11. How should you check that your service brakes are working properly?
Park on level ground, wait until normal air pressure is reached, release the parking brake and move forward slowly at about 5 mph. Then apply the brakes firmly.
12. A straight truck or bus air brake system should not leak at the rate of more than ____ psi per minute with the engine off and the brakes released.
13. During normal driving, spring brakes are usually held back by:
14. The air compressor stops pumping air at what psi?
15. The driver must be able to see a low air pressure warning which comes on before the pressure in the service air tanks falls below ____ psi.