Does Car Sharing Reduce Your Driving?


A spirited debate broke out a few weeks back on the Car-free Living listserv run by Livable City about the merits of car sharing. Does it reduce driving and car ownership or increase the impetus to drive among the car-free? One poster who didn’t own his own car called car-sharing a gateway drug that encouraged him to increase the number of times he uses a vehicle for all manner of trips, while others argued that VMT is reduced when fewer people own their own cars and share more.

Despite an initial analysis of San Francisco’s City CarShare service showing an inducement to drive, in large part because early adopters were "self-professed environmentalists and avid cyclists," a 2003 study on car sharing found that over time the service showed the opposite trend.

By City Car Share’s second anniversary, 6.5 percent of emember’s trips and 10 percent of their vehicle miles traveled were in carshare vehicles.  Mathed-pair comparisons with a statistical control gropu suggest that, over time, member have reduced their total vehicular travel.  Because carshare vehicles tended to be small and fuel-efficient, per capita gasoline consumption and greenhouse gas emissions among members also appeared to go down.

The study also found that 30-percent of members had sold one or more vehicles and that two-thirds had decided not to buy a vehicle.

Adam Millard-Ball of Nelson Nygaard Consulting, who authored the definitive car-share report several years ago for the Transportation Research Board (TRB), cited a recent report (PDF) presented at TRB by Susan Shaheen demonstrating that car sharing removes 4.6 to 20 cars per shared-use vehicle from the transportation network depending on the city. The same report showed that car-share program members increased walking and transit use by wide margins.

"I think that we are confident now that mature, large-scale car-sharing programs bring great benefit in reducing vehicle ownership and vehicle travel," said Millard-Ball

Tom Radulovich of Livable City asserted that there is an environmental benefit to shared cars that is mostly overlooked: the embodied energy of a vehicle, or the amount of carbon required to produce, maintain, and ultimately dispose of the vehicle.

Estimates of the ’embodied energy’ of a car vary quite a lot from authority to authority, but could be anywhere from 10 to 40 percent of all the energy a car  A car in the city generally gets driven a lot less than a suburban car. That means that the urban car‘s embodied energy is a higher percentage of its life-cycle cost, even if the car‘s overall energy consumption over its lifetime is lower. If a group of people share
a small fleet of cars, rather than all purchasing their own cars, they
will save energy and reduce their environmental impact, even if their
driving habits don’t change at all.

Both Millard-Ball and Radulovich were confident that a further car-sharing benefit to land-use policy would become evident as more data is collected.

"In a city like San Francisco that has great constraints on parking,
scarce parking is the thing that keeps people from owning a car," said Millard-Ball.
"Car Sharing is helping to change the built environment by reducing
parking so that we lock in these reductions in vehicle ownership, and
not just free up on-street spaces that someone else can take advantage

Said Radulovich: "Think of what the city would be like if all of the folks
who seldom use their cars were instead to share cars; they would save money, reduce greenhouse gas emissions, and free up tremendous amount of precious urban space."

Streetsblog SF would like to know how you feel about
car-sharing services, whether they’ve changed your transportation
choices and travel behavior, whether you’ve sold your personal car, or held off on buying a new vehicle.  In addition to the comment section below, feel free to send us your story at

Flickr photo: The Sierra Club

  • Moved to the city in 2006. Sold my Honda Civic several months later. Join Zipcar, and would often find myself making unnecessary joyrides with the car to ‘get my money’s worth’ ($30 prepaid per month) and often driving to the grocery store, then realized this was silly, starting paying a yearly membership fee and a higher hourly rate, started driving much less, never to the grocery store or Target (good god), and at this point use the car share membership I still maintain just in case at most one every three months for a few hours–have stopped using it even for excursions because it’s expensive and not really that fun, and started a Post-Car Adventuring blog to help get others doing this.

    So, for what it’s worth, these services definitely got me to drive A LOT less.

    – J

  • You didn’t plug your own blog, Justin!

  • We have one car in our family. I’m a member of City CarShare for a few years. For me City CarShare helps to take the pressure off from owning a second car. In reality I use it perhaps once a year. The primary reason is it is actually not very convenient for me because there is a hill between me and the car. The second reason that is more relevant for everybody else is that I need to make a reservation to secure the car. This means I need advance planning. This planning step really reduce car usage compares to car owner. My wife and my neighbors drive everywhere instintively because the car is 100% at your disposal with no restriction. To use a shared car you need to reserve a time window so you’d make lot less spontaneous trip and it will force you to evaluate the alternatives.

  • I sold my car when I joined City Car Share a few years back. I don’t know if it has reduced my VMT, but it has certainly saved me a lot of money. Just the cost of insuring and registering my car was higher than my total annual car share bills.

    I used to only drive our car — a Mazda Miata — for fun, but my wife had a habit of driving it to the grocery store, to the gym, and to every other place. Since joining the car share we never make those trips in cars. For one thing the grocery store is four blocks in one direction and the car share is two blocks in the other direction, making it the same net amount of walking. For another, the ability to just jump in a shared car right this second is pretty low. You have to think ahead at least a few hours to reserve the vehicle.

    I think a relevant question is whether the pricing schemes at City Car Share and ZipCar differently impact VMT. ZipCar is much more expensive per hour, but less per mile. City Car Share is far less per hour, but more per mile. It is economical to drive a ZipCar to San Jose but you probably wouldn’t do that on a City Car Share plan. Also ZipCar requires you to commit to a certain number of miles driven per month, which is obviously a direct incentive to drive more. City Car Share has no such minimum miles feature, so you only pay for miles driven.

  • In one and a half years, I’ve used my ZipCar Account 4 times.

    2 times to pick up bike parts in San Jose/Pleasanton/North Bay.
    1 time to drive with 3 friends to Monterey Aquarium.
    1 time to drop off 45 pounds of direct mail for work across the bay.

    I didn’t feel guilty for any one of those– they were all things that would have been very difficult to do by bike/foot over long distances, far from any easy 2-transfer transit trips.

    …the only complaint I have: forgetting to factor in the $30 fee- making my ‘good deal’ from Craigslist into ‘about average’…

  • Tag

    I gave up on owning a car about six years ago. So many headaches, so much money, so little joy. A couple years back, though, I found myself lamenting how little I knew about the peninsula, about Marin, and so I signed up for ZipCar. ZipCar, specifically, as its cost structure worked out slightly better for long trips (as Mr. Baker suggests). Yes, sometimes at the end of the month I find myself having to burn off credit, but mentally that’s been a good thing for me. Just driving until you discover something, exploring wherever for whatever reason. Cars are a nuisance when they’re treated as a necessity, but treating them like a luxury is, I think, more alright.

    I rarely use it for in-town trips. Seems pointless and expensive.

    Also, I know I could make those long trips by other means, and sometimes I do. But I don’t know. Having quick access to random, semidistant places is so nice. I still think of canceling it, but eh.

  • Matt

    I’ve been with Zipcar for about 2 years. I tend to use it 2 or 3 times per month, mainly on the weekends for trips out of the City.

    I’d disagree that car sharing leads to more car use, as the requirement to pre-plan your trip often makes local trips more convenient by bus or bike. What it does do is give you access to a car for trips when driving makes sense.

    Car sharing makes you assess your transportation choices in a rational way. How long will it take me? How much will it cost? Compare this to owning a depreciating car – you’d be mad not to use it!

  • I would like to reiterate David B’s comment about the effect of the pricing structure of city car share vs zip car. CCS encourages one to drive less miles b/c of the per mile fee. One can drive to about Pacifica or a little ways into Marin before the mile fee adds up to more than a rental car. It looks like Zip car’s structure encourages folks to drive a little more than CCS. But at least all those Zip car people are not adding another car to the streets.

    I use CCS to pick people up at the airport at times, take visitors to the beach, and other times I am too lazy to walk or cycle. My grocery stores are all about 2 blocks away and thus are easier to walk to. Work is also a 10 min. walk.

  • crzwdjk

    I’d say that you have to look very closely at what car trips are actually substituted by car sharing. There’s the obvious direct substitution of driving your own car for driving a shared car, but there’s also the less obvious trips where if you don’t have your own car, the options are to either use a ZipCar or beg a friend for a ride. The net change in driving is zero, but it’s an increase in *your* driving.

    Also, I think the place where carshare services can make the biggest positive contribution is in the suburbs, where sometimes you just absolutely need a car, even if you can get by with biking and/or transit most of the time.

  • Josh

    The whole question of whether car sharing reduces an individual’s aggregate driving is irrelevant! That’s not the measure that tells you whether car sharing leads to less driving overall. The real measure that needs to be looked at is whether members of car sharing organizations have lower average overall household VMT and higher average household transit/bike/ped rates than comparable households (same income, housing location, etc.) that own their own car(s). That will tell you what is happening in the big picture and whether on a per capita average there is progress being made. You need to look at the overall growth of the forest, not that of an invididual tree.

    “The study also found that 30-percent of members had sold one or more vehicles and that two-thirds had decided not to buy a vehicle.”

    It’s the 2/3 that didn’t buy a car that are actually making the biggest difference in aggregate, not the 1/3 that sold their cars. But we get so focussed on the the 1/3 that sold their cars because it’s such a good story and it’s a clear action, as opposed to the 2/3 who aren’t out there saying “I didn’t buy car today!”

    These happy stories of “I drove less once I switched to car sharing” are a distraction of doing useful analysis of the macro benefits of car sharing. The key to getting our transportation and environmental mess in order are to lower overall per capita personal car use for the average member than a comparable Joe SixPack.

    A lot of people who join car sharing organziations already have lower than average car use, so it’s not useful (or accurate or fair) to point to a increase in their individual use and say that it’s having the opposite effect by enabling them to drive more. Because the reality is exaclty the opposite — to the extent that having car sharing available keeps their average VMT lower than that of Joe SixPack and keeps them from buying a car longer than they would have otherwise, that is the big win. And to the extent that it keeps one car families from becoming two car families. That is the silent 2/3 that is the holy grail of car sharing.

  • As a City CarShare (CCS) representative, I appreciate this post and subsequent comments. I am glad to see that some key insights have been made, which point to very large differences in car share models. CCS’ mileage fee and low hourly fee is designed to encourage efficient driving. If we charged a flat rate per hour, people who drive locally would be subsidizing people who drive longer distances. (Also, CCS does offer a “day-use” rate, which is priced at a lower level than other day rates.) We never have “commitment pre-pay pricing” because it encourages driving–that’s precisely why we don’t do it. All of our cars are low-emission and fuel efficient (most are hybrids) because we want our fleet to have as low an impact as possible on the environment. We also often place the same type of car at one location, which increases turnover, a key indicator of success for us. Our members can reserve cars in 15-minute increments as well. Because of this, fewer cars serve more people. We place cars in low income, under-served areas to make car sharing available to as many people as we can. We also have the nation’s first-ever wheelchair accessible vehicle and other special programs that are designed to reduce the need for car ownership, whether one is shedding a car or foregoing the purchase of one. City CarShare co-drafted and signed the car share industry’s code of ethics, found here: So far, CCS is the only Bay Area provider that has agreed to these standards of practice. Thank you Matthew Roth for providing me with the opportunity to highlight some often overlooked differences and thanks to all those who share them with others.

  • Josh

    There are different niches and models for car sharing, and CCS’ model is not necessarily better than Zipcar’s or others…

    But if you want to get down to brass tax, I think that in the big picture, CCS’ model is kind of missing the big picture, the “grail” I call it, of car sharing — which is to eliminate the need for car ownership completely, such that car sharing can offer pricing models to satisfy all types of use — short trips, long trips, more frequent use, less frequent use, etc. Because in the end, if you can get people not to own their own cars and to switch to a per-use model (which all car sharing is, regardless of pricing model), then you will make huge, radical reductions in overall driving and other associated impacts. If you can get people to do all in-city trips by transit, bike or walking and to use a car only for those long, out of the city trips for which cars are the only option, you will solve 80-90% of the transportation problem.

    A pricing model that discourages driving may not actually reduce driving if the model is not appealing to the majority of people. If the pricing model is only geared to using the car to drive short distances, you have to be willing to live with that limitation on your life if you want to be otherwise car free. It works fine for urbanites who don’t like to leave the city much. Most people, particularly those who are active, outdoors-loving type people are not willing to live like that (and even if they don’t actually hit the trails or the slopes every weekend, they want the option and don’t want to have to pay for the nose). People don’t want to be trapped in a 20-mile circumference of their house, and regular car rental is a pain in the ass and inconvenient (not something you want to do on a regular basis). So if the pricing and membership model is too limited and punitive to longer drives and longer reservations, in the big picture you’ll get a relatively small subset of the population that find that the model can fit with their lives. The “committment pre-paid model” is actually quite a good one, and is more in line with the kind of use the average person is likely to use. A $75/month pre-paid rate (that offers discounts over standard rates for additional hours/days is actually not that much driving) — it’s only a little more than 1 full day a month at average daily rates! If only we could get the average person to drive an average of one full day a month!

    Yes, of course you don’t want to have more consumptive drivers subsidizing those who don’t drive much, but you want to try to find the happy middle, or at least offer varied plans for different kinds of people, in which you can attract the most number of people to the program.

  • Dave Snyder

    For me, City CarShare has drastically improved the quality of my mostly car-free life, admittedly by facilitating slightly more car driving than I would do if it did not exist. Most of that, however, would have been unnecessary if there were such a thing as “City Bike Trailer Share.”

    The SFBC’s bike trailers for use by members are cool, but a little inconvenient compared to the city car, which for a few bucks I can pick up and return a half block from my house at any hour of the day or night. If City CarShare had a bike trailer at my pod, I’d use it half the time I currently use city car share.

  • Once every 3 weeks, we drive a scion from CCS 17th/Hoff to Potrero Center to hit Petco and Safeway, then to CostCo, on tto 555 9th Street, for TJ’s and BloodBath and Beyond and then a stop by Rainbow and we’re home, the scion’s suspension tested to the limit by the laden vehicle.

    I don’t think that’s even 5 miles in all, but it would have taken days of shuttling by bicycle, and it does not account for daily stops at Rainbow to get fresh ingredients.

    I’ve done CarShare to the Richmond to pick someone up after day surgery w/sedation, not everyone is healthy and fully abled all the time.

    It is not necessary for any car share model to provide a full spectrum of car services. At the end of the day, if we spend <$2000/yr on various car rentals for road trips, we’re still coming out ahead over owning a car, depreciation, insurance and fees.


  • Here give a nice post. Even with lower overall energy consumption of the car in its life cycle. If a group of people sharing small fleet of cars, but not all buy their own car, they will save energy and reduce the environmental impact of their driving habits do not change.



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