Seems to be the A19, Stagecoach's last few tweets:

Stagecoach NEast ‏@StagecoachNE  21m21 minutes ago
Sun ops: Servre delays to ser's in the S/wick, Washington area. Sorry for inconvenience.

Stagecoach NEast ‏@StagecoachNE  43m43 minutes ago
Tees Ops - RTA on A19 (North) leading to additional traffic and delays in and around Middlesbrough especially Portrack/Newport

Stagecoach NEast ‏@StagecoachNE  45m45 minutes ago
Sun ops: Beaumont St blocked by Go-ahead bus ser's  4,16 diverted. Sorry for inconvenience.

Stagecoach NEast ‏@StagecoachNE  50m50 minutes ago
Sun ops: Heavy congestion S/wick Rd, Washington Rd area causing major delays to ser's 3,4,13. Sorry for inconvenience.

Stagecoach NEast ‏@StagecoachNE  1h1 hour ago
Sun ops: Ser's 3,4 13 delays due to earlier RTA on the A19. Sorry for inconvenience.

Stagecoach NEast ‏@StagecoachNE  2h2 hours ago
Sun ops: RTA A19 traffic diverting via Durham Rd effecting ser's 3 and 4. Sorry for inconvenience.

Go North East:

Services are delayed in Sunderland due to heavy traffic around the Wheatsheaf and a broken down vehicle at Southwick.