What is the reason total stopping distance for air brakes is longer than that for hydraulic brakes?

The total stopping distance for air brakes is longer than that for hydraulic brakes primarily due to brake lag. When air brakes are applied, there is a noticeable delay caused by the time it takes for air to travel through the system to engage the brakes. This delay is known as brake lag. It occurs because compressed air must fill the brake chambers before the brakes can fully apply, leading to a slower response compared to hydraulic systems where the brake fluid is already in place and can immediately apply pressure to the brakes.

Understanding this concept is crucial, especially for drivers of large commercial vehicles that use air brake systems. The added time it takes for the brakes to engage can significantly affect stopping distances, making awareness of this lag essential for safe driving practices. This factor emphasizes the need for drivers to maintain greater following distances and increase their stopping distances when operating vehicles equipped with air brakes compared to those with hydraulic brakes.