Analytical Framework to Assess Air Quality Impacts of Free-floating Car Sharing System

Focus Area

Air Quality


Air Quality






1-2 years

Research Idea Scope

This project aims to model the environmental effect of a new form of car sharing system with free-floating vehicles. The free-floating vehicle system, unlike traditional car-sharing systems, is based on flexible parking stations. Thus, in order to fill the research gap between traditional and upcoming way, and also gain a better understanding of emissions associated with free-floating car sharing systems, this research project proposes the following tasks: 1) Understand mechanism of free-floating (e.g., traveller patterns with regard to issues of trip generation and distribution) of free-floating car sharing systems; 2) Develop travel behavior models for free-floating car sharing system using data mining techniques; and 3) Develop an emission model for a free-floating car sharing system. With regard to gaining a better understanding of free-floating car sharing systems (themselves a component of the so-called “sharing economy”), it is important to realize that the free-floating car sharing system has some characteristics in common with general car-sharing systems. Therefore, in order to understand the system’s structure and better determine our research target, several objectives shall be considered. The first objective will involve investigation of existing applications of the sharing economy; specific attention will be given to the applications in the transportation sharing system. Another portion will focus on the basic structure of existing free-floating car sharing systems such as Zipcar, Car2go etc.. Yet another goal will involve studying specific effects of the sharing economies in the context of free-floating car sharing systems such as community belonging, cost savings, and environmental impact specially. An integral part of the project will involve travel behavior modeling, which itself will be an essential prerequisite for the emission estimation. Modeling of factors that influence travel will be one of the first steps with regards to behavior modeling. In general, factors considered will be derived from a subset of those pertaining to general sharing economies such as cost savings, mobility, and environmental impact. After analyzing these factors, data mining methods will be applied to explicitly model the travel behavior. At this point, two types of methodologies are proposed to be used in the modeling efforts. One method will rely on traditional statistical inference like linear and nonlinear logit models, and the other one will focus on machine learning techniques such as classification and clustering methods. The aforementioned methods will be compared to select a most suitable one on the basis of related data collection. Once the travel behavior model has been developed, to further estimate the environmental effect, one carefully designed emission model will be applied. Considering a future time horizon, different scopes of car sharing penetration rates will be tested to find an optimal environmental effect. The emission model includes two parts, one will be an empirical model, and the other part will involve simulation and visualization methods in order to clearly demonstrate environmental effects. The necessary data supporting model need to be collected extensively. In summary, the project will present a concise account of the methods and results, with appendices that contain all data compiled and analyzed, along with any outputs from the models developed under the project. Key components will include a detailed description of the structure of free-floating car sharing systems and a carefully designed travel behavior model coupled with supporting emission simulation methods.

Urgency and Payoff

Currently, a large proportion of the global population lives in urban areas, and the proportion is expected to exceed 80% by 2030. In some areas, around 23% of total CO2 emissions are produced by transportation activities. Both figures also appear to continue to show increasing trends into the future. As a consequence of the aforementioned, new environmental challenges continue to emerge, such as climate change, energy consumption, air quality issues, and difficulties tackling congestion and accessibility. For these reasons, a current priority objective of many transportation agencies is to enhance mobility and accessibility while, at the same time, reducing congestion, accidents, and pollution in cities. Car-sharing transport services have been considered as a useful means to promote sustainable mobility in cities and thus may be a viable means to solve some of the aforementioned problems. In a service-sharing economy, a free-floating car sharing service is defined as a service that applies a dynamic car sharing scheme (i.e., pick-up and drop-off points are flexible), such as that exhibited by Car2Go. Since changes in traveler behavior and corresponding emission patterns may result from increased usage of car sharing systems, the mechanisms underlying a free-floating car sharing system and the associated environmental effects need to be explored. Thorough understanding of such systems may help aid in policy development and further guidance for car sharing system implementation/usage, as well as benefits from environmental improvements due to decreased emissions.

Suggested By

Yinhai Wang STARLab, University of Washington (206) 616-2696

[email protected]