The A38 re-opened at around 7am today after the fatal crash
It is thought the three victims were work colleagues, with friends on social media paying tribute.
The road was closed overnight near Plymouth following the incident yesterday afternoon, but re-opened at around 7am today.
Devon and Cornwall Police confirmed the news in a statement and said the families of the victims have been informed.
They said officers received a report of a serious collision involving one vehicle on the Plymouth-bound carriageway of the A38.
A spokesman for the force added: "A white van overturned and no other vehicles are thought to have been involved.
"Motorists are advised to avoid the area and follow any police diversions and expect delays."
The whole Plymouth-bound carriageway, along with lane three of the Exeter-bound carriageway, remained closed all night.
Three people died on the road after a van overturned
Friends of the victims have paid tribute to them on social media.
Ben Parkinson wrote: "RIP lads. Was a pleasure working with you. Taken far too soon. I'm devastated but can't imagine how your family are feeling."
Sammie Sinkins added: "So sad. My beautiful friend's partner was involved. I'm so sorry to hear that anyone has passed.
"My thoughts are with everyone involved. Heart broken for all the families."
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