Direct Traffic Control, or DTC, is similar to TWC, except that the rail line is divided up into predefined blocks—somewhat similar to ABS blocks without the signals—and dispatchers authorize trains to proceed in a specified number of blocks. Only one train may occupy a stretch of authority (which may consist of a single block or a stretch of dozens) at any given time, unless movements are to be made at restricted speed. Like TWC, DTC may be combined with ABS in high-traffic areas to aid with train separation and safety.