How many vehicles does carsharing replace?

Ask any carsharing company and they'll quote a number - 6, 9, 13, even as high as 20 vehicles replaced for every carsharing vehicle on the road.

In a nationwide survey of over 6,200 carsharing members, Eliot Martin and Dr. Susan Shaheen came up with the most authoritative number to date: between 9-13 vehicles shed for every carsharing vehicle in the fleet.  Of those, 4-6 vehicles were directly shed by households as a result of joining carsharing and the remainder were avoided/not purchased as a result of membership.

The detailed analysis was conducted on a household level, since there may be several members in a household, and excluded the the behavior of inactive members, those no longer actively using the program, about 10% of the sample.  The survey included most of the non-profit carsharing companies in the US, as well as Zipcar members.

The major finding was that household ownership of a vehicle dropped from 0.47 to 0.24 vehicles per household (at a 90% confidence level).  Most of the shift, about 80%, was from one-car household going car-free.  

Further, 25% of the respondents said they would might buy a vehicle if carsharing were not available. 

The fuel economy of vehicles that were shed was about 23 mpg, being replaced by the average of 33 mpg for carsharing vehicles.  About 60% of the vehicles shed were between 5 and 15 years old, with 15% being between 1 -5 years old.

The study did not include those using carsharing on college campuses or in business situations since they are a minor part of the total and because their joining and usage motivations are likely to be somewhat different than those members joining in a neighborhood.

This is a good reminder that the benefits of carsharing will vary depending on the location and type of service - downtown residents will respond differently than those in less dense neighborhoods

And, I would add that new types of carsharing, such as peer to peer carsharing or even mobility on demand services, such as car2go, will probably not have the same impact as "classic" carsharing.

A very readable version of this report was printed in the Spring 2011 University of California Access magazine, available here (PDF) or the much more detailed TRB report here (PDF).

Comprehensive Carsharing Bibliography

I've been aware of it for years but recently had occasion to use the wonderful archive of documents and links of historical reports and data about carsharing put together by CommunAuto of Montreal. These include PDFs of the Crain & Associates STAR (short term auto rental) report from San Francisco and other reports back to the late 1960s.

There are a wealth of European reports that people on this side of the Atlantic (or Pacific, for that matter) may not be familiar with. Of course, many familiar reports from Dr. Susan Shaheen, Peter Muheim and Robert Cervero are archived here as well. The documents in the CommunAuto bibliography are in a variety of languages, not surprisingly including many in French. Benoit Robert and his staff are to be congratulated for taking the time to put together such an excellent resource.

By the way, I recently used another interesting research tool to dredge up the historic image of Flexcar's Los Angeles web page in my previous post (below) - waybackmachine.org. It links into an incredible archive of web pages all the wayback to 1996 updated every couple of months. (Don't ask me why but due to some technicality the original CarSharing Portland web site doesn't show up in the archive.)

New Swiss Carsharing Evaluation

For years (since 1998 to be exact), everyone has been quoting the "classic" carsharing evaluation of Mobility Carsharing Switzerland written by Peter Muheim, CarSharing the key to combined mobility. The interest in the Swiss government in carsharing hasn't diminished and the Swiss Federal Office of Energy recently issued a new report "Evaluation Carsharing" that confirms many of the good things we've been saying about carsharing and gives some interesting perspective on what's happening in a "mature" carsharing organization.

The evaluation is based on a survey of Mobility Carsharing Switzerland members - 520 households composed of 1400 members as well as 144 business carsharing members.

When the report was compiled at the end of 2005 Mobility had 63,000 members and 1700 vehicles. This is almost double the membership in 2000. 70% had used the service at least once in 2005. These customers took an about 16 trips per year with an average of 42 km per trip (26 miles). This has remainded remarkably constant during the past few years but is down from the usage levels in 2000. The typical customer used Mobility to drive only about 500 km per year (310 miles). The amount of usage does not appear to be declining the longer a person is a member, as has been observed in early US evaluations.

The average length of membership has gradually been increasing from 2.4 years in 2000 to 4.4 years in 2005 - probably somewhat related to the slower growth of Mobility during the past few years. The ratio of active users and passive (non-user) members has also increased during that time - to about 2/3rd active and 1/3 passive.

Some key findings from the report:

• The Mobility fleet of vehicles uses about 26% less gas than all cars in Switzerland, resulting in a 25% reduction in CO2 greenhouses gas emissions.

• Just like in the US, many Swiss households sold a car after joining carsharing - dropping from 47% to 31% who owned at least one motor vehicle after joining Mobility.

• And 73% of member households own a railroad or other public transit pass, an increase for 25% of the households and a decrease in 8% of households

If carsharing didn't exist 22% of survey respondents reported they'd buy a car and the report calculates a 26% increase in kilometers traveled and public transport use increase by 12%.

The report specifically mentions that about 10% of carsharing trips are "induced" - a phenomenon that has been the subject of speculation in transportation circles for a long time. The surveys indicate that 77% of members reported increased car usage after joining carsharing. However, this is offset from the savings from the 22% of the members that reported they would have driven 26% more kilometers if carsharing weren't available. This is where the real energy savings comes from since there would have been a substantial increase in private vehicle trips and a reduction in public transit trips. (See graph.)

Business carsharing was also included in the analysis, based on a survey of 144 business members. The average business customer took 33 trips per year, averaging 55 km (34 miles). The number of companies owning a fleet dropped from 57% to 52%. There was no increase in kilometers traveled by car after joining.

Estimates of the future growth of carsharing in Switzerland are made, but the report cautioned it is difficult and makes the assumption (which I don't necessarily agree with) that it will grow largely in proportion to the growth of public transport use in Switzerland - or about 2-3% per year. Given the history of creative partnerships that Mobility has established over the years, including the recent venture with the Swiss Post, I imagine they'll do far better.

The report calculates that Mobility members saved 660,000 gallons of gasoline, which corresponds to a reduction of about 200 kg (400 lb.) of C02 per customer. While not huge we must remember we're talking about people who already use public transport, walk and cycle far more than most people in the US.

You can download the full report in German, with a five page English summary (pages 15-20 of the PDF) by clicking on the title of this blog post above.  The German version has additional graphs showing much more detail and the full survey instrument used to compile the report. And if you haven't been to the Mobility website, almost all of it is available in English now.