What should you do if your brakes fail while driving?

When your brakes fail while driving, pumping the brake pedal can often build up brake pressure and provide some stopping ability, especially in vehicles with hydraulic brakes. This action is recommended in emergency situations because it allows for a potentially momentary return of braking power, giving you a chance to control your speed.

Downshifting to a lower gear is also an effective strategy. By shifting to a lower gear, you can utilize engine braking to help reduce your speed. This technique can slow the vehicle down more effectively than coasting alone, helping you come to a more controlled stop.

While coasting to a stop on the shoulder can be a part of your strategy, it may not provide enough stopping power on its own if your brakes are completely failing. Turning off the engine is generally not advisable because it disables power steering and other systems, making the vehicle harder to control.

Thus, the recommended action combines both pumping the brakes to regain pressure and downshifting to slow down safely, making option B the most effective response to brake failure.