The incident happened shortly before 4.45pm when a car was in collision with a motorbike near Orchard Way on the A38.
The road was closed and it re-opened just after 6.30pm and rush-hour traffic had to be diverted.
The 54-year-old Suzuki motorcyclist went to the Queen’s Medical Centre with serious injuries. No one else was injured, including the female driver of the Peugeot. Police say the motorcyclist is now in a stable condition.