What about forbidding old cars travel to reduce air pollution?

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In Lombardy, a region of Northern Italy, the regional government decided to forbid cars sold before 1993 to travel on Lombard roads. The claimed reason is to reduce air pollution. But hints show it would be useless: - air pollution levels never reduced during the experimental stops of all the traffic in Milan that occurred in some weekends in the last years - the only matter that sometimes exceeds the limits is PM10, and only diesel vehicles expel PM10, but this law stops gasoline cars and bikes too - in Italy 65% of new sold cars is diesel and most old cars use gasoline; that means PM10 will grow up Moreover, I think this law is wrong because: - a law cannot force citizen to buy a new car - it's poor people who still drive old cars - ancient cars will disappear - now they stop 14 years old cars, but tomorrow they could stop 10, then 8, or 6 years old cars, forcing people to often change their cars. To all the Italians, and to all the people who plan to come to Italy by car, there is a petition against this law: http://www.petitiononline.com/mod_perl/signed.cgi?Euro10 What do you think about such a law? Is there something like that in your country?