HOV => High Occupancy Vehicles - carpool lanes, known as "diamond lanes" 'round these parts back in the day
They are not to be confused with:
HOT => High Occupancy/Toll - toll lanes, but carpool lanes also, since you don't pay (at least in this area) if you have enough occupants in the vehicle
However, they are and will be confused, since , in the past year or so, some HOV lanes in the area have been converted to HOT lanes