The construction of new motorway routes leaves lasting consequences on the nature and the living world along the corridor through which the adopted motorway alignment extends. Therefore, it is necessary that in the initial stage of the project (Conceptual design) the analysis of all potential impacts of the motorway on the environment be done very rigorously. The subject of this paper is the road environmental impact assessment methodology implemented in conceptual design of Kragujevac - Mrčajevci motorway. Within the motorway environmental assessment for different variants of motorway corridor, traffic noise, air pollution, rainwater and groundwater pollution, soil pollution, climate change, occupation of surfaces for expropriation and other relevant impacts were investigated. In the paper the methodology used to assess the initial ("zero") state of the environment in the studied area was briefly described. In addition, the methodology based on which the project alternatives were compared regarding environmental requirements was also presented, and finally, what was the conclusion of such a comparison.