What valve is closed when cutting out brakes to a car?

The branch pipe cutout cock is the correct answer because it serves a vital function in managing the air supply to the brake system of each car. When cutting out the brakes on a specific car, the branch pipe cutout cock is closed to isolate that car from the air brake system. This action prevents the loss of air pressure from the rest of the train and enables the braking system of the remaining cars to function normally.

This valve is typically located on the branch pipe that carries air to the brake equipment of each individual car. By closing the cutout cock, maintenance or inspections can be performed on the isolated car without affecting the performance of the entire train’s braking system. This practice ensures safety and efficiency during train operations and maintenance activities.