During an air brake test, what indicates brake release?

During an air brake test, what indicates brake release?

• A. 5 PSI brake pipe increase.
• B. 5 PSI brake pipe reduction.
• C. 0 PSI change.
• D. 2 PSI increase.

Answer: (A)

When brakes release, the system recharges the brake pipe with air from the reservoirs, so the brake pipe pressure climbs back up. The indicator you look for is a rise of about 5 psi in the brake pipe after you let the brakes off. That small, consistent increase shows the valves are allowing air back into the line and the brakes have released; it also helps confirm there isn’t a leak preventing release. If you saw no change, or a decrease, or only a tiny rise like 2 psi, that would suggest the brakes aren’t releasing properly or there’s a leak.

When brakes release, the system recharges the brake pipe with air from the reservoirs, so the brake pipe pressure climbs back up. The indicator you look for is a rise of about 5 psi in the brake pipe after you let the brakes off. That small, consistent increase shows the valves are allowing air back into the line and the brakes have released; it also helps confirm there isn’t a leak preventing release. If you saw no change, or a decrease, or only a tiny rise like 2 psi, that would suggest the brakes aren’t releasing properly or there’s a leak.