Car type codes were developed by the Association of American Railroads at the same time car records were being computerized , Each car code consists of letter followed by three numbers. The letter identifies the general equipment or trailer/container type and the numbers provide specifics about the size, capacity and Other features of the car. The numeric code changes according to equipment type.

The codes are explained i n the Association Of American Rail roads section in the back The Official Railway Equipment Register. This section was later part Of the UMLER Data Specification Manual and appeared in the Register through 2002. Exhibit D of the UMLER Data Manual listed the equipment type and trailer/containers type axles. Exhibit
M listed the major classes Of tank cars which correspond to the first two tank car numerics.

Substantial have been made since the ear type codes were first introduced, so they are not necessarily consistent from year to year. The AAR may have intended to do away with mechanical designations after car type codes were introduced, but that has never happened.

Freight Cars

• XM - Box car, general service
• XML/XL - Loader equipped box
• XMI/XI - Insulated box
• XAR/XA - Auto box
• XAP/XP - Autoparts/Appliance box
• XF - Furniture box, later Food box (none on the Rio Grande)
• VA - Ventilated box
• RB - Bunkerless reefer/insulated box
• RBL - Loader equipped
• RS - Reefer w/ ice bunkers
• RSM/RA - Meat reefer
• SM - Stock, single deck
• SF - Stock, double deck
• FM - Flat
• FMS - Flat, Specially equipped
• FB - Bulkhead flat
• FC - TOFC flat
• FA - Auto rack
• GA - Gon, drop bottom, cross doors dump between the rails
• GB - Gon, solid floor, may have drop ends for mill service
• GBS - Gon, specially equipped
• GBSR - Gon, w/ roof
• GD - Gon, side doors, Add S or C if equipped with coke/beet racks
• GH - Gon, convertable ballast
• GK - Gon, solid floor & ends (not used after mid 1920s)
• GRA/GA - Gon, hopper bottom (not used after mid 1920s)
• GS - Gon, drop bottom, doors dump outside the rails, Add S or C if racks
• GT - High side rotary dump gon
• HM - Hopper, 2-bay
• HT - Hopper, 3 & 4 bay
• HK - Hopper, longitudinal doors for ballast
• LG - Gon or flat set up to carry containers
• LO - Covered hopper
• T - Tank car
• TA - Tank, acid
• NE - Caboose

Passenger Cars

• BE - Baggage-Express
• BR - Express reefer, ice bunkers
• BVA - Express ventilated
• CA - Combination baggage/passenger
• CS - Combination baggage/smoking car
• CSB - Combination baggage/dormitory
• DA - Diner
• DB - Cafe car
• DL - Buffet/Lounge
• MA - RPO
• MB - Mail/Baggage
• MBE - Mail/Baggage/Express
• PAS - Coach/Sleeper
• PB - Coach
• PC - Parlor/Chair
• PE - Emigrant or Colonist car
• PL - Lounge car
• PO - Obs
• PS - Sleeper
• PT - Tourist car
• PV - Private/office/official car

M-o-W Cars

• MWB - Ballast car
• MWC - Work Caboose or office car
• MWD - Dump car
• MWE - Ballast spreader
• MWF - Work Flat
• MWK - Snow plow/spreader
• MWM - Materials car (can be box, gon, flat, tank, etc.)
• MWP - Pile driver
• MWS - Steam shovel/ditcher
• MWT - Tool & block car
• MWV - Derrick fitted to flat car, e.g., NG Derrick "OP"
• MWW - Derrick, wrecking, steam or diesel
• MWX - Boarding car, kitchen/dining car, potable water car