As much as I enjoy driving tractor-trailers, one thing that has irked me for many years is the parking brake valves on the dashboard. The two push-pull valves -- the yellow one for tractor brakes and ...

Typical, medium-duty, hydraulic brake system with front discs (red circuit) and rear drums (green circuit). Boost, or assist (blue circuit), is provided by an engine-driven pump, although the power ...

The emergency and supply lines that stretch between a tractor and trailer offer a colorful reminder that compressed air is the lifeblood of your brake system. The hoses are a respective red and blue, ...