Officers remain at the scene of a serious collision on the A142, Wentworth.
Police were called at 9.17am on 29 January to reports of a four-vehicle collision involving a lorry, two cars and a van.
Emergency services attended and a man was taken to hospital with serious injuries.
A man in his 40s was arrested on suspicion of driving under the influence of drink or drugs. He was taken to Parkside Police Station.
Cambridgeshire Police are asking anyone who witnessed the collision, has dashcam footage or drove on the A142 around the time of the crash to call the police on 101 quoting incident 106 of the 29 January.