IMPACT OF ADOPTING CANADIAN INTERPROVINCIAL AND CANAMEX LIMITS ON VEHICLE SIZE AND WEIGHT ON THE MONTANA STATE HIGHWAY SYSTEM

Abstract

The impact on the Montana state highway system of adopting Canadian Interprovincial, Canamex, or Canamex Short limits on vehicle size and weight was determined. Canadian Interprovincial vehicle configurations were developed based on an investigation of vehicle safety, economy, and damage to the highway system. Canamex and Canamex Short limits are hybrid size and weight systems that retain existing Montana axle weight limits coupled with Canadian gross vehicle weights. All scenarios allow vehicles to operate at higher gross weights than are presently allowed in Montana. The impact of these vehicles on the highway system was determined by a) developing traffic streams that included these vehicles, b) determining the engineering impact these traffic streams would have on existing bridges and pavements and on the future designs required to support these vehicles, and c) assigning a cost to these impacts based on the current cost of equivalent work. These analyses found that 16 to 20% of the bridges system-wide are deficient to carry Canadian Interprovincial vehicles (above and beyond the bridges already deficient under HS20 loads). Incremental deficiencies under Canamex and Canamex Short vehicles are between 1 and 3% of the bridges system-wide. The results were found to be sensitive to the assumed level of bridge capacity and the specific segment of the system being considered (i.e., interstate, primary, etc.). Long term pavement demands under all scenarios considered increase by less than 5% compared to demands under the existing traffic stream. Based on these impacts, an increase in equivalent uniform annual cost (EUAC) for bridges and pavements of 12 to 42 million dollars was calculated for Canadian Interprovincial limits. These costs represent a 11 to 36% increase in cost over that projected for the same activities under the existing traffic stream. An increase in EUAC of 4 to 7 million dollars was calculated for Canamex limits, which represents a 4 to 6% increase in cost over that projected for the same activities under the existing traffic stream. Similar but slightly higher costs were determined for the Canamex Short scenario relative to the Canamex scenario. These costs are for the interstate and primary systems. These costs represent an increased cost of 0.01 to 0.18, 0.02 to 0.08, and 0.02 to 0.15 dollars per mile driven on the interstate system by the new configurations for Canadian Interprovincial, Canamex, and Canamex Short limits, respectively. Similar costs per mile driven on the primary system were 1.3 to 10 times higher than these costs.