Track Warrant Control
The train crew copies the instructions onto a pre-printed paper form and reads back the warrant to ensure that nothing was misunderstood.The dispatcher may also issue time constraints (known as "Box 6" on a standard form), although the track warrants remain in effect until cleared by a member of the receiving crew.Track warrants are sometimes used in conjunction with a block signal system to provide rear-end protection against following trains.[2][better source needed] Track warrants usually allow a train to move in one direction only—a "proceed" instruction.This is done by providing the maintenance crew with a form or protection, or allowing work to be done behind a passing train.Furthermore, track warrants are not limited to fixed blocks and can be issued and released from almost any explicitly identified landmark along the rail line.