A new pound 2 million scheme is beginning to upgrade the Conwy Tunnel on the A55 in north Wales and it is expected to take four weeks to complete.
There will be a new lighting system put in place in the westbound tunnel using LED outdoor lights.
Transport minister Carl Sargeant said that improving the reliability of the tunnel was vital in trying to meet the needs of the local economy.
He confirmed that a 40mph speed restriction will be in place while the work is carried out.
A total of three km of support steelworks, four km of cabling and 2,500 LED lamps will be installed in the tunnel.
The Welsh government has said that the new LED technology will provide an efficient method of lighting that will not only be brighter, but will also reduce power consumption and the need for ongoing maintenance due to their long life.
It is hoped that with the improvements being carried out now, it will minimise disruption as traffic flows are at their lowest at this time of year, according to the government.
The Conwy Tunnel was initially opened by the Queen in 1991 and is considered a feat of engineering considering the fact that it carried the A55 under the River Conwy. This was the first such tunnel of its kind in the UK.
Mr Sargeant commented: "The Conwy Tunnel plays a vital role for the economy of north Wales. Ensuring that the A55 meets the needs of local businesses and residents in order to improve the local economy and regenerate the surrounding areas is paramount. Improving the reliability of Conwy Tunnel is integral to this aim."
The authorities in Wales have joined a growing number of organisations in the UK that are looking to take advantage of energy-saving benefits of LED lights.
Indeed, Notts County Council recently announced that they would be trialling LED outdoor lights in four residential streets to see if they can save the authority money.
