In Canada, non-signaled and Automatic Block Signal (ABS) territories are operated according to OCS rules. The only authority for movement in OCS territory is possession of a Clearance or Track Occupancy Permit (TOP) While the line might be equipped with signals (ABS), these signals are unsupervised and uncontrolled by the Rail Traffic Controller. Their indications are strictly governed by track conditions and the passage of trains, and serve to tell operating crews at what speed to operate, and warn of an occupied track ahead.