Environmental Impact Assessment (EIA) is necessary before starting any mega project. It is compulsory by PEPA Pakistan Environmental Protection Act 1997, under (Section 12). Present research study conducts EIA Performance Index for Orange line Mega train Project OLMTP. In the current era of development and advancement, time requires to make a strategy and smart evaluation of the gaps, errors, and mistakes in the previous projects to reduce the repetition chances of the same errors in the new or future projects. In this research study, we collect data from both primary and secondary sources. We use existing EIA Reports and gather data through designed Questionnaires. We pick out 43 experts, environmentalists, and related Faculty members from different Universities and consultancies. Primary Data was collected with the help of a Designed Questionnaire and Online Google Questionnaire form based on all EIA Process Stages and evaluated by sub-indices. Finally, evaluate the EIA Performance Index of OLMTP. The EIAI obtained value for OLMTP is 0.59. OLMTP shows EIAI (0.59) that reflects an average performance Index of EIA as good and effective index must show the value of at least (0.8). We conclude that the EIA Report of the Orange Line Mega train project has some flaws and gaps that need to cover and avoid these errors in future projects to meet sustainability goals. Recommendations include keeping the sustainable goals in view, during the planning and operational phases. During the construction of transportation projects, environmental consideration and green transportation keep in step ahead.