User's Guide to the Overweight Truck Route Analysis (OTRA) Program (0-4184-P3)

The 75th and 76th Texas Legislatures passed bills allowing trucks with gross vehicle weights (GVWs) of up to 125,000 1b to routinely use a route in south Texas along the Mexican border. This route proceeds from the Veterans International Bridge 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 (TxDOT) sponsored a research project with the Texas Transportation Institute (TTI) to characterize the effects of routine overweight truck traffic along SH4/48 and develop pavement design guidelines for roadways subjected to routine overweight trucks. ~ product of this project is the Overweight Truck Route ~alysis (OTRA) program, which is described in this report. OTRA is a modification of the Program for LoadZoning ~alysis (PLZ~) developed in an earlier TxDOT project. OTRA may be used to evaluate the structural adequacy of an existing route to carry routine overweight truck traffic over a specified design period. ~dditionally, it may be used to estimate the thickness of asphalt concrete overlay required to carry the expected number of truck axle loads over the design life based on a user-prescribed reliability level. The program incorporates a layered elastic pavement model for predicting the induced response under surface wheel loads. Both linear and nonlinear pavement materials may be modeled. The predicted horizontal strain at the bottom of the asphalt layer and the vertical strain at the top of the subgrade are used to determine the service life for a given pavement and loading condition. To combine the effects of different axle loads and axle configurations, Miner's hypothesis of cumulative damage is used to predict pavement service life. Instructions on using OTRA are provided in this guide.