Under the locomotive cab occupant protection research program sponsored by the Federal Railroad Administration (FRA), Sharma & Associates, Inc. (SA) developed a Secondary Impact Protection System (SIPS) for locomotive engineers. The system uses a large, automotive-style, passenger airbag in combination with a deformable knee bolster to provide the level of protection needed for the locomotive engineer, without compromising the normal operating environment and egress.
A prior version of the system  was prototyped and tested in a dynamic sled test with a 23g crash pulse and was shown to meet most limiting human injury criteria defined in the Department of Transportation (DOT)’s Federal Motor Vehicle Safety Standards (FMVSS 208)  for the head, chest, neck, and femur. The system also showed marginal performance for the chest injury index and indicated potential for an improved airbag design to fully meet all requirements.
In the current study, simulations with an optimized airbag and higher capacity inflator system showed that SIPS can provide excellent occupant protection for an unbelted locomotive occupant in a frontal crash. Sled testing of SIPS confirmed the performance, and the system successfully met all eleven (11) criteria of the FMVSS 208 standard .
The shape and position of the airbag module and its attachments to the desk were generally the same as those presented in previous research. The key changes that helped meet all criteria were the higher capacity inflators, knee bolster system brackets moved forward, thicker knee plate, higher volume airbag and additional vents.