This report compiles the first phase of a Federal Railroad Administration (FRA)-sponsored project to evaluate lateral ballast behavior and how mechanics-based track geometry deterioration models forecast field behavior. The lateral ballast behavior section analyzed historical and recent single tie push test (STPT) results, compared the influence various ballast parameters, and evaluated the potential ability of a model to estimate lateral track strength from outputs of track inspection vehicles. The results suggest that a track location could eventually be placed into broad risk categories based on the measurable ballast condition. The second aspect investigated the ability of mechanics-based track geometry deterioration models to forecast field behavior. Field data that included aligned track geometry records and ground penetrating radar (GPR) was analyzed and relationships were developed between the ballast condition and track geometry deterioration rate. The existing mechanics-based models were compared against the statistically fit models and recommendations on how to improve the models were made.