From the seaport of Felixstowe, the road heads west, bypassing Ipswich, Stowmarket, Bury St Edmunds, Newmarket, Cambridge, St Ives, Huntingdon and Kettering. The entire road is a busy dual carriageway, heavily used by lorries running from mainland Europe to Ireland.
There is a six-lane stretch (three lanes each way) between Newmarket and Cambridge where this road is also the A11, carrying traffic from London to Norwich.
The section between Cambridge and Huntingdon is badly congested and in 2003 was the subject of a government study called CHUMMS (Cambridge to Huntingdon multi-modal study), which recommended a partial diversion, and widening of the whole section to three lanes.