Research on a previous train collision clarified the occurrence of a pattern whereby passengers sitting on a bench seat sustained chest injuries caused by the dividers installed to the side of the seat. Numerical simulations were performed under several conditions to estimate the likelihood of thoracic injuries fitting this pattern. According to the results, rib deformation caused to passengers by panel-type side dividers is less than that caused by the tubular type, meaning that fewer thoracic injuries occur with the panel-type divider. An impact test was also performed to verify the results of these numerical simulations.