A man who suffered life-threatening injuries in a hit-and-run on the A14 in Cambridgeshire is being treated for a broken neck, police have said.
Officers released further details of Sunday's crash at Stow Cum Quy and renewed their appeal to find a silver Audi that failed to stop.
The man, 53, was a passenger in a Vauxhall Zafira. He and the female driver, 48, sustained head injuries.
Both are from Cambridge. Police have appealed for witnesses to contact them.
The crash happened at 1115 BST on the westbound carriageway, which was closed for more than six hours.
The Audi has alloy wheels and tinted windows, police said.
Sgt Chris Huggins: "The silver Audi was seen driving off towards Cambridge with significant front-end damage.
"Anyone who has seen this vehicle, or knows anyone who has an Audi that sustained damage over the weekend, should call police to help us piece together what happened.
"I am also keen to hear from anyone who saw either vehicle prior to this collision."