Characteristics of large truck–trailer combinations operating on Manitoba's primary highways: 1974–1984

Weight and dimension regulations governing large truck operations in Manitoba and western Canada generally have been substantially relaxed since 1974. These changes have facilitated the use of larger and heavier truck–trailer combinations on highways throughout Manitoba and on interconnecting highways in adjacent jurisdictions. Effective engineering of these highways and their bridges requires a solid understanding of the physical and use characteristics of the truck–trailer combinations that have been, and are being, adopted by the trucking industry in response to the relaxed regulatory environment.This paper examines certain of these characteristics based on an analysis of hitherto unpublished on-road truck surveys conducted over the years by the Manitoba Department of Highways and Transportation. The following characteristics are examined: (i) changes in the truck fleet mix, (ii) changes in the tare weights of large vehicle combinations, (iii) distributions of gross vehicle weights for particular vehicle combinations, (iv) distributions of weight payloads handled by particular vehicle combinations, and (v) certain dimensional characteristics of import to understanding vehicle loads on highways and bridges. As possible, these characteristics (and changes in them) are related to prevailing weight and dimension regulations (and changes in them). Key words: weight and dimension regulations, truck–trailer combinations, truck weights, axle spacings, on-road truck surveys.