What is the primary danger when driving an articulated vehicle during severe winter ice storms across the Salang Pass?

1. Loss of tire grip causing drive-wheel spin, trailer sliding into the opposing lane, total jackknife, and road blockage in freezing temperatures
2. Diesel fuel waxing in the tank, which is the main cause of jackknife incidents
3. Reduced tyre pressure from the cold, which improves grip on ice
4. Snow chains becoming unnecessary once the road has been gritted once