The work will be carried out to address issues with the structure of the flyover, which has been causing large potholes to appear on the bypass’s road surface for several months.
The holes have been causing damage to vehicles but after trying to fill them in, Highways England have discovered the root of the problem.
Nick Harris, operations executive director of Highways England, said: “We are aware of the poor road surface across the A21 Medway Viaduct and have recently completed an investigation into the cause of the problem.
“We have found that the surface here is breaking up due to problems with the movement joints in the viaduct itself.
“Unfortunately simply resurfacing the road will not solve the problem and we need to carry out a more complex repair here.”
He added: “We will shortly start designing and carrying out the detailed planning for the repair work needed with the aim of starting construction as soon as possible.”
“In the meantime we will continue to inspect the road regularly and, should we find any potholes which present a possible risk to road users, we will aim to repair them within 24 hours.”
There was widespread congestion on the A21 for more than two years up to September 2017 while a new dualling section was added between south Tonbridge and Tunbridge Wells Industrial Estate.
Tom Tugendhat, MP for Tonbridge & Malling, has liaised with Highways England on the issue.
He said: “Over the past few months many drivers have noticed the significant potholes which have been developing very quickly on the A21 bridge over the River Medway, by the Leigh Flood Storage Area. It’s resulted in lots of puncture and the costs that go with this.
“If you live in Tonbridge or Hildenborough you’ll remember the disruption caused when the dual carriageway to North Farm was being built, so sadly we might have more.
“But the potholes develop so quickly, it’s important for Highways England to get to grips with this as soon as possible. Let’s hope they can do so, and minimise disruption at the same time.”
