Insulate Britain protesters caused delays on the M25 by walking alongside oncoming traffic, police said.
The protest group said the decision to stop sitting in the middle of roads had been made following “feedback” from frustrated drivers.
Essex Police said it was called to a stretch of the motorway between junctions 28 and 29 near Great Warley at 8 am and 10 arrests were made.
It said both sides of the carriageway were reopened within half an hour.
Protesters later began walking along the white lines of the motorway near junction 21a for Bricket Wood at about 10.30am.
Hertfordshire Police said on Twitter that officers were “working to resolve the disruption as quickly as possible” and “several arrests” had been made.
Ch Insp Lee Deval, of Essex Police, said: “Not only will incidents of this nature be frustrating for road users trying to reach their destination, walking into fast-moving traffic is extremely dangerous.
“I’d like to thank road users today for their patience and understanding.
“You’ve helped us to clear the area quickly, to keep people safe, minimise disruption, and keep Essex moving.”
Four court injunctions are in place banning Insulate Britain from obstructing major roads.
Speaking before Friday’s protest, a man calling himself “Biff” said: “We’ve had feedback that people are frustrated that they spent time in traffic queues.
“We’re not planning to stop traffic but it could slow down to five miles an hour.”
The campaigning organisation has been calling for a national programme to ensure homes are insulated to be low energy by 2030.
It has blocked major roads around London in recent weeks, including the M1, M4 and M25.
During this time, images and video from the protests have been shared showing first response vehicles such as ambulances being caught in the blockades.
As well as angry drivers confronting protesters, one unknown man was filmed “I hope you know what it’s like. My father needs treatment and you sit here doing this.”
He branded the group “scum” as they stared at him, saying nothing.
“If anyone gets cancer, I hope your parents… Are your parents alive? Do you know what it’s like? Someone trying to get treatment for cancer and you’re standing here like this. People are trying to get to hospital. Of all places.
“If anyone gets cancer, please let it be your family, let you know what it feels like.”