In a collaboration between the Federal Railroad Administration (FRA) and the Association of American Railroads (AAR), Transportation Technology Center, Inc. (TTCI) investigated the benefits of modified No. 20 frogs on mitigating damage to the frog point, heel, and wing rails under heavy-haul operations. This long-term study, which began in 2013, is being conducted on a heavy-haul mainline in the eastern United States. The latest iteration began in 2019 and focused on evaluating longitudinal wing slopes in No. 20 frogs. Results to date have not conclusively shown that the wing designs help mitigate the studied issues. It is likely that additional tonnage may be required to demonstrate a clear benefit.