If a heavy commercial truck carrying dangerous chemicals breaks down or catches fire inside a long expressway tunnel, what emergency actions must the driver take?

1. Stop near the tunnel curb, shut down engine, activate hazard flashers, use the tunnel wall SOS emergency phone to alert the control center, and evacuate occupants via emergency cross-passages (人行横洞/车行横洞)
2. Lock the cab doors and go to sleep inside the tunnel until morning
3. Accelerate in reverse against the flow of tunnel traffic to exit the entrance
4. Discharge the chemical cargo onto the tunnel roadbed to lighten the vehicle