In the last couple of years, DKI Jakarta has been mentioned several times in the news as one of the top cities with the worst air pollution in Asia or Southeast Asian countries. According to the previous studies (Rahmawati, 2009; Mungkasa et al., 2018), transportation has the highest contribution to the emission inventory of CO₂ in DKI Jakarta in particular. Most of the study in Indonesia (Nur et al., 2008; Adhi, 2018; PT. Delima, 2012) used the calculation of CO₂ emission by using the total fuel consumption. The age of vehicle has rarely been included as one of the important factors in this calculation of the CO₂ emission. Therefore, the author will use the vehicle age cohort models using the STELLA application. With this model, emission inventory for important air pollutants (based on regulation from the Government of Indonesia: CO, HC, NOx, PM₁₀, CO₂, and SO₂) can be calculated in more detail and prediction of important air pollutants emission in year 2040 after the application of Euro 4. To assess whether the current strategy is effective enough or not and to identify the possible new strategy to enable the local government of DKI Jakarta to reach its goal in CO₂ emission and other key air pollutants reduction, the research objectives are (1) to know the total emissions of key air pollutants from road transportation source in DKI Jakarta from 2007 to 2017; (2) to estimate or predict the total key air pollutants emission from road transportation source in DKI Jakarta in 2040 with the scenarios of business as usual and of implementation of Euro 4 starting March 2019.