The following video illustrates some of the properties of
Crash Energy Management. A fleet of retired standard cars telescope when pushed against an F40 while another set of cars with improvised crush zones and push back couplers perform much better (although the cars were not supposed to uncouple during the test). These crush zones are presumably not much of a factor in a typical crossing accident but the "push back coupler" design may play a role if the coupler was shoved back into the car body allowing the vehicle to ball up under the lead truck.
FRA Testing at TTCI