What causes 'brake lag' in air brake systems compared to hydraulic systems, and how do relay valves minimize it?

1. Air is thinner than hydraulic fluid; relay valves compress it further to speed up transmission
2. Air takes time to flow through long lines; relay valves speed up application by using a small air signal to release high-pressure air locally at the axles
3. Engine power loss slows down air transmission; relay valves use electric pumps to compensate
4. The slack adjuster takes time to move; relay valves lubricate the camshaft