You are driving a laden motor vehicle equipped with a manual gearbox. On a steep descent your speed is steadily increasing even though the permanent brake is activated. What should you do?

Your answer is correct. When driving a heavily loaded vehicle with a manual gearbox downhill, and your speed increases even though the permanent brake (such as an engine brake or retarder) is already on, you need to use the service brake and shift into a lower gear. Selecting a lower gear helps increase engine braking, which assists your permanent brake in controlling the speed, especially on steep descents. This reduces stress and overheating on your service brakes, making it safer and preventing brake fade.

In summary: Always use both the service brake and engine braking (by shifting down) to safely control your speed on long, steep downhills. Never rely solely on the service brake, as this can lead to brake failure.