LIFELINE island ferry services face more disruption this winter as vital infrastructure is overhauled.

Port operators have announced closures of ramps for ro-ros on both Coll and Harris in the latest Hebridean travel problems.

The shutdown were announced as state ferry operator CalMac continued its bid to take crossing to Orkney and Shetland in to public hands.

Quango Transport Scotland said it had sought tenders from three bidders for the Northern Isles links, understood to include both Calmac and Serco, the current private sector operator. The eight-year contract is worth £370m.

The planned closures of linkspans on Coll and Harris come amid growing concern about the age of ferries and ferry infrastructure on both Western and Northern Isles routes.

Half the ships on Clyde and Hebridean services have served more than their expected 25 years lifespan. Ports are also ageing.

Cables supporting the linkspans, which take vehicles off ro-ros, need replacing. This work has been brought forward to avoid disruption during the tourist season.

That means cars, buses and lorries cannot make all crossings to either Tarbert on Harris or Mull while work is underway.

In a notice to Coll travellers, CalMac said: “During these periods of closure we would expect there will be the normal timetable and service pattern but on certain days it will be a passenger only service. “This will also affect inter-island traffic movements.”

The linkspan at Coll will be closed after the lunchtime departure of MV Lord of the Isles on Tuesday, January 22, and will reopen the following Saturday morning.

The structure will be out of action again after the first ferry sails on the following Monday with work completed in time for morning ferry on Thursday 31 January.

Vehicles for the Harris - Skye run are expected to be diverted onto the Stornoway - Ullapool route. A passenger-only service is anticipated to operate to timetable.

The Tarbert linkspan will shut when the MV Hebrides departs on the afternoon of Wednesday, February 27, departs and should be ready for the ferry docking late morning on Tuesday 5 March.

This will allow both sets of wire rope replacements to be carried out during a single closure period.

Ramsay Muirhead, head of civil engineering at Caledonian Maritime Assets Limited, or CMAL, which owns the ports, said: “Following routine inspection of the linkspans at Coll and Tarbert, it was deemed that the replacement of the wire lifting ropes at both harbours was required.

“We would have preferred to carry out the work at Coll during the already scheduled linkspan closure in October.

“However, for safety reasons, we have decided not to delay the replacement.

“We are working with the team at CalMac and our contractor to ensure this work is carried out with as little disturbance to services as possible.”

CalMac, which operates ships owned by CMAL, have advised that services for foot passengers will be provided during the disruption on normal service days on both routes.

However, passengers are advised that an amended timetable may be operated and ask customers to refer to their website, www.calmac.co.uk, for details.