Four ASEAN countries Indonesia, Malaysia, the Philippines and Thailand are facing major air pollution problems due to rapid economic growth, urbanization and motorization. Mortality and respiratory diseases caused by air pollution are believed to be endemic in cities of these countries. Regulations and standards are the first requirement for reducing emissions from both fixed and mobile sources. In order to reduce vehicle emissions, governments of the four countries are making efforts to introduce vehicle emission regulations for new vehicles.
This paper attempts to estimate the 2015 car stock by emission regulation levels from past trends. Considering these car stock results, this paper emphasizes monitoring problems such as vehicle registration systems, inspection and maintenance (I/M) systems and fuel quality monitoring systems for vehicles in use. Monitoring problems in developing countries share similar characteristics such as a weakness in government initiatives and inadequate operation of government agencies, which results from a lack of human resources and analysis of facilities. Finally, this paper proposes a method to assure air quality improvement under the different shares of emission regulations in these four ASEAN countries and introduces an example of an evaluation method based on a policy survey to improve air quality.

JEL Classification: N75, Q53, Q56, R41, R48