Police who arrested six youths in connection with a stabbing in Leighton Buzzard on Saturday evening are appealing for witnesses.
It happened at around 5.35pm in Clarence Road when a young woman walked in front of a car, which was travelling towards Vandyke Road, forcing it to stop.
The passenger, a 38-year-old man, got out to protest but was surrounded by 10 to 12 youths who assaulted him before making off.
The victim drove home and was taken to Luton and Dunstable Hospital by ambulance where he was treated for injuries including a stab wound to his back.
He is in a serious, but not life threatening, condition.
Later police arrested four male youths and two females on suspicion of causing grievous bodily harm and they are currently being interviewed at two police stations in the county.
Det Insp Zara Brown, investigating, said it is a busy road and it is possible other motorists, pedestrians and dog walkers may have seen something. They should come forward as soon as possible.
Police have stepped up patrols, stressing they will not tolerate violence in Leighton Buzzard.
They want to hear from anyone with information, or has been intimidated in a similar way, but has not reported it to police.
Det Insp Brown said: “This was a nasty, unprovoked assault on a motorist and could easily have resulted in more serious consequences.
“We are determined to nip this behaviour in the bud as soon as possible.
“There may be people in that group who did not agree with what they saw, in which case we would urge them to contact us before we come knocking at their door.”
Anyone with information can contact Det Insp Brown, in confidence, on 101 or Crimestoppers, anonymously on 0800 555 111.