National Highways said lane closures on a 13-mile stretch of the M20 between junctions eight and nine will be required from later this month until October as it moves the Operation Brock barrier from the hard shoulder to the central reservation.
Speed limits will be cut to 50mph while this happens.
There will also be several overnight closures.
National Highways said the work, which involves an “extensive” drainage upgrade and new signage, will be carried out in phases and could take “up to 12 months”.
The moveable concrete barrier is used as part of Operation Brock to create a contraflow system on the M20 during delays with travel across the English Channel.
This enables vehicles heading to the Port of Dover or Eurotunnel terminal at Folkestone to queue on the motorway while enabling other traffic to keep moving in both directions.
The barrier was first deployed in December 2020, but is currently being stored on the hard shoulder.
Steve Gooding, director of motoring research charity the RAC Foundation, said: “Drivers using the M20 corridor will be dismayed at this latest news which comes after years of disruption caused by a series of major projects including the initial installation of the barrier, smart motorway upgrades and the building of Junction 10A.
“Users of the M20 might reasonably be asking whether this latest set of works could have been carried out when the barrier was first put in, why they need to take so long, and what is being done to minimise disruption while the works are under way.
“The M20 clearly has to cope with a unique set of pressures but all those driving on this key route must be fervently hoping that this, the latest in a long line of disruptive works, is going to be the last for the foreseeable future.”
