This summary covers an emission program for in-use vehicles implemented in the 1990s. As the targeted vehicle fleet is no longer in circulation, the program has only a historical significance.
In 1992, to cope with NOx pollution problems from existing vehicle fleets in highly populated metropolitan areas, the Ministry of the Environment adopted the “Law Concerning Special Measures to Reduce the Total Amount of Nitrogen Oxides Emitted from Motor Vehicles in Specified Areas”, called in short The Motor Vehicle NOx Law. The regulation designated a total of 196 communities in the Tokyo, Saitama, Kanagawa, Osaka and Hyogo Prefectures as areas with significant air pollution due to nitrogen oxides emitted from motor vehicles. Under the Law, several measures had to be taken to control NOx from in-use vehicles, including enforcing emission standards for specified vehicle categories.
The regulation was amended in June 2001 to tighten the existing NOx requirements and to add PM control provisions. The amended rule was called the “Law Concerning Special Measures to Reduce the Total Amount of Nitrogen Oxides and Particulate Matter Emitted from Motor Vehicles in Specified Areas”, or in short the Automotive NOx and PM Law.
The amended regulation became effective in October 2002.
The NOx and PM Law introduced emission standards for specified categories of in-use highway vehicles including commercial goods (cargo) vehicles such as trucks and vans, buses, and special purpose motor vehicles, irrespective of the fuel type. The regulation also applied to diesel powered passenger cars (but not to gasoline cars).
In-use vehicles in the affected categories had to meet 1997/98 emission standards for the respective new vehicle types (in the case of heavy-duty engines NOx = 4.5 g/kWh, PM = 0.25 g/kWh). In other words, the 1997/98 new vehicle standards were retroactively applied to older vehicles already on the road. Vehicle owners had two methods to comply:
- Replace old vehicles with newer, cleaner models
- Retrofit old vehicles with approved NOx and PM control devices
Vehicles had a grace period, between 9 and 12 years from the initial registration, to comply. The grace period depended on the vehicle type, as follows:
- Light commercial vehicles (GVW ≤ 2500 kg): 8 years
- Heavy commercial vehicles (GVW > 2500 kg): 9 years
- Micro buses (11-29 seats): 10 years
- Large buses (≥ 30 seats): 12 years
- Special vehicles (based on a cargo truck or bus): 10 years
- Diesel passenger cars: 9 years
Furthermore, the regulation allowed to postpone the requirements by an additional 0.5-2.5 years, depending on the age of the vehicle. This delay was introduced in part to harmonize the NOx and PM Law with the Tokyo diesel retrofit program.
The NOx and PM Law was enforced in connection with Japanese vehicle inspection program, where non-complying vehicles cannot undergo the inspection in the designated areas. This enforcement mechanism could trigger an injunction on the vehicle operation under the Road Transport Vehicle Law.