owning trailers 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 containers. 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. 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: Europe since 2006 A railway vehicle must be registered in the relevant state's National Vehicle Register (NVR), as part of which process it will be assigned a 12-digit European Vehicle Number (EVN). The EVN schema is essentially the same as that used by the earlier UIC numbering systems for tractive vehicles and wagons, except that it replaces the 2-digit vehicle owner's code (see ) with a 2-digit code indicating the vehicle's register country. The registered keeper of a vehicle is now indicated by a separate Vehicle Keeper Marking (VKM), usually the name of the owning company or an abbreviation thereof, which