Fractures in the stub sills of tank cars pose a significant problem for the rail industry due to the potential for damage to the tank structure and possible release of the contents. Previous FRA research revealed that high magnitude coupling forces that occur in yard operations have the potential to exceed yield limits of mild steel. A research team conducted a cooperative test program to characterize coupling loads for tank cars in yard operations. In a continuation of this research, the team evaluated revenue service for both main and yard operations for 10 months and 14,000 miles. The testing showed that the train dynamics from mainline and yard operations are nearly equally important for longitudinal coupler forces and the resulting stub sill strains.