Characterizing the Effects of Routine Overweight Truck Traffic on SH4/48

The 75th and 76th Texas Legislatures passed bills allowing trucks with gross vehicle weights (GVWs) of up to 125,000 lb to routinely use a route in south Texas along the Mexican border. This route proceeds from the border checkpoint at the terminus of US77 to the Port of Brownsville via US77, SH4, and SH48. The portion of the route along US77 is on a new concrete pavement and includes an elevated structure over half of its length. Most of the permitted truck route runs along SH4 and SH48 in Brownsville. Concerned about the effects of routine overweight truck traffic on its roadways, the Texas Department of Transportation sponsored a research project with the Texas Transportation Institute to characterize the effects of routine overweight truck traffic along SH4/48 and develop pavement design guidelines for roadways subjected to routine overweight trucks. This report documents research efforts and findings to characterize the effects of routine overweight truck loads on SH4/48 in Brownsville. The project offered the first opportunity to study the effects of routine overweight truck traffic on pavement performance. The characterization of these effects showed that accelerated pavement deterioration is expected due to the higher rate of accumulation of 18-kip equivalent single axle loads (ESALs), and the fact that routine overweight truck use was not considered in the original pavement design for SH4/48. The higher loading rate is a consequence of the additional overweight trucks that the route now serves, and the higher allowable axle loads on these trucks that produce more pavement damage per application relative to legal or non-permitted trucks. While the findings summarized herein were probably expected based on engineering principles and experience, this project provided evidences based on test data, which point to the conclusion that accelerated pavement deterioration is likely as a consequence of routine overweight truck use on SH4/48.