What should be your first action if you notice the trailer is rolling while parked?

The correct answer is to install chocks immediately because using wheel chocks is a vital safety measure designed to prevent a trailer from rolling when parked. Chocks are wedge-shaped blocks placed against the wheels of a parked trailer to ensure stability and prevent any movement. When a trailer is parked, especially on inclines or uneven surfaces, there is always a risk of it rolling if not properly secured.

While using the hand brake is important for keeping a truck stationary, it is not foolproof, especially if the brake system has issues or if it isn't engaged fully. Simply accelerating to stop a rolling trailer is dangerous and ineffective. Additionally, checking air pressure isn't directly related to the immediate action needed to prevent the trailer from rolling; it's more relevant to ensuring the safe operation of the vehicle's tires but does not address the urgent need for stability in this scenario. Therefore, installing chocks is the most practical and effective first response to mitigate the risk of a rolling trailer safely.