In the event of a supply circuit failure, what should the driver do to conserve air pressure?

In the event of a supply circuit failure, it is essential for the driver to conserve air pressure in the braking system to maintain control of the vehicle. Keeping a steady pressure on the brake allows the driver to prevent the brakes from fully engaging or releasing. This strategy helps in maintaining enough pressure to manage the vehicle effectively and ensures that braking capabilities can be controlled, which is crucial given that air pressure is vital for the operation of air brakes.

By keeping a steady pressure, the driver can potentially prevent the brake system from depleting its air supply too quickly. This deliberate management of brake pressure ensures that the driver does not exhaust the available air pressure, which could lead to a complete brake failure and increase the risk of an accident. Other options may not provide the necessary control or could lead to further issues, which is why maintaining steady pressure is the optimal choice in this scenario.