HOV is the Highway Overcrowding of Virginia. Actually, it stands for High-Occupancy Vehicle, and it means that on the crowded highways of northern Virginia, you need to have a minimum number of people in your car, van, truck or bus in order to use certain reserved lanes on the highway, which are presumably therefore less crowded and bypass the people who sit alone in their cars stuck in very heavy traffic on the other lanes. HOV comes in 2 varieties in northern Virginia: HOV-2 and HOV-3, the numeral being the number of people you need in your vehicle before taking advantage of the HOV lanes. The HOV lanes of I-395/I-95, which are fence-separated from the rest of the traffic and reversible to run in the direction of traffic flow and run for almost 40 miles south of Washington DC, even past Prince William, are, I believe, HOV-3. Just a way that people living in overcrowded regions try to cope with an superabundance of traffic.

--Charlie Baum