I suspect that this was the main road between Carlisle and Glasgow before the A74 was built as a dual carriageway. Ironically, the A74 itself has now been downgraded to the B7076 following the opening of the A74(M).
Uploaded to Geograph by David Purchase on 31 March 2017
Photo © David Purchase, 31 March 2017. Licensed for reuse under this Creative Commons licence