If a driver experiences brake failure, what should be their first action?

When a driver experiences brake failure, the most appropriate immediate response is to pump the brake pedal. This action can sometimes build up enough pressure in the brake lines to restore some braking function, allowing the driver to slow down or stop the vehicle more effectively. It's crucial to try this method first because it directly addresses the issue with the brakes in an effort to regain control.

While the other actions may seem relevant in certain situations, they do not address the immediate need to stop the vehicle. Letting go of the steering wheel would be dangerous, as it would severely diminish the driver’s control over the vehicle. Shifting into neutral could help in reducing speed in some cases, but it's not the first step a driver should take when trying to regain braking ability. Using the horn is more a measure for alerting other drivers rather than helping the driver manage the vehicle after experiencing brake failure. Thus, the correct initial action is to pump the brake pedal to attempt to stop the vehicle safely.