One billion. By 2020 or sooner, that’s how many cars and light trucks there will be on the road around the world. That’s one for every 6 1/2 people on the planet — and over 25 percent more vehicles than we have today.

So begins a piece in yesterday’s Wall Street Journal, which, I know, you can’t access without a subscription. The story continues a paragraph later, setting up the general premise: What does that one billion figure mean for the future of cars?

The auto boom will only add to the congestion in major cities, as well as deepening the world’s thirst for petroleum and spewing even more carbon dioxide into the air. That will leave drivers facing rising costs and traffic headaches, and force the auto industry to deal with rising demands for fuel efficiency, pollution control and a host of other rules and regulations …

Longer term, the struggle to accommodate one billion autos on the planet may lead to a rethinking of the car’s place in society.

Rethinking the car’s place in society? Not an easy task, for sure. And one that the industry, environmentalists, and others are pondering at this very moment. (And will continue to ponder, to the point that their heads hurt. And then they’ll ponder some more.)

The article goes on to talk about measures already under way: taxes on cars entering city centers during rush hour, fancy-pants traffic lights that sync to traffic patterns, alternative fuels, hybrid development, and even a flying car in the works.

Says one GMer, “the next 10 years will be fascinating.” Indeed.