This article is about the Class III road numbered C340 maintained by DfI Roads.
For other roads numbered C340, see C340
The C340 is a lengthy route which starts at a roundabout at Sheephill with the A1 and the A28. The road follows the A1 across the Clanrye River and comes to a T junction. The C337 heads west while the C340 TOTSOs right. To the east the road TOTSOs north and multiplexes with the C338. The road crosses the route of the C341 at McGaffin's Corner and eventually reaches Ballynaskeagh Crossroads where it meets the B3. The road continues in a north east direction and TOTSOs north just before crossing the C345. Almost immediately beyond the C345 the road ends on the B10.