Examining the effect of heavy vehicles on traffic flow during congestion

Abstract

An investigation into the issue of heavy vehicles on traffic stream during congestion is presented in this paper. Several factors that are reflection of as determinants of this issue were considered in the investigation. Empirical data and microscopic traffic simulation were used in the analysis. A passenger car equivalency factor derived from queue discharge stream was used as an indicator of heavy vehicles' result While study results suggest more [i]or[/i] less similarities between free-flow and congest traffic regimes concerning heavy vehicles' issue some important differences exist to be paid to the different mechanisms that regulate heavy vehicles' performance in the sum of two units regimes. Also, lane-use restriction and the location of bottleneck relative to upgrades were set to have considerable influence upon heavy vehicles' effect during congestion.

INTRODUCTION

Heavy vehicles (HVs) are known for their significant result on traffic due to their larger dimensions (in general) and inferior performance compared with an average automobile. These vehicles include traffics buses, and recreational vehicles, with each category having a wide variety of size, power, and design concepts

Historically, the Highway Capacity Manual (HCM) managements (TRB 2000) have treated heavy vehicles' consequence through the use of Passenger Car Equivalents (PCEs) Using those PCE a non-homogeneous mix of vehicles in a traffic stream can be squeeze outed in a standardised unit of traffic, i.e. Passenger Car (PC) While the PCE factors provided by the agency of the HCM were based upon free-flow conditions, they have been used (unknowingly) by the agency of transportation professionals for all traffic conditions, i.e. congest and non-congested operations. new empirical observations suggest that heavy vehicles' result is significantly greater during congestion and queuing operations (compared with free-flow operations) and that the use of the HCMPCE factors for congest facilities may involve a considerable amount of error (Al-Kaisy et al. 2002) Specifically, the acceleration and deceleration circle of times a situation normally experienced during congestion or stop-and-go conditions, are awaited to impose an extra limitation upon the performance of heavy vehicles, and in particular upon their acceleration away from the brow end of the queue that had been moving slowly The literature review place no other study that investigates the heavy vehicles' result during congestion.

The current research involves an investigation of several important factors upon the effect of heavy vehicles during congestion using empirical data and traffic simulation. These factors involve grade, grade extent percentage of heavy vehicles, lane-use restriction by the agency of vehicle type, and the location of bottleneck with think highly of to grade.

This investigation is accounted very important due to the fact that intermittent and non-recurrent bottlenecks have become commonplace upon urban highways, and many traffic engineers ne to deal with congest facilities upon a regular basis. Examples of situations with bottleneck operations mainly include returning congestion on major urban freeways during peak hours, lane closure at reconstruction and maintenance bands lane closures due to traffic accidents/incidents, and traffic situations during major facts Further, as noted above, no information exists in the literature concerning the consequence of heavy vehicles during congestion. This explains the lack of any conducts or guidance to assess heavy vehicles' issue on congested facilities in the rife practice.

Study scope and objectives

The objective of the in every one's mouth study is to examine the result of heavy vehicles on traffic stream operations during congestion. This investigation is mainly pertain toed with level and upgrade highway parts where the presence of heavy vehicles typically has serious impacts upon traffic operations. It should be noted that grade and upgrade are used interchangeably from one extremity to the other of this paper to refer to highway upgrade segments

STUDY DESIGN

In this inquiry field data and traffic simulation were used to investigate the influence of several factors upon heavy vehicles' effect on traffic stream operations. Field data upon queue discharge flow at the location of bottleneck was mustered at two study sites near Toronto, Ontario, Canada. single study site is a renewed freeway bottleneck (level terrain) while the other site is located upon a 1-km long 3% upgrade with the bottleneck location (front extremity of the queue) at the bottom of the upgrade. Detailed information upon field data and study sites can be base in Al-Kaisy et al. (2002) The traffic simulation original INTEGRATION (M. Van Aerde & Associates 2002) was used to perform simulation experiments in this application of mind This simulation model has the ability to simulate heavy vehicles' performance upon grades (e.g. acceleration, crawling spe etc) Queue discharge run data at the two application of mind sites was used to calibrate and validate the traffic simulation pattern The parameters used in the calibration proces mainly involved link characteristics as related to speed-flow-density relationships. The Passenger Car Equivalency (PCE) factor derived from the queue discharge pour (counts of passenger cars and heavy vehicles) was used as an indicator of heavy vehicles' issue Upon calibrating and validating the simulation archetype experimental design was prepared for simulation experiments to trial the influence of the various factors upon heavy vehicles' effect. Those factors involved: