Real-Life Math
It takes a calculating mind to keep on top of the action in a yard. This quick thinking is demanded most often in the building of trains -- lining up the right cars on the right track in the right order, keeping in mind what's waiting down the line.
"Heavier cars have to go at the front of the train, near the locomotive," says yardmaster David Belcher. "You have to arrange them in a certain order to get up a grade, according to operating rules -- there are so many rules it almost swamps you."
"Even geometry plays a part," says railroad historian Ella Rayburn. "Tracks curve to go around mountains, but certain kinds of locomotives can't make the curve because their wheels aren't set to freely move. Yardmasters have to know their arc to build a capable train."
But it's the same brainteaser for yardmasters everywhere: how long is the track, how much weight can it hold, and how long and heavy is the train? If it's too long to fit on a track, it will hold up other trains. If it's too heavy, it could spread the track and derail.
"It's not hard math, it just has to be quick and constant," says yardmaster Steve Lucas. "I do tonnage and footage totals -- matching the right amount of horsepower to the weight of a train, and the length of a train to a track. In this yard, which is pretty standard, a train is allowed to be 10,000 feet, 12,000 tons. I have to make sure it's within that."
You're a yardmaster in the same yard as Lucas. Westbound train no. 585 to Detroit arrives. It weighs 8,500 tons and measures 7,000 feet. But you have to add a huge steel shipment -- 56 cars, each measuring 72 feet long and weighing 66 tons.
How many of these cars can you add to the train? Remember that it has to be within the yard's limit of both weight and length. How many will have to be held over to the next train?
The next train weighs 9,800 tons and measures 8,000 feet long. Will you fit the remaining cars on the next train, or hold a few more back?