When economics develops and purchasing capacities improves the number of vehicles and traffic intensity are increasing promoting an improvement and development of infrastructure of motor roads. These and many other trends increase significantly environmental load and also potential risks, raise quality requirements for roads and building technologies. Eco-effective, qualitative and strategically well-positioned development of traffic infrastructure is the basis of economical development in every region and in whole Latvia. Mentioned conditions increase an importance, complexity and quality requirements of EIA a number of times – it should be based on the newest scientific conclusions and should synergistically include national strategies and regional spatial development planning. Environmental impact assessment (EIA) is the first and the most important step to forecast a possible environmental load of planned economical activities and implement preventive environmental protection measures. EIA should give a reasonable answer to the questions how and how much planned project will impact the environment, what changes are anticipated if technological or environmental parameters will change. This answer can be given only using measurable, verifiable numbers – environmental indicators, and not using general environmental description and assessment based on assumptions. During the last years critical attitude of society against credibility of EIA results is appears more and more often, formal nature and uncertainty of results of EIA reports can be noticed, but with implementation of method of environmental indicators the cooperation among project developer, society and decision makers would be facilitated to support the best possible alternative of project development. The indicator approach developed as a result of this doctoral thesis and use of benchmarking method in the process of EIA can significantly improve efficiency of financial investment of road building during the next 20 years as well as life quality of society. Implementation of benchmarking method in EIA is economically profitable, it does not need significant financial investments and the credibility of results is high. The method is based on actual measurement results of environmental parameters. Using this methodology EIA road project appraisal the risk of possible speculations with information and interpretations is reduced giving to society and decision makers numerical and verifiable data. The methodology is approbated in this research and it can be used in practice. The use of indicator method can give a huge methodological and informative support to EIA developers, society and decision makers.