What should a commercial truck driver do before entering a steep mountain tunnel known to have heavy smoke or exhaust haze?

1. Ensure low-beam headlights are on, close all windows, set cabin air to recirculation, and verify emergency breathing escape masks are accessible
2. Drive through with high beams on while honking the horn
3. Accelerate to 100 km/h to exit the tunnel faster
4. Turn off the engine and coast through in neutral