The Clooney Road in Derry has re-opened to traffic but is expected to close again to facilitate the recovery of a vehicle.
The vehicle in question was involved in what the PSNI described as a "serious road traffic collision" on Wednesday evening.
Inspector Mark Knowles said: “Police received a report of a one-vehicle road traffic collision close to the Enagh turn-off, between the Gransha roundabout and the Maydown roundabout, involving a silver-coloured Renault Clio at around 9:45pm.
Police attended the scene along with the other emergency services.
A female, aged in her 20s and who was a passenger in the car, sustained injuries to her head and neck and was taken to hospital where she remains.
A male, aged 18, was arrested on suspicion of a number of driving related offences and remains in custody, helping police with their enquiries.
We are appealing to anyone who was on the Clooney Road last night around the time of the collision and witnessed the collision, or who saw the vehicle travelling on the Clooney Road , to contact police at Strand Road on the non-emergency number 101, quoting reference 1595 of 20/12/17.
Alternatively, information can also be provided to the independent charity Crimestoppers on 0800 555 111 which is 100% anonymous and gives people the power to speak up and stop crime."