According to experts, it was yali cha (pressure differential) that toppled a 13-story building in Minhang District on June 27.

Yali cha is quickly catching on as a buzzword.

This refers to the enormous pressure created by a huge pile of excavated earth on one side and the huge void of an excavated multi-level underground parking garage on the other.

The district government is to decide soon if another building in another neighborhood (South City) has sunk due to an underground garage.

Although we are beginning to understand the destructive impact of "pressure differential" in building construction, I observe that the drastic increase in private cars is quickly building up another kind of "pressure differential" that can be no less overwhelming.

For the past six consecutive months, China has been the world's No. 1 auto market, supplanting the United States.

As late as last year, the purchase of a car by a friend is still notable, but today those who still are without cars are likely to be even more remarkable.

During her 10-year university class reunion over the weekend, my wife discovered to her dismay that nearly all her roommates at the university own a car.

One old classmate has two and she let drop that her husband spends an average of 2,000 yuan (US$294) a day.

One month ago my son observed to me that a lot of his kindergarten classmates' families have bought cars.

I drew his attention to the poisonous car emissions, the cost of resources, and so on, but he was certainly well prepared. "If so many people are buying and poisoning the air, why can't we do so too?"

I should thank my lucky stars that my son has not yet learnt to invoke such holy words as "internal demand."

Apparently the truly aspirational thing today is no longer having a car, but having a certain brand of car.

Traffic snarls are a fact of life that commuters are resigned to. But if you hear someone talking animatedly about the morning's traffic congestion in an elevator, the chances are that he or she is really letting you know they own a car.

As a parent I have been tipped off by a number of other parents that they have discovered a fabulous place where their children can enjoy themselves. I have learned to respond to their effusive descriptions with restraint, for these places are likely suburban destinations (read: you need a car to get there).

When such destinations are mentioned on a regular basis, the "pressure differential" is building up.

Cars are not only massacring our own neighborhoods, but they are also closing in on our neighbors like Hangzhou.

A couple of months ago during a weekend escape to Hangzhou, our family of three had to walk several kilometers to catch the train after the auto traffic to and from the West Lake area was paralyzed.

The image of the "heaven on earth" was also tarnished in early May by a fatal traffic accident in which a driver of a speeding car appeared quite indifferent after sending a passerby flying several meters through the air. Indifferent because he had money.

The incident was eclipsed on June 30 by a drunk driving scandal in Nanjing which left five people dead and four injured.

China is taking over as the world's No. 1 auto market, but we should regard this as a dubious honor, not to be regarded with complacency.

When the United States embraced the car culture, its people had before them a virtually virgin continent. There was promise of unlimited space, resources, possibilities, and decades of cheap oil. But Detroit is dying.

We are not starting out with any of North America's advantages.

(Shanghai Daily July 8, 2009)