When should you test the stopping action of your service brakes?

Testing the stopping action of your service brakes when the truck is moving at about 5 mph is crucial for ensuring that the brakes are functioning properly before driving at higher speeds. At this speed, the driver can safely assess the brakes' response without risking loss of control. It allows for a practical evaluation of brake performance and helps identify any potential issues that could arise at higher speeds, providing an opportunity to address them before they lead to dangerous situations.

Testing the brakes at the other suggested times—such as when the truck reaches its top speed, before starting the engine, or when parked—would not provide a true indication of how the brakes will perform during regular driving conditions. It's essential to conduct this test in a controlled environment where the vehicle is already in motion, rather than relying on stationary conditions where the effectiveness of the service brakes cannot be accurately judged.