The project aims to safeguard 10 million Seoul citizens from harmful air pollutants and ensure clean living conditions for them. To this end, Seoul has launched the In-use Diesel Vehicle Emissions Reduction Project which includes measures such as requiring emissions control devices on in-use diesel vehicles, retrofitting LPG engine cars, and encouraging early car scrapping.
 

Launched with the passage of the Special Act of Seoul Metropolitan Air Quality Improvement, the In-use Diesel Vehicle Emissions Reduction Project was initiated in 2013 with a pilot run to retrofit LPG engines of the 135 public garbage trucks of 2.5 tons used for public purposes. In the following year, another pilot project was introduced to attach emissions control devices on 880 public cars. With the passage of the Special Act of Seoul Metropolitan Air Quality Improvement initiated by the central government, the Seoul Metropolitan Government is now making more active moves towards the emissions reductions initiative.

In accordance with the Special Act and relevant city ordinances, Seoul is implementing various support systems to cars that fall in the following categories.
- Diesel cars whose warranty expired (2 years for over 3.5-ton truck, 5 years for less than 3.5-ton truck), and
-Total weight over 2.5 tons and over 7 years of vehicle age

Subsidies
Installation of a certified emission control devices has been required since the beginning of 2008. To reduce financial burden on citizens, the SMG is providing up to 90-95% of the installation costs. For qualified individuals who choose to scrap their pollutant-emitting vehicles, it is financing 90% of the financial value of the car set by Korea Insurance Development Institute.
 
Other Incentives
Seoul provides several incentives to those who partake in the project. Participating individuals are exempt from environment improvement charges as well as emissions inspection for the first 3 years. From 2008, however, those who install DOC, a device known to have little pollutant reduction efficiency, can no longer be exempt from paying the environment improvement charge.
 
Minimizing Ultrafine Particles (PM-2.5)
Nitrogen Oxides (NOx) that can be found in both fine dust (PM-10) and ultrafine particles (PM-2.5) directly affect health of human beings. To reduce NOx, Seoul is running a pilot project which aims to install devices that are associated with both NOx and PM emissions control on 797 vehicles, including dilapidated construction machinery and large trucks. Main features of the project include:
• Changing three-way catalyst converters (TWC) on LPG taxies (527 units)
• Installing PM-NOx dual control devices on large diesel buses (106 units)
• Changing engines of old garbage trucks and construction machinery (143 units)
 
Follow-up Measures
To maintain high performance of emissions control devices, continuous monitoring and follow-up measures should follow. In this context, Seoul applies a thorough monitoring scheme to measure the performance of already installed devices. Corrective measures are in place in case a malfunction is identified. In other cases where a device is destroyed to the extent it cannot deliver desired performance, the city government offers refurbished replacements for free. Furthermore, free filter cleaning service is offered for the first 3 years after the installation for cars with DPF that have traveled more than 100,000km or the ones have passed 10 months after filter cleaning. Cars with retrofitted LPG engines are also entitled to free check-up services.

Participation of 300,000 Diesel Vehicles
From the inception of the project in 2003 to the end of 2014, a total of 276,055 vehicles have successfully participated in the project, including 93,480 vehicles with DPF installed, 68,203 with retrofitted LPG engines, 53,054 with DOC installed, and 63,006 undergone early scrapping.
 
Reduction in Fine Dust Levels
Although the In-use Diesel Vehicle Emissions Reduction Project requires an extended period of time for a more accurate evaluation, results so far show that fine dust pollution has been gradually mitigated. The number of days of dust content over 100㎍/m3 decreased whereas the number of days with low concentration (over 30㎍/m3) increased.
 
Nitrogen Oxides (NOx) Reduction Project in Full Swing
The NOx reduction pilot project has delivered a 70% reduction in NOx in 2013. Based on the proven effectiveness, Seoul expanded the scope of the pilot project into full swing to install such devices on an additional 324 vehicles in 2014 and on 240,000 (including old construction machinery) by 2018.
 
Project Evaluation and Future Objectives
A comprehensive evaluation of the diesel car emissions reduction project reveals that although a measureable success was achieved in curbing fine dust (PM) concentrations in the air, it has not yet reached the level of advanced nations in the environment area. To give a further boost to the air quality improvement project, Seoul continued to apply the measures to additional 15,000 diesel vehicles in 2014. Seoul’s target is to reach 390,000 diesel cars that would be subject to some form of emissions control measures from 2003 to 2018.