Can two parcels share a driveway?

an entrance (i) that serves up to two private residences and is used for the exclusive benefit of the occupants; (ii) that allows agricultural operations to obtain access to fields; or (iii) to a civil or communication infrastructure facility that generates 10 or fewer trips per day

24VAC30-73-10, definition of a private entrance

That definition is the fork. Two houses sharing one drive where it meets a state road are still using a private entrance, the same class as a single home. The class changes once a third residence uses it, and the class above private counts lots meant for residences as well as built homes.

VDOT's regulation also has a name for the arrangement itself: a shared entrance is a single entrance serving two or more adjoining parcels. Sharing, in other words, is a recognized shape, not a workaround. What the sharing does to the class depends on the count.

The step from private to low volume commercial is not a paperwork change. Under 24VAC30-73-110 the tenure of a commercial entrance is conditional, and that section applies to low volume commercial entrances: reconstruction, relocation, consolidation or upgrading may be required at the owner's cost when the designee finds a listed condition. For a full commercial entrance, Va. Code 33.2-241 requires a permit first, lets the Commissioner of Highways require joint use with adjacent owners or evidence of efforts toward it, and puts maintenance on the owner of the premises. The design standards each class has to meet are set out in what VDOT considers a safe entrance.

Counties touch a shared drive at three points: when the lots are platted, when access is recorded, and when a structure on the drive needs a number.

On the plat. Floyd County's Land Division Ordinance requires plats of divisions with any lot on a private road, and it names shared driveways and easements in that phrase, to state that the roads do not meet state standards, will not be maintained by VDOT or the county, and are not eligible for rural addition funds.

In the land records. Pulaski County's Unified Development Ordinance requires all access, whether easement or right-of-way, to be deeded and recorded with the circuit court clerk, and a subdivision relying on access that is not deeded is denied. The same ordinance lets the UDO Administrator require shared access for multiple lots, to limit the number of access points along existing roads, and requires lot frontage topographically suitable for building an entrance.

At the mailbox. Floyd County requires every habitable structure to have a 9-1-1 address, even if it is not the mailing address. Where two numbered structures share a driveway, the number goes at the driveway entrance and at the structure, at least three inches high and visible from the entrance and from both directions, and any drive used by three or more residential or business structures is assigned an E-9-1-1 street name, private or public. For an E911 address in Carroll, the new-dwelling cover sheet sends applicants who need one to the Twin County E-911 Commission, and Grayson requires the address before its building permits issue; the sequence is set out in how to get a 911 address for vacant land.

This answer cites no shared-drive rule for Carroll, Grayson, Wythe, Montgomery or the City of Galax. Ask that locality's subdivision office (Land Use and Planning in Carroll) and its addressing office before a plat shows two lots on one drive.