headways, locations of the heavy vehicles and the four types of headways. Field studies were implemented at 18 approaches of 6 intersections in Nanjing, China. The results show that the existence of heavy vehicles has significant influence on both of headways and SULT at signalized intersection. Supplemental signal is effective countermeasure to reduce the influence of heavy vehicles. The study will be helpful when measuring SULT at intersection with supplemental signal.

Highlights

As a critical node, signalized intersection plays an important role in the whole road network
A heavy vehicle among the first few queuing vehicles will significantly increase the Start-Up Lost Time (SULT), which results in low traffic capacity; (b) block factor
The study measures the impacts of heavy vehicles and supplemental signals on SULT for both left-turning and through vehicles at signalized intersections

Summary

Introduction

As a critical node, signalized intersection plays an important role in the whole road network. Heavy vehicles will block views of the subsequent queuing vehicles (especially for cars) due to different height of vehicles, which will prevent related drivers from seeing and reacting to the change of the signals timely at the intersections. This slow reaction will increase the SULT and lessen the traffic capacity. The proportion of heavy vehicles around signalized intersections has already reached 15% ~ 30%, which is 5 to 10 times more than the default proportion 3% assumed in the Highway Capacity Manual 2010 [1] This high level of heavy vehicles makes an important impact on SULT and the traffic capacity. How to reduce the influences of heavy vehicles at signalized intersection and the measurement of effectiveness of related countermeasures are very important and meaningful

Objectives

Methods

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Conclusion