A system and method for allowing failover between an autonomously controlled braking system and a human controlled braking system in a truck having pneumatic brake lines is provided. A cab-mounted brake actuator is arranged to be handled by the human operator and is arranged to selectively deliver pressurized air to truck brakes and a trailer brake air supply. A controller performs autonomous braking operations in response to control inputs and senses when a human operator is handling the actuator. A plurality of valves, interconnected between a pressurized air source on the truck, the actuator, the truck brakes and the trailer brake air supply, are responsive to the controller, and are arranged to override selective delivery of pressurized air to the truck brakes of the truck and the trailer brake air supply in response to the autonomous braking operations in favor of selective delivery of pressurized air via the actuator.