Using grey system theory to evaluate transportation effects on air quality trends in Japan

Japan's Air Pollution Control Law signed in 1968 prescribes the maximum permissible limits of motor vehicle exhausts as well as establishing mechanisms for monitoring air pollution In this paper, the grey relational grade of air pollutants from ambient air pollution and roadside air pollution monitoring stations is used to look at the relationship between air pollution and transportation. The results indicated that the ambient and roadside air quality increased by rose from 1975 to 2004 but less fast than the growth in traffic. Some of this may be attributable to the legislation but there have also been other measures since 1968 that have also contributed. (c) 2007 Elsevier Ltd. All rights reserved.