PENNSYRR.COM by Jerry Britton

Jerry Britton's PRR Middle Division in HO Scale

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.