Safety is another challenge in China, with e-bikes zipping down sidewalks, sometimes with multiple riders. Lead-acid batteries are not adequately recycled, creating an environmental problem, and a proliferation of small e-bike makers in China makes crafting effective safety rules a challenge.

Some big automakers are edging into the e-bike business. BMW has presented an e-bike that can fold into the trunk of a car. Although it is still in the prototype stage, 200 will be used during the London Olympics. Audi and Smart are also working on e-bikes.

Manufacturers can get premium prices outside China. Whereas electric bikes cost 1,060 renminbi, or $167, on average in China, according to Pike, they average over $800 in the United States and more than $1,500 in Western Europe. And top-notch bikes can go higher: those at Rocket Electrics are assembled in California (from Chinese-made components) and sell for $1,900 to $2,400 — far more than some varieties sold at places like Walmart .

One factor affecting price is battery type. Many (though not all) electric bikes sold in Europe and the United States have lithium-ion batteries, which are more energy-dense and costlier than the lead-acid type predominant in China. Other factors include the motor’s power and the warranty length.

In Germany, e-bike sales have soared from about 25,000 in 2005 to 300,000 last year, according to Max Grünig, a Berlin-based fellow with the Ecologic Institute. He said that German e-bikes consumed little electricity and were good from a climate perspective — especially, of course, when they replace car trips.

In the Netherlands, the No.2 market in Europe, seniors are an important clientele. Aided by an electric bike, “older people will continue to cycle longer,” said Jeroen Buis, a bicycle consultant who works with the Dutch Cycling Embassy, a public-private networking initiative. Bicycle highways between cities are becoming more popular, he said — for example, a route between Rotterdam and The Hague, about 24 kilometers, or 15 miles, long, is planned. Such paths make it easier for cyclists to travel long distances and go faster, but they can be expensive, and the intersections with roadways require careful design.

One of the toughest markets may be the United States, where people are accustomed to driving even short distances. Still, more than 105,000 e-bikes will be sold in the United States this year, Pike Research projects, with sales more than tripling by 2018. The high price of oil, traffic congestion and an aging baby boomer population may create demand, but Americans must learn that the technology exists.