A woman has died and several people have been injured in four accidents on the A40 in Oxfordshire.
Up to 20 cars have been involved in the collisions. Roads are closed between Witney and Burford Road.
Another eyewitness arrived at the scene later and described the "carnage" as multiple cars swerved and crashed on the busy road.
The woman, who asked not to be named, said she "luckily" saw hazard warning lights ahead as she approached on the slip road from Carterton, and moved on to a grass verge before witnessing the pile-up.
"I saw cars going zooming past me and trying to swerve out the way of the stationary cars but crashing into them," she said.
"I saw one car try swerve in between a Mini and another car, ending up crashing into the Mini and (flying) up in the air.
"I saw two cars swerve as they braked so hard and go flying into the barrier in the middle of the road ... it was carnage," she added.
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