A scheme to widen a busy section of the A21 between Tonbridge and Pembury will overrun by six months.
Work to widen the 2.5m stretch to a dual carriageway has been delayed due to asbestos removal.
A Highways England spokesman said: "More than 35,000 tonnes of contaminated earth has been removed, which has taken additional time and delayed construction."
They added: "This means the scheme is cannot be completed as we had hoped in December 2016 however we are committed to completing it as soon as possible."
It comes as the authority announced today new additional improvements of a pedestrian, cycle and equestrian route.
Extra links connecting the upgraded paths to Tonbridge Station to the north and Pembury Hospital to the south will be built.
The work to build the new links will be funded by Highways England and carried out by Kent County Council.
Matthew Balfour, Kent County Council cabinet member for environment and transport, said: “I’m very grateful to the investment Highways England is making.
"Not only will the dual carriageway help reduce congestion but the new pedestrian and cycle route will provide a safe and healthy route, helping residents get between Tonbridge Station and Pembury Hospital."