Police are investigating after a man was seen climbing on top of a car roof as it drove down a busy dual carriageway.
The incident was captured on camera by people travelling behind the car on the A469 between Ystrad Mynach and Llanbradach shortly after 6pm on Wednesday.
A man was pictured climbing through the window of the vehicle and then clambering on top of the car.
Witnesses said the man was then seen lying down in a "starfish" position on the roof.
"As we approached the roundabout towards Llanbradach a man climbed out of the Audi and lay down on the roof ‘star fishing’ with the occupants of the other two cars appearing to egg him on," said a witness.
"The bloke on the roof nearly came off as the Audi went around the next roundabout before climbing back to his feet as the Audi exited the roundabout.
"It was at this point my mate took both pictures.
"Once the bloke climbed back inside, the Audi sped off".
Gwent Police's Area Support Unit Sergeant, Rob Ball said: "I’d encourage anyone that witnessed or witnesses this type of behaviour on the road to contact the police immediately.
“Not only is the driver and person on top of the vehicle putting their own lives at risk, they are also putting the lives at risk of other innocent, motorists using the road.
“This is reckless behaviour of the driver who has responsibility for their vehicle and passengers – illegal driving on our roads will not be tolerated.
"There are a number of offences committed by both driver and the person on the roof, including dangerous driving and holding onto a vehicle whilst moving. We will be taking this seriously and we will be investigating.
“The consequences to this sort of behaviour could be devastating and I’m surprised that no one was injured. I’d like to remind dangerous drivers that if you were to cause a fatality on the roads, if prosecuted for death by dangerous driving, you could expect a custodial sentence up to 14 years.
“I’d like to appeal to anyone with any information on this or anyone who may have dash-cam footage of this incident to please get in touch with Gwent Police on 101."