An Overview of Vehicular Emission Standards

In India, the ambient air quality has been degrading from past few decades especially in urban areas. Vehicular emissions are amongst one of the major reasons for the deterioration of ambient air quality in such areas. This article is an effort to review the vehicular emission standards of the major countries (USA, Europe, Japan and Australia) and compare with Indian emission standards. However, there exists several differences in present emission standards followed by different countries. For instance, emission standards in USA are fuel neutral, while no separate weight categorization exists among light-duty vehicles (LDVs). In Europe, Japan, Australia and India, separate weight categorization and emission limits for both petrol and diesel vehicles are provided. It was observed that different driving test cycles used by different countries are the reasons for numerical differences in vehicular emission standards. To rectify this, a worldwide harmonized test cycle (WHTC) is introduced by United Nations Economic Committee for Europe (UNECE) that would represent real-world driving and verifies that the statutory emission limits are not exceeded during actual driving. Countries like Japan and Europe have already been following the WHTC, while some other countries may introduce the same in near future. Yet the real-world emissions across the world keeps on diverging. In such situation, harmonization of vehicle emission standards worldwide is a bit challenging, based on dynamics of road conditions, driving patterns, environmental conditions, etc. Thus, more concerted research is needed for evolution of a common universal emission standards implementable worldwide so that the uniformity in information and policies available to the common public could be maintained.