How fast would the average Amtrak train take to stop using that cord?
And what are logical reasons to pull it anyway?
Clearly the stop distance depends on the speed when the cord is pulled, and the weight of the train. I've been on two trains that went into emergency. The first was a Surfliner, to avoid a collision at a grade crossing. Collision avoided, but had to sit for a few minutes while the train was inspected. Second was on the return to L.A. during the Santa Fe 3751 steam excursion last June. That was chalked up to an air dump of "unspecified cause." Again an inspection wait before proceeding. In neither case was a cord pulled, but an emergency stop is an emergency stop.
A train in emergency is not like a car slamming on the brakes, but you definitely feel the unusually rapid deceleration. On the Surfliner, riding alone, I thought "Bet that was an emergency stop." Hadn't experienced one before, but it was pretty obvious. Then an attendant came on the PA and said, "For those of you who were wondering, yes, that was an emergency stop. We didn't hit anything." Major relief, cuz I was on my way to the airport; a collision woulda screwed me.
On the excursion a number of us were talking when we went into emergency. Everybody's eyebrows went up, we all looked at each other, and several of us said, almost in unison, "This isn't good." Upon learning that it was an air dump, and all was well, we launched into a discussion of the history of train braking.
As for a logical reason to pull the cord, one leaps to mind: A murderous wacko shooting passengers, as happened on the Long Island Rail Road a few years back.