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The A229 Fairmeadow in Maidstone has now reopened after overnight roadworks overran.
But drivers are still stuck in long queues on the southbound carriageway, heading into Maidstone, as a result of the Maidstone Bridges works taking longer than expected.
A broken down vehicle on Staceys Street, between the White Rabbit roundabout and Lower Boxley Road, added to the congestion.
A Kent County Council spokesman revealed the delays were due to a deep trench under the road.
He said: "We would like to apologise for the overnight road closures, which overran this morning into the morning rush hour.
"It happened because a trench under the road, which spanned all four lanes on Fairmeadow, needed additional material to fill it because it was so deep.
"As a result, the resurfacing curing time had to be extended before the road could safely be re-opened to traffic.
"All lanes have now reopened."
Kent County Council's Highways department earlier warned motorists to expect long delays and advised people to use alternative routes where possible
The road reopened just after 8am but the area remained congested for another two hours.
The closure has caused congestion all around the town centre, along the A20 and on Blue Bell Hill.