On the upper bound of the distribution of bridge traffic loading

Bridges are a vital part of the infrastructure network, facing highly varying traffic loads, which have been the subject of numerous studies. Some of these studies have suggested that traffic loading is a physical process with finite physical limits (e.g. mass). Yet, almost all studies still model probabilistic traffic loading as unbounded, implying the possibility of loads beyond what is physically possible or, worse, infinite load. This work argues that bridge traffic loading probability models should be bounded. A method based on Bayesian statistics incorporating the physical boundedness of traffic and limits based on engineering information is proposed. Diagnostic tools to detect misspecified engineering information are developed. Common causes of supposed observations of unbounded traffic load distributions in the literature are presented. Finally, the proposed methodology is applied to Australian highway traffic. The approach demonstrates a reduction in lifetime load estimation uncertainty and avoidance of physically impossible results, compared to the conventional unbounded bridge traffic load model.