Slugging, also known as casual carpooling, is the practice of forming ad hoc, informal carpools for purposes of commuting, essentially a variation of ride-share commuting and hitchhiking. Typically slugging is motivated by an incentive such as a faster HOV lane or a toll reduction. While the practice is most common and most publicized in the congested Washington, D.C. area, slugging also occurs in San Francisco, Houston, and other cities.

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