What is the critical safety rule when crossing a railway level crossing (Eisenbahnkreuzung) with a heavy tractor and twin trailers?

1. Make sure the road beyond the crossing is clear for the whole length of the combination before moving onto the tracks
2. Stop on the tracks to get the clearest view along the line in both directions
3. Select neutral and coast across so the engine cannot stall on the rails
4. Cross only once the barrier has begun to descend, since the train is then still distant