Measurement and analysis of traffic loads across the Texas-Mexico border

Axle load and gross-vehicle weight characteristics of Mexican-origin commercial trucks processed through the US Customs yard in the City of Laredo, Texas, are described in this report. Investigation of these characteristics particular to Mexican-origin trucks is directed by a Texas Department of Transportation (TxDOT)-sponsored study entitled 'Multi-Modal Planning and the US-Mexico Free Trade Agreement' as a prerequisite to evaluating the potential damage to Texas highways posed by international trade traffic. Justifiable concern exists not just with the increasing volume of trade-related truck traffic, but also with the loads carried by Mexican-origin trucks. This study is facilitated by the installation of a weigh-in-motion system at the preeminent South western commercial truck port-of-entry, Laredo. Load summaries are presented on five basic truck classes (by axle count) and are based on the original Association of American State Highway and Transportation Officials (AASHTO) pavement damage relationships. Load characteristics of each basic class include: 1) load status (empty or loaded), 2) ESAL factors (ESALs per truck), and 3) distribution of axle loads and gross-vehicle weights. Histogram summaries are provided for axle-group loads and gross-vehicle weights with the greatest propensity for exceeding current US legal load limits. Finally, damage implications are explored for the hypothetical integration of Mexican-origin commercial traffic, typified by that currently crossing at Laredo, and by that typified in a 1991 Mexican truck weight survey, into the current Texas traffic population.