What is "brake lag"?

Answer: B — The delay between applying the brake and when the brakes engage

Brake lag refers to the delay that occurs from the moment the driver applies the brake to the moment the brakes actually engage and start the stopping process. This delay can be influenced by several factors, including the type of brake system, the vehicle's weight, and the air pressure in the lines for air-braked vehicles. Understanding brake lag is crucial for drivers, especially in vehicles equipped with air brakes, because it directly impacts how much distance is required to bring the vehicle to a stop after the brakes are applied. This concept highlights the importance of maintaining a safe following distance and being mindful of the weight of the load, as heavier loads can increase stopping distances. Brake lag does not relate to stopping distance itself, the time taken to perform maintenance on the brakes, or the time it takes for air pressure to build up in the tank, which are all distinct elements. Recognizing the significance of brake lag is vital for all commercial drivers to ensure safety on the road.