MOTORISTS are facing a year of delays and disruption on the A82 at Loch Lomond as work begins to remove "temporary" traffic lights that have been in place for 30 years.

Details of an £11 million upgrade at Pulpit Rock, a notorious bottleneck on the route connecting the central belt to the Highlands, were published yesterday, though the exact timing of the scheme is still unclear.

While work on the route takes place, traffic measures will include closing the road for 14 weeks and introducing a 20mph or 30mph speed limit for up to a year, together with an extension of the single carriageway that has operated since the traffic lights were introduced.

The project will involve the construction of a new viaduct over the loch and widening of an existing section of road to ensure that two-way traffic can flow once it is complete.

A spokesman for Transport Scotland, the Government agency overseeing the project, said it was unable to say when work would commence.

He added this would depend on whether objections are submitted over the next six weeks that would require a public local inquiry to be held.

Transport Minister Keith Brown said the upgrade will enable the free flow of traffic in the area.

He said: "The Scottish Government is committed to upgrading the A82, as set out in the Infrastructure Investment Plan. The route sits in one of the most unique and challenging landscapes in Scotland.

"It is important we carefully plan a solution that fits well with the geographical challenges of this route and better connects the businesses and communities in the Highlands and Islands with those in the central belt, while maintaining the renowned beauty of the area."

The improvements include a new quarter-of-a-mile section of two-lane carriageway, a viaduct running parallel to the loch shore for 196 yards and the widening of the existing carriageway.

As the road is wedged between Loch Lomond and steep hillside, the works provide "real engineering challenges", Mr Brown said.

He added: "This is an important milestone and signals a step forward with this long-awaited scheme.

"However, infrastructure projects such as this are huge undertakings and simply do not, cannot, happen overnight.

"The work involves consider-able design and development work that is absolutely essential to get the right scheme at the right price and keeping the impact on communities and businesses to the absolute minimum. Meaningful engagement with directly affected communities is at the heart of all our major infrastructure projects and we will seek public feedback on this scheme at key stages of the project.

"Scottish ministers remain committed to improving the traffic-flow situation at Pulpit Rock and will continue to progress the scheme with a view to completing it at the earliest possible opportunity."

Water-based environmental surveys will be carried out next week on the west bank of the loch between Tarbet and Inverarnan, part of a programme of engineering and environmental surveys on this stretch, which Transport Scotland says will help inform the next stage of design work on the A82.