Under Article 81 of the Road Traffic Safety Law Implementation Regulations, what actions must a heavy truck driver take when driving on an expressway in dense fog with visibility under 50 meters?

1. Turn on fog lights, low beams, clearance lamps, and hazard flashers, reduce speed below 20 km/h, and exit the expressway via the nearest exit immediately
2. Accelerate to 80 km/h to pass through the fog bank as quickly as possible
3. Stop immediately in the middle travel lane, turn off all vehicle lights, and wait for sunrise
4. Honk the horn continuously while driving at 60 km/h in the leftmost overtaking lane