I'm not suggesting they could stop in time, or even over a few miles, but in the movies they don't stop at all. Surely these real conductor's don't just demolish a car and/or people and just keep on going until their next stop. Surely there is some kind of law on this.
Oh,
there's laws, all right!
I volunteer as a brakeman on a local tourist RR and I had to pass the GCOR test before running trains.
Federal RR Administration regulations require that the moment an emergency has happened or is clear will happen (as in a car clearly parked on the tracks that doesn't appear will move in time), the engineer
has to put the train into emergency by dumping the air from the brakes, which applies full brake application. The crew would then radio the dispatcher to tell them what has gone on. If an accident happened, then the bosses have to come out with the law and it's then a big thing. If the disaster is averted, the dispatcher will tell the crew to proceed when safe to do so.
Yeah, a long freight train going fast takes
some time to stop, but you should see and hear the brake application as soon as the person at the head end hits the train brakes (and if on a modern diesel, applies dynamic brakes).
That scene at the end of BTTF3 where the DeLorean suffers its catastrophic disassembly by Ventura County Railway # 11 (an old ALCO S6, formerly Southern Pacific #4641 and later #1277, if anyone cares), that is a short train trailing. It wouldn't take too long to stop that as it's only moving around 20-25 MPH from the look of it, at best. The back end would have been stopped by the time the last car was out of sight at the crossing.
Watch this, starting at a few seconds before 2:00:
The popping sound is a brake line getting severed (most likely, the air line connections between cars hit something on the tracks and it popped the metal fittings apart). A long freight moving at least 30MPH is stopped dead in
less than 40 seconds!
So it's easier for, for example, the Secret Service to say "Where's POTUS currently?" than saying that whole thing, which would take a little longer.
The Secret Service has a different code word for each person they protect (usually inspired by something specific to the person). They wouldn't say POTUS
at all.
President Trump is referred to as "Mogul" as his Secret Service code word. The First Lady is called, "Muse". Vice President Pence's code word is "Hoosier".