Sri Lanka, July 30 -- The narrow streets of Kathmandu - sized for pedestrians and rickshaws - are choked with engines. Buses, motorbikes, small trucks and taxis fill the sprawling valley with horns and exhaust. For its more than three million residents, just getting around is a dangerous, eye-stinging ordeal.

But recently, a new kind of motor has started to ease the crush. Sleek electric vehicles glide by with a quiet hum. Gleaming showrooms do a brisk business in the latest models, and charging stations on the highways have turned into rest stops with cafes for drivers to pass the time.

The transition is moving quickly. Over the past year, electric vehicles accounted for 76 percent of all passenger vehicles and half of the light commer...