In the 1860s, bicycles ridden mostly by foreign businessmen, students and missionaries began plying the streets of China's port cities, eventually spreading to interior cities and provincial capitals. But only after 1949, with the founding of the People's Republic of China, did bicycling see the kind of explosion that made for the popular image of Chinese thoroughfares jammed curb to curb with bikes.
According to bicycle historian Amir Moghaddass Esfehani, China's Communist Party leaders embraced the bicycle industry by merging small manufacturers into national firms, giving the industry preferential allowances of rationed materials and providing subsidies to Chinese workers to purchase bikes.
Cherry, the University of Tennessee engineering professor, said that while traditional bicycles remain part of the transportation mix, Chinese consumers have embraced the e-bike with revolutionary zeal. On recent trips to cities like Shanghai and Beijing, Cherry said, thoroughfares that used to carry a mix pedestrians and bicycles have become "veritable rivers of e-bikes."
'As clean as it gets'?
That transition, experts say, has netted huge benefits for China's urban air quality and has helped rein in greenhouse gas emissions from the country's transportation sector.
Recent research published by Cherry and colleagues in the journal Environmental Science & Technology identified e-bikes as the least-polluting form of motorized transportation in China, with significantly lower emissions of fine particulates (PM 2.5) and greenhouse gases than even conventional electric vehicles (EVs), when accounting for the source of electricity used to charge the cars' larger batteries.
While China's electricity sector is not uniform -- with some regions relying more on hydropower than on fossil fuels -- it remains, on the whole, dominated by coal plants that emit millions of tons of pollutants per year.
According to Cherry's recent study comparing vehicle emissions in 34 Chinese cities, carbon dioxide emissions from both internal combustion vehicles and EVs were an order of magnitude higher than those for e-bikes, which average just 250 watts and can be charged overnight using a standard wall plug. Conventional vehicle emissions came directly from tailpipes, while those associated with EVs come from power plant smokestacks, often located outside cities.
The result, he said, is that some urban areas are experiencing cleaner air conditions because the emissions-free electric vehicles are moving pollutants from city streets to power plants, but that the country's overall pollution budget remains unchanged or even slightly higher due to the additional generation by coal plants.
"Hands down, electric bikes are about as clean as it gets in terms of addressing these primary pollutants," he said.
To be sure, there are some downsides. Critics have noted that 95-plus percent of e-bike motors produced in China today rely on lead-acid batteries, which until recently were discarded as trash when they wore out, according to Benjamin. A gradual shift toward lithium-ion batteries, combined with an aggressive campaign by Chinese government officials to encourage battery recycling, has helped, but concerns about lead pollution persist in some areas.
And in some Chinese cities, where e-bike riders are vying for lane space with cars, traditional bikes and pedestrians, sometimes there are disastrous results. According to Chinese government data, the death toll from accidents involving e-bikes reached more than 3,600 in 2009, compared with 2,500 in 2007.
While some cities -- including Beijing and Shenzhen -- have responded to public safety concerns with e-bike bans, most have been poorly enforced or scrapped after the measures had little effect on e-bike ridership, Benjamin said.