Evaluating Impacts of Overloaded Heavy Vehicles on Freeway Traffic Condition by a Novel Multi-Class Traffic Flow Model

Xiang Wang,Yanyun Tao,Po Zhao

doi:10.3390/su10124694

Abstract

Overloaded heavy vehicles (HVs) have significant negative impacts on traffic conditions due to their inferior driving performance. Highway authorities need to understand the impact of overloaded HVs to assess traffic conditions and set management strategies. We propose a multi-class traffic flow model based on Smulders fundamental diagram to analyze the influence of overloaded HVs on traffic conditions. The relationship between the overloading ratio and maximum speed is established by freeway toll collection data for different types of HVs. Dynamic passenger car equivalent factors are introduced to represent the various impacts of overloaded HVs in different traffic flow patterns. The model is solved analytically and discussed in detail in the appendices. The model validation results show that the proposed model can represent traffic conditions more accurately with consideration for overloaded HVs. The scenario tests indicate that the increase of overloaded HVs leads to both a higher congestion level and longer duration.

Highlights

Heavy vehicles (HVs) have significant impacts on traffic conditions
We developed a multi-class traffic flow model to analyze the impact of overloaded HVs on traffic conditions
(2) A new multi-class kinematic wave traffic flow model based on dynamic Passenger Car Equivalent (PCE) is proposed with consideration for the driving performances of overloaded HVs

Summary

Introduction

Heavy vehicles (HVs) have significant impacts on traffic conditions. It is a common practice in China for commercial carriers to overload (i.e., load trucks with goods heavier than the factory recommended weight limit) their fleets to reduce their operating costs [1]. In China, if one heavy vehicle is detected as an overloaded heavy vehicle, the toll station staffs will still allow this heavy vehicle entering the freeway but charge additional fines for overloading. The toll station staff will not forbid the overloaded HVs entering the freeway, but punish with fines, which mainly considers the pavement fatigue, but not the negative impacts on traffic condition. The average overloading ratio (i.e., (total weight − weight limit)/weight limit) is 35%, and the overloading ratio of tractor-trailers could exceed 100% in some extreme circumstances [2,3]

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Results

Conclusion