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Emission Standards


Regulatory Authorities

Japanese emission standards for engines and vehicles and fuel efficiency targets are jointly developed by a number of government agencies, including:

In developing engine emission standards and policies, the Ministry of the Environment relies on recommendations of its advisory body known as the Central Environment Council (CEC).

Engine and vehicle emission standards are developed under the authority of the “Air Pollution Control Law”, while fuel efficiency targets are adopted under the “Law Concerning the Rational Use of Energy” (Energy Conservation Law).

New Engine and Vehicle Regulations

On-Road Engines and Vehicles

Japan introduced fist new engine emissions standards for onroad light-duty vehicles and heavy-duty engines in the late 1980’s. The Japanese standards, however, remained relaxed through the 1990’s.

In 2003 the MOE finalized very stringent 2005 emission standards for both light and heavy vehicles. At the time they came to power, the 2005 heavy-duty emission standards (NOx = 2 g/kWh, PM = 0.027 g/kWh) were the most stringent diesel emission regulation in the world. Effective 2009, these limits were further tightened to a level in-between the US 2010 and Euro V requirements, and the 2016 limits are comparable in stringency to the US 2010 and Euro VI standards.

Japanese emission standards are occasionally referred to by the English translation of the regulation title. These regulations and their phase-in period are as follows:

  • Long-term regulations (1997, 1998, 1999)
  • New short-term regulations (2003, 2004)
  • New long-term regulations (2005)
  • Post-new long-term regulations (2009, 2010)
  • Future regulations (2016, 2017, 2018)

Most categories of onroad vehicles, including passenger cars and heavy-duty trucks and buses, are also subject to mandatory fuel efficiency targets. The Japanese fuel efficiency requirements for heavy trucks and buses were the world’s first fuel economy regulation for heavy vehicles.

Nonroad Engines

First emission regulations for new off-road engines and vehicles, known as MOT/MOC standards, were adopted by the former Ministry of Transport (MOT) and Ministry of Construction (MOC).

After the reorganization of Japanese government in 2001, nonroad engine emissions fell under the jurisdiction of MOE and MLIT, the same ministries that are responsible for regulating emissions from highway engines. First MOE/MLIT standards for nonroad engines were promulgated in 2005.

Marine Engines

In 2003, the MLIT proposed emission regulations for new and existing ocean-going ships. The regulations, aligned with the 1997 MARPOL 73/78 Annex VI limits (by International Maritime Organization), require cutting NOx emissions by about 10% from previous non-regulated levels.

In-Use Vehicle Regulations

Two emission programs were implemented in the 1990s and in early 2000s to reduce emissions from in-use diesel vehicles: the Automotive NOx and PM Law and the Tokyo retrofit program. As the vehicle population targeted by these programs is no longer in circulation, the regulations have only historical significance.

  • Automotive NOx and PM Law—In 1992, to cope with NOx pollution from existing vehicle fleets the MOE adopted the Motor Vehicle NOx Law, which aimed at the elimination of the oldest, most polluting vehicles from in-use fleets in certain geographical areas. In 2001, the regulation was amended to also include PM emission requirements, and renamed as Automotive NOx and PM Law.
  • Tokyo Retrofit Program—The Tokyo government and several neighboring prefectures adopted diesel emission regulations, which required retrofitting of older in-use diesel vehicles with PM control devices (catalytic converters or particulate filters), or else replacing them with newer, cleaner models. The Tokyo retrofit requirements became effective in October 2003.