Instant Carpooling – Just Add Passengers and Go: the Phenomenon That Is Casual Carpooling Net Conference

This March 31, 2011 net conference featured 3 presenters who highlighted the use of casual carpooling or “slugging” in Northern Virginia, Houston, and San Francisco Bay Area. They discussed how these ad hoc, informal carpools are formed, who uses them, and what differentiates “sluggers” or casual carpoolers from a traditional carpooler.

Summary: Your mother told you never to ride with strangers.  Obviously, your mother wouldn’t understand slugging or casual carpooling.  Slugs (as they are called in Washington DC and Houston areas) or casual carpoolers (in the San Francisco area)  travel that way on a daily basis! However, slugging is a very organized system with its own set of rules, proper etiquette, and specific pickup and drop-off locations.  With thousands of vehicles at their disposal, thousands of commuters move daily by jumping in the car and flying down the high occupancy vehicle lane without (usually) paying anything. Slugging gets people to and from work faster than the typical bus, metro, or train without the need to be tied to a specific carpool.  This unique form of commuting usually associated with access to 3+ high occupancy vehicle (HOV), high occupancy toll (HOT), and managed lane facilities.

The National Center for Transit Research (NCTR) at the University of South Florida, Best Workplaces for Commuters and the Association for Commuter Transportation (ACT) arranged for three presenters who participated in a recent FHWA funded scanning tour of casual carpooling/slugging in the U.S. to share their previous research and observations from the field.

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Northern Virginia
Marc Oliphant, U.S. Department of the Navy, described how “slugging” works in Northern Virginia.   Since the moment that the I-95/395 managed lanes first opened to carpoolers in the mid 1970’s commuters have been matching up with strangers to take advantage of 27 miles of free-flowing HOV lanes.  More than 5,000 commuters participate every workday.

Mark Burris, PhD, Texas A &M discussed the evolution of slugging in Houston before and after the opening of managed lanes.  The Katy Freeway recently changed from HOV3+ free in the peak to HOV2+ free in the peak – resulting in a significant impact on casual carpooling.  Dr. Burris discussed this impact, his experience as a slug during the scan tour, the results of a travel survey of casual carpoolers, and counts of casual carpoolers performed on an infrequent basis over the last 5 years.

Casual Carpooling in San Francisco Bay Area
Susan Heinrich, Metropolitan Transportation Commission discussed casual carpooling in the San Francisco Bay Area, including the response from introducing tolls for carpoolers across the Bay Bridge in July 2010.  The Metropolitan Transportation Commission’s Regional Rideshare Program has conducted three comprehensive counts and travel surveys of casual carpoolers over the past thirty years – most recently just before the carpool toll was implemented.  Ms. Heinrich compared the casual carpool trends in these studies and discussed the “don’t-fix-what-isn’t-broken” role that MTC’s traditional rideshare program has played over the years.

Download Instant Carpooling slides

Studies from San Francisco:

The 77 minute netconference was co-sponsored by the Association for Commuter Transportation ( , National Center for Transit Research ( and Best Workplaces for Commuters (  The session was moderated by Donna Smallwood, URS/MassRides.

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