The road starts on the eastern side of Bodmin at a junction with the A30 before traversing the edge of the town to meet the A30 again. It travels through the picturesque Glynn Valley to Dobwalls and Liskeard, which are bypassed by a dual carriageway. The Dobwalls section contains the most sophisticated bat bridge yet constructed in the UK. The A38 continues through the Cornish countryside, bypassing the centre of Saltash and continuing through the Saltash Tunnel. Immediately after the tunnel the River Tamar is crossed using the Tamar Bridge where the route resumes dual carriageway status. The section from Plymouth to Exeter is known locally as the Devon Expressway; it forms the southern border of Dartmoor National Park, and serves as a southward extension of the M5 motorway opening in 1977. It is long and was completed in the early 1970s. There are several grade separated junctions along its length mainly for local traffic; including a three-level stacked roundabout for the A386, which heads out towards Dartmoor National Park. The route was reserved for the Parkway as early as 1943, when it was included in the Plan for Plymouth.