The A14 at Rougham is expected to remain closed eastbound for some time following a collision which has a left a woman seriously injured.
Drivers have been warned to expect delays and to plan ahead as the carriageway between junctions 43 in Bury St Edmunds and 47 near Woolpit is currently closed.
Traffic is also slow on the westbound carriageway while emergency services attend to the incident.
A spokesperson for Suffolk Police said: “Police are currently on the scene of a serious road traffic collision on the A14 in Rougham near Bury St Edmunds.
“Officers were called just after 5pm today to reports a woman had been seriously injured in a collision on the eastbound carriageway.”