Final answer:
In the event of brake failure, using engine compression is the safest method to slow down; shifting to lower gears can help reduce speed gradually.
Step-by-step explanation:
If you are driving on a clear and level road and your brakes fail, the best thing to do is use engine compression to slow down. This can be achieved by downshifting your vehicle's gears, if possible, which allows the engine to act as a natural brake. Options such as weaving from side to side or relying solely on the parking brake are less safe and less effective. In such cases, you should also activate your hazard lights to warn other drivers and judiciously apply the parking brake to further reduce speed if necessary. It's important not to panic and to look for a safe place to bring your vehicle to a stop.