What is the primary danger when driving an unloaded (empty) box truck or high-sided curtain-sider semitrailer in strong crosswinds (bočni vjetar)?

1. The large vertical surface area acts like a sail, and lack of payload weight makes the vehicle highly susceptible to wind-induced lane departure or rollover
2. The tires will overheat and blow out
3. The engine will stall due to air intake turbulence
4. The fifth wheel kingpin will unscrew automatically