The Science of Car Sharing: Can Shared Vehicle Services Reduce Transportation Emissions?

, senior policy analyst, Clean Vehicles | September 2, 2016, 11:01 am EST
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I’m a fan of car sharing services like Zipcar and car2go. Both offer instant access to vehicles that are scattered throughout my city, and car2go offers the unique benefit of being able to drop a vehicle off at any parking spot, even one with a meter. Using these services is super easy—but from my vantage point as someone concerned about emissions from transportation, they’re almost too easy.

I’ve frequently grabbed a car2go instead of using public transit, my bicycle, or my feet, and consequently burned more oil and created more emissions because I had access to an on-demand vehicle. Given that there are over a million car sharing subscribers, the rise of car sharing services raises the question of whether they are creating more emissions by increasing the number of vehicle trips and vehicle miles travelled (VMT) from each user. They may also decrease emissions by alleviating the need to own a personal vehicle that users would otherwise drive more than a shared vehicle.

Ready to ride!

Sharing is caring. Car sharing means fewer cars

Researchers from UC – Berkeley recently released a study that found “car2go is on net reducing vehicles that would be owned by households, reducing driving, and thus lowering GHG emissions.” They reached this conclusion by asking over 9,000 car2go members how car2go impacted their driving habits and vehicle purchases. Based on the results across the five cities that were surveyed (San Diego, Seattle, Washington D.C., Calgary, Vancouver), the researchers estimated each car2go vehicle removed an average of 7 to 11 vehicles from the road.

Considering that there are over 500,000 car2go users, this study estimated that car2go alleviated the need for over 28,000 vehicles across the 5 cities surveyed in 2015. Removing vehicles means removing a serious amount of driving. The average age of the passenger vehicles on the road in the U.S. has climbed from 8.4 years in 1995 to 11.4 years in 2014, and my first car lasted for over 15 years. Considering that people drive an average drive an average of 13,476 miles each year (which could be spread out over multiple vehicles), each new car sold today will likely be in service for well over 100,000 miles and perhaps more than 200,000.

And therefore less vehicle miles traveled

The Berkeley researchers also asked car2go members the extent to which the car sharing service changed their use of other transportation modes, like public transit, walking or bicycling. Interestingly, a majority of respondents reported that car2go did not substantively change how much they used other transit options, though some did respond that the service decreased how much they used public transit and walking.

In the densest cities surveyed (Washington D.C., and Vancouver), almost half of respondents reported that car2go increased their overall driving. But even with increased driving, the amount of miles a car2go subscriber drives is substantially less than the amount they would have otherwise driven in a personal vehicle. As a result, the study found that on an aggregate basis car2go decreased vehicle miles traveled and therefore emissions.

Adding in the relatively high mpg of each car2go (a 2015 Smart fortwo coupe gets a combined 36 mpg) and average driving distance of a shared vehicle, this study found that car2go reduced carbon emissions by 4 to 18 percent in the 5 cities that were surveyed. These results echo the positive results of earlier surveys by the University of Texas and the University of British Columbia.

Pairing car sharing with electric vehicle technology will expand the benefits

One of the most exciting facets of shared vehicles is the opportunity to pair these services with electric vehicle technology. Considering that shared vehicles can displace personal vehicle ownership, making them as efficient as possible will expand their benefits. UCS analysis has found that over their lifetime, battery electric vehicles produce far less global warming pollution than their gasoline counterparts—and electric vehicles are only getting cleaner as our nation transitions away from fossil fuel derived energy to renewable energy resources like solar or wind power.

Moreover, car sharing allows drivers to “right-size” their vehicle for the job, meaning that you don’t need to own an 8-passenger SUV just because you might need to carry 8 passengers twice a year. Instead, car sharing allows a driver to rent an 8 person SUV for the couple times they really need it, and otherwise drive a fuel efficient, or electric vehicle for the majority of trips that don’t require such a large vehicle.

Stay tuned for more insight on how the shared economy can fundamentally change transportation in the United States, but in the meantime, check out a shared vehicle and let me know whether it changed your transit habits!

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  • Ben

    This makes good sense. It seems possible that the same sorts of benefits accrue from services such as Uber, too, right? It would be nice to see the analysis broadened to include that type of car-sharing model. In what ways is it similar, in what ways is it different?