A few engineers talk about turning their heads at the moment of impact. They'll remember hearing the impact. It stays with them, and a similar sound can trigger the memory. Often a smell or particular weather conditions or the section of track where the accident occurred can trigger the memory too. We try to tell them not to freak out if they're reminded.
People have very individual reactions.
It's rare that anyone refuses treatment. Clark tries to explain what a debriefing involves, calming the fears of those who think they'll be psychoanalyzed. Clark goes step by step and leaves the decision to the individual. Metro-North engineers don't have to be cleared for service, as long as they've been offered the debriefing. The crews hold up surprisingly well.