Strategic Plan of the Texas Department of Transportation for Implementing NCHRP 1–37A Pavement Design Guide

Abstract

The Texas Department of Transportation (TxDOT) used the recently released NCHRP 1–37A guide and software to develop a strategic plan for its implementation of operations. The new guide includes all possible variables that may affect the performance of the pavement. A general sensitivity study of these variables was conducted with an early version of the software. A few focused studies were conducted, including ( a) a preliminary local calibration of the guide with 11 Strategic Highway Research Program General Pavement Studies sections in Texas, ( b) traffic composition effect compared with that of the traditional 80–kN equivalent single-axle loads (ESALs) and of the design load, and ( c) effect of the choice of the weather station and of changing the water table depth on the performance of the pavement. The results indicate that ( a) the use of the 80–kN ESALs leads to underdesigning the structure, ( b) the design load concept can be used in screening runs to determine a preliminary design, and ( c) in the case analyzed, changing the depth of the water table resulted in changing the moduli of the unbound material but did not affect the performance. Finally, a strategy for implementation was recommended to TxDOT, including ( a) training, ( b) laboratory testing and equipment acquisition, ( c) field forensic studies for calibration, ( d) calibration and validation of the guide, and ( e) additional studies.