In this paper, we measured the potential avoidable emissions in Jakarta city, one of the busiest cities in the world for traffic. We analyzed its impact on the total emissions from passenger gasoline cars. We recorded each designated road to estimate the idling time during travelling and calculated the avoidable emissions of CO, NO, and HC gas from vehicles. We determined that more than 46.0% of the recorded lost travel distance occurred with an average speed <5 km/h. Expanding idling driving to <10 km added a +10.0% contribution to the avoidable emissions. The 46.0% portions contribute to the current emission levels. However, because of the limitations of the work in this field, the last portion is often neglected in past work. In 2040, CO, NO, and HC showed similar tendencies with an emission difference of more than 46.0% or 481.79 thousand tons for CO, 2,275 thousand tons for NO, and 20,472 thousand tons for HC. Idle driving contributes to the emissions in traffic jam conditions in Jakarta city. The increase of avoidable emissions is strongly supported by the high growth rate of vehicles by more than 9.0% every year, which is larger when compared to the annual road growth that only averages 0.01%. We have concluded that avoidable emissions during traffic jams needs to be urgently solved. Eliminating emissions during idling conditions using a technological approach or by conducting idle driving education are two potential ways to reduce avoidable emissions during traffic jams.­­­Â