Innovative Method for Evaluating Overweight Vehicle Permits

Abstract

Any vehicle whose gross weight exceeds 356 kN (80,000 lb) and/or does not conform to the restriction imposed by the Tennessee Department of Transportation (TDOT) requires a permit issued by TDOT in order to use the Tennessee roads. The current practice in the TDOT Permit Section is that a detailed structural analysis is required for all vehicles with a gross weight over 667.5 kN (150,000 lb). Due to the volume of overload permit applications received, this policy resulted in a large demand in man-hours to perform the structural analysis. Furthermore, the policy does not give consistently safe or conservative assessment. A method has been developed empirically to efficiently extract any suspicious overweight vehicle requesting a permit, regardless of gross weight, for further detailed analysis. The technique utilizes the combination of gross weight, axle loads, and axle spacings. The algorithm can be easily implemented to a computer program for users with limited technical training, since the only input information is the axle load and spacing configurations. The method is intended to be conservative. A study, based on actual permit applications and detailed bridge analyses, has shown that this approach would reduce the number of structural analyses required by approximately 50% when compared to the current policy.