What safety risk must a coach driver consider when heavy passenger luggage is loaded entirely in the rear luggage bay or in an external rear ski box (Skibox)?

1. The rear axle may become overloaded while the front steering axle is significantly unloaded, reducing front tire grip, degrading steering control, and increasing understeer and crosswind instability
2. The front tires will explode from lack of weight
3. The vehicle will stop in half the distance
4. The engine will run in reverse