A controversial contraflow will be lifted within days as road bosses prepare to reopen a closed-off tunnel after months of delays.

The Chestfield Tunnel on the coastbound A299 Thanet Way between Herne Bay and Whitstable will finally open, having been closed since Kent County Council (KCC) discovered critical safety faults in June.

A contraflow system was introduced on the stretch so faulty ventilation equipment could be replaced, much to the chagrin of residents who had been subjected to similar misery when a nearby stretch of road was reconstructed.

However, the authority says it will now be in a position to reopen the coastbound route and do away with the traffic restriction by Sunday – though a 50mph speed limit will remain.

But, the temporary road restrictions - which snarl up traffic as drivers can only use one side of the tunnel - will return when the fans are eventually fully replaced within the next two years.

There will be full closures in both directions overnight on Thursday, Friday and Saturday as crews work to remove the temporary safety fencing.

It will also mean daytime right-hand lane closures in both directions on Thursday, Friday and Saturday to re-install permanent safety barriers.

It comes after the council admitted shelved plans to install new jet fans in the tunnel could have taken more than 18 months to complete.

KCC originally said it would take three months to manufacture and install the bespoke fans, which are used to clear smoke in the event of a fire and toxic fumes spewing from vehicles.

But transport bosses decided to only patch up the equipment for now, conceding the initial proposal would have required a full redesign and seen the contraflow remaining in place for a year and a half or longer.

The authority’s cabinet member for transport, Neil Baker, spoke to KentOnline inside the Chestfield Tunnel earlier this month, explaining why the new fans cannot be installed now.

“There are not many places you can get fans. You can’t walk into a DIY store – these are incredibly large bits of equipment,” he said.

“A decision was made to actually, having looked at it and got the consultants in and seen what could be done, if we were to get a brand new set of kit in, up to modern regulations, that would involve having the contraflow in for a significantly longer period, perhaps 18 months, perhaps longer.

“Absolutely it's been a delay and we don't like delaying the public [but] the reality is this isn't a set of equipment you can get off the shelf.

“Even [with] the repair work we're doing, we have to source those spare parts from all over the place just to get the system working for a little bit longer before a new system gets designed and put in place.”

Cllr Baker could not give an estimated cost on the new fans or a “hard and firm timescale” on when they could be installed given how specialist the equipment is.

He says of most importance is that it is reliable to avoid ongoing closures along the stretch.

Since being introduced in the 1990s, the jet fans have been activated manually five times – all of which were for emergency smoke management.

The vents are also used throughout the week and trigger when there are high pollution levels from older vehicles or stationary vehicles due to incidents or slow-moving traffic, and when the tunnel becomes misty or foggy.

They have a lifespan of about 25 years, meaning the existing set-up is already outdated, and bosses hope replacing the fans with higher-tech units will keep the tunnel in sync with safety guidelines.

The Mont Blanc tunnel fire in March 1999 claimed the lives of 39 people and has been credited as one of the key reasons there are such stringent regulations.

Prior to the current contraflow being introduced, similar restrictions were imposed earlier this year to allow for the reconstruction of the road surface on the coastbound carriageway near Whitstable.

Combining that with the tunnel fan works, a contraflow has been in place for six months of this year.