South Wales Police is investigating a serious collision which occurred on the M4 on Sunday evening (June 6).
Officers were called to the single-vehicle collision on the westbound carriageway near junction 32 for Coryton, Cardiff, shortly after 6.45pm.
A 28-year-old man was taken to the University Hospital of Wales with serious injuries after a red Vauxhall Astra collided with the central reservation.
A 27-year-old man was arrested at the scene on suspicion of dangerous driving. He is currently in police custody.
Officers would like to speak to anyone who witnessed the collision, or saw the car being driven prior to it. Anyone with any dash-cam or mobile phone footage is also urged to make contact.
Please quote occurrence 2100197846 in any correspondence about the collision.
A section of the road was closed in both directions for a number of hours while initial investigations were carried out, and motorists are thanked for their patience and cooperation.