Environmental impact of mutualized mobility: Evidence from a life cycle perspective

Today's urban transportation systems face increasing challenges such as greenhouse gas (GHG) emissions, urban air quality, and traffic congestion. In this context, various initiatives of mutualized mobility have emerged. However, notably lacking is assessing the environmental impacts of mutualized transportation modes from a life cycle perspective. Using the actual urban transportation big data and related product life cycle data, this study combined with the life cycle assessment methodology and a "bottom-up" approach, explores the effect of mutualized mobility on greenhouse gas emissions of urban transportation systems for both Beijing and Toronto. The results showed that mutualized mobility might positively affect the sustainability of urban transport systems, albeit in very different ways. In Toronto, the annual per capita greenhouse gas emissions in 2016 decreased by 2.8 kg of carbon dioxide equivalent (CO₂-eq) compared to 2011. Both carpooling and car-sharing displayed a higher curbing potential than ride-hailing. In a city characterized by higher population density like Beijing, ride-hailing created negative impacts. Deadheading (i.e., pulling an empty trailer) was the critical factor affecting ride-hailing's environmental performance, which accounted for about 30% of the total vehicle life cycle emissions. Counter-intuitively, greenhouse gas emissions of station-based bike-sharing (SBBS) were almost six times that of privately-owned bicycles and even higher than public transportation. This study's results can be used as a starting base for decision-makers to devise more appropriate strategies and programs to promote the sustainability of mutualized mobility and urban transportation systems. Meanwhile, it can also help the public at large to better understand the characteristics and environmental impacts of mutualized mobility to adopt more sustainable mutualized mobility alternatives.