Supposition alert!

A torrent of supposition is flying around because of this oil-train catastrophe in Quebec.
It’s because I’m a railfan amidst other railfans, and unfortunately there’s a few things we think we know about railroading.
It’s also because we’re far from the disaster, and are getting our reports from the media, who can be just as misinformed.
A friend of mine, who would be all-too-familiar with the occasional stupidity of workers, wonders if the train’s operator forgot to set the train’s brakes when parked, so it ran away causing the disaster.
I have a hard time imagining that, although it’s possible (see end of blog).
I’ve read two possible scenarios: -1) that teenagers (or possibly terrorists) released the brakes, or -2) the local Fire-Department shut off the only running locomotive that would be maintaining air-pressure to keep the brakes on.
I no longer understand how train-brakes work. I know how they worked at first. Air-pressure took the brakes off, and lack of air-pressure applied them.
I think this is still true. If an air-hose coupling parts releasing the air-pressure, the train-brakes set (the train “goes into emergency”).
But train-brakes are more complicated now.
At Transit, our buses had “air brakes.” The bus’s motor worked an air-compressor to maintain 100-150 pounds air-pressure in a holding-tank.
The brake-pedal released this air-pressure to apply the brakes. Floor the pedal and you got full pressure to the brakes. Just caress the pedal and you might get only a 10-pound application.
I think something like this might now apply to train-brakes, although as I say I don’t understand.
So, for such a system to keep working, something has to maintain air-pressure.
I’ve read various reports.
The train had four locomotives, and was parked because one was on fire, or a tankcar was on fire — sounds like a frozen wheel-bearing (a “hot wheel”).
(What was on fire has never been made clear.)
The local Fire-Department had been called to put out the fire.
The train’s engineer shut down three of the locomotives. One was left running to maintain air-pressure.
The Fire-Department shut down that locomotive, so now the train-brakes could bleed off, and the train run away.
It’s a train, an assemblage of 73 cars. There’s bound to be a minor air-leak somewhere.
With that locomotive no longer active to maintain air-pressure, you’re asking for a runaway.
Unfortunately the train-engineer wasn’t around to not allow this shut-off.
I’ve also read about teenagers tampering with train-brakes. While that’s entirely possible, they’d have to be knowledgeable. Train-brakes are very sophisticated, although it’s possible to try a few things until the train starts rolling.
I like the Fire-Department story, that they were ignorant of the significance of shutting down that locomotive.
I also received an e-mail decrying the use of a rudimentary line to move such dangerous cargo. My earlier friend noted the line was “secondary.” —I’ve never heard of Montreal, Maine & Atlantic Railway.
My friend was wondering if a secondary line would have Automatic-Train-Stop (ATS). ATS is a system to apply the train-brakes to stop the train if the engineer doesn’t respond properly to a restrictive signal.
But I don’t know as ATS keeps the brakes set. It just stops the train. I have this on a train-video. ATS stops a Northeast Corridor train, then the engineer restarts it.
I have since received a Reuters story that seems to have it right.
Each car of a train has independent-braking. A wheel cranks chains or cables that set the brakes. It’s a last-resort safety-measure. If a train is parked, someone has to set these independent brakes, in this case the train’s engineer.
That person doesn’t have to set brakes on all the cars, just enough to keep the train from running away.
The train-engineer set brakes on 11 cars. The train was parked on a 1.2 percent grade (1.2 feet up for every 100 feet forward), not very steep, but steep enough to cause a runaway.
Setting independent car-brakes is time-consuming. It’s one car after another.
It was a heavy train. Prevailing wisdom is the engineer should have set 20 cars, maybe 30, not just 11.
Okay, this is the most plausible explanation yet, like the media finally got it right. Not just winging it with wild supposition. (Everything I’ve read previously was filled with wild supposition = first right-or-wrong.)
But on the other hand, a locomotive left running to maintain air-pressure is also credible. The railroad’s rules say all locomotives are to be shut down.
But the engineer left one running, perhaps to maintain air-pressure to offset the shortage of cars on which he set independent brakes.
Once parked the train ran away, and disaster ensued.
One also wonders why it “exploded” when it derailed. Crude-oil is flammable, but not explosive.
Investigation is trying to determine if the train also had explosive cargo.
Then too the crude-oil leaked into the town’s storm-drain system.
That crude was of course on fire. Fire was distributed all over the town via the drainage-system. Some even drained into a nearby lake, causing fire on the lake.
The Reuters story sounds plausible, that the train’s engineer didn’t set enough independent car-brakes to hold the train even if all locomotives were shut down.
It sounds like he took a shortcut that destroyed a town.

• “Transit” equals Regional Transit Service, the public transit-bus operator in Rochester, NY, where I drove transit-bus for 16&1/2 years (1977-1993). My stroke October 26, 1993 ended that. I retired on medical-disability. I pretty much recovered.