Slugging: Casual Carpooling for Urban Transit

81 Pages Posted: 24 Aug 2019 Last revised: 5 Oct 2020

See all articles by Shiliang Cui

Shiliang Cui

Georgetown University - McDonough School of Business

Kaili Li

Beijing Jiaotong University

Luyi Yang

University of California, Berkeley - Haas School of Business

Jinting Wang

Beijing Jiaotong University; Central University of Finance and Economics

Date Written: August 10, 2019

Abstract

Problem Definition: "Slugging," or casual carpooling, refers to the commuting practice of drivers picking up passengers at designated locations and offering them a free ride in order to qualify for high-occupancy-vehicle (HOV) lanes. Academic/Practical Relevance: It is estimated that tens of thousands of daily commuters rely on slugging to go to work in major U.S. cities. As drivers save commute time and passengers ride for free, slugging can be a promising Smart Mobility solution. However, little is known about the welfare, policy, and environmental implications of slugging. Methodology: We develop a stylized model that captures the essence of slugging. We characterize commuters’ equilibrium behavior in the model. Results: We find that slugging indeed makes commuters better off. However, the widely observed free-ride tradition is socially suboptimal. As compared to the social optimum, commuters always under-slug in the free-slugging equilibrium when highway travel time is insensitive to slugging activities but may over-slug otherwise. The socially optimal outcome can be achieved by allowing pecuniary exchanges between drivers and passengers. Interestingly, passengers may be better off if they pay for a ride than if they do not under free slugging. We also find that while policy initiatives to expand highway capacity or improve public transportation always increase social welfare in the absence of slugging, they may reduce social welfare in areas where free slugging is a major commuting choice. Nevertheless, these unintended consequences would be mitigated by the introduction of pecuniary exchanges. Finally, contrary to conventional wisdom, slugging as a form of carpooling can result in more cars on the road and thus more carbon emissions. Managerial Implications: Our results call upon the slugging community to rethink the free-ride practice. We also caution that slugging benefits commuters possibly to the detriment of the environment.

Keywords: Smart Mobility, slugging, HOV carpooling, welfare, equilibrium vs. social optimum, emissions

Suggested Citation

Cui, Shiliang and Li, Kaili and Yang, Luyi and Wang, Jinting, Slugging: Casual Carpooling for Urban Transit (August 10, 2019). Available at SSRN: https://ssrn.com/abstract=3441901 or http://dx.doi.org/10.2139/ssrn.3441901

Shiliang Cui (Contact Author)

Georgetown University - McDonough School of Business ( email )

Washington, DC 20057
United States

Kaili Li

Beijing Jiaotong University ( email )

No.3 of Shangyuan Residence Haidian District
Beijing, 100089
China

Luyi Yang

University of California, Berkeley - Haas School of Business ( email )

545 Student Services Building, #1900
2220 Piedmont Avenue
Berkeley, CA 94720
United States

Jinting Wang

Beijing Jiaotong University ( email )

No.3 of Shangyuan Residence Haidian District
Beijing, 100089
China

Central University of Finance and Economics ( email )

Beijing, Beijing 100081
China

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