What is a sign that the air brake system is functioning properly when moving the vehicle forward?

The correct response indicates that the air brake system is operating correctly when the vehicle remains straight during movement. This stability suggests that the brakes are evenly engaging on all wheels and functioning as designed, providing balanced braking force. If the vehicle veers off to one side, it could signify an imbalance or malfunction in the brake system, which could lead to safety hazards.

The presence of any unusual noises, such as squealing brakes, often indicates wear or malfunction, making it a sign of potential issues rather than proper functioning. Warning signals from the braking system typically serve as alerts for maintenance or problems but do not indicate that the system is working correctly during operation. Therefore, the ability of the vehicle to maintain a straight path correctly demonstrates that the air brake system is performing as it should.