Purpose – The quantitative assessment of environmental effects should be carried out using the indicators that ensure the best objectivity and efficiency of the environmental impact assessment (EIA) process. The aim of this paper is to clarify the effectiveness of the methods used for prognoses of air pollution from roads. The benchmark method proposed in this paper is based on theoretical knowledge and on analysis of data collected from EIA reports. Design/methodology/approach – The paper includes a literature review and developing of the benchmark method. This research was based on data dispersion analysis, determination of benchmarks, usage of regression method, as well as confrontation of different methods of determination of air emission concentration used in EIA.