Understanding and Estimating In-Service Axle Weights of Transit Buses

Abstract

Despite evidence that certain transit buses exceed axle weight limits (sometimes without any passengers on board) and mostly anecdotal indications of the concomitant pavement impacts, relatively little empirical evidence substantiates these impacts. The number of transit buses exceeding weight limits has been exacerbated by regulatory changes directed at improving emissions and accessibility. These changes have required manufacturers to include heavy auxiliary equipment, such as emissions reduction components and hydraulic systems, on transit buses and have been introduced without commensurate increases in the weight limits of transit buses. Public agencies have limited knowledge about transit bus weights and their pavement impacts. Further, estimating in-service weights of transit buses is difficult. To help improve knowledge about issues of transit bus weights, this paper describes the legal and regulatory factors surrounding transit bus weight, basic estimates of in-service bus weights, contributing factors to transit bus weights, challenges for reducing bus weights, pavement impacts of transit buses, and challenges for estimating in-service weights of transit buses. The paper also develops and applies a methodology for estimating in-service weights of transit buses by using Winnipeg, Manitoba, Canada, as a case study. Application of this methodology ( a) demonstrates the need for reliable local data when in-service weights of transit buses are estimated and ( b) empirically corroborates regulatory compliance and pavement-related concerns by using data collected from in-service transit buses.