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Car-Sharing: Where and How It Succeeds Chapter 4. Impacts of Car-Sharing 4.1 Introduction The chair of the UK government's advisory body, the Commission for Integrated Transport, has called car-sharing a "mode without a downside,"1 and car-sharing proponents have identified a number of public benefits that can be produced by car-sharing. These range from environmental benefits, such as reduced vehicle travel, to social impacts such as increased mobility for low-income households. Exhibit 4-1 summarizes the potential benefits from car-sharing. This chapter discusses each in turn, and analyzes the extent to which the benefit has been confirmed by empirical evidence both from previous research, and from the member survey and focus groups conducted as part of this research. While there is a considerable body of existing empirical research on the impacts of car-sharing, much of it, with some notable exceptions, is disappointing in quality, or conducted by operators themselves or other advocates with a strong interest in promoting car-sharing. Sample sizes are often small, and in-depth research is often conducted early in the program's history, meaning that the behavior of early adopters may not reflect that of members in later years. Many studies particularly those conducted by operators are not published in full, with only a summary "fact sheet" released. Meanwhile, many car-sharing members are themselves evangelists for the concept a particular problem where the methodology relies on respondents to predict how they would have behaved in the absence of the car-shar- ing program, for example if they would have bought a car. Having said that, there is remarkable consistency between the ma- jority of studies regarding the overall impacts of car-sharing, if not their precise magnitude. There is general agreement that car-sharing reduces vehicle travel and vehicle ownership, and while the extent of these benefits is still in doubt, this is likely as much due to local circumstances both geographic and the nature of the car-sharing program as to research design. 1. Professor David Begg, cited in Cousins (2001). Page 4-1
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Chapter 4 · Impacts of Car-Sharing Exhibit 4-1 Potential Benefits of Car-Sharing Page September 2005 4-2
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Car-Sharing: Where and How It Succeeds Another way of understanding the impacts of car-sharing is to consider "layered" benefits (Exhibit 4-2). The first layer relates to benefits to the individual household or business member. The second layer consists of transportation system impacts, while the third considers the wider envi- ronmental and community benefits, which are often the desired outcomes. As this chapter will show, and Exhibit 4-2 indicates, the best data on the impacts of car-sharing exist at the individual level. While the gains at the environment and community level are substantially greater, they are not as well understood at present. Exhibit 4-2 Layered Benefits of Car-Sharing Environment/ Lower emissions Community Cost savings for development Less congestion Better urban design More compact development Less energy/resources for vehicle manufacturing Transportation Lower parking demand System More fuel-efficient vehicles Less vehicle travel More transit ridership Individual/ Cost savings Business Greater mobility Convenience Firm Data More Speculative This chapter assesses a number of actual and potential environmental, eco- nomic, and social impacts of car-sharing. Does car-sharing eliminate second and third vehicle purchases per household? Many car-sharing companies make substantial claims in this area (from 4 to 10 fewer vehicles on the road for each one car-shared vehicle). This could be one factor in calculating reduced vehicle trips in a metropolitan area, leading to the environmental benefits mentioned above regarding increased public transit usage. How does use of car-sharing services change the number and type of auto trips? Do car-sharing members make more effective use of transportation Page 4-3