A serious crash, believed to be a collision between a tanker and a motorcyclist at the roundabout at Carkeel, has closed the A38 with motorists being diverted to the Torpoint Ferry instead.
The road is shut eastbound at Trerulefoot and westbound at Carkeel.
Police are advising motorists not to use St Germans as a cut through.
In addition, the Saltash Tunnel is closed westbound and traffic is being diverted through the town centre.
More top news
Hundreds of police jobs are at risk in the region as Dorset and Devon and Cornwall forces agree to pool resources.
Ofsted unveiled a damning report today which uncovered "serious and widespread failures" when it comes to looking after vulnerable children.
A ban on growing genetically modified crops is to be lifted next week. But opponents say it could threaten the future of organic farms.