There were delays on the A12 in north Essex on the morning demonstrators planned to block the road in protest of rising fuel prices.
Twelve miles of queues formed on the southbound carriageway at Kelvedon, near Colchester, shortly after 8am on Monday, according to the AA traffic map.
There were also tailbacks on the same carriageway around Colchester.
The AA traffic maps says the delays are due to a demonstration being held on the road, but Essex Police has been unable to confirm this.
Despite reports of a planned protest on the A12 at Copdock, there are no significant delays on the roads in Suffolk.
The protest was organised as part of the Stand Up to Fuel Prices' campaign, which aimed to block major roads on Monday morning.
Essex Police said it was aware of the potential protest and has made plans "to minimise disruption".
Organisers of the protest reminded participants to "leave space between the cars for emergency services to get through".
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