In North American practice, a distinction must be made between "absolute" signals, which can display a "Stop" (or "Stop and Stay") indication, and "permissive" signals, which display a "Stop & Proceed" aspect. Furthermore, a permissive signal may be marked as a "Grade Signal" where a train does not need to physically stop for a "Stop & Proceed" signal, but only decelerate to a speed slow enough to stop short of any obstructions. Interlocking ('controlled') signals are typically absolute, while automatic signals (i.e. those controlled through track occupancy alone, not by a signalman) are usually permissive.