Those parts of Durham, Cleveland and North Yorkshire bounded by:

On the North the A689 from St. Johns Chapel (via Stanhope), A690 (via Crook and Willington) to Durham. A181, B1281 to junction with A1086, a straight-line eastwards to the sea. On the South a straight line from Ravenscar to South Kilvington roundabout (A168 / A61) and A168 to Northallerton. The A684 from Northallerton to the A1. A684 (via Leyburn) to Cumbria boundary at Hawes. On the West a straight line from Hawes to St.Johns Chapel / A689.