Signage
The markers for primary routes show the route number in a rounded shield shape, while those for secondary roads and frontage roads use a circular highway shield. A separate series of signs, posted at intersections, shows the route number on a small rectangular strip and does not distinguish among the various types of highways except by using the F prefix for frontage roads or the T prefix for state-maintained town roads (where they exist).
Read more about this topic: State Highways In Virginia