What is the meaning of the following traffic sign?

1. Level crossing 300 meters ahead.
2. Correct answer: Direction and warning posts at the side of the road.
3. Guardrail marking.
4. Railway barrier ahead at a work-site

WhyThese are white-and-black posts along the edges of the road: they show its width and bends, especially at night. They have nothing to do with crossings or railings.