A semi-autonomous vehicle couplable to a parent vehicle is described, and includes a chassis supported on first and second axles coupled to a plurality of wheels, a propulsion system configured to transfer torque to one of the wheels, a steering system configured to control direction of travel of the semi-autonomous vehicle, a braking system configured to apply braking force to the wheels, a high-voltage electrical energy storage system, an extra-vehicle communications system, and an extra-vehicle sensory system. A control system operatively couples to the propulsion system, the steering system, and the braking system. A coupling device is configured to electrically couple the semi-autonomous vehicle to the parent vehicle, the coupling device consisting essentially of a high-voltage DC electrical power bus electrically coupled to the high-voltage electrical energy storage system.