The A406 North Circular is blocked between Palmers and Bounds Green because of a huge concrete spillage.
A lorry has been completely stuck on the eastbound carriageway of the north London transport artery since the accident at midday between the junction with Green Lanes and Wilmer Way, in Enfield.
It has caused traffic chaos, with queues backing up in Palmers Green and Bounds Green.
Emergency workers have been desperately working since then to remove the liquid concrete, and to push it into drains before it sets.
A spokesperson for TfL said workers are still currently clearing the concrete, but hope to reopen the road later this evening.
They could not confirm how the accident happened.
Drivers were advised to leave the A406 at New Southgate and to rejoin in Tottenham.
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