TRB's National Cooperative Highway Research Program (NCHRP) Report 670: Recommended Procedures for Testing and Evaluating Detectable Warning Systems explores a set of recommended test methods for evaluating the durability of detectable warning systems. These methods address exposure regimes, test procedures, and evaluation criteria to help select detectable warning systems that provide long-term performance and durability while meeting the requirements of the Americans with Disabilities Act Accessibility Guidelines. The appendix contained in the research agency's final report provides further elaboration on the work performed in this project. This appendix titled Research Leading to the Development of Methodology for Durability Assessment of Detectable Warning Systems is available online.