Transportation have a greatest impact on air pollution due to their dominant role in the fuel
consumption and the number of vehicles are continued increase day by day, especially in the
Phnom Penh . Phnom Penh is the Capital City with highest population in the country . The
more population the more transportation means and fuel used; therefore, air pollution can be
concentrated in Phnom Penh is, of course, can not be avoided as most of vehicles and
motorcycles are second hand imported. At present, there is a concern with the rapidly
increasing number of vehicles and motorcycles in the city and the frequently traffic jam. In this
concentration, second hand vehicles and motorcycles generally produce more pollutants than the
new one.