What does the term "lag time" refer to in air brake systems?

The term "lag time" in air brake systems specifically refers to the delay experienced between the moment the brake pedal is pressed and the moment when the brakes actually engage. This delay is a critical concept because it can significantly affect the stopping distance of a vehicle.

When the driver applies pressure to the brake pedal, the air pressure must first travel through the system to reach the brake cylinders, and only then does the braking action occur. Understanding this lag time is essential for drivers, particularly in large vehicles, as it influences how they should judge their stopping distances and anticipate the vehicle's response when braking. Being aware of lag time helps in maintaining safe driving practices, especially in situations that require abrupt stops or when driving at high speeds.