Editing Reporting mark (section)

===North America===
[[File:Train-connections.jpg|thumb|A [[covered hopper]] with SHPX markings]]

The [[Association of American Railroads]] (AAR) assigns marks to all carriers, under authority granted by the [[Surface Transportation Board|U.S. Surface Transportation Board]], [[Canadian Transportation Agency|Transport Canada]], and Mexican Government. [[Railinc Corporation|Railinc]], a subsidiary of the AAR, maintains the active reporting marks for the North American rail industry.

Under current practice<!--not historic practice - see MILW and ROCK for counterexamples-->, the first letter must match the initial letter of the railroad name. As it also acts as a [[Standard Carrier Alpha Code]], the reporting mark cannot conflict with codes in use by other nonrail carriers.<ref name=register/><ref name=trains/>

Marks ending with the letter "X" are assigned to companies or [[Private railroad car|individuals]] who own railcars, but are not operating railroads;{{efn|"X" originally meant "express", as the first non-railroad car owners were express companies such as [[Adams_Express_Company#History|Adams Express]].}} for example, the [[TTX Company]] (formerly Trailer Train Company) is named for its original reporting mark of TTX. In another example, the reporting mark for [[Amtrak California|state-funded]] Amtrak services in [[California]] is CDTX (whereas the usual [[Amtrak]] mark is AMTK) because the state transportation agency ([[Caltrans]]) owns the equipment used in these services. This may also apply to commuter rail, for example [[Metrolink (California)|Metrolink]] in [[Southern California]] uses the reporting mark SCAX because the equipment is owned by the [[Metrolink (California)|Southern California Regional Rail Authority]]—which owns the Metrolink system—even though it is operated by Amtrak. This is why the reporting mark for [[CSX Transportation]], which is an operating railroad, is CSXT instead of CSX. Private (non-common carrier) freight car owners in [[Mexico]] were issued, up until around 1990, reporting marks ending in two X's, possibly to signify that their cars followed different regulations (such as bans on friction bearing trucks) than their American counterparts and so their viability for interchange service was impaired. This often resulted in five-letter reporting marks, an option not otherwise allowed by the AAR.

[[File:RTDX 4001 reporting mark sign seen from RTDX 4004 cab.jpg|thumb|upright=0.5|A temporary window sign with [[Regional Transportation District|RTDX]] markings]]

Companies owning [[trailer (vehicle)|trailer]]s used in [[trailer-on-flatcar]] service are assigned marks ending with the letter "Z", and the [[National Motor Freight Traffic Association]], which maintains the list of Standard Carrier Alpha Codes, assigns marks ending in "U" to owners of [[intermodal container]]s.<ref name=register/><ref name=trains/> The standard [[ISO 6346]] covers identifiers for intermodal containers.

When the owner of a reporting mark is taken over by another company, the old mark becomes the property of the new company. For example, when the [[Union Pacific Railroad]] (mark UP) acquired the [[Chicago and North Western Railway]] (mark CNW) in 1995, it retained the CNW mark rather than immediately repaint all acquired equipment. Some companies own several marks that are used to identify different classes of cars, such as boxcars or gondolas.<ref name=trains/>  If the acquiring company discontinues the name or mark of the acquired company, the discontinued mark is referred to as a "fallen flag" railway. Occasionally, long-disused marks are suddenly revived by the companies which now own them. For example, in recent years, the Union Pacific Railroad has begun to use the mark CMO on newly built covered hoppers, gondolas and five-bay coal hoppers. CMO originally belonged to [[Chicago, St. Paul, Minneapolis and Omaha Railway]], a predecessor of the CNW, from which the UP inherited it. Similarly, during the breakup of [[Conrail]], the long-retired marks of the [[Pennsylvania Railroad]] (PRR) and [[New York Central Railroad]] (NYC) were temporarily brought back and applied to much of Conrail's fleet to signify which cars and locomotives were to go to CSX (all cars labeled NYC) and which to Norfolk Southern (all cars labeled PRR). Some of these cars still retain their temporary NYC marks.

==== List of North American reporting marks ====
Because of its size, this list has been split into subpages based on the first letter of the reporting mark:

{{Contents - AAR reporting marks|Explain=N}}