What should you do if you experience brake failure while driving a commercial vehicle?

The correct choice emphasizes a critical response to brake failure, which involves shifting to a lower gear while simultaneously using the emergency brake. When faced with brake failure, it's essential to lower the vehicle's speed to regain control. Shifting to a lower gear helps slow the vehicle down through engine braking, which is particularly effective for maintaining control in a situation where the conventional braking system is no longer functioning properly.

Utilizing the emergency brake is another vital action because it can help bring the vehicle to a stop if the regular brakes fail. However, it’s important to apply the emergency brake gradually to avoid locking up the wheels, which could lead to loss of control or a skid.

In contrast, accelerating in an attempt to gain control would likely increase speed and make stopping more difficult, enhancing the danger of the situation. Likewise, applying the regular brakes repeatedly can be ineffective and may exacerbate the problem if the brakes have already failed. Coasting to a stop in a clear area could be part of a strategy but doesn’t specifically address the immediate necessity of using engine braking and the emergency brake to safely reduce speed more effectively and gain control over the vehicle.