Interest is building across the United States in allowing heavier and larger commercial vehicles across the national road network. By 2009 at the latest, the U.S. DOT and AASHTO will want to be in a position to advise the Administration and Congress on whether or not there should be changes to the current federal size and weight provisions.
Canada offers a readily available source of data and insight into the impacts of allowable (non permit) vehicle size and weight limits that are greater than those allowed nationally in the United States today. Furthermore, the unique process used in Canada for the national harmonization of truck size and weight limits in the 1980s will provide considerable insight to policy makers who are evaluating changes to truck regulations in the United States.
Mexico also allows commercial motor vehicles that are larger and heavier than those in the United States to operate on federal highways, and the Mexican experience could be the subject of a subsequent research phase.
The objective of this study was to review and summarize the most current information on the Canadian experience with the changes in truck size and weight limits and to evaluate the potential applicability of this experience to size and weight limits in the United States.
The research consisted of the following tasks.
Phase 1 (1.) Summarize the current truck size and weight limits in Canada and the scientific and historical basis for them. Include regional differences between provinces. Describe the institutional mechanisms in place to coordinate size and weight regulations across jurisdictions in Canada. Describe the process used to harmonize truck size and weight limits in the 1980s. (2.) On the subject of Canadian commercial vehicle size and weight limits, compile all relevant published literature, research in progress, and current practice based on selective interviews. Focusing on work in the past 20 years, develop an annotated bibliography of studies, articles, papers, and interviews on the impacts of changes in size and weight limits in Canada on key issues such as the following:
· Pavement and bridge impacts,
· Vehicle handling characteristics,
· Modal shift,
· Environmental impacts,
· Changes in truck fleet design and configuration,
· Traffic congestion and roadway capacity,
· Public perception, and
· Impacts on trucking operations or regulations in U.S. border states.
(3.) Submit an interim report, within 4 months, to document Tasks 1 and 2 for review by the NCHRP. The contractor shall not begin work on the remaining tasks without NCHRP approval. (4.) Summarize the impacts of changes in truck size and weight regulations in Canada through an analysis of the information collected in Task 2. Describe the impacts that had been anticipated and to what extent the actual impacts met those expectations. (5.) Summarize elements of the Canadian experience (both impacts of the size and weight limits and the process used to harmonize them) which may have relevance for U.S. regulators. Identify areas where the Canadian truck size and weight limits have resulted in particular successes or problems. Identify constraints that might limit that applicability of Canadian practices in the United States.
(6.) Submit a final report that documents the entire research effort.
Status: The project is completed and the final report published as NCHRP Report 671. The report can be purchased or downloaded from our publications office.