What action is crucial to preventing a rollback when starting on an incline?

Engaging the parking brake is crucial for preventing a rollback when starting on an incline. When a vehicle is stopped on an incline, the force of gravity can cause it to roll backwards when shifting from a stationary position to moving forward. By engaging the parking brake, the driver ensures that the vehicle remains securely in place while preparing to accelerate. This adds an extra layer of safety, allowing the driver to focus on smoothly transitioning to the gas pedal without the immediate concern of the vehicle rolling back.

Besides, while other actions may contribute to controlling the vehicle, they can’t substitute for the stability provided by the parking brake in this situation. Switching to a lower gear can help with better power transfer during a start, and accelerating quickly may also assist in moving forward quickly, but reliance on these methods increases the risk of rolling back if the vehicle is not secured with the parking brake. Turning the steering wheel does not provide any benefit in preventing rollback and is unrelated to managing the vehicle's position on an incline.