Modern cities are having an increasingly difficult time controlling the amount of pollution that their citizens are exposed to.

Noise pollution, contaminated drinking water, and fumes from buses and cars all have a negative impact on the quality of life of most urban dwellers.

While improving access to public transportation has made some progress in convincing people to leave their cars at home, particularly when traveling to the downtown core of a city, in some cases more extreme measures are being contemplated.

One proposal that is increasingly being batted about in European and Japanese cities is the concept of banning high-emissions vehicles from city driving.

While this might seem like an egregious affront to personal liberties, for others, it’s a simple matter of health and ecology.

Many cities around the world already keep large diesel powered trucks and transport vehicles, (with the exception of buses) out of downtown areas, and it seems like a short leap from that type of policy to one which would extend to other diesel vehicles like pickup trucks and light delivery vans.

In fact, three cities in Germany have recently acted to do exactly this. The only vehicles which are allowed to access specific zones in Berlin, Cologne and Hanover are those which have a special sticker indicating that they conform to new, stricter pollution standards.

There are also countries like Japan which in 2003 tightened the emissions standards across their entire country, and as a result, many aging diesel vehicles were effectively removed from the road and either crushed or exported abroad.

This was in line with similar Japanese initiatives which penalized owners of older vehicles with higher registration fees in an effort to force drivers to purchase newer, more efficient cars and trucks.

Of course, there are practical limits as to what can be banned and from where. The entire worldwide economy is dependent on deliveries carried out by large diesel trucks, and if these vehicles are no longer able to serve certain markets, or certain parts of a city, chances are that it will be difficult for businesses to flourish in these areas.

Perhaps the solution is to make exceptions for certain types of vehicle ownership, or to allow transport companies to pay for carbon credits or other environmental initiatives in order to offset the emissions from their activities.

Regardless of the proposed solution, it will certainly be complicated in terms of deciding when personal freedom stops and the collective environmental good begins.