A woman was killed and a man and a teenage boy were left with life-threatening injuries after an accident involving two lorries and a car.
The woman, in her 50s, was driving a Fiat Punto involved in the accident on the A14 at Trimley St Mary on the outskirts of Felixstowe, Suffolk Police said.
A man in his 60s and the teenager, who were passengers in the car, were taken to hospitals in Ipswich and Cambridge respectively after the crash on Monday, which closed the road in both directions.
Police said the three are not thought to be from the local area and were involved in a crash on the eastbound carriageway close to a slip road.
A 50-year-old man from Dovercourt in Essex has been arrested on suspicion of causing death by dangerous driving in connection with the crash, Suffolk Police added.
The East of England Ambulance Service (EEAST) said three rapid response cars, a senior officer, two ambulances and the East Anglian Air Ambulance attended the scene.
"Sadly, on our arrival the woman was pronounced dead at the scene," an ambulance service spokesman said.
"A man received serious injuries and has been taken to Ipswich Hospital for further care.
"A teenage boy also received serious injuries and has been flown to a specialist trauma centre at Addenbrooke's Hospital in Cambridgeshire."
Any witnesses to the incident are asked to contact Suffolk Police's serious collision investigation team on 101.