Many people have been stuck in their vehicles for several hours after the M5 was closed in both directions.
It follows “concerns for the welfare of a man” on a bridge at junction 28 near Cullompton at about 16:00 GMT said police.
“We are working hard towards a safe resolution,” said Devon and Cornwall Police.
The force tweeted: “We understand there are people with needs or children stuck on the M5.”
They said: they were “working as effectively as we possible can. All we ask for is your patience.”