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Berkeley TSRC study quantifies VMT and GHG benefits of car2go car-sharing in North America

car2go NA is currently the largest flexible one-way carsharing service in North America. Now, a study conducted by the University of California Berkeley’s Transportation Sustainability Research Center (TSRC) concludes that car2go’s carsharing model can complement existing mass transit options; reduces the overall number of vehicles on the road; and ultimately improves mobility in densely-populated urban areas.

Among the study’s conclusions were that, on balance, car2go changes VMT (vehicle miles travelled) by -6% to -16% per car2go household; GHG emissions change by -4% to -18% per car2go household. Overall, the results of this study suggest that car2go one-way carsharing is substantively impacting travel behavior, miles driven, GHG emissions, and the number of vehicles on urban roads within operating regions.

The UC Berkeley study is the first-ever multi-city study to focus on one-way carsharing rather than the traditional round-trip car-sharing model. Since UC Berkeley first conducted its previous multi-city carsharing survey in 2008, many innovative mobility options have launched—including one-way carsharing—and this new study specifically analyzes the impact of one-way carsharing in North America.

Car-sharing background. There are currently four forms of carsharing in North America, the study notes:

  • Roundtrip. Members begin and end a trip at the same vehicle location and typically pay for use by the hour, mile, or both. Roundtrip carsharing has been operating in North America for more than 20 years. As of July 2015, there were 39 roundtrip carsharing operators in North America with a total membership of 1,005,893 and a collective fleet of 18,582 vehicles.

  • One-way. Members pay by the minute to begin and end a trip at different locations—either throughout a free floating zone or station-based model with designated parking locations. One-way carsharing launched in North America in Austin, Texas in 2010 with the car2go service. As of July 2015, there were three one-way operators in North America, serving 511,000 members with a collective fleet of 6,870 vehicles, according to a study to be published.

    Car2go is currently the largest carsharing operator in the world, with a presence in nine countries and nearly 30 cities.

  • Peer-to-peer. Peer-to-peer carsharing functions much like roundtrip carsharing; however, the vehicle fleet is typically owned/leased by private individuals and facilitated by a third-party operator.

  • Fractional. The fractional ownership model enables users to co-own a vehicle and share its costs and use.

The study. In the study, Dr. Elliot Martin, a research engineer at TSRC, and Dr. Susan Shaheen, co-director of TSRC and Adjunct Professor at UC Berkeley, surveyed car2go members in five cities to determine the impacts on vehicle ownership, modal shift, VMT, and greenhouse gas (GHG) emissions.

The five cities were Calgary, San Diego, Seattle, Vancouver, and Washington, D.C. They asked questions that required respondents to attribute specific changes in their life as caused by the presence of and access to car2go. They also used vehicle activity data to evaluate the total driving that car2go vehicles travel in a city during a year, as well as a profile of the frequency of use by the broader car2go population.

Car2go provided a year of anonymized trip activity data to support reweighting of the sample dataset and measurement of car2go vehicle travel. Analysis of the survey and activity data was solely conducted by TSRC/Innovative Mobility Research Scientists.

Findings. Among the key takeways of the study were that, first, car2go has a diverse impact on travel behavior. A majority of members use public transit less frequently; walk more frequently; use taxis less frequently; and have a range of impacts on other modes.

Findings included:

  • Car2go members were found to have sold between 1 to 3 vehicles for every car2go vehicle. 74% of the vehicles reported sold by car2go members were at least ten years old, helping to remove thousands of vehicles with outdated emission systems from urban roads. The average age of vehicles reported sold was 14.4 years old.

  • Each car2go vehicle was found to suppress between 4 to 9 vehicles. Taking sales of older vehicles and avoided (suppressed) purchases together, each car2go vehicle replaced between 7 to 11 privately owned vehicles across the five cities studied—reducing vehicle miles traveled, greenhouse gas emissions (GHG) and the overall number of cars in urban cores.

  • Based on car2go NA’s fleet and membership size in 2015, the presence of car2go in the five cities studied was estimated to have taken more than 28,000 cars off of city roads, reducing traffic and parking congestion.

  • car2go was responsible for a 6% to 16% reduction in vehicle miles traveled (VMT) across the study population (average of 11%), as well as a 4% to 18% reduction in GHG emissions across the study population (average 10%).

  • It is estimated that car2go’s one-way carsharing service prevented between 10 to 29 million VMT per year per city, depending on assumptions of suppressed mileage, which in-turn removed between 5.5 to 12.7 metric tons of GHG per car2go vehicle annually (on average).

  • Car2go members paired their car2go trips with a bus trip up to 7% more frequently, and rail up to 8% more frequently since joining car2go. UC Berkeley researchers believe that continued integration between car2go and mass transit systems will extend shared mobility into larger and more diverse metropolitan regions.

The vast majority of respondents indicated that car2go did not result in a vehicle sale or a postponed purchase. However, overall, car2go causes a net vehicle reduction despite the fact that only a minority of the sample indicated a causal effect on vehicle holdings. The balance of these impacts is tilted considerably toward vehicle suppression, the authors said.

One possible reason for this is the timing of this study relative to the shared mobility industry today (i.e., there are many shared modes now available, such as bikesharing, ridesourcing, etc.). At present, carsharing is a known option in many cities that people can opt into. Hence, it is likely that the suppression effect (in contrast to vehicles sold) will increasingly dominate the impacts found within large-scale studies on the impacts of carsharing and other shared modes in core urban areas.

—Martin and Shaheen

The minority of members who do sell and avoid a private vehicle purchase are causing the car2go VMT reduction, while the broader population does not appear to drive car2go for large distances, the authors said.

This suggests that one-way carsharing is almost certainly reducing VMT overall, even though the magnitude of the reduction may not be precisely determinable. This is evident by the relatively low average mileage per customer driven on car2go vehicles, which is bounded between 75 and 150 miles per customer per year (on average) across the five cities studied.

—Martin and Shaheen
Martin and Shaheen Click to enlarge.

Vehicle ownership in cities can be expensive and inconvenient, with private vehicles sitting unused approximately 95% of the time. Our three-year research effort into one-way carsharing in North America revealed that car2go is having a beneficial impact on mileage driven, greenhouse gas emissions, and the total number of vehicles in the cities we studied. Participation from car2go and its members—the largest free-floating, one-way carsharing service in North America—gave us unprecedented access to activity data and member insights into this innovative mobility service in densely-populated cities.

—Susan Shaheen


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