Impacts of truck axle loading on pavement damage: A case study of T1 highway in Tanzania

Abstract: High heavy vehicle volume is one of the primary causes of premature pavement structural and functional failure. Pavement damage caused by heavy vehicles (primarily trucks) is a function of the Gross Vehicle Mass (GVM) and the GVM distribution on the pavement, which are influenced by aspects such as the vehicle axle and wheel configurations. Road agencies increasingly embrace the need to maintain an effective and efficient vehicle axle-load control program to mitigate pavement damages due to traffic loading, enhance safety, and concurrently reduce pavement rehab/maintenance costs. The enforcement of the axle-load limits requires weighing heavy vehicles (trucks) to obtain the vehicle’s GVM and the weight of the individual axles. As part of its vehicle axle-load control program, the Tanzania National Roads Agency (TANROADS) operates numerous fixed electronic weighbridges across its national road network. Using weighbridge data from T1 highway (Tanzania’s most heavily truck-trafficked road) as a case study, this work numerically evaluated the potential pavement damage caused by different truckloads comprising single and multiple axles. Mechanistic-empirical pavement analysis was conducted to determine the Load Equivalent Factors (LEFs) and assess the damage from the various truck axle-loading configurations. As quantified in terms of the LEF, the study found that tridem axle configurations with single wide-base tires are prone to impacting more pavement damage than those with conventional dual tires. Additionally, the numerical results indicated that single steering axles approaching the legal load limit could significantly contribute to pavement damage. Furthermore, many trucks were overloaded and exceeded the +5% tolerance above the legal load limit, potentially contributing to accelerating pavement damage. From the study findings, it was recommended that there is an imperative need to assess the adequacy of Tanzania’s current axle-load limits and the impacts of the +5% tolerance on pavement damage.