an adhoc form of car pooling > http://hamptonroads.com/2008/08/stand-line-ride-strangers-zip-past-traffic-city

Known as “slugging,” the process is essentially instant carpooling with strangers. The nickname sounds funny, but it's a common expression among Northern Virginia commuters, who sometimes have commutes of up to two hours one way. Sluggers can slash a lengthy commute on I-95 into a quick, quiet trip to the Pentagon or D.C. They save money on gas, get a free ride at flexible times, and avoid parking once they get to work.