Just a note on US 17 and US 52 in Charleston, from my visit there in late September:
The route files for both routes have points for US52Spr. However, there is no route file for that spur route. The spur is shown on the state highway map. But I didn't see any US 52 Spur junction markers on the relevant part of US 52, nor any route markers northbound on the part of the spur I drove (starting north of US 17, to US 52).
ISTM that there should be a route file if the route is signed someplace I didn't look, or otherwise the points on US 17 and US 52 should be renamed.