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We organized this Special Issue on “The Environmental and Behavioral Consequences of Interventions for Sustainable Travel” with the aim of attracting interdisciplinary perspectives on the environmental and behavioral consequences of different interventions for sustainable travel [...]

This introductory paper to the Special Issue “Shared Mobility” aims (1) to present and differentiate the diversity of practices and services that constitute the shared mobility sector; (2) to emphasize the contribution of each published article; and (3) to identify knowledge gaps of knowledge and provide further research avenues. With the contribution from 29 authors affiliated to social sciences and transportation research institutions in seven countries (Sweden, Germany, Netherlands, Greece, Belgium, Norway, and Australia), new understandings of the potential, drivers, barriers, and limitations of diverse shared mobility solutions for a more sustainable society are presented. The common message across the special issue is that the shared mobility sector is constantly evolving, while aiming to attain sustainability goals. Several papers have taken a psychological approach to explain the adoption of shared mobility practices (e.g., carsharing), yet these findings may be context-dependent, which future research should further investigate (e.g., differences between platform-based and self-service modes). We also call for researchers to pay attention to how traditional transit services can be combined with newer shared mobility services (e.g., micro-mobility), but also to informal public transport systems, as we identify these as important developing areas.

A cycling campaign was assessed that used three different nudging conditions to progress people’s stage of motivation to make travel behavioral changes. The results of three waves of survey data showed that this cycling campaign generally strengthened their stage of motivation to reduce car use and that this stage-change, in turn, reduced actual car use while increasing bike use. It was observed that an improvement of cognitive psychological mechanisms was positively related to people’s motivation to change. Although the effect of the campaign was stronger just after it had ended (Wave 2), a reduction in car use, an increase in bike use, and an increase in the stage of motivation were still found three months after the campaign had ended. This is important as it shows that effects favoring sustainable travel last beyond the timeframe of the intervention. We conclude that travel interventions should aim to integrate processes that emphasize cognitive psychological mechanisms and people’s motivation to change as these drive a sustainable behavioral change.

Carpooling can be viewed as a simple intervention to reduce congestion, environmental problems, and land use for parking spaces. The present study assembled 18 studies on carpooling from all over the world that were published during the last five years (2014–2018) for a meta-analysis. By calculating effect sizes of 20 different factors, the study aimed to understand user characteristics, motives, and barriers to carpooling, and to gain insights about carpool interventions. Our results indicate that carpooling is very weakly related to socio-demographic variables, and that psychological factors are becoming more important, including monetary and time benefits, reducing congestion, and environmental concerns. Policy-makers can increase carpooling by offering cheaper parking or special parking spaces for carpoolers and introducing high-occupancy vehicle (HOV) lanes. Not surprisingly, fuel prices influence mode choice. The overall findings support previous results, but we found judgmental factors becoming more important for the choice to carpool. We conclude that carpooling services still fail to include many potential users and to serve users adequately. The challenge of meeting the needs of all users requires new approaches to designing carpool concepts, systems, and encounters.