The erosion of material beneath a concrete slab is an important performance-related factor. If applied to the selection of base materials, this factor can enhance the overall design process for concrete pavement systems. However, erosion of the subbase has not been included explicitly in analysis and design procedures because there is no well-accepted laboratory test or related erosion model suitable for design. Therefore, this paper focuses on advancing a simple laboratory test method to evaluate erodibility of a subbase material and then introducing and validating an erosion model that incorporates the results from the new laboratory test method. Erosion-related design procedures were reviewed relative to previous test methods. Erosion models were evaluated for their utility to characterize the erosion resistance of subbase materials. With this information, a new test configuration was devised; it used a rapid triaxial test and a Hamburg wheel-tracking device for evaluating erodibility in relation to the degree of stabilization, base type, and cement content. Test devices, procedures, and results are explained and summarized for application in mechanistic design processes. A proposed erosion model is validated by comparing erosion predictions to erosion results.