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
Fancy taking a trip back in time to see how Devon looked more than half a century ago?
Weather wizard Kate Haskell gives an insight into the rainy July we've had, and what might be in store for the rest of the summer.
Fancy taking a trip back in time to see how Cornwall looked more than 70 years ago?