All-wheel-drive highway trucks with a “flexible” or hydrostatic drives are lately coming into increasingly wide use. These trucks are provided with step-less control of power supplied to the wheels, something that improves the traction and velocity performance, conserves fuel and reduces the environmental impact of these vehicles. This article presents principles of design and layouts of systems for controlling “flexible” transmission of power to AWD highway trucks.It presents relationships defining the optimum distribution of power to the driving wheels of the AWD vehicle that allow obtaining optimum traction and minimum power losses. The methods described in the article make it possible to control the distribution of power between the wheels of a vehicle with any number of wheels. Analytically and experimentally obtained curves of parameters that describe the motion of a vehicle, including over soil, on the basis of the herein described theory of interaction of a single wheel with the support surface, are presented.The article is concerned with the ecological aspect of controlling the power supplied to the driving wheels of an AWD vehicle. The method for assessing the effect of a wheeled drive system of a vehicle that makes allowance for both the vertical load and the slip of the wheel on the soil is suggested.The automatic-control principles and the system as a whole are presented for the case of a 6×6 wheel drive vehicle with a gross weight of 12 ton with controlled hydrostatic wheel drive. This system continuously redistributes the power to the driving wheels on the basis of the conditions and of the vehicle operating modes.