A passenger bus approaches a drawbridge with an attendant present, but the attendant is turned away and the draw warning bells begin. What should the driver do?

1. Proceed because an attendant is somewhere on the bridge
2. Slow or stop as needed and obey the active warning, proceeding only when the bridge is clearly safe
3. Honk and accelerate before the bridge opens
4. Ask passengers to watch the bridge while the driver checks mirrors only