Locomotive model abbreviations

Deciphering an alphabet soup
Letters in locomotive models do indeed stand for something.

Often the words they represent describe some feature of the locomotive, like wheel arrangement or type of propulsion equipment. Sometimes the letters stand for the type of service the locomotive is intended for. A few are just catchy marketing terms, like Century or Consolidation.

Here's a list of the letters found in the more common model series, grouped by builder:

SC Six-hundred h.p., Cast frame
SW Six-hundred h.p., Welded frame
NC Nine-hundred h.p., Cast frame
NW Nine-hundred h.p., Welded frame
E Eighteen-hundred h.p.
F Fourteen-hundred h.p.
TR Transfer
BL Branch Line
GP General Purpose
SD Special Duty
F Full-width carbody (as in F40)
DD D-D wheel arrangement
MP Multi-Purpose
M Wide nose and safety cab
I Partially isolated "whisper cab"
MAC Wide nose and safety cab or whisper cab, plus an alternating-current (A.C.) drive system
ACe A.C. drive system meeting EPA Tier 2 emissions requirements

U Universal
B B-B wheel arrangement
C C-C wheel arrangement
P Passenger
AC Alternating Current
DC Direct Current
W Wide nose and safety cab
ES Evolution Series

HH High Hood
DL Diesel Locomotive
S Switcher
T Transfer
FA Freight, A-unit (FB indicates Freight, B-unit)
PA Passenger, A-unit
RS Road-Switcher
C Century
M Montreal Locomotive Works

VO Model VO engine
DS Diesel Switcher
S Switcher
DRS Diesel Road-Switcher
RS Road-Switcher
AS All-Service
DR Diesel Road
RF Road Freight

H Hood carbody
CFA Consolidation Line (C-Line), Freight, A-unit
CPA C-Line, Passenger, A-unit

Model designations sometimes persist after the series has evolved beyond the letters' original meaning. Long after EMD's welded-frame yard engines surpassed their original 600 h.p. rating, the line was still tagged SW, with the letters coming to be understood to mean switcher. Descendants of the first E's and Fs hit 2400 and 1750 h.p., respectively, but EMD retained their letter series for the sake of continuity.
Leave a Comment
Want to leave a comment?
Only registered members of TrainsMag.com are allowed to leave comments. Registration is FREE and only takes a couple minutes.

Login or Register now.
Please keep your feedback on-topic and respectful. Trains staffers reserve the right to edit or delete any comments.


The Genesee & Wyoming 

Newsletter Sign-Up

By signing up you may also receive occasional reader surveys and special offers from Trains magazine.Please view our privacy policy
Subscribe Up To 58% off the newsstand price!
Subscribe To Trains Mag Today