Part of the A12 southbound is blocked after a stalled vehicle caused delays.
Traffic jams are building on the route during the morning rush hour after the incident at Stratford St Mary.
There is also slow traffic heading towards Ipswich on the A14 at junction 55, the Copdock interchange.
Elsewhere in Suffolk, there are some delays in Bury St Edmunds due to roadworks on Nowton Road, Beetons Way, Barons Road and Hollow Road.
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