Home › CDL Practice Tests › Air Brakes Questions › Question 101
What are the colors and shapes of the standard parking control knobs in a combination vehicle cab?
- A.Two identical round blue knobs
- B.A green lever and a black switch
- C.A yellow diamond-shaped knob for the tractor parking brakes and a red octagonal knob for the trailer air supply
- D.Color and shape do not matter or vary randomly
Correct answer
C. A yellow diamond-shaped knob for the tractor parking brakes and a red octagonal knob for the trailer air supply
Why
Standard shapes let the driver identify the controls by touch in an emergency or in the dark. Yellow-diamond controls the tractor's parking brakes, while red-octagon controls air supply to the trailer.
Manual topic: Air Brakes - Spring Brakes and Parking Brakes · From the Air Brakes practice bank (AB-101).