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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations

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Publication Number:  FHWA-HRT-13-053    Date:  May 2013
Publication Number: FHWA-HRT-13-053
Date: May 2013


Exploratory Advanced Research Program

Casual Carpooling Focus Group Study


This report documents a qualitative research study sponsored by the Federal Highway Administration (FHWA) Exploratory Advanced Research (EAR) Program that was conducted from June 2012 through September 2012 to explore the phenomenon of casual carpooling. FHWA’s EAR Program addresses the need to conduct longer term and higher risk breakthrough research with the potential for transformational improvement to plan; build; renew; and operate safe, congestion-free, and environmentally sound transportation systems. This study is one component of a two-part study that explored the mechanics, logistics, and success of the practice. During November and December 2010, the EAR Program supported a team that consisted of transportation professionals, academic faculty, and business entrepreneurs who visited casual carpooling lines in Washington, DC; Houston, TX; and San Francisco, CA, to observe and compare practices among the three locations. The Casual Carpooling Scan Report is documented in a separate report, and Appendix B to the Casual Carpooling Scan Report is also available separately.(1,2)

AMENDED June 3, 2013

Casual carpooling is just like traditional carpooling in that a ride is shared between a driver and one or more passengers. The practice of casual carpooling, however, is a unique variation on the traditional form of carpooling with two distinct differences:

Other terms commonly used to describe casual carpooling include “slugging” and “dynamic ridesharing.” According to David LeBlanc, a veteran slug, author of Slugging, and creator of Slug-Lines.com, the term “slug” came from bus drivers who had to determine if there were genuine passengers at their stop or just people wanting a free lift, in the same way that they look out for fake coins—or “slugs” being thrown into the fare-collection box.(3) Of these terms, “casual carpooling” and “slugging” describe an approach where there is a predetermined physical meeting place for the driver and passengers and there is no required use of technology to participate.

Though the authors recognize that there are connotative and denotative differences between these terms and that their use varies by region, for purposes of continuity, this report refers to the practice generally as “casual carpooling” and those who participate in it as “casual carpoolers.”


As a response to the opening of high-occupancy vehicle (HOV) lanes in the Washington, DC–Northern Virginia metro area in the mid-1970s, a unique commuting phenomenon developed: slugging. This type of carpooling evolved from drivers and passengers coming together to fulfill each party’s needs: drivers needed additional passengers to meet the HOV requirement of four occupants (in Washington, DC, this was later reduced to three) and passengers needed faster ways to reach their destination than public transit without the expense of driving. This win–win situation eventually spread from the original slug line in Springfield, VA, to roughly 24 sites in the region today.

Particularly in the Washington, DC, region, casual carpooling has not just continued but has thrived as an alternative to driving or using transit. After roughly 35 years, casual carpooling is still going strong in Washington, DC, and is taking hold in other metropolitan areas. Although some changes have occurred, by and large, people still wait in lines for cars going to a particular destination. They no longer wait at bus stops—today, casual carpoolers wait in parking lots (at retail locations, park-and-ride lots, etc.)—but the concept is not vastly different from when it began. Academic and entrepreneurial types alike are looking at ways to facilitate casual carpooling. Some suggestions for enhancing casual carpooling include Web-based forums that connect drivers with passengers, smartphone applications that would allow drivers and passengers to register and connect with each other, and other incentive-based programs.

Academics and transportation professionals have undertaken few studies about casual carpooling. This focus group study provides additional insights into the casual carpooling systems in the three locations (Washington, DC; Houston, TX; and San Francisco, CA) also toured by the Casual Carpooling Scan team during the winter of 2010. Two to three focus groups were held in each of the locations with drivers and passengers who are active participants in casual carpooling. The goal of the research was to gain additional insight and knowledge into the practice of casual carpooling and find opportunities for enhancing the process through technological means. The findings in this report, together with those found in the Casual Carpooling Scan Report,(1) document the current practices in three of the Nation’s largest and longest running casual carpooling systems.

Research Objectives

With an ultimate goal of enriching the transportation community’s understanding of casual carpooling systems from the participants’ perspective, this research held three key study objectives:

The research findings will inform future dialog and planning by FHWA and others interested in casual carpooling.

Research Limitations

The qualitative, focus group–based research method used in this study offers a number of benefits. It provides the opportunity to obtain a large, rich body of information, can be organized relatively quickly, and can be conducted almost anywhere. The open, flexible nature of focus groups also encourages participants to talk about topics they normally would not discuss with strangers. Qualitative research offers a flexible way of collecting data, and as new insights are gained or new leads open up, the observer can shift perspective quickly and explore new areas of inquiry. This is not possible using quantitative survey methods; once the survey questions are set, they are asked in the same way to all participants. The major limitation of this method, however, is that the findings are limited to descriptions of what happens in small groups of people that may not be fully representative of the population, which in turn, also limits the ability to generalize the results. Consequently, the findings presented in this report are only representative of the opinions, attitudes, and behaviors of individuals who participated in the focus groups.

Report Organization

This report presents findings in three perspectives:

In the final section of this report, a brief set of conclusions and recommendations is presented.


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