Received the following via email. Link to video follows text.
A spectacular meteorological event was recorded earlier this year (Jan. 7, 2008) by an automatic video camera mounted inside the cab of a locomotive hustling across Illinois. These forward-facing cameras are installed to document information through a locomotive's front windshield of grade-crossing and train/pedestrian accidents. This locomotive (and thus its camera) was, however, facing backwards, as it was the 'trailing' engine of a multiple-unit locomotive consist. The gray Union Pacific covered hopper car visible from the beginning and through most of the clip is the first car behind the engines on a long manifest freight. The passing scenery barely visible along the periphery of the camera's view suggests to my eyes that this train was making perhaps between 40 and 50 m.p.h. at the time it was struck by the hand of Mother Nature.
The tornado that intercepted the train apparently lifted and threw several cars right out of the front of the train, just behind the first car. As the rear of that first car is then dragged off the rails by derailing equipment behind it, the trailing freight cars can be seen independently sliding on their sides down the embankment at left. Lots of sparks! Also note that the track structure behind the engines, where all of those cars had just derailed, remained intact! The integrity of the track is, however, about to be compromised, big time.
The engines grind to a fairly abrupt halt on a bridge: their air brakes went into emergency application when the compressed air brake line between the train's cars was broken in the initial derailment. They had only their own mass to stop. The rest of the train's automatic brakes are still engaging and trying to soak the momentum out of many more thousands of tons of moving steel and lading. This is why, out of the mists like some terrifying specter, being shoved ahead at a pretty high rate by the inertia of the rest of the train still in motion behind it, comes a white -- and derailed -- tank car loaded with Ethylene Oxide, bouncing along the track centerline, throwing sparks of molten metal as freight car steel grinds hard in a most unnatural manner along the steel rails. Had the tank car been breached, these sparks would almost certainly have been a (literally!) "sure-fire" source of ignition.
The careening tank car collides with that derailed U.P. covered hopper still coupled to the rear locomotive (tight-lock couplers DO work), which then unceremoniously flips off the bridge. The still-moving tank car immediately glances off the back of the locomotive and veers over into the vacant area of the bridge spans where there had once been a second track between the girders. A Hi-Cube Norfolk Southern box car that had been coupled behind the tank car then does a hyper-dramatic "high-speed/slow-motion" pirouette around the end of the now-stopped tank car. Just before the whole caravan of angry, twisted steel finally comes to a tangled, crumpled halt, you can see the end of one last Hi-Cube car being launched and plunging down the embankment and into the gully at left, rolling on its side as it dissipates the last of its stored kinetic energy. The physics at work here are staggering, when you consider that the cars, themselves, weight 30-40 tons when empty, and may be carrying up to 100 tons of cargo.
http://www.youtube.com/watch?v=azV5bC2br-Q