What is the meaning of the sign?

1. Correct answer: Portable flashing caution sign situated before a road works.
2. Portable flashing sign upon leaving an inter-urban road to enter a motorway (freeway).
3. Portable flashing sign for advertising to drivers.
4. Portable flashing sign before entering an airport.

WhyA portable flashing board warns of road works ahead and shows which way to go around.