Some types of vehicles may soon face restrictions entering the center of the capital ― 16.7 square kilometers of land within the four ancient gates.
If implemented, the plan will mark Korea's most stringent air pollution measure so far.
The city has tightened its crackdown on old diesel vehicles since early this year. In March, Mayor Park Won-soon vowed to adopt the Global Car Scoring System for checking emissions of vehicles operating in the city.
As home to millions of people and businesses, the city center is one of the major tourist destinations of the capital, drawing many cars and chartered buses.
"The goal is to keep the traffic volume to a minimum," a city official handling the plan said. She said the city wants to block old diesel-powered cars and chartered buses without eco-friendly certification from entering the area.
Also, the city wants to control all vehicles entering the area and strictly punish violators.
More details on how the authorities will do this are yet to come.
"The plan is still in its infant stages. More details will come later. We'll commission a study on the methods we'll use to control the traffic," she said.
Some news outlets reported traffic control will be based on license plate numbers.
To fill the transportation gap in the area, the city will expand bus and bike lanes. The city will also encourage local residents to use more electric vehicles and install more chargers.
The measures reflect Seoul's worsening air pollution. The city-commissioned studies blame air pollution on fine dust and greenhouse gases such as nitrogen and sulfur oxides.
The city views most of the fine dust is coming from China. When pollution comes from within the city, though, vehicles are the major polluters emitting nitrogen and sulfur oxides, motivating local authorities to regulate traffic.
Supporters have extolled the plan as a positive move to keep the air and environment clean, but critics are skeptical about the efficacy of the plan.
Air pollution is a major threat to public health in Korea. On Monday, President Moon Jae-in ordered a temporary halt on eight old coal-fired power plants in an attempt to curb fine dust levels. He added that the halt will be initiated whenever the fine dust levels are high, until the plants are eventually shut down.