This article is about the Class III road numbered C642 maintained by DfI Roads. For other roads numbered C642, see C642.
The C642 is a Y shaped route in east Tyrone. It starts on the western branch of the B520 from a mini roundabout in Coalisland town centre. The road heads east and reaches the main line of the B520 in Clonoe. The road continues from another junction to the south and soon the route splits onto two separate roads with one continuing east and another turning off to the south east. The road heading south east reaches the C640 at Derrytresk while the road to the east also meets the C640, to the west of Washing Bay in the south west of Lough Neagh.