A bus approaches a drawbridge with no signal light, no attendant, and a sign showing the draw span ahead. What is the correct action?

1. Stop at least 50 feet before the draw, verify it is completely closed, then proceed only when safe
2. Proceed without stopping because drawbridges are treated like ordinary intersections
3. Stop 15 feet before the draw because that is the railroad minimum
4. Open the front door and listen for bridge machinery instead of stopping