What does this road sign indicate?

Explanation

These signs warn that, outside a built-up area, you are approaching a railway level crossing, and they stand on the left side of the road. They follow one after another, so the farther you go the closer the crossing — the number of bars shows the distance left. When you see them, ease off, stay very alert, watch the crossing signals, and be ready to stop safely, because a train can appear at any moment.