Abstract Increase of amount greenhouse gas (GHG) emissions from human activities in the form of an increase the number of vehicles indirectly impacting climate change. The purpose of this study is to calculate GHG emissions, namely carbon dioxide (CO2) generated from the transportation sector and determine the scenario of reducing CO2 emissions from the sector transportation in Medan City. The method of calculating GHG emissions in this study uses TIER II from IPCC. The study was conducted in 12 locations of sampling points with a traffic counting time of 12 hours per each point with variations in the time of workdays and weekdays. The results showed that CO2 emissions generated at the twelve sampling locations amounted to 484.41 - 561.16 tons CO2 / year. The scenario of reducing CO2 emissions in this study is the application of Bus Rapid Transit (BRT), parking management systems and fuel substitution. Comparison of the average of the three scenarios in reducing CO2 namely; the application of BRT ± 24.28% with the number of BRT units needed per road segment ranging from 11 - 57 units; fuel substitution of ± 9.16% and parking management system ± 12.08%.