VTrans' 2006 Route Log lists the official length of VT 5A to be 19.498 miles (31.379 km), with the last milepost reading at VT 105 in Charleston. However, VT 5A continues along a silent concurrency with VT 105 from Charleston to Derby Center. The only mention of a concurrency between VT 5A and VT 105 is from VT 111 at its western terminus.
VT 5 begins in the south at an intersection with US 5 in the village of West Burke. Both routes connect from Burke to Derby, but VT 5A uses a more direct, easterly route than US 5. VT 5A proceeds north into Orleans County and the town of, traversing through the Willoughby State Forest and along the eastern side of Lake Willoughby before intersecting VT 16 at its eastern.
While the designation of VT 5A has changed since its initial construction, its routing and function have not. The entirety of modern VT 5A was first designated as New England Interstate Route 2A (NEI 2A), part of the New England road marking system that existed between 1922 and 1927. NEI 2A was designated as an alternate to NEI 2, a designation which covered the entirety of modern US 5. When the New England Interstate system was supplanted by the United States Numbered Highways, NEI 2 was designated as US 5 in 1926 and NEI 2A was redesignated as a state highway.