After watching coal trains on the tracks parallel to South Santa Fe Drive that "seem to go on forever," LouAnn is wondering how many cars there can be on a single coal train.

Billy, who identified himself as an engineer for BNSF Railway Co., wrote that his railway's coal trains average 120 to 125 cars. BNSF spokesman Steven Forsberg put the average at 110 to 120 cars, making the trains 7,000 to 8,000 feet long.

Fifteen to 20 years ago, the biggest trains topped out at 6,000 feet, Forsberg said. Today's cars are longer and lighter.

The limitation on length isn't locomotive power, which can be boosted by adding locomotives at the front or rear of big coal trains, said Forsberg; it's the length of sidings along the route.

Dispatchers put a train in a siding to allow another train to pass, but you can't put a train in a siding if it's longer than the siding.

On a route between Southern California and Chicago (which doesn't pass through Colorado), BNSF runs 10,000-foot trains. Sidings aren't an issue, because there are two tracks almost all the way.

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