encyclopedia

FOULING POINT

The location near the intersection of two converging tracks beyond which adequate clearance does not exist for concurrent passage of on-rail equipment; point on a track where equipment may interfere with movements on a roadway or adjacent track.

FOURTH GENERATION LANGUAGE

English-like, user friendly, procedural computer languages used to program and/or read and process computer files.

FOURTH RAIL

An electrical conductor that provides ground return or negative return for systems in which the running rails are not used for that purpose. (TRB)