Abstract: Provided is a hill holder system operative to prevent a vehicle such as a truck having a fluid operated brake system from rolling backward down an incline or to assist an operator in braking when descending an incline. The system utilizes a control signal (C) provided by a central processing unit (10) operative to instruct a brake control valve (22) to close the brake balve exhaust port(s) (27) to maintain the brakes in an engaged condition whenever a selected speed condition such as vehicle ground speed is below a predetermined value. In other embodiments, selected vehicle drive train conditions such as either or both throttle and clutch position are processed in combination with the selected speed signal to effect braking in the manner desired.