Two people have been taken to hospital with life-threatening injuries after a crash involving three vehicles.
Police said a 73-year-old woman and a man, 76, were seriously injured after the crash at 21:45 GMT on Saturday on Southern Way in Cardiff.
An eight-year-old girl who was also in the car suffered minor injuries.
A 44-year-old man from Tottenham in London was arrested on suspicion of drink driving and causing serious injury by dangerous driving.
The three injured people were taken to to the University Hospital of Wales, along with the 33-year-old driver of the third car who attended hospital as a precaution.
South Wales Police said the road was closed for several hours while investigations took place and the vehicles were removed.