EU engineers have been determining and recommending relevant criteria and design requirements for passenger accommodations in order to achieve the maximum vehicle crashworthiness and improvement in passenger safety. The study of past railway accidents revealed that secondary impacts within a rail vehicle seldom result in fatalities. However, passengers have received major injuries while seated or in a standing position during a collision. Studies have revealed that the speed of vehicles and their interior components reduces rapidly after a collision. However, the velocity of a projected occupant remains relatively constant. They will impact a table or the back of another seat while seated, or a pole, wind screen, stanchion or other object within the car before coming to rest. Engineers have utilized the science of biomechanics to study specific injuries that are sustained to the body when subjected to a collision with an obstacle within a rail car. Through actual tests conducted on crash dummies, 18 body segments have been studied: head, two arms, two forearms, two hands, two thighs, two feet and the vertebral column including five segments. Computer simulations have been developed through which dummies wired with sensors have simulated human injuries when subjected to collisions with objects within a rail vehicle.
Passive Safety — Seats and Table Designs
As noted earlier, EU rail officials and the FRA are concerned that occupant impact with seats represents the main cause of secondary impact injuries. Seats, however, also provide the most efficient way to restrict the bodily movement, and therefore minimize the seriousness of any inflicted injuries. Concerning the arrangement of seats, it has been determined that:
- Unidirectional seating is best for injury mitigation.
- The second best arrangement is an open bay with table. However, the table must possess thick round edges that have crush zones embedded into the table structure. The table must be firmly attached to the floor of the vehicle to prevent it from becoming a projectile.
- The third safest is an open bay without a table.
EU engineers have determined that the design of seats must satisfy several requirements. New seating designs will incorporate the following criteria. Engineers within the United States are also looking at these while looking to design safer seats.
- Resisting the impact forces occurring on collision.
- Possessing a seat back sufficiently high and well padded on both the front and back sides so as to afford proper support for the head and neck of a rearward traveling passenger, and not to cause face or neck injuries to a forward traveling passenger who impacts with the seat ahead.
- On a unidirectional seat equipped with a folding snack table, the table should be designed as to not constitute an injury hazard. Tables that automatically lift or fold in an accordion manner are being studied.
- The low back side of a unidirectional seat should also be equipped with an energy-absorbing padding element for the protection of knees and lower legs of the passenger in the seat behind.
- Finally, seats must be firmly mounted to the vehicle floor to prevent dislodging during the initial collision and secondary impact of passengers striking the seat.
- Seat belts were considered. However, it has been determined that they do not provide the utmost in desired protection. This deduction was made taking into account that all passengers would not wear seatbelts. In a unidirectional arrangement, passengers not wearing seatbelts would become projectiles that would collide with the seat ahead of them. If occupants in the forward seat were wearing the seatbelts, they would be thrown forward with the compounded weight of the non-seat belted passengers who were projected forward from behind. Studies are still being conducted concerning this and other seat considerations.
Utilizing Lessons Learned From Past Events
EU transportation officials and FRA officials have both looked at past events and are considering critical aspects of safer interior designs that will enhance emergency exiting of passengers. EU engineers presented detailed scenarios of past accidents with our Eno study team. They discussed lessons that were learned through their investigations of the accidents, including examinations of damaged rail cars and interviews that were conducted with surviving passengers. The engineers directly associated what they learned through their investigations with programs that have been implemented to design safer interiors.
Members of our team also discussed incidents that occurred in the United States which directly brought about changes in rail car safety. Two incidents specifically discussed were the collision of a Southern California Metrolink commuter train with an SUV that had been deliberately parked upon the right-of-way, and the head-on collision of a MARC commuter train with the Amtrak Capitol Limited in Maryland. Both incidents involved cab car collisions, the first with an auto, and the second with a locomotive. Fire, and the inability of trapped passengers to escape from the burning cab car coach of the MARC train were given particular attention.
Seats and Tables, Interior Appurtenances — Fire, Smoke Retardation