Bridge Load Posting Based on Actual Arkansas Truck Traffic

Abstract

Bridge load posting limits are safety and economic decisions. Bridge load posting limits restrict truck traffic to ensure safety. Therefore, trucks that exceed bridge load posting limits are required to take alternate routes. The Arkansas Department of Transportation (ArDOT) uses a family of CMV (commercial motor vehicle) configurations and loadings with the designations CODE 4, CODE 9, and CODE 5 for state legal loads in calculating bridge load posting values. These state legal loads are used to represent trucks using Arkansas bridges. However, these truck configurations were initially considered in the 1980s. Since then, truck configurations and axle loadings have significantly changed. Therefore, the currently used ArDOT state legal load configurations and weights may be outdated and may not be representative of critical truck loads actually supported by Arkansas bridges. This article investigates the appropriateness of using the current ArDOT state legal load family to model existing truck traffic within Arkansas. An analysis of the historical truck weight data between 2005 and 2015 derived from weigh-in-motion (WIM) sensors reveals that a high percentage (75%) of Class 7 trucks during this time period exceeded the Federal Bridge Formula (FBF) maximum allowable weight.