Automobiles are the linchpin of suburbs, where middle-class families from Chicago to Shanghai tend to make their homes. And that, experts say, is a huge impediment to current efforts to drastically reduce greenhouse gas emissions from tailpipes. Passenger cars are responsible for twelve percent of greenhouse gas emissions in Europe, and up to fifty percent in places in the U.S.

Levittown and Scarsdale, New York suburbs with spread-out homes and private garages, were the dream towns of the 1950s, and still exert a strong appeal. But some new suburbs may well look more like the German town of Vauban, not only in developed contries, but also in the developing world, where emissions from an increasing number of private cars, owned by the burgeoning middle class, are choking cities.

In the U.S, EPA (the Environmental Protection Agency) is promoting car reduced communities, and legislators are starting to act, if cautiously. Many experts expect that the public transport serving suburbs, will play a much lager role in a new six-year federal transportation bill to be approved this year, In previous bills, eighty percent of appropriations have by law, gone to highways, and only twenty percent to other transport.

After days of near-record pollution, Paris enforced a partial driving ban to clear the air of the global city.

On Monday, motorists with even-numbered license plates were ordered to leave their cars at home, or suffer a 22-euro fine (31 dollars). The same would apply to odd-numbered plates the next day.

Almost 4000 drivers were fined, according to Reuters (an international news agency), 27 people had their cars impounded for their reaction to the fine. That's easier to imagine than a car-free Champs-Elysees (a famous street in Paris).

Congestion (car traffic), was down 60 percent in the capital of France after five-days of intensifying smog. the smog riveled Beijing, China, which is known as one of the most polluted cities it the world.

Cold nights and warm days caused the warmer layer of air to trap car emissions. Diesel fuel was blamed, since France has a tax policy that favors diesel over gasoline. Diesels make up 67 percent of vehicles in France, compared to a 53.3 percent average of diesel engines in the rest of Western Europe, according to Reuters.

Paris typically has more smog than other European capitals. Last week, Paris had 147 micrograms of particulate matter (PM) per cubic meter, compared with 114 in Brussels and 79.7 in London, Reuters found.

Delivery companies complained of lost revenue, while exceptions were made for plug-in cars, hybrids, and cars carrying three or more passengers. Public transit was free of charge from Friday-Monday, according to the BBC.

The smog cleared enough Monday for the ruling French party to rescind the ban for odd-numbered plates on Tuesday.