Pennsylvania Railroad Diesel Classification System

The Pennsylvania Railroad had its own classification system for its diesel locomotives. This system used the manufacturer, the intended purpose of the engine, and its horsepower as a generic class, adding a suffix when necessary to designate modifications to an engine or a group of engines at manufacture or when modified later while in service. To the novice Pennsy fan, these can be confusing at times, as an Alco switcher could be of class AS16 while Baldwin manufactured a locomotive with this model designation! The Pennsylvania never owned any AS16's (the Baldwin variety) but you can see how an outsider might become confused.

The system

First letter: Manufacturer

A:American Locomotive Company/Alco Products Incorporated
B:Baldwin Locomotive Works/Baldwin-Lima-Hamilton Corporation
E:Electro-Motive Corporation/Electro-Motive Division of General Motors
F:Fairbanks, Morse and Company (including the so-called "Erie-builts")
G:General Electric
L:Lima-Hamilton Corporation

Second letter (and optionally third letter): Service

F: Freight
FP: Freight-Passenger
FS: Freight-Switcher
H: Helper
P: Passenger
PS: Passenger-Shifter
S: Shifter

Modification suffixes

a: new body style or new engine
m: equipped for multiple-unit control
s: equipped with steam generator
z: converted from passenger to freight service

Examples

A locomotive designated class BP20 would be a Baldwin passenger locomotive with 2000 horsepower. The real class BP20 locomotives were the unique-to-PRR passenger Baldwin Sharknoses.

A locomotive designated class ES12m would be a EMD switcher (shifter, if you prefer) with 1200 horsepower, equipped for multiple-unit control. The real class ES12m units were EMD SW-7 units.

A trickier designation is class ABF18. It does not hold to the above rules; A number of the Baldwin freight Sharknose locomotives were sent to Alco Products for repowering, and were subsequently reclassed ABF18. This indicated Alco/Baldwin freight units with 1800 horsepower. Who would have guessed?

Variants

Prior to this system coming into use, first a system used for steam locomotives was in use. Later it changed to a system like the above, excepting that instead of the numbers after the initial letters designating horsepower, they denoted the number of independant units comprising a "locomotive" Thus for example the Baldwin Centipede, being a single unit (actually a permanently married pair), were initially class BP1, and the passenger sharks, acquired in A-B-A configuration, were BP3. The Centipedes, by the way, fit as delivered into class BP60, but after they were run through Altoona and modified for helper service, they finished out their years as class BH50, meaning the units had been derated to 5000 horsepower.

Thanks to Andy Miller for reminding me of this.

These pages created by Daria P. Brashear, shadow@dementia.org