How is a 70-psi reduction of the brake pipe accomplished?

How is a 70-psi reduction of the brake pipe accomplished?

• A. Place the handle in the emergency position and reduce by 70 psi.
• B. Place the automatic brake valve handle in the handle off position and make a 70 psi brake pipe reduction. Place the handle in the suppression position to stop the brake pipe reduction.
• C. Place the handle in release and trigger 70 psi reduction automatically.
• D. Use the vent valve to drop 70 psi.

Answer: (B)

In train air-brake systems, braking is produced by lowering the pressure in the brake pipe. A controlled, 70-psi reduction is accomplished by moving the automatic brake valve handle to the off position, which starts a deliberate drop in brake-pipe pressure by the designed amount. Once that 70-psi reduction is achieved, you stop further decrease by placing the handle in the suppression position. This sequence creates a predictable brake application across the train. Other options don’t fit because emergency position would cause a full, rapid brake application, not a measured 70-psi drop; the vent valve is used for venting air and isn’t how you achieve a precise 70-psi reduction in normal operation; release methods don’t trigger a defined 70-psi reduction automatically, and the suppression position’s role is to halt the reduction, not to start it.

In train air-brake systems, braking is produced by lowering the pressure in the brake pipe. A controlled, 70-psi reduction is accomplished by moving the automatic brake valve handle to the off position, which starts a deliberate drop in brake-pipe pressure by the designed amount. Once that 70-psi reduction is achieved, you stop further decrease by placing the handle in the suppression position. This sequence creates a predictable brake application across the train.

Other options don’t fit because emergency position would cause a full, rapid brake application, not a measured 70-psi drop; the vent valve is used for venting air and isn’t how you achieve a precise 70-psi reduction in normal operation; release methods don’t trigger a defined 70-psi reduction automatically, and the suppression position’s role is to halt the reduction, not to start it.