| 1 | TTKX | Trailer Train Co. | added 4/1968; 10/1968-1/1980; eliminated 1/1992 | | NAKINA |
| 2 | TTKX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 3 | TTKX | Trailer Train Co. | added 4/1968 | | NAKINA |
| 4 | TTKX | Trailer Train Co. (89'3"" or over FA flats equipped with tri-level automobile carrying superstructures with moveable end sections of second or second and third decks, furnished by member railroads. Cars are not equipped with hitches or bridge plates. Equipped with hydraulic draft gears) | 10/1968 | | NAKINA |
| 5 | TTKX | Trailer Train Co. (flat cars, 89'4"" or over, equipped with hinged end tri-level auto racks furnished by participant railroads) | 4/1970 | | NAKINA |
| 6 | TTKX | Trailer Train Co. (flat cars, equipped with hinged end tri-level auto racks furnished by participant railroads) | 1/1975-1/1980 | | NAKINA |
| 7 | TTKX | Trailer Train Co./TTX Co. (flat cars, equipped with hinged B deck tri-level auto racks furnished by participant railroads) | 7/1985-7/2000 | | NAKINA |
| 8 | TTKX | Trailer Train Co. | added 4/68 | | NRHS |
| 9 | TTKX | Trailer Train Co. (89'3" or over FA flats equipped with tri-level automobile carrying superstructures with moveable end sections of second or second and third decks, furnished by member railroads. Cars are not equipped with hitches or bridge plates. Equipped with hydraulic draft gears) | Oct-68 | | NRHS |
| 10 | TTKX | Trailer Train Co. | Apr-70 | | NRHS |
| 11 | TTKX | Trailer Train Co. (flat cars, equipped with hinged end tri-level auto racks furnished by participant railroads) | 1/75-1/80 | | NRHS |
| 12 | TTKX | Trailer Train Co. | eliminated 1/92 | | NRHS |
| 13 | TTKX | TTX Co. | added 1/92 | | NRHS |
| 14 | TTKX | TTX Co. (flat cars, equipped with hinged B deck tri-level auto racks furnished by participant railroads) | 1/94-7/2000 | | NRHS |
| 15 | TTKX | TTX COMPANY {TRAILER TRAIN COMPANY} | | | PWRC |
| 16 | TTKX | Trailer Train (TTX Corporation) | | | RSRV |
| 17 | TTKX | TTX COMPANY | | | SCAC4 |
