| 601 | RTTV | ROYS TOW & TRANSPORT SERV | | | SCAC3 |
| 602 | RTTX | TTX Co. | added 1/1992; 1/1994-7/2005 | | NAKINA |
| 603 | RTTX | Trailer Train Co. | added 1/1961; 4/1961-1/1980; eliminated 7/1984; added 7/1986; eliminated 1/1992 | | NAKINA |
| 604 | RTTX | Rapid Transit Tank Car Line | 7/1923 | | NAKINA |
| 605 | RTTX | Trailer Train Co. (not defined) | added 1/1961; 4/1961 | | NAKINA |
| 606 | RTTX | Trailer Train Co. (FCS flat cars equipped with tri-level automobile carrying superstructures furnished by member railroads. Cars are not equipped with hitches and bridge plates) | 4/1963 | | NAKINA |
| 607 | RTTX | Trailer Train Co. (FA flat cars equipped with tri-level automobile carrying superstructures furnished by member railroads. Cars are not equipped with hitches and bridge plates) | 7/1965-10/1968 | | NAKINA |
| 608 | RTTX | Trailer Train Co. (flat cars, equipped with fixed tri-level auto racks furnished by participant railroads) | 4/1970-1/1980 | | NAKINA |
| 609 | RTTX | Trailer Train Co. | eliminated 7/1984 | | NAKINA |
| 610 | RTTX | Trailer Train Co. (standard deck, 3-hitch flat cars with non-collapsible hitches at the ends of the car and a collapsible hitch at the centre of the car, capable of carrying 3-28' trailers with kingpin spacing of 36"" or less, or any two trailers with 36"" kingpin spacing, whose overall combined length does not exceed 90' (i.e. 2-45', 1-42' & 1-48', 1-40' & 1-48', etc.), between lift-on/lift-off facilities only) | 7/1985 | | NAKINA |
| 611 | RTTX | Trailer Train Co./TTX Co. (89' and 360' TOFC cars. 89' cars (6 digit car numbers other than 165000 series) are standard deck, 3-hitch flatcars with non-collapsable hitches at the ends of the car and a collapsable hitch at the centre of the car, capable of carrying 3-28' trailers with kingpin spacing of 36"" or less, or any two trailers with 36"" kingpin spacing, whose overall combined length does not exceed 90' — i.e., 2-45', 1-42' & 1-48', 1-40' & 1-48', etc. — between lift-on/lift-off facilities only. 360 | added 7/1986; 10/1991-1/1992 | | NAKINA |
| 612 | RTTX | TTX Co. (89' and 178' TOFC Flat cars. 89' cars (6 digit car numbers other than 165000 series) are standard deck, 3-hitch flatcars with non-collapsable hitches at the ends of the car and a collapsable hitch at the centre of the car, capable of carrying 3-28' trailers with kingpin spacing of 36"" or less, or any two trailers with 36"" kingpin spacing, whose overall combined length does not exceed 90' — i.e., 2-45', 1-42' & 1-48', 1-40' & 1-48', etc. — between lift-on/lift-off facilities only. 178' cars (6 dig | 1/1994-7/2000 | | NAKINA |
| 613 | RTTX | Trailer Train Co. | 4/61-7/65 | | NRHS |
| 614 | RTTX | Trailer Train Co. (FA flat cars equipped with tri-level automobile carrying superstructures furnished by member railroads. Cars are not equipped with hitches and bridge plates) | 10/66-10/68 | | NRHS |
| 615 | RTTX | Trailer Train Co. | Apr-70 | | NRHS |
| 616 | RTTX | Trailer Train Co. (flat cars, equipped with fixed tri-level auto racks furnished by participant railroads) | 1/75-1/80 | | NRHS |
| 617 | RTTX | Trailer Train Co. | eliminated 7/84 | | NRHS |
| 618 | RTTX | Trailer Train Co. | added 7/86; eliminated 1/92 | | NRHS |
| 619 | RTTX | TTX Co. | added 1/92 | | NRHS |
| 620 | RTTX | TTX Co. (89' and 178' TOFC Flat cars. 89' cars (6 digit car numbers other than 165000 series) are standard deck, 3-hitch flatcars with non-collapsable hitches at the ends of the car and a collapsable hitch at the centre of the car, capable of carrying 3 28' trailers with kingpin spacing of 36" or less, or any two trailers with 36" kingpin spacing, whose overall combined length does not exceed 90' -- i.e., 2-45', 1-42' & 1-48', 1-40' & 1-48', etc. -- between lift on/lift off facilities only. 178' cars (6 dig | 1/94-7/2000 | | NRHS |
| 621 | RTTX | *RAPID TRANSIT TANK CAR LINE | | | PWRC |
| 622 | RTTX | +TTX COMPANY | | | PWRC |
| 623 | RTTX | TTX Corporation | | | RSRV |
| 624 | RTTX | TTX COMPANY | | | SCAC4 |
| 625 | RTTY | ROCKY TOP TRUCKING | | | SCAC4 |
| 626 | RTTZ | UP [(REAZ) RETIRED 04-06-93 ATP (ACI 2384)] | | | PWRC |
| 627 | RTTZ | Union Pacific Railroad | | | RSRV |
| 628 | RTU | Aerotucan, S.A. de C.V. | Callsign: Aerotucan, | MEX | AVCODES |
| 629 | RTU | Aerotucan | | | ICAO1 |
| 630 | RTUC | R & R TRUCKING | | | SCAC3 |
| 631 | RTUC | R & T TRUCK INC | | | SCAC4 |
| 632 | RTUD | RENTALS UNLIMITED INC | | | SCAC3 |
| 633 | RTUE | RODAN TRANSPORT USA LTD | | | SCAC4 |
| 634 | RTUG | RATH TRUCKING, INC | | | SCAC3 |
| 635 | RTUG | RATH TRUCKING INC | | | SCAC4 |
| 636 | RTUI | RUSSELL TRUCKING INC | | | SCAC3 |
| 637 | RTUL | Rail Technologie und Logistics GmbH | Magdeburg | D | privat-bahn.de |
| 638 | RTUL | ROLLEN TRUCK LINES INC | | | SCAC3 |
| 639 | RTUL | Rail Rechnology & Logistics GmbH | | DE | VKM |
| 640 | RTUN | RTS TRUCKING CO | | | SCAC3 |
| 641 | RTUQ | RTL TRUCKING LTD | | | SCAC4 |
| 642 | RTUS | RATLIFFS TRUCKING SERVICE INC | | | SCAC3 |
| 643 | RTV | Nortavia | Callsign: Tic-Tac, | P | AVCODES |
| 644 | RTV | Nortavia | | | ICAO1 |
| 645 | RTVA | R & T TRUCKING INC | | | SCAC3 |
| 646 | RTVC | ROAD TRIP TOURS | | | SCAC3 |
| 647 | RTVE | R T EXPRESS | | | SCAC4 |
| 648 | RTVI | R T SERVICES INC | | | SCAC3 |
| 649 | RTVL | ROBYNS TRUCKING SEVICES LTD | | | SCAC3 |
| 650 | RTVR | RETRIEVER TRANSPORTATION INC | | | SCAC4 |
| 651 | RTVS | RELIABLE TRANSPORT SERVICES | | | SCAC4 |
| 652 | RTVU | DAILY RENTAL SERVICES BV | | NL | BIC |
| 653 | RTW | Rail To Water | | USA | TRAFFIC |
| 654 | RTWA | RITEWAY TRANSFER | | | SCAC3 |
| 655 | RTWD | ROUND THE WORLD (USA) CORP. | | | SCAC3 |
| 656 | RTWD | R TWO (R2) LOGISTICS INC (LTL DIVIS | | | SCAC4 |
| 657 | RTWE | RTW ENTERPRISES | | | SCAC3 |
| 658 | RTWE | RTW ENTERPRISES INC | | | SCAC4 |
| 659 | RTWF | READS TOWING | | | SCAC3 |
| 660 | RTWH | REDWAY TRUCK & WAREHOUSE COMPANY | | | SCAC3 |
| 661 | RTWH | RAIL TRANSFER AND WAREHOUSING INC | | | SCAC4 |
| 662 | RTWK | ROSS TOWING AND TRANSPORTATION SERV | | | SCAC4 |
| 663 | RTWP | RITE-WAY TRANSPORTATION INC | | | SCAC3 |
| 664 | RTWQ | RITEWAY MOTOR FRT CO | | | SCAC3 |
| 665 | RTWQ | RITEWAY MOTOR FRT CO | | | SCAC4 |
| 666 | RTWR | ROAD-RUNNER TOWING & RECOVERY | | | SCAC3 |
| 667 | RTWR | RONS TOWING AND RECOVERY INC | | | SCAC4 |
| 668 | RTWT | RITE WAY TRANSPORTATION INC | | | SCAC3 |
| 669 | RTWT | RITE WAY TRANSPORTATION INC | | | SCAC4 |
| 670 | RTWY | RITE-WAY TRANSPORT COMPANY INC | | | SCAC3 |
| 671 | RTWY | RITE-WAY TRANSPORT COMPANY INC | | | SCAC4 |
| 672 | RTX | Railtraxx BVBA | | BE | VKM |
| 673 | RTXA | RELIABLE TRANSPORTATION | | | SCAC4 |
| 674 | RTXC | R TRANSPORTATION LLC | | | SCAC4 |
| 675 | RTXD | RENEW TRANSPORTATION LLC | | | SCAC4 |
| 676 | RTXE | RELIANT TRANSPORT INC | | | SCAC4 |
| 677 | RTXG | RTX LOGISTICS | | | SCAC4 |
| 678 | RTXH | ROLYNNS TRANSPORTATION INC | | | SCAC4 |
| 679 | RTXI | RAYTRUX INC | | | SCAC3 |
| 680 | RTXI | ROMERO TRUCK EXPORTATION | | | SCAC4 |
| 681 | RTXJ | REDWOOD TRANSPORT INC | | | SCAC4 |
| 682 | RTXK | ROUNDTREE TRANSPORT LLC | | | SCAC4 |
| 683 | RTXL | READY TAXI AND LIMOUSINE INC | | | SCAC3 |
| 684 | RTXM | ROE TRANSPORT INC | | | SCAC4 |
| 685 | RTXO | ROCKSTAR TRANSPORTATION INC | | | SCAC4 |
| 686 | RTXP | RAPID TRANSFER XPRESS | | | SCAC4 |
| 687 | RTXS | ROM TRANS EXPRESS INC | | | SCAC4 |
| 688 | RTXV | ROORDA TRANSPORT CO | | | SCAC4 |
| 689 | RTXW | RUETHER TRANSPORTATION INC | | | SCAC4 |
| 690 | RTXY | RITTER TRANSPORTATION SYSTEMS INC | | | SCAC4 |
| 691 | RTY | Aims Community College | Callsign: Aims College, | USA | AVCODES |
| 692 | RTYE | ROAD TRAIN EXPRESS INC | | | SCAC4 |
| 693 | RTYI | ROBERTS, TOMMY TRUCKING INC | | | SCAC4 |
| 694 | RTYS | RASMUSON, TYSON | | | SCAC4 |
| 695 | RTYT | REYNA TRUCKING INC | | | SCAC4 |
| 696 | RTZ | Regional Air Services | Callsign: Aerotuzla, | RO | AVCODES |
| 697 | RTZA | RETZLAFF, BRIAN TRUCKING | | | SCAC4 |
| 698 | RTZB | ROTZ, BRUCE | | | SCAC4 |
| 699 | RTZC | R T Z TRUCKING COMPANY LLC | | | SCAC4 |
| 700 | RTZF | RETZLAFF, ARTHUR | | | SCAC3 |
