Archive for the ‘e-bikes’ Category

highlights from BAQ2008 – Chris Cherry and e-bikes

Friday, November 28th, 2008

Electric bikes (e-bikes) may not be on the tip of the sustainable transportation community’s tongue yet, but I think they should be, and in this post I’ll explain why.

Dr. Chris Cherry of UT Knoxville is a (the?) leading international expert on e-bike development in China. His BAQ2008 presentation, “Environmental Impacts of E-bikes in China (and Beyond),” did an excellent job framing the e-bike discussion and current status.

First, take a look at this graph of recent e-bike production in China:

Cherry e-bike production

2007 e-bike production in China was over 20 million units, two and a half times more than motor vehicles. Anyone who has traveled regularly to China recently can attest to the reality that e-bikes are proliferating like crazy in Chinese cities. The sheer magnitude of these numbers (and the rapid rate of increase) demands that we investigate the energy, environmental, and social impacts of e-bikes.

Regarding the energy and environmental impacts, here is an incredible table Dr. Cherry developed on per passenger-km emission factors of various different transportation modes in China:

Cherry ebikes impact

The values in the table are colored by impact. As expected, of the modes compared here, bicycling is the only one that receives “greens” across the board, while cars and motorcycles are generally “red” for highest impact. E-bikes, on the other hand, are competitive with buses for environmental impact for most pollutants except lead. (The extremely high lead emissions result from the e-bike batteries, which are comparable to car batteries; this makes it absolutely critical that lead pollution from increased e-bike production and use be controlled with lead acid battery production management and recycling programs.)


In my opinion, e-bikes should be given high priority as an urban sustainable transportation solution. E-bikes provide much greater urban mobility than buses, with comparable environmental impact, but result in significantly less air pollution and greenhouse gas emissions than cars or motorcycles.

However, e-bike development (and modal shift) should be carefully managed and understood. Direct modal shift from bikes to e-bikes clearly results in a net negative environmental impact, while the net environmental impact of modal shift from buses to e-bikes is unclear. Exploring this question, another slide of Dr. Cherry’s presentation shows the results of mode choice surveying in Kunming:

Cherry ebike modal shift

The fact that most respondents chose an e-bike over a bus or standard bicycle may indicate that the e-bike proliferation has had a net negative environmental impact in Kunming.

That having been said, though, the primary, future environmental challenge in the transportation sector in China is controlling the impacts of a rapidly motorizing population. Therefore, the proliferation of e-bikes should be considered both in the context of current modal shift (e.g. what transportation mode would you choose today if not an e-bike) as well as the context of future behavior and mode choice. For example:

- How has the use of an e-bike transformed a customer’s perceptions of the future need and use of a motorized vehicle?
- Has the owning of an e-bike delayed the inevitable purchase of a private car?
- Even if a car is purchased, what trips are the e-bikes still used for?

Most of all, whether you are for or against e-bikes, due to the massive growth in their production, at least two things are clear:

1) There is much more research to be done (modal share, lead pollution, safety, impact on regular bikes);
2) It is time for the sustainable transportation community to expand greatly the discussion of e-bikes and their impacts. (I told Dr. Cherry after his talk that at BAQ2010 there should be a whole panel on e-bikes, not just one presentation!)