This article is about the Class III road numbered C640 maintained by DfI Roads. For other roads numbered C640, see C640.
The C640 is an L-shaped route on the south west banks of Lough Neagh. The road commences from Junction 14 on the M1 near Tamnamore and heads north. After bending eastwards the road TOTSOs north towards Lough Neagh and crosses the Coalisland Canal, built in the 18th Century to serve the Tyrone coalfields but disused since the 1950s. A branch of the route soon turns off to the east and runs as far as the next junction at Derryloughan. The road TOTSOs north west and turns away from Lough Neagh as it crosses the B161 at Killeen. Soon the road reaches the village of Stewartstown where it meets the B520.