Concrete pavement systems have great capacity to provide long service lives; however, if the subbase layer is improperly designed or mismanaged, service life would be diminished significantly since the subbase layer performs many important roles in a concrete pavement system. The erosion of material beneath a concrete slab is an important performance-related factor that if applied to the selection of base materials 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 since there is not a well accepted laboratory test and related erosion model suitable for design. Previous erosion test methods and erosion models are evaluated in terms of their utility to characterize subbase materials for erosion resistance. With this information, a new test configuration was devised that uses a Hamburg wheel-tracking device for evaluating erodibility with respect to the degree of stabilization and base type. Test devices, procedures, and results are explained and summarized for application in mechanistic design processes. A proposed erosion model is calibrated by comparing erosion to lab test results and LTPP field performance data. Subbase design guidelines are provided with a decision flowchart and a design assistant spread sheet for the economical and sustainable design of concrete pavement subbase layers by considering many design factors that affect the performance of the subbase.