Before driving a passenger bus across a flooded road section or bridge, how must the driver assess the wading safety depth (涉水深度)?

1. Stop the vehicle to check water depth; do not attempt to cross if the water level exceeds the wheel hub center / exhaust pipe level, or if the water flow is rapid
2. Proceed immediately if smaller sedans ahead are floating through the water
3. Accelerate to create a large bow wave that pushes the water aside
4. Wading depth is irrelevant because heavy buses have sufficient mass to maintain traction regardless of water depth