If you are driving on a clear and level road and your brakes fail, what should you do?

Using engine compression to slow down is a recognized and effective technique in the event of brake failure. When you downshift to a lower gear, the engine RPM increases, which creates resistance against the vehicle's motion, aiding in deceleration. This method allows for a gradual slowdown without causing panic or harsh maneuvers that could endanger you or other road users.

Applying the parking brake, while it can help in some situations, is generally not advisable to engage suddenly, especially at higher speeds, as it could cause the rear wheels to lock up and lead to a loss of control. Weaving from side to side might help reduce speed, but it risks instability and complicates the situation further.

In emergency scenarios, focusing on one method that maintains control is critical rather than attempting multiple actions that could lead to confusion and danger. Hence, using engine compression is the most reliable strategy to manage a situation where brakes have failed effectively.