The Atmospheric Group Automotive Pollution Specialist Committee, a body affiliated with the Central Council for Environmental Pollution Control, submitted an interim report entitled "Long-Term Policy on Automotive Emissions Permissible Limits" in August 1972, calling for the immediate establishment and implementation of automotive emissions controls. In addition, the following numerical targets for automotive emissions permissible limits in the Japanese government's fiscal years of 1975 and 1976 (ended in March 1976 and 1977, respectfully) were set based on the Muskie Act (the Clean Air Act Extension of 1970):

Target for permissible limits in fiscal 1975

1. 1.CO emissions: 2.1 grams per kilometer
2. 2.HC emissions (excluding emissions released as steam and blow-by gas): 0.25 grams per kilometer
3. 3.NOx emissions: 1.2 grams

The NOx target for permissible emissions limits was 0.25 grams per kilometer for fiscal 1976.

In October 1972, the Environment Agency announced a policy based on the interim report, and from May 1973 the agency summoned nine automakers to testify at hearings on the current status of emissions controls and future systems for technology development.

At the hearings, Toyota stated that it had overcome the technical issues related to the fiscal 1975 regulations by installing supplementary control components on catalytic converters and that it was building a new plant to produce the catalytic converters, but requested phased implementation of the emissions regulations because the time to test practical use had not been adequate and quality assurance issues remained unresolved.

Concerning emissions regulations, Toyota expressed the straightforward opinion that it was necessary to distinguish between achieving targets in the test lab and achieving targets with commercial products and that adequate preparation time was needed for a commercial launch.

But the Environment Agency decided to implement the regulations for fiscal 1975 as specified in the interim report. In addition to the already in place 10-mode test cycle1, the agency adopted an 11-mode test cycle2 as a measurement method and decided detailed specifications including permissible limits and implementation timing by vehicle type. The regulations for fiscal 1975 were announced in January 1974. In response, the Ministry of Transport (now the Ministry of Land, Infrastructure, Transport and Tourism) promulgated the regulations the same month. Implementation of the Muskie Act in the United States was delayed3, and as a result, Japan's emissions regulations became the strictest in the world.