Police are investigating whether an unwell man found on the A5 near Caddington last week had been attacked.
At around 7.05pm on Thursday, June 16 police received reports of concern for a man on the carriageway.
Emergency services attended and the man was arrested on suspicion of drink driving.
He was taken to hospital before being discharged and taken to police custody, but later fell ill and was sent back to hospital where he is now in a serious condition.
Det Insp Iain Morgan said: “We are investigating the possibility that the man may have been assaulted prior to the arrival of emergency services, and we believe there may have been a number people who could have witnessed the incident when driving past.
“I’m appealing for anyone who may have witnessed an altercation between two drivers on the A5 southbound, just prior to the traffic lights at the Dunstable Road junction, to get in touch.
“The man is currently in a serious condition in hospital so it’s vital that anyone with information, no matter how small, contacts us, so that we can help piece together what led to his injuries.”
Anyone with information is asked to contact police on 101 quoting Operation Donatelli.
The Independent Police Complaints Commission (IPCC) is investigating the police contact with the man during the incident, as is standard procedure when a person who has had recent police contact falls unwell.