Those parts of North and South Somerset, Wiltshire, North and South Gloucestershire, Dorset and Oxfordshire bounded by:

On the North the A438 from Ledbury to Tewkesbury, A46, B4077 to Stow-on-the-Wold, A436 and A44 to Chipping Norton. On the East by A361 to Burford, A40, B4020, B4474, B4020, A4095 to Faringdon, A420, A419 to junction 15 (M4) at Swindon, A346 to Marlborough and the A345 to Salisbury. On the South the A36 from Salisbury to Wilton, the A30 via Shaftesbury, Sherborne, Yeovil, Crewkerne and Chard to the Somerset / Devon boundary and north westwards to the Bristol Channel. On the West the A466 from the Severn Bridge to Monmouth and A40, A449 to Ledbury.