COLUMN ONE - Somehow, some way, subway - Shanghai is on the fast track to build the world's largest rail system. Development is far easier when no one can say 'slow down.'

In 1990, four years after Los Angeles broke ground on its Red Line subway, Shanghai began to build a subway system too.

Los Angeles was one of the richest cities in the world, with an extensive freeway network, top-notch engineers and serious congestion problems. Shanghai was poor, a decaying post-colonial metropolis shaking off decades of economic stagnation. Its streets were congested too -- with bicycles.

Most Los Angeles residents know the story of what happened to the Red Line, which was designed to carry passengers from Downtown to the sea but hasn't quite gotten there. Only recently have planning discussions seriously revived to add a rail line extending farther west.

Shanghai? It is well on its way to building the largest urban rail mass transit system in the world.

You can't walk very far in a straight line in Shanghai these days without coming across construction of a new subway line or station. Already, Shanghai has opened five subway lines and 95 stations serving 2 million people a day, and as many as six more lines are scheduled to open in the next couple of years. Sometime in the next decade, its subway system probably will surpass the world's largest and busiest systems, those in New York, Moscow and Tokyo.

In fact, transit experts say, only one thing short of a cataclysmic disaster could conceivably prevent Shanghai from winding up with the world's largest subway system. That is the very real possibility that another Chinese city -- specifically, Guangzhou, Beijing or Chongqing -- could build an even larger system.

In all, 36 Chinese cities are in the midst of building rail-based public transit systems, said Zhang Jianwei, president of Bombardier China, the Chinese arm of the Canadian company that has supplied rail cars to a number of Chinese cities.

What explains this sudden frenzy of infrastructural one- upmanship? It's simple, experts say.

China's economy is booming. Its people are moving from the countryside into cities as part of the greatest human migration in history. Car ownership is growing explosively. And the government has decided that it needs to do something about congestion before its busiest cities grind to a standstill.

China seems little hindered by the pressures that plague transit projects in the West.