Abstract
Over the course of the past fi ve decades, as the vehicle population around the world has exploded, a great deal has been learned about the implications for the local, regional and global environment. A great deal of effort has been focused on addressing the local and regional problems with some success but continued growth has offset some of these gains. In recent years, global pollution concerns have increased and the motor vehicle contribution has been found to be increasingly important. The thrust of this paper would be a revi ew of the developments to date around the world and a focus on remaining problems such as toxic emissions, global warming and in use emissions performance.