Which of the following functions does the retarder in a bus serve?
Show the correct answer
Correct answer
C. It ensures constant braking during a lengthy downhill drive.
Explanation
The question is about the function of the retarder in a bus. It ensures constant braking of the vehicle on long descents - answer C.
The Road Traffic Act requires you to drive at a speed that ensures control of the vehicle, taking into account the shape of the terrain. The retarder is an additional brake, usually hydraulic or electromagnetic, which can work much longer than friction brakes without losing effectiveness, so on a long descent it keeps the speed of the bus constant, and the service brakes stay cool in case of sudden braking. The retarder does not increase speed (answer A) - on the contrary, it creates resistance. It also does not stabilise the path of the vehicle on a slippery road (answer B) - that is the job of the stability control system, and strong use of the retarder on a slippery surface can even make the driving wheels skid.
Legal basis: Art. 19 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)