The A1 (Western Bypass).
Historically, the southbound carriageway always struggled between the Metrocentre and Coal lhouse, clearing as you passed the angel/Bowes Incline - where the road becomes wider and ultimately faster (the 50mph limit is reduced there).

However, since the widening of the traditionally slower section, traffic is now coming to a standstill on the faster, motorway section.

Has me baffled as there is no logical reason for it to slow down and there appears to be no more traffic joining at the coalhouse than previous.