During a full-service application, what happens to brake pipe, auxiliary reservoir, and brake cylinder pressures?

During a full-service application, what happens to brake pipe, auxiliary reservoir, and brake cylinder pressures?

• A. They all become equal pressure
• B. Brake pipe pressure drops to zero
• C. Brake pipe becomes highest
• D. Brake cylinder becomes zero

Answer: (A)

During a full‑service application, the brake signal lowers brake pipe pressure while air is admitted from the auxiliary reservoir to the brake cylinder. The braking system is arranged so that air flows between the brake pipe, the reservoirs, and the brake cylinder until their pressures align to a common value. This balanced pressure across the three parts helps produce a uniform braking force along the train. The other possibilities imply an extreme or opposite relationship (pipe at zero, cylinder at zero, or pipe higher than the others) that doesn’t reflect how the control valves coordinate air flow during a service brake.

During a full‑service application, the brake signal lowers brake pipe pressure while air is admitted from the auxiliary reservoir to the brake cylinder. The braking system is arranged so that air flows between the brake pipe, the reservoirs, and the brake cylinder until their pressures align to a common value. This balanced pressure across the three parts helps produce a uniform braking force along the train. The other possibilities imply an extreme or opposite relationship (pipe at zero, cylinder at zero, or pipe higher than the others) that doesn’t reflect how the control valves coordinate air flow during a service brake.