On a sunny but brisk spring morning near the Charles River in Cambridge, I took a test ride on the bicycle of the future. No rockets or lasers (alas), the bicycle of the future looks pretty much like the bicycle of the present. But with the first pumps of my feet on the pedals, I felt the difference.

The bike wasn't just moving, it was pushing, adding extra propulsion to my own pedaling, giving me a boost with every revolution of the pedals. Faster than expected, I reached the end of a quiet block leaning into a corner. I took a straightaway for a few blocks and pushed 20 miles an hour without hardly trying. My feet were putting out a solid paper-route effort, but the bike had me racing in the Tour de France.

The bike I tested was equipped with the Copenhagen Wheel, an electric pedal-assist motor fully contained in the oversized red hub of an otherwise normal back bicycle wheel. Inside that red hub is a delicately crammed array of computing equipment, sensors, and a three-phase brushless direct current electric motor that can feel the torque of my pedaling and add appropriately scaled assistance.

Replace the back wheel of any bike with the Copenhagen Wheel and it's instantly an electric bike—one that not only assists the rider but senses the surrounding topography and can even collect and share data about environmental, traffic, and road conditions.

First developed in 2009, through a partnership between MIT's Senseable City Lab and the City of Copenhagen, the wheel is now in its first stages of commercial production. By the end of 2014, thousands will be shipped out to fulfill pre-orders around the world.

With its focus on design and simple application of complex technology, the Copenhagen Wheel is perhaps the sleekest version of the electric bike. But it's hardly the only one.

Millions of electric bicycles are being used in cities all over the world, offering cheap and accessible forms of transportation in developing countries and dense urban environments. And though bicycling has long been considered recreation in the United States, the electric bicycle is about to become the next big thing in urban transportation.

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The electric bicycle is a relatively new idea. In its basic form, it's a battery-powered motorized bike operated either by a manual throttle on the handle bars or by an automatic system that adds power when pedaling. About 20 years ago manufacturers began to offer these lighter and cheaper alternatives to mopeds and motor scooters.

Frank Jamerson has been watching the market evolve since the beginning. An engineer who helped build the first nuclear submarines at Westinghouse and who later helped run the EV-1 electric vehicle program for General Motors, Jamerson started publishing the Electric Bikes World Report, a bi-annual profile of the global market for electric bikes, in 1995. Then, as now, China led the way, according to report co-author and chairman of the Light Electric Vehicle Association, Ed Benjamin.

China was an early adopter of electric bikes and still leads the world in sales, with 32 million in 2013. 2 dogs / Flickr Benjamin and Jamerson estimate that 32 million electric bikes were sold in China in 2013, though they note that the Chinese bikes are often low-quality, costing a few hundred dollars on average and only lasting for a year or two before breaking down.

In Europe, the next biggest market, where most of the electric bikes are higher quality and sell for upwards of $3,000, Jamerson and Benjamin estimate about 1.4 million sales in 2014. Japan and India are other major markets, with sales in the hundreds of thousands.

In the United States, the numbers are smaller but growing. From July 2011 to June 2012, American consumers bought about 100,000 electric bikes, according to Jamerson's estimates. The next year, sales reached 185,000. By 2016, as more manufacturers and retailers get into the electric bike market, Jamerson expects annual sales above 400,000. Within 20 years, he thinks the number could be as high as 2 million, and that the United States will be one of the top markets for electric bicycles in the world.

"We've got an ever-expanding population in the world that's moving more and more to denser and denser cities. Those cities require transportation solutions much more like a bicycle or an electric bicycle," says Benjamin. "The fact that the United States is transitioning a little bit slower than the rest of the world, I don’t see that as important. It's going to happen. It is happening. It will continue to happen."

There's certainly no shortage of manufacturers. There are nearly a hundred brands of electric bikes currently on the market. From Chinese manufacturers building millions of electric bikes a year to small garage-based startups, the supply side of electric bikes has developed rapidly over the past 20 years. And though Chinese manufacturers like Geoby are leading the global market, much of the U.S. market is led by three American companies: Pedego, Prodecotech, and Currie Technologies.

Currie, based in Simi Valley, California, has been building electric bikes since 1997. The company now offers more than two dozen different types of electric bikes, ranging from beach cruisers to mountain bikes, as well as a variety of conversion kits. Currie president Larry Pizzi concedes that the U.S. market has been slower to develop, but he's also seen strong recent growth in sales.

Without offering specific figures, he says sales were up 25 percent from 2011 to 2012, and another 25 percent from 2012 to 2013. And the trend is continuing upwards, with Pizzi saying business with dealers "more than doubled" through the first quarter of 2014.

But retailers have been slow to adopt electrics as a viable product—especially in the United States. Pizzi says retailers have been hesitant because electric bikes are "counter-intuitive" to what they think their customers want. "It's a passionate industry in North America, and it focuses on the enthusiast core," he says. Think weekend century rides and skin-tight outfits. "That's all well and good. But they're not thinking about bikes for transportation."

The shift is happening, although slowly. Jamerson says that of the roughly 4,000 bicycle-specific retailers in the United States, about 900 sell electric bikes today. And some of the world's biggest vehicle manufacturers and technology companies have plans to enter the U.S. market, too.

Smart recently began selling pedal-assist electric bicycles in its U.S. car dealerships, as did Ford. The German engineering and electronics company Bosch has made major investments in electric bike drive units, which are now used by more than 60 different brands. Industry insiders say General Motors will likely be entering this market soon as well.

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The bike of the future I rode in Cambridge, equipped with the Copenhagen Wheel, also had an iPhone mounted on the handle bars. I swiped my finger across it to switch from Turbo mode to Regular, bringing my top speed down to about 15 miles per hour, according to the phone's display. I pedaled normally, but didn't exert myself.

When I stopped pedaling the motor stopped, too, and I coasted, which also recharged the battery. Once I started pedaling again the motor almost instantly kicked back in, boosting me forward with a subtle but noticeable push of extra power.

Cyclists using the Copenhagen Wheel can change speeds by swiping a smartphone fixed to the handlebars. Courtesy of Superpedestrian

After riding around for a while, I took this prototype bike back to the offices of Superpedestrian, the company that's been developing the commercial version of the Copenhagen Wheel. In a small conference room, whiteboards and white walls were covered in drawings of gizmo components and schematic printouts. Next to a hand-drawn sketch of the wheel's internal parts somebody's scribbled the words "puzzle building."

Assaf Biderman, founder of Superpedestrian and associate director of the Senseable City Lab, from which he spun off the company, explained how the original idea for the Copenhagen Wheel emerged. It sprouted in a class of about 10 students working on ideas related to a partnership with Copenhagen meant to develop urban solutions. Even with Denmark's already high rate of cycling, the city was looking for ways to get more people on bikes by understanding what was holding some of them back. The major factor was distance.

"We decided instead of thinking about the whole bike, let's think about where the crux of the matter here is, which is motorizing it and giving people access," says Biderman.

They finished a prototype of the electric-assist wheel in time to unveil it at COP 15, the United Nations Climate Change Conference held in Copenhagen in 2009. Mayors and government officials from around the world took it for a test ride. "The goal was to send world leaders home with a message that almost any city in the world could become as cycling-friendly as Copenhagen," says Biderman.

Back at MIT, the Senseable City Lab continued to develop the wheel, and Biderman licensed the idea from the university in late 2012. He quietly opened the Superpedestrian office in Cambridge and stocked it with engineers and roboticists who'd previously built vehicles like UAVs and the Segway. In December 2013, they began accepting pre-orders, with the wheel priced at $699. (It's now selling for $799.)

One of the main principles guiding the design of the Copenhagen Wheel was that it should be incredibly simple. "The bike should stay a bike," says Biderman. Ease of use is certainly part of the appeal. Once installed, the wheel is operated by a smartphone app via Bluetooth. The wheel unlocks itself when the user's phone is close by, and the app includes several speed-assist settings from Turbo to Flatten My City, which uses sensors in the hub to detect hills.

The wheel imitates the rider, integrating its own propulsion seamlessly as the rider pedals: pedal more, get more power; pedal less, get less. Braking and coasting recharges the lithium ion battery, which holds about 30 miles of range. To facilitate global use, the Copenhagen Wheel's specifications can be altered to comply with local cycling regulations for wherever it's sent.

From the user perspective, the wheel is simple. But inside it's literally a robot computer. Many sensors and control algorithms are working constantly to understand the motion of the bike, its position in space, the torque of the rider, and the additional torque it must use to achieve the desired speed. Superpedestrian has also created an open API, enabling developers to make their own modifications to the app and its interactions with the wheel. Of the pre-order group, about 20 percent of buyers self-identified as programmers and have volunteered to provide feedback on how their hacks work with the first iteration of the wheel.

The Copenhagen Wheel (above, in red) can turn any bike into an electric bike. Superpedestrian / Michael D Spencer Initially the design included a number of other environmental sensors and sharing capabilities that would turn the wheel itself into a sort of roving urban sensing unit.

Ideas included CO2 and noise sensors, and an option to collect road condition and traffic data that could be sent to a database for the city's use in addressing dangerous streets or adding bicycle infrastructure where ridership is high. For now, that's been set aside to get the first version finished at an affordable price; more sensors cost more money, after all.

Biderman says some of that may come later, but it all depends on how people want to use the wheel. Ultimately, he expects to see some ways of collecting and sharing data widely (and anonymously), from neighborhood cycling communities to City Hall.

"I think there's a very exciting future for planners and local governments when it comes to being able to address demand in a quantitative way and a rigorous way based on real usage," he says.

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Americans have a mental block about bicycling that's mentioned again and again by industry insiders: While people in places like Europe think of the bicycle as transportation, people in the United States largely still think of it as recreation.

There's a long history of urban development patterns and transportation policies that have led to this perception, and those tendencies are hard to break. Though there does seem to be a general uptick in cycling in pockets of the country, the reality is that most U.S. transportation happens in a car. If the electric bike is to be successful here, it will have to overcome the national perception of bicycles as playtoys.

Transitioning the bicycle from recreation to transportation could hinge on something as simple as a sweaty armpit. "For 30 years, I've seen surveys about why people don't ride," says Andy Clarke, president of the League of American Bicyclists. "They don’t ride because it's too far or because they get hot and sweaty. And these are things that electric-assist bikes can help overcome."

A recent survey of U.S. electric bike owners suggests some progress on the problem of the stinky commute. John MacArthur of Portland State University found that 74 percent of 553 respondents said they don't need to shower after the end of the average trip on their electric bike. But sweat, or lack thereof, isn't the only thing pushing people onto electric bikes. According to MacArthur's survey, almost 70 percent of respondents said they purchased their electric bikes to replace some of their car trips.

MacArthur notes that while his survey wasn't the most scientific, it did reveal some interesting demographics about who is using electric bicycles. About 45 percent of respondents were 55 or older, and about 30 percent indicated that they had a physical condition that made riding a standard bike difficult. He argues that these should be indications to retailers that the market for electric bicycles isn't just hip Millennials; older people are interested, too.

"I think the survey alludes to the potential that electric bikes really can get more people biking and to bike more often," says MacArthur.

The international nature of the electric bicycle market has posed some problems, too. Different countries have different standards for how fast and powerful electric bicycles can be. For example, electric bike motors in the European Union can be only 250 watts, while they can be up to 750 watts in the United States. China allows a top speed of about 12 miles per hour; the EU, about 15 miles per hour; the United States and Canada, 20 miles per hour.

Assaf Biderman, founder of Superpedestrian, says the goal of electric wheel-assist design was to make almost any city "as cycling-friendly as Copenhagen." Dylan Passmore / Flickr Much of the confusion has to do with what, exactly, counts as an electric bike. Some places consider electric bikes and mopeds with internal combustion engines to be essentially the same thing, while others draw strong lines between them. Some places require helmets or registrations, while others don't.

The United States, for its part, has at least come up with a standard definition (put forth in H.R. 727, an amendment to the Consumer Product Safety Act that became law in 2002). Even with federal guidance, confusion remains. State and local regulations of electric bicycles vary widely across the country, especially with regard to whether they belong in roads or bike lanes (or both).

"Some municipalities and states are more equating electric bikes with the bicycle, and others are more equating them with a moped or motorized cycle," says MacArthur. The inconsistency has led to some places restricting electric bikes from using bike lanes.

Clearing up the regulations will take time, and it may take more electric bikes on city streets. Though numbers are rising, the main challenge for electric bike makers and evangelists is to make them mainstream. Convincing the U.S. market to consider electric bikes as transportation will be key, according to Benjamin and Jamerson, the industry trackers. A big way to open the market will be to make them more affordable. Even more important will be to make them cool.

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Superpedestrian has done the first run of production in the workshop of their Cambridge office, and are working on industrializing the process for factory production by the thousands later this year. The project is venture-backed, and Superpedestrian has inked deals with a few undisclosed major international companies to get even more of the bikes on the road.

The design and idea behind the Copenhagen Wheel has even inspired some competition. A very similar back wheel pedal-assist add-on called FlyKly raised $701,239 on Kickstarter in November 2013, and the company expects to ship its first wheels in the fall.

Benjamin, who works as an adviser to many electric bike manufacturers, says he's happy to see these new players get into the electric bike market. They're worlds away from the low-quality lead acid battery bikes he saw in China in the mid-'90s, and he thinks that these newer, sleeker, simpler electric bikes could finally help transition the U.S. bike market to start thinking seriously about going electric. The Copenhagen Wheel is leading the way, he says.

"The Superpedestrian wheel is so far in the lead in terms of the engineering and coming to market that they are probably going to define the market entirely," says Benjamin. "I'd say that on my list of customers that are going to hit a home run, that one's at the top."

But changing perceptions takes time. Jamerson, who's been watching the electric bike market since it first emerged, says electric bike makers will have to do all they can to take advantage of America's cycling momentum. He even suggests one of the oldest tricks in the marketing playbook: the celebrity endorsement. "We have not had enough pictures of celebrities riding electric bikes," he says.

He's got some ideas. He says that a few years ago, during a reception with then-Energy Secretary Steven Chu, a Chinese delegation gave electric bicycles to Chu and Barack Obama as gifts. If someone could get Obama to ride his electric bike, says Jamerson, that could really get them into the hearts and minds of the American public. "If you know anybody in the White House," he says, "tell them there's an electric bike somewhere in storage that they ought to pull out."