Evaluation of longitudinal forces in freight trains is of primary importance for safe operation. To adequately predict the most harmful scenario, including the coupled impacts squeezing the cars, it is necessary to account for deformability, inhomogeneity, and energy dissipation. A robust mathematical model has been derived to incorporate the aforementioned phenomena. It was embedded into Amsted Rail Inc. software, directly impacting on the prediction of end-of car systems performance, calculation of the longitudinal forces in fluid-filled tanks, and implementation of accelerometers. The developed methodology had important applications in pre-sale customised modelling, optimisation of experimental setups, and patent activities.