The A39 at the Northload Bridge roundabout, Glastonbury, has been reopened following a single vehicle collision overnight.
A car collided with a wall at 2.50am causing it to collapse onto the carriageway. The road remains fully closed while officers conclude their investigations at the scene and pending recovery of the vehicle and clearance of debris.
The occupants of the vehicle, a man and a woman, were taken to hospital. The woman remains in hospital with injuries not currently believed to be life-threatening but potentially life-changing.
A man in his 30s is now in police custody having been arrested on suspicion of drug driving offences and causing serious injury by dangerous driving.
If you saw the collision or who have any information which could help the investigation, call 101 quoting reference 522022755.