The Material Reference Library was conceived and initiated under the Strategic Highway Research Program to store selected highway materials and, later, make them available for the evaluation and verification of new pavement designs and material tests that are expected to result in substantial improvement to pavement performance. The Material Reference Library was therefore conceived to maintain "standard" materials that were representative of locations throughout North America for future research. The Material Reference Library originally contained the Strategic Highway Research Program asphalt binders, aggregates, and material from Long-Term Pavement Performance General Pavement Studies and Specific Pavement Studies projects. Over time, the Material Research Library has expanded to contain the following: Strategic Highway Research Program asphalt binders and aggregates, Specific Pavement Studies materials (asphalt, aggregates, and mix), Specific Pavement Studies and General Pavement Studies cores, crumb rubber modifier samples, WesTrack samples, National Center for Asphalt Technology test track samples, Federal Highway Administration Accelerated Pavement Testing Facility samples, Western Research Institute samples, and miscellaneous samples. Many of the samples in the Materials Reference Library are from projects with performance data, which makes these samples very valuable to researchers. Requests to the Materials Reference Library come from around the world. Projects funded by the National Cooperative Highway Research Program and Federal Highway Administration make use of the materials in the Materials Research Library. At the completion of the American Association of State Highway Officials (predecessor to the American Association of State Highway and Transportation Officials) Road Test, there were no materials available to verify the models developed from the research. By maintaining the Materials Research Library, this will not happen.