Abstract Collision reconstruction often involves calculations and computer simulations, which require an estimation of the weights of the involved vehicles. Although weight data is readily available for automobiles and light trucks, there is limited data for heavy vehicles, such as tractor-semitrailers, straight trucks, and the wide variety of trailers and combinations that may be encountered on North American roads. Although manufacturers always provide the gross vehicle weight ratings (GVWR) for these vehicles, tare weights are often more difficult to find, and in-service loading levels are often unknown. The resulting large uncertainty in the weight of a given truck can often affect reconstruction results. In Canada, the Ministry of Transportation of Ontario conducted a Commercial Vehicle Survey in 2012 that consisted of weight sampling over 45,000 heavy vehicles of various configurations. This paper analyzes that weight data according to the vehicle configuration, body style, and total number of axles. Results are presented for the empty and in-service weights of the surveyed trucks. Comparison of the results of this study to prior studies indicates that the results likely apply to most jurisdictions throughout North America. Introduction Collision reconstruction often involves calculations and computer simulations, which require an estimation of the weights of the involved vehicles. Although weight data is readily available for automobiles and light trucks, there is limited data for heavy vehicles, such as tractor-semitrailers, straight trucks, and the wide variety of trailers and combinations that may be encountered on North American roads. Although manufacturers always provide the gross vehicle weight ratings (GVWR) for these vehicles, tare weights are often more difficult to find, and in-service loading levels are often unknown if bills of lading are lost or inaccurate because deliveries were made prior to an incident, if the truck never entered a weight station en route, or if the truck was loaded at a location without a weigh scale (such as a construction site). Because of the high load capacity of these vehicles, the tare weight and GVWR values differ greatly and the differences can affect reconstruction results. The objective of this work was to study data collected in an impromptu fashion by weighing trucks in service on Ontario roads to determine whether or not conclusions could be drawn regarding the distributions of ‘typical’ truck weights for various heavy vehicle types. Literature Review A literature review was conducted to determine whether there was existing data describing the weights of heavy trucks populating North American roadways. Various published studies touched on truck weight statistics, however no studies were found that gave weight information along with axle configuration and vehicle body style. A 2007 study by Hamsley, et al. [ 1] examined weight data from 24 forest product mills across the Southeastern United States in an attempt to locate trucking inefficiencies arising from weight variability. Data was gathered on over 79,000 truckloads over four weeks, and the mean and variability of gross vehicle weights (GVW), tare weights, and payloads were evaluated for each mill. Short bed trucks were excluded from the data points, as were any trucks from suppliers that delivered fewer than 10 loads over the four weeks. The study found that the trucks delivering to the analyzed mills had mean gross weights ranging from 35,616 kg to 39,263 kg with coefficients of variance ranging from 2.90% to 7.77%. The mean tare weights ranged from 12,537 kg to 13,889 kg, and had coefficients of variance between 4.11% and 11.33%. A study by Owusu-Ababio and Schmitt [ 2] provided an analysis of truck weight data collected from two logging facilities in Wisconsin between December 2011 and May 2012. The data included truck axle weights and spacing from platform scales, as well as