The functioning of the driver–car–road–environment (DCRE) system in mountainous conditions is characterized by a change in its parameters over a wide range and sometimes in an unpredictable manner. The need to assess the functioning of the DCRE system, taking into account the influence of a large number of factors on the formation of its efficiency by modelling energy exchange processes, becomes acute. The studies were carried out to assess the efficiency of the functioning of the DCRE system and develop proposals for identifying reserves to reduce energy costs when solving issues related to the efficiency of the transport process in mountainous conditions. Until now, when assessing the efficiency of the functioning of the DCRE system according to the energy indicator, methods based on assessing the effectiveness of its elements have been used. The proposed mathematical models for assessing energy exchange processes in the DCRE system differ in sufficient adequacy for practical purposes. For practical purposes, the chapter proposes a mathematical model for a comprehensive energy assessment of the efficiency of the functioning of the DCRE system by linear fuel consumption. The research results can be introduced into production when calculating the efficiency of the transport process.