Bad TV Technology: NCIS: LA and Trains - RonO's Ramblings
Pretty much right on all counts. The person driving the train (usually called the engineer in the USA) doesn't actually control where the train goes — the dispatcher running the switches remotely does so. (At least in the LA Metro area, most or all main line switches are controlled by a dispatcher. Only industrial sidings are manually operated. It is generally possible to defeat remote switches manually, but you have to stop the train, unlock, and manually throw a power switch, which sort of defeats any plan of driving your train at speed into LAUPT.
If a dispatcher knew of a "rogue" train in the system, s/he would almost certainly have routed it into a place where it would have deliberately derailed, albeit hopefully without doing so much harm. With a hazmat load, it gets pretty dicey to do that, particularly in built-up areas. (I do worry sometimes about all those tank cars of non-odorized natural gas parked across from my house in Fernley, for instance. Not a good place for a derailment, not at all.)
Trains in the USA do indeed still use the Westinghouse air brake, and if the train breaks apart, the brakes automatically apply. In the scenario described, the train should have "gone into emergency" and ground to a halt eventually. There are ways to defeat this (turning the angle cock on the air lines so that the parts of the train are isolated from each other), but that generally requires deliberate sabotage, since the entire system is specifically designed against such accidental failures.
As described, the engineer could have been trying to first engage dynamic braking, which, as you imply, turns the engines into resistors. That won't stop the train entirely, but it will slow it down. Alternatively (and this is the only thing that could have caused the sparks), you could possibly get the engine grinding the wheels in reverse. This has been done very occasionally, such as one case when a train got out of control coming down into the LA Basin and in a last-ditch (and ultimately futile) effort to stop it before it derailed, the engineer put the train into reverse. This did slow it down, but also turned a set of million-dollar locomotives into very large, heavy paperweights as it destroyed the engines. (The train ultimately derailed anyway, just not as badly as it would have done.) And as you say, the cars behind the engine wouldn't have been sparking unless they'd already come off the rails and were scraping them from the wrong side.
Nobody in movies/TV knows anything about how trains work. It's a pity, really, because there are perfectly dramatic stories about real train accidents that could be told. Indeed, in the days before radio communications and lineside signals and interlockings, you had situations where a dispatcher could issue what was known as a "lap order" and realize that he'd just killed people -- long before they were dead! That's because it might take an hour for the collision to play out, but there was no way to get word to the crews to stop their trains before disaster struck on account of there being no open train order stations between the trains.