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.
DTC is only a mechanism to transfer movement authority and can work only within an arrangement of predefined blocks.
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.
Functionality includes 'proximity' warnings and 'out of authority' alarms to improve driver situation awareness.