New Delhi, April 8 -- For the emerging megacities of Asia, the oil crisis that spread out from the Strait of Hormuz is like the acute phase of a chronic condition. The largest migration in human history is filling their streets and alleyways to bursting point.

Urbanization and births will add a billion more people between now and 2050. Jakarta and Dhaka, with 42 million and 37 million people respectively, have overtaken Tokyo at 33 million as the world's biggest metropolises. Delhi, Shanghai, Guangzhou, Manila, Kolkata, Seoul, Karachi, and Bangkok aren't far behind.

Keeping that many people on the move is a challenge at the best of times. When the price of road fuel doubles, it becomes a nightmare.

The good news is that one country has...