 In Durham, 15-501 upgrades to an urban freeway, allowing for quick access from south Durham to north; the freeway ends merging into Interstate 85.At exit 176B (on I-85), US 501 splits off towards Roxboro, while US 15 continues with I-85 towards Oxford.After Durham, US 15 continues to follow I-85 till exit 186A, where it goes first to Creedmoor, then on into Oxford.