When testing air leakage rates for single vehicles, initial loss rate should be less than _________.

The initial loss rate for single vehicles should be less than 2 psi in one minute. This is the amount of air pressure that is expected to drop in the first minute after the air brakes are fully charged. If the initial loss rate is more than 2 psi, then there is a leak in the air brake system and it will need to be repaired before the vehicle is driven.

Here are the steps on how to test the air leakage rate for single vehicles:
- Make sure the vehicle is parked on a level surface.
- Turn off the engine and set the parking brake.
- Close all the air valves.
- Use a pressure gauge to measure the air pressure in the air brake system. The air pressure should be at least 100 psi.
- Wait one minute and then measure the air pressure again. The air pressure should not have dropped by more than 2 psi.
If the air pressure has dropped by more than 2 psi, then there is a leak in the air brake system. You will need to identify the leak and repair it before driving the vehicle.