US 15 and US 29 become concurrent with US 17, which heads southeast as Marsh Road toward Fredericksburg, at Opal on their way to Warrenton. South of the town, the U.S. Highways' respective business routes split northwest and the U.S. Highways bypass the town on a freeway to the east. US 15, US 17, and US 29 have a diamond interchange with SR 643 (Meetze Road/Lee Street) before reaching a directional interchange where US 17 diverges from the other U.S. Highways toward Winchester and US 15 and US 29 receive their business routes. US 15 and US 29 head northeast as Lee Highway, which passes through New Baltimore and intersects SR 215 (Vint Hill Road) just west of Buckland, where the highways enter Prince William County cross Broad Run. Just east of the county line, US 29 continues east as Lee Highway toward Washington while US 15 turns north onto two-lane James Madison Highway.