  Car-sharing platforms provide access to a shared rather than a private fleet
of automobiles distributed in the region. Participation in such services
induces changes in mobility behaviour as well as vehicle ownership patterns
that could have positive environmental impacts. This study contributes to the
understanding of the total mobility-related greenhouse gas emissions reduction
related to business-to-consumer car-sharing participation. A comprehensive
model which takes into account distances travelled annually by the major urban
transport modes as well as their life-cycle emissions factors is proposed, and
the before-and-after analysis is conducted for an average car-sharing member in
three geographical cases (Netherlands, San Francisco, Calgary). In addition to
non-operational emissions for all the transport modes involved, this approach
considers the rebound effects associated with the modal shift effect
(substituting driving distances with alternative modes) and the lifetime shift
effect for the shared automobiles, phenomena which have been barely analysed in
the previous studies. As a result, in contrast to the previous impact
assessments in the field, a significantly more modest reduction of the annual
total mobility-related life-cycle greenhouse gas emissions caused by
car-sharing participation has been estimated, 3-18% for three geographical case
studies investigated (versus up to 67% estimated previously). This suggests the
significance of the newly considered effects and provides with the practical
implications for improved assessments in the future.
