C E Lee

Truck Traffic Crossing Texas-Mexico Border

U.S.-Mexico trade continues to grow strongly, with much of the non-petroleum surface trade moving by truck. Trade flows through a number of key ports-of-entry at the southern border, and future truck traffic has raised concerns over infrastructure needs, congestion, and safety. Although it was known that Mexican trucks are frequently overloaded, little data were available to show whether this extended to trade movements at the border. This paper reports the results of a research study commissioned by the Texas Department of Transportation and represents the first comprehensive analysis of truck axle loads undertaken at the southern Texas border. Weigh-in-motion systems were installed at the Laredo and El Paso ports-of-entry. WIM data for 1995 show that 25 percent (El Paso) and 35 percent (Laredo) of the observed tandem-axle loads on loaded northbound five-axle trucks (three-axle tractor with tandem-axle semi-trailer) exceeded the U.S. limit (15.4 Mg). This truck type comprised about 80 percent at El Paso and 70 percent at Laredo of all observed weekday northbound border-crossing trucks. In 1995, 80 percent at El Paso and 87 percent at Laredo of the observed tridem-axle loads on loaded six-axle (three-axle tractor with tridem-axle semi-trailer) trucks exceeded the U.S. limit (19 Mg). This truck type, however, typically comprised only 43 trucks per weekday (3 percent of loaded trucks) at Laredo and 13 (2 percent) at El Paso. The occurrence of overloads on tridem axles was reduced substantially at one port-of-entry when the Texas Department of Public Safety temporarily applied enforcement activities in the Customs yard at the Laredo port-of-entry. The WIM technologies worked well under unusual conditions and indicated that they can possibly be used to aid enforcement of size and weight regulations when the next phase of the North American Free Trade Agreement is implemented.