Which automatic brake handle position is used to make a 26 psi brake pipe reduction?

Which automatic brake handle position is used to make a 26 psi brake pipe reduction?

• A. Emergency
• B. Full service
• C. Release
• D. Direct

Answer: (B)

In an automatic air brake system, braking force is controlled by how much the brake pipe pressure is reduced. A drop of about 20–30 psi is typical for a normal service brake application, and a 26 psi reduction fits that range. So the position that causes a moderate, controlled decrease in brake pipe pressure—enough to apply the brakes without triggering an emergency action—is the service position. The emergency position would drop brake pipe pressure much more rapidly to cause a full emergency brake, the release position restores pipe pressure to release the brakes, and the direct position operates the brakes without using the pipe pressure in the usual way.

In an automatic air brake system, braking force is controlled by how much the brake pipe pressure is reduced. A drop of about 20–30 psi is typical for a normal service brake application, and a 26 psi reduction fits that range. So the position that causes a moderate, controlled decrease in brake pipe pressure—enough to apply the brakes without triggering an emergency action—is the service position. The emergency position would drop brake pipe pressure much more rapidly to cause a full emergency brake, the release position restores pipe pressure to release the brakes, and the direct position operates the brakes without using the pipe pressure in the usual way.