BERLIN (AP) — How best to get cleaner air? Some officials in Germany want residents to leave their polluting cars at home.

German ministers have discussed considering offering free public transportation to get more people to use environmentally friendly mass transit, but their idea has run into opposition by some German cities and towns, who think the plan is too expensive.

The head of the German Association of Towns and Municipalities said Wednesday "the communities and public transportation services cannot pay for that." Gerd Landsberg told the dpa news agency the transportation services needed the income from bus and subway fees to fund and improve their operations.

Several German cities may have to impose driving bans for certain cars later this year because of high levels of air pollution.