How should tire pressure be adjusted when a passenger car is fully loaded for a vacation trip with passengers and luggage?

1. Tire pressure should be reduced by 50% for comfort
2. Tire pressure should remain unchanged under all circumstances
3. Tire pressure should be increased to the manufacturer's recommended 'full load' specification (typically 0.2 to 0.5 bar higher) as indicated on the door pillar or fuel flap
4. All four tires should be inflated to the maximum pressure molded on the tire sidewall