How does the ECAS system react automatically when a large group of 40 passengers boards a touring coach through the rear door?

1. It locks the suspension at a rigid mechanical stop until the bus reaches 30 km/h
2. Level sensors detect chassis deflection and the electronic control unit commands valves to pump additional compressed air into the rear bellows, maintaining nominal ride height
3. It discharges air from the front suspension to equalize tire pressure across all axles
4. It disables the engine throttle until the driver manually recalibrates the load distribution switch