When is it obligatory to operate the speed retarder while driving downhill?

1. Only when the slope rate is indicated in the “steep descent” sign.
2. In every downhill road section.
3. When the slope rate of the descent exceeds 6% and the length of the descent exceeds one kilometer.
4. Correct answer: When a “dangerous descent” sign is posted.

WhyThe retarder must be used when a dangerous descent sign is posted. Not on every descent and not by percentages.