With Amtrak, each crew member is given the option of asking to be relieved. Sometimes the entire crew asks for relief, sometimes only one or two individuals do so, or maybe none of them do. It just depends on individual temperment, and what they saw or had to deal with. A look in the eye from someone an instant from being killed, or walking back and finding a severed head or a dead baby effects everyone differently, and no two incidents are the same.