I have been researching the railroad industry lately and the nerd in me enjoys understanding the minutae of how it works. So, I was happy to stumble upon a basic glossary of rail terminology offered by the Paducah & Louisville Railroad. Some of the more interesting and sometimes humorous terms include:
High Wide: Oversized (height or width exceeding standards) or overweight loads. NOTE: carloads not exceeding 11’4″ in height from the top of the railcar’s bottom (15’6″ above rail for loaded railcar) or which are less than 10’8″ wide are usually considered “Standard”. Standard maximum gross weight for the PAL is 163,000 pounds per car or car capacity, whichever is the least.
Hump Yard: A switching yard built on an incline where, after movements by the engine, the cars are shunted by gravitational pull to their destination in a yard.
Mother/Slug: Power Unit/Power Mate; two locomotive units operating in tandem, both of which are equipped with traction motors (which furnish the tractive power to the rail, physically moving the train along the tracks); only one of the locomotive bodies is equipped with diesel engine and main generator which provide the electric power for traction motors in both units. The crew can operate the train from the cab of either unit. The Power Unit (“MOTHER”) can operate independently of the Power Mate(“SLUG”); the Power Mate cannot operate independently of the Power Unit.
For the record, the Paducah & Lousivlle Railroad is a Class II Railroad. The Surface Transportation Board classifies Class I railroads as those having operating revenues of $250 million or more. Class I railroads include CSX, BNSF, Amtrak, Union Pacific, Norfolk Southern and Kansas City Southern. The Paducah and Louisville is Class II railroad, having more than $20.5 million in annual revenue, and Class III railroads have less than $20 million in revenue and are frequently local or switching railroads.