The A680 was once an important strategic route across East Lancashire, now made largely redundant by the A56/A6068/A671 combination.
Rochdale – Whalley
On the moors
The road starts on the A58 in the centre of Rochdale and heads west out of town. There's a long slog uphill (which included, if I remember rightly, a section that was still cobbled until the early 1980s). The road continues over the moors to Edenfield where there's a sharp left turn at a mini-roundabout followed by a TOTSO right to reach a roundabout on the A56 and A676. This is also the northern end of the M66 but there's no access to that from here.
After a multiplex north for a couple of miles along the A56 the A680 regains its number at Bent Gate to run through Haslingden and meet the A56 at the other end of the bypass, at a roundabout this time. The road is now largely urban into the centre of Accrington, where there is a short dual-carriageway section along the town centre relief road, which becomes a multiplex with the A679 between adjacent sets of traffic lights. The A680 then turns off (with the A679 continuing on the remainder of the D2) to head north. It crosses over the M65 with no junction then crosses the A678 at traffic lights immediately afterwards. Turn left along that road to reach the motorway (although you should just have stayed on the A56).
From the A678 it is possible that the A680 has primary status - although maps and signs give no clear consensus. The road continues north past Great Harwood and finally reaches open country once more. After crossing the (Lancashire) River Calder the road ends at traffic lights on the A671, where that road TOTSOs.
Originally, the A680 started on the original line of the A56 by the church in Edenfield before running along the present B6527 to Haslington and then on to Whalley. Much later (possibly in the early 1980s), the road from Edenfield to Rochdale, which was the A627, became an eastern extension of the A680.
In 1971, the A56 bypass of Edenfield was built, and the old A680 got downgraded to B-road status, and resurrected itself at Haslingden following a multiplex along the A56. The two TOTSOs in Edenfield date to this time as the road turns onto the original A56 then off it onto the eastern end of the A676.
Haslingden itself was bypassed in probably the late 1970s (it has that look), but the new bypass (the present A56) took the somewhat out of place number A622, with the A680 continuing through Haslingden. It still appeared on maps and most signs as a primary route, but officially, I think it must have been downgraded with the completion of the A56 diversion in the mid 1980s.