When should you engage parking brakes in an air brake system?

Answer: B — Always when the vehicle is parked

Engaging parking brakes whenever the vehicle is parked is essential for ensuring safety and stability. When a vehicle is stationary, especially in an air brake system, applying the parking brakes helps prevent unwanted movement caused by gravity or external forces. This is particularly important in vehicles that are equipped with air brakes, as the system relies on air pressure to operate properly. By consistently engaging the parking brakes, regardless of the terrain, you reduce the risk of rolling or shifting when parked. This practice is a standard safety measure and contributes to the overall reliability of the vehicle's braking system. It's a fundamental practice taught to all drivers to promote safe habits and ensure that the vehicle remains securely in place when unattended. Additionally, engaging parking brakes is crucial in various situations, not just on steep inclines, further underlining the importance of this action every time the vehicle is parked.