How should you proceed when driving a loaded truck downhill?

In the photo, you are driving on a road in mountainous terrain, where there are long descents. When driving a loaded lorry downhill, you use the retarder or the exhaust brake (engine brake) for braking - answer C.

The Road Traffic Act requires you to drive at a speed that ensures control of the vehicle, taking into account the terrain and the load, and to brake in a way that does not cause danger. On a long descent the service brakes work continuously and heat up; overheated linings lose effectiveness, and in a combination weighing several dozen tonnes this ends with a loss of braking. That is why speed is held with the exhaust brake or the retarder, which turn the energy into engine resistance or into heat carried away by the cooling system, and the service brake is used briefly and rarely. A higher gear (answer A) reduces engine braking and makes the combination speed up, and the emergency brake (answer B) acts abruptly on the wheels of the drive axle and the semi-trailer, so it risks the combination jackknifing. The rule is: you start down a hill in the gear in which you would drive up it.

Legal basis: Art. 19 para. 1 and para. 2 point 2 of the Road Traffic Act (Prawo o ruchu drogowym); Art. 66 para. 1 point 1 of the Road Traffic Act (Prawo o ruchu drogowym)