A research investigation was conducted on the erosion potential of stabilized subbases under concrete pavements and asphalt layers supporting concrete overlays. Through field surveys and testing in Illinois, this project evaluated if existing concrete pavements with stabilized subbases and concrete overlays were exhibiting potential erosion of the underlying support layer. The field evaluation testing included falling weight deflectometer testing, distress surveys, coring, and ultrasonic tomography scanning. A laboratory performance test was also established using the Hamburg wheel-tracking device to assess the erodibility of the various stabilized subbase layers for new construction and existing asphalt layers available for a concrete overlay. The analyzed field test results were coupled together with the laboratory performance testing to provide recommendations for updating the Illinois Department of Transportation’s “Bureau of Design and Environment Manual” guidance. No changes were recommended for hot-mix asphalt stabilized subbases, but testing using the Hamburg wheel-tracking device should be considered for Portland cement concrete stabilized support layers (eg, CAM II) under concrete pavements. For testing of asphalt support layers for concrete pavement overlays, the Hamburg wheel-tracking device is recommended with performance criteria similar to flexible pavements for appropriate functional classes.