List of reporting marks: X

Note: Marks ending in U are for container owners; marks ending in X are not common carriers; marks ending in Z are for trailers without flanged wheels. All other marks are of common-carrier railroads.

• XCLX - Xcel Energy
• XCWZ - Union Pacific Railroad
• XFEZ - Florida East Coast Railway
• XNWZ - Norfolk Southern Railway
• XOMX - Exxon-Mobil Corporation
• XRFZ - CSX Transportation
• XSCZ - CSX Transportation
• XSLZ - Soo Line Railroad
• XTRX - XTRA, Inc.; First Union Rail
• XTTX - Trailer Train Company