AAR Mechanical Designations

AAR Mechanical Designations are intended to group cars by general type, and appear to have been introduced in 1910, although it was a number of years before all railroads so designated their cars in the Official Railway Equipment Register.

The following are a subset of the AAR Mechanical Designations which are appropriate for use on the HO Scale Middle Division during the 1950s.

 Freight Cars
  • FB - Flat Car, bulkhead
  • FC - Flat Car, trailer service
  • FD - Flat Car, depressed center
  • FM -  Flat Car, general service
  • FW - Flat Car, well hole
  • GA -  Gondola, drop bottom, cross doors dump between the rails
  • GB -  Gondola, solid floor, may have drop ends for mill service
  • GD -  Gondola, solid floor, side doors
  • GH -  Gondola, drop bottom, longitudinal doors dump outside the rails
  • GS -  Gondola, drop bottom, longitudinal doors dump outside the rails
  • GT -  Gondola, high side rotary dump
  • HM - Hopper, 2-bay
  • HT -  Hopper, 3- & 4-bay
  • HK -  Hopper, longitudinal doors dump outside the rails
  • LG -  Gondola or Flat Car, equipped to carry containers
  • LO -  Hopper, covered
  • NE -  Caboose, eight wheel
  • NM - Caboose, four wheel
  • RA - Refrigerator, brine cooled
  • RAM - Refrigerator, brine cooled, beef rails
  • RB - Refrigerator, ice cooled, no ice bunkers
  • RCD - Refrigerator, solid carbon dioxide cooled
  • RP, RPA, RPB - Refrigerator, mechanically cooled, powered by car axle
  • RS - Refrigerator, ice cooled
  • RSM - Refrigerator, ice cooled, beef rails
  • SA - Stock Car, single deck
  • SC - Stock Car, convertible single or double deck
  • SF - Stock Car, double deck
  • SH - Horse Car
  • SM - Stock Car
  • SP - Stock Car, poultry
  • TA -  Tank Car, specialized
  • TG - Tank Car, glass lined
  • TL - Tank Car, lined other than glass
  • TM, TMU - Tank Car, specialized
  • TP - Tank Car, specialized
  • TR - Tank Car, specialized
  • VA - Ventilated Box Car, fruits or vegetables
  • VM - Ventilated Box Car, fruits or vegetables, partially insulated
  • VS - Ventilated Box Car, fruits or vegetables, insulated
  • XAF - Box Car, automobile or furniture
  • XAP - Box Car, automobile parts with racks
  • XAR - Box Car, automobile with loading racks, end door
  • XF - Box Car, furniture
  • XI - Box Car, insulated
  • XM - Box Car, general service
  • XME - Box Car, merchandise with racks
  • XMP - Box Car, specially equipped racks not otherwise specified
  • XMR - Box Car, automobile with loading racks, end door
  • XT - Box Car, metal lined or containing one or more tanks
 Passenger Cars
  • BE - Baggage Express
  • BEM - Baggage Express Messenger
  • BH - Horse Express
  • BM - Milk Car, non-refrigerated
  • BMR - Mike Car, refrigerated
  • BP - Refrigerator Express
  • BR - Refrigerator Express, ice cooled
  • BRS - Refrigerator Express, brine cooled
  • BX - Box Express
  • CA - Combination baggage/passenger
  • CAD - Combination baggage/passenger w/food service
  • CO - Combined passenger/baggage/mail
  • CS - Combination baggage/smoking car
  • CSA - Combination baggage/dormitory/kitchen
  • CSB - Combination baggage/dormitory
  • CSP - Combination mail or baggage/dormitory/passenger
  • DA - Dining Car
  • DC - Cafe Car
  • DCL - Lunch Counter Lounge
  • DD - Diner Dormitory
  • DE - Dining Car, less kitchen
  • DG - Grill Room Car
  • DK - Dormitory-Kitchen Car
  • DKP - Kitchen Car
  • DL - Buffet-Lounge Car
  • DLC - Lunch Counter Car
  • DO - Cafe Observation Car
  • DP - Dining and Parlor Car
  • DPA - Diner-Lounge Car (pantry instead of kitchen)
  • EB - Electric Baggage Car
  • EC - Electric Combination Car
  • ED - Rail Motor Car
  • EG - Motor Propelled Car
  • EM - Electric Mail Car
  • EP - Electric Passenger Car
  • ET - Electric Passenger Trailer Car
  • IA - Instruction Car
  • MA - Postal Car
  • MB - Baggage and Mail Car
  • MBE - Combination Mail-Baggage-Express
  • MBD - Combination Mail-Baggage-Dormitory Car
  • MD - Comination Mail-Dormitory Car
  • MR - Postal Storage Car
  • MS - Mail and Smoker Car
  • PAS - Coach-Sleeping Car
  • PB - Coach or Chair Car
  • PBC - Parlor-Coach
  • PBO - Coach-Observation Car
  • PC - Passenger, Parlor or Chair Car
  • PD - Tavern Car
  • PL - Lounge Car
  • PO - Observation Car
  • PS - Sleeping Car
  • PSA - Dormitory Car
  • PT - Tourist Car
  • PV - Private Car, including business cars

M-o-W Cars

  • MWB -  Ballast Car
  • MWC -  Caboose or Tool Car
  • MWD -  Dump Car
  • MWE -  Ballast Spreader and Trimmer
  • MWF -  Flat Car
  • MWG - Section Gang or Track Inspection Car
  • MWH - Hand Car
  • MWJ - Ballast Unloader
  • MWK -  Snow Removing Car
  • MWL - Hand Car
  • MWM -  Store-Supply Car
  • MWP -  Pile Driver
  • MWS -  Steam Shovel
  • MWT -  Tool & Block Car
  • MWU - Wrecking Derrick
  • MWV -  Wrecking Derrick, flat car mounted
  • MWW -  Wrecking Derrick
  • MWX -  Boarding Car, boarding, sleeping, cooking, etc.