Impact on Montana’s Highways of Adopting Canadian Interprovincial and Canamex Limits on Vehicle Size and Weight

The impact on Montana’s highways of adopting Canadian Interprovincial, Canamex, or Canamex Short limits on vehicle size and weight was determined. Canadian Interprovincial size and weight limits were developed with due consideration to safety, economy, and damage to highways. Canamex and Canamex Short limits are hybrid size-and-weight systems that retain Montana axle weights coupled with Canadian gross weights. Infrastructure impacts from these new and heavier vehicles were determined by developing new traffic streams, determining the physical impact of these streams on bridges and pavements, and assigning a cost to these impacts. These analyses found that 16 to 20 percent of the bridges systemwide are deficient under Canadian loads (incremental deficiencies above and beyond bridges already deficient under HS20 loads). Incremental deficiencies under Canamex and Canamex Short limits are between 1 and 3 percent of all bridges. Pavement demands on the Interstate and primary systems increased by less than 5 percent under all scenarios. These impacts represent cost responsibilities of $0.01 to $0.13, $0.01 to $0.05, and $0.01 to $0.09 per km driven on Interstate routes by the new configurations for Canadian, Canamex, and Canamex Short limits, respectively. Corresponding costs on the primary system were 1.2 to 10 times higher than these values.