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Easy as Riding an E-Bike

April 9, 2012

Chris Cherry swipes his university ID card to check out a bike at the e-bike station.

By Whitney Heins

He went there not knowing exactly what he was looking for, but when Chris Cherry arrived in Kunming, China, he immediately knew he had found it.

It had two wheels, two pedals, and a battery. It was called an electric bicycle, or e-bike.

An e-bike is a bicycle with an attached motor that kicks in when pedaling gets more difficult for the rider, such as navigating up a hill.

When Cherry visited China in 2001 for graduate school research, he had never laid his eyes on one. Streets were congested with cars, buses, and the occasional bicycle. Flash forward to 2005, and the city was buzzing with them.

“In a span of just four years, electric bikes had gone from zero to being ubiquitous on every street in Kunming,” says the assistant professor of civil and environmental engineering. “I was incredibly curious. I started to investigate what made them go and whether they were good or bad.”

A National Science Foundation (NSF) grant returned Cherry to Kunming in 2005. His mission was to find a research topic for his dissertation at the University of California, Berkeley. He found it. In 2006, Cherry began biannual surveys to investigate why e-bikes had become so popular and how they were affecting China’s transportation system. In 2011, he received a Faculty Early Career Development (CAREER) award from the NSF to continue his research through 2016.

Chris Cherry and one of the environmentally friendly e-bikes now available on campus.

Chris Cherry and one of the environmentally friendly e-bikes now available on campus.

Cherry’s initial survey results in Kunming found 60 percent of e-bike users were public transit users. They were attracted to e-bikes for their speed and convenience. His 2006 research also found one in six e-bike riders were would-be car users. Four years later, that number had grown to nearly one in four.

“That means a quarter of all trips are displaced car trips,” says Cherry. “That makes a lot of difference in energy, congestion, local air pollution, and safety.”

As an environmentally friendly alternative to driving, Cherry immediately saw e-bikes as part of a solution to three related problems in the United States: environmental degradation that impacts public health, quality of life, and economic security; over-reliance on insecure energy; and a health crisis of obesity related to inactivity. Therefore, he wanted to make a difference in the U.S., too.

He decided to launch the nation’s first e-bike sharing system at UT in 2011. It includes two bike sharing stations with ten bikes each—seven e-bikes and three traditional bicycles—and serves as a pilot project to gather information on e-bikes, their impacts, and their users.

“I had a lot of questions I wanted to answer,” Cherry says. “Are e-bikes something someone would adopt? If not, is it an education issue or awareness or technology or pricing issue? Are e-bikes inherently unsafe? Can we make a sharing system work?”

Cherry had the dream. Stacy Worley and Dave Smith in the Department of Biosystems Engineering and Soil Science (and the department’s sensors lab) helped make it a reality. Cherry dreamed of a fully automated sharing station that consisted of an integrated bike rack with a battery-charging kiosk that distributed batteries to those who checked out e-bikes. Users would simply swipe their university ID cards to check out and return bikes to the station when finished. Worley and Smith designed the hardware, software, sensors, and controls, fabricating the entire station in the civil engineering fabrication shop.

Cherry removes a charged battery from the integrated bike rack/battery station built by civil engineering's fabrication shop.

Cherry removes a charged battery from the integrated bike rack/battery station built by civil engineering's fabrication shop.

The first station launched in fall 2011 and is centrally located in Presidential Court. It utilizes power from the grid to charge the batteries. The other station launched in spring 2012 on the Institute of Agriculture campus and is solar-powered. It’s unique because it does not buy power from a utility company. However, if there’s not enough sunlight, it pulls power off the grid. Conversely, if too much energy is stored, it sends energy back to the grid. The researchers also have the ability to completely cut the grid connection and operate independently.

Cherry’s pilot test involved about fifty volunteers who used bikes and e-bikes. His first modus operandi was to see if e-bike sharing was technically feasible. Because he was blazing a trail, there were some technical glitches that had to be ironed out by rewriting software and figuring out finicky sensors.

It quickly became clear that the system does work. Furthermore, by sharing relatively expensive e-bikes, the cost of the technology can be spread out over many users per day, reducing the average investment per trip.

Cherry was also intrigued by user behavior. “One day I was walking into Earth Fare when I saw a student roll up on one of the e-bikes,” he recalls. “What the project figures out is what mode of transportation did that e-bike replace? Was it a bike, car, public transportation, or no trip at all?”

Preliminary results show that e-bike users travel about one-third farther than their counterparts on regular bikes. Trips on both bicycle types range from short trips around campus to longer trips more than a mile away.

GPS monitoring has been implemented to confirm or debunk the hypothesis that e-bikes are inherently unsafe by tracking bike and e-bike user habits like running red lights and stop signs, speeding, and wrong-way riding. Preliminary data shows a variety of user behaviors. E-bike users’ average top speeds are about 20 percent or 2.5 mph faster than regular bike users. Additional statistical analysis will show differences in behavior at red lights and stop signs, as well as other behaviors.

The battery is then slid into place on the e-bike.

The battery is then slid into place on the e-bike.

The system also employs sensors to track its environmental impact. Cherry has found that the entire charging station at Presidential Court only uses ten cents of energy per day.

In a separate study conducted in China, Cherry discovered that e-bikes are the greenest mode of transportation. Using overall emission data and emission rates from literature for five vehicle types—gasoline cars, diesel cars, diesel buses, e-bikes, and e-cars—Cherry and his colleagues calculated the proportion of emissions inhaled by the population and then estimated health impacts. E-bikes were the clear victor.

Interestingly, the research found e-cars—long heralded to be environmentally friendly—actually caused much more overall harmful particulate matter pollution than gasoline cars. This is because the combustion emissions occur where electricity is generated rather than where the vehicle is used. In China, 85 percent of electricity production is from fossil fuels, and about 90 percent of that is from coal. This study caused a firestorm of national media attention and speculation that all e-cars were bad. However, the study’s takeaway is that what matters is where the e-cars are powered and driven. Because China relies mostly on poorly regulated fossil fuels, e-cars emit more fine particles. In the U.S., the power sector is much cleaner, so e-cars are more environmentally friendly.

“Our calculations show that an increase in e-bike usage improves air quality and environmental health by displacing the use of other, more polluting modes of transportation,” Cherry says.

Cherry is also investigating if—and how much—people in the U.S. are willing to pay to use an e-bike. He is experimenting with how to price users effectively—for example, how to charge, how to pay for this, and how to build a business case for something like this. One of the challenges with any shared-vehicle system is managing demand for a finite resource with appropriate price points. That means that the prices might change over the day, depending on how heavily the system is used.

Cherry’s ultimate goal would be to bring something like e-bike sharing to market. But it isn’t about him seeing green—it’s about the earth seeing green.

“If it turns out that e-bikes are a good thing, I would like this thing to spread like wildfire,” says Cherry. “But would I be the CEO? Probably not. My goal is not to strike it rich but to really just see e-bikes improve transportation systems in our cities and campuses and ultimately improve the health of our communities and environment.”

To learn more about UT’s e-bike sharing service, visit the cycleUshare website.