Train Length

Both times I've gone to Dan's house recently, I've had to stand on the sidewalk for what seems like fifteen to twenty minutes while a train rolls past.  That's his apartment through the tanker.  You can just see the upper edge of the building.  What amazed me, more than the wait, and more than the insanity of renting an apartment next to a train track - I'm reminded of the Triplets of Bellville; I hope train proximity severely drives down your rent - was the number of cars rolling through on one train in St. Paul.  The second time I was certain I counted more than 100 cars, and I skipped the beginning and end of the thing.  I should have asked the trainspotter that was in the parking lot to the left on this picture.  He probably knew the count as he was there the whole time and had been waiting for it, although he seemed primarily interested in the locomotive and got back in his car with his camera to hang out after it went by.

According to GreasyJack over at the Straight Dope:
"There used to be practical limits on the length of freight trains because of the amount of force exerted on the couplers. Just like the old high-school physics demonstration with the blocks hanging from strings, the couplers in the front of the train have to handle the entire weight of the train while accelerating. Distributed power, which is a relatively new technology, allows the addition of remote controlled locomotives in the middle or at the end of a train, which can allow much longer trains. Another limiting factor was the delayed and reduced braking effectiveness near the end of the train with conventional airbrakes, which has been addressed with electronic controlled airbrakes.

The limit has recently been 12,000 feet (about 2.3 miles or 3,658 meters) for trains with electronically-controlled brakes. I'm not sure if this limit is (or was) legally enshrined or just the position of the AAR. Some of the big rail roads have been running some experimental "monster trains", such as this 3 and a 1/2 mile long one, but I don't know if any are regularly running them yet or not."

And Mr. Downtown refers to a picture of a train pulling 197 cars.

The interesting bit to me is that when I see a train and think, "Wow, that seems much longer than when I was a kid", I'm right, thanks to strides in coupler technology.  And when Dan'l sees the plaster falling off his roof and thinks, "That seems to go on longer than I would have ever guessed when I rented this apartment," he's not wrong given the trains of our youth.