Highway-railroad crossing identifiers Each highway-railroad crossing is assigned a unique identifier - a U.S. DOT/AAR Crossing Inventory number, normally referred to as an FRA number.  The number consists of 6 digits followed by a letter and is posted on a metal plate at each crossing. FRA number on a signal support FRA number on a crossbuck Most highway-railroad crossings also have a sign posted that includes the railroad and a telephone number to contact in an emergency. To find the FRA number for a highway-railroad crossing remotely The Federal Railroad Administration, Office of Safety Analysis' web site includes a number of ways a user can query the highway-railroad crossing inventory information to identify a single or group of crossings.