If an identification sign is installed on the vehicle "Road Train," in which of the listed cases must it be turned on?

1. 1It must be turned on at all times while travelling.
2. 2It must be turned on during a forced stop, stopping, or parking on the road during the hours of darkness.
3. 3It must be turned on during a forced stop, stopping, or parking on the road in conditions of reduced visibility.
4. 4Answers 2 and 3.
5. 5Answers 1, 2, and 3.