Police were called to the A14 eastbound carriageway between Godmanchester and Fenstanton at 7.30am.
An HGV has collided with a Volvo, which has subsequently hit a coach.
Two lanes are blocked but traffic is using the slip road to pass. There are long delays in the area however.
Ambulance crews have attended and treated one person for minor injuries.
UPDATE: All lanes have now reopened, but there are delays of 30 minutes.