Historically, the goriest rail diasters, those involving both greatest loss of life and loss of limbs among the survivors, have involved the phenomenon known as telescoping -- the penetration of a passenger car by another piece of equipment, particularly if end-to-end.
The worst example of this within the life span of most of us at this forum was the Illinois Central (Gulf) commuter train wreck in Chicago in the fall of 1972.
http://en.wikipedia.org/wiki/1972_Illin ... rail_crash
In that instance, the engineer of a new lighter-weight and wider-bodied suburban train overshot a station platform and, in defiance of a cardinal saftey rule, backed up toward that station without realizing that the automatic block signal sytem operated in only one direction. A following train, consisting of older, narrower, and heavier equipment, then rear-ended the lightweight, telescoping into the end car.
The reinforced vestibules at the ends of all passenger cars are designed with the specific intent of reducing the possibility of telescopng on impact. Unfortunately, in the case of Friday's Metrolink accident, the combined speeds at impoact of 100 MPH was so great as to force the entire vestibule structure back into the passenger compartment.
Although it's much too early to speculate, the interface between the locomotive and the front end of the lead car may also have been a factor in the structural damage upon impact.
Mr. CarterB's advice is something I'd heed: Stay away from the ends of the train, but there's no absolute security on this side of the cemetery.