By Michael Bristow
BBC News, Beijing
Competition between bike makers is becoming fierce
Office worker David Dai is one of a growing army of Beijing residents returning to two-wheeled transport.
But the 28-year-old does not rely on his own pedal power - like hundreds of thousands of others, he has bought an electric bike.
These battery-powered, and virtually silent, machines have become increasingly common on the streets of the Chinese capital.
With roads often clogged with cars - there are now four million vehicles in Beijing - they offer a speedy way to get around.
But not everyone seems to like them: government officials are unsure about how to deal with this explosion of electric bicycles.
China used to be known as the "kingdom of bicycles". In the 1980s, four out of five commuters pedalled to work on them in Beijing.
But as the capital's residents became richer following economic development, they ditched their bikes for four-wheeled transport.
Recent statistics suggest that only one in five city residents now use an ordinary bicycle to travel around.
In a matter of just a few years Beijing has gone from a city with few private cars to one where traffic jams are commonplace.
But many Beijing residents are now buying electric bicycles to avoid wasting time on congested streets.
"It takes only 10 minutes to ride my electric bike from home to work," said Mr Dai.
Hundreds of thousands of people have bought electric bicycles
"If I took the bus, I'd have to spend time waiting for it, and then I could be trapped in a traffic jam. It could take me half an hour to make the same journey."
These bikes are on sale everywhere, with shops sometimes clustered together. Their wares are lined up on the pavement in neat rows.
Zhang Zhiyong, the manager of a store selling a brand of electric bike called "Capital Wind", said it is easy to see why sales are booming.
"Beijing is not like other smaller cities - it's big. If people ride their bicycles to work, they get really tired. If they drive to work, the roads are often congested," he told the BBC.
"But an electric bike is environmentally friendly and convenient. Promoting the use of these bikes would benefit us all."
And they are much cheaper than cars. The most expensive model in Mr Zhang's shop is only 2,680 yuan ($390:£260).
But not everyone is convinced by the shop owner's argument.
Many ordinary bike riders complain that the fast, silent electric bikes that now whizz about the city are a menace to other road users.
Late last year the government announced it was going to issue guidelines on what could be considered an electric bike.
Officials initially planned to bring in rules that defined an electric bike as a something weighing less than 40kg and travelling at less than 20kmh.
A bicycle that was heavier and travelled faster would be considered an electric motorbike.
Bicycles once used to rule the roads in central Beijing
The owners of these larger machines would have to get a licence, register their motorbikes and buy insurance.
But the government scrapped the introduction of the new guidelines after a public outcry.
"There's been a big debate in China about exactly how to deal with electric bikes," said Vance Wagner, who works for a transport research centre linked to China's Ministry of Environmental Protection.
But with the number of electric bicycles increasing all the time, the government might find it hard to put off forever a decision on how to classify them.
"Many people don't realise that the population of electric bikes is actually growing way faster than the population of cars," explained Mr Wagner.
The sale of electric bikes has slightly dropped off recently as people wait to see how the government will tackle the problem of how to define one.
But, ultimately, it is something else that might kill off sales.
Some experts believe they are a stop-gap form of transport; a link between an ordinary bike and a car.
As Beijing car owner Richard Liu put it, cars give a clue to a person's status - the more successful they are, the bigger the car they own.
"I think 80% of Chinese people want to have a car, even if they don't have much money they will buy cheaper ones," he said.
So while they are popular now, electric bicycles might one day prove as unwanted as the pedalled variety.