The eastbound section of the A30 between the Woodleigh and Ide junctions has been closed following a serious collision near Pathfinder Village.
The incident involved a lorry and a car shortly after 11.30 am.
Eastbound traffic is currently being diverted at the Woodleigh junction via local roads to rejoin the A30 at Ide.
National Highways is advising drivers travelling on the eastbound carriageway to plan ahead and allow extra time for their journeys, as the road is expected to be closed beyond the evening peak while police continue their investigations.
Up-to-date travel information is available from National Highways by visiting www.trafficengland.com.
Twitter updates are also available at @HighwaysSWEST.
For urgent real-time assistance, the company’s 24/7 contact centre team is able to provide up-to-the minute information on 0300 123 5000.