If a tram, equipped with a shoe brake rolls on despite the brake being pressed and parking brake lights flashing, it may indicate:
Show the correct answer
Correct answer
C. wear of the friction linings.
Explanation
The question is about a tram with a shoe brake which rolls on despite the brake being applied and the parking brake warning light being on. This may indicate wear of the friction linings - answer C.
A shoe brake works through the friction of the linings against a drum or disc. When the linings are worn, the friction force decreases and the brake cannot hold the tram in place, even though the system shows that the brake is applied. An excessive number of passengers (answer A) increases the mass, but a working parking brake will hold the tram. Too low a battery charging voltage (answer B) does not reduce the friction of the linings. The tram driver reports such a fault immediately and does not continue driving.
Legal basis: Art. 66 para. 1 point 1 of the Road Traffic Act (Prawo o ruchu drogowym)