A brake system includes a service brake and a parking brake that brake a vehicle including a lift axle capable of ascending and descending. The brake system further includes a brake blocker device and a controller that controls the brake blocker device. The brake blocker device blocks at least one of supply of compressed air to the service brake and supply of compressed air to the parking brake. The service brake and the parking brake act on the lift axle. The controller actuates the brake blocker device when the lift axle is at a lifted position.