A 23-year-old man has been seriously injured in a single vehicle crash.
Police were called to the incident at B4265 at St Athan, Vale of Glamorgan, at about 13:10 GMT on Thursday.
The injured man was taken to Cardiff's University Hospital Wales for treatment, South Wales Police said.
A 27-year-old man was arrested at the scene on suspicion of drink driving and further arrested on suspicion of causing serious injury by dangerous driving.
Officers have appealed for witnesses and dashcam footage.