When a driver notices dense smoke billowing from the closed rear doors of an enclosed dry freight van trailer (厢式货车), what is the proper emergency protocol?

1. Pull over in an open area away from structures/traffic, shut down the engine, prepare fire extinguishers, call 119, and do NOT swing the rear doors wide open immediately (to avoid oxygen flashover)
2. Open the rear doors wide immediately to inspect the cargo while standing inside the van
3. Drive as fast as possible to the nearest downtown fuel station to use their water hose
4. Disconnect the trailer and leave it burning in the middle travel lane of the expressway