X20: Durham - NON STOP - West Rainton (Chantry Place) - NON STOP - Houghton Le Spring - Doxford Park - Board Inn - NON STOP - Sunderland
X20A: Low Moorsley - Hetton - Gillas Lane - Houghton Le Spring - Doxford Park - Board Inn - NON STOP - Sunderland
20: Durham - Bowburn - West Rainton - Middle Rainton - Gillas Lane - Houghton Le Spring - Newbottle - Herringtons - Board Inn - A690 - Hospital - Sunderland
20A: Durham - Bowburn - West Rainton - Middle Rainton - Rainton Business Park - Houghton Le Spring - Newbottle - Herringtons - Board Inn - A690 - Hospital - Sunderland
X20/X20A: Sunderland to Houghton, Every 15 Minutes Combined
20/20A: Durham to Sunderland, Every 15 Minutes Combined
35: Withdrawn South of Sunderland
39(?): Withdrawn Doxford Park to Houghton Le Spring
Would open all sorts of links and give Hetton etc a quicker route to Sunderland than a detour around the world especially with the number of houses being built around the Herringtons with an appalling service.
Quick diagram to explain better below (pinks are the expresses, green are the slows, arrows point at the express sections).