The number of diesel vehicles have risen quickly in a metropilitan area ; as a result, vehicle polution has become worse repidly.　However,　Vehicles have made great contributions to the betterment of our lives by transporting people and cargo in cities but at the cost of our environment.　The difficulty in handling vehicle pollution lies in the fact that all citizens and businesses in the Metropolis are both victims and perpetrators of vehicle pollution..　

   Because of the vehicle polution, "Diesel Vehicle Emission Control Regulation" will be enforced in Tokyo, Kanagawa, Saitama, and Chiba from October 1st, 2003.　The regulation applies buses and trucks witch are past seven years after first registration, so any vehicles that do not pass the regulation will not be driven through the metropolitan are, yet vehicles equipped with Desel Particulate Matter Reduction Systems certified by Tokyo Metropolitan Government will be allowed to travel through the motropolis.　The system costs about 300,000 yen through 500,000 yen.　National Tax Agency Japan says that subscription will be categorize as mend expenses.　That means the expense uses as fixed assets so that it dones not need to be depriciated. Diesel vehicles equipped with Diesel Particulate Matter Reduction Systems are able to remove black smoke and other particulate matter. Diesel Particulate Matter Reduction Systems are thus an integral part of a diesel vehicle for it to obtain certification, but no serious attention had been paid to development of the filter system since no PM regulation has been effected in Japan thus far.

   The regulation will start from October 1st, 2003 in Kanagawa, yet it will be a direction period until March 31st, 2004.　After that period,　violation will be　penalty of maximum 500,000 yen.