Reaction distance refers to the distance a vehicle travels from the moment a driver perceives a hazard until they begin to brake. This distance is influenced by the driver's reaction time, which can be affected by factors such as fatigue, distractions, or alcohol consumption. The total stopping distance of a vehicle includes both the reaction distance and the braking distance, which is the distance it takes to come to a complete stop after the brakes are applied. Understanding reaction distance is crucial for safe driving, as it helps drivers maintain a safe following distance behind other vehicles and react appropriately to unexpected situations.