Belco's island-wide replacement of ageing underground transmission cables, launched in 2021, is headed into its final phase, with the upgrade complete in the East End.

A spokesman said that from Monday, trenching would start on Middle Road in Southampton by Seymour Farm Road and progress to Evans Bay, where it will end.

Drivers were advised to use South Road to avoid congestion.

However there will be no alternative route once trenching reaches Barnes Corner, and motorists were advised to allow extra time.

Traffic lights will be in place for the project with manual controls during rush hour.

A break for the holidays will begin in December with work to resume in January.

The spokesman said transmission upgrades in the East End were now complete, and that the final work would finish the island's transmission, distribution and retail asset upgrades to improve reliability and expand grid capacity.

He added: "Belco's entire transmission network has been underground for decades.

"The trenching work that has been taking place across the island is to replace 40 per cent of the old, high-voltage underground transmission cables -- some of which are more than 50 years old."

He said almost 25 per cent of the underground cables had served Bermuda for more than 60 years.

The cables and transmission and distribution equipment had gone beyond their useful lifespans, leading to faults, system vulnerabilities and higher maintenance costs.

The enhanced grid will also improve Belco's ability to connect with large-scale renewable energy.

Transmission cables connect to substations around the island, where their voltage is stepped down and fed into the distribution network.

Power supply gets stepped down further to connect with homes and businesses.

The spokesman said: "The new cables are being installed in multiservice duct banks that will eliminate the need to dig up the roads for cable replacement in the foreseeable future.

"Working closely with Works and Engineering and other utilities, the construction phase was designed to complement the Government's future water and sewage plans as well as any cabling needs for other utilities."

He said the island had not seen a grid upgrade project on the present scale since the 1950s, when the roads held "significantly less traffic, causing less disruption".

Shelly Leman, the Belco managing director, added: "This multimillion-dollar transmission upgrade project is one of the biggest, most important projects Belco has undertaken in recent times.

"The works are substantially complete and once the project reaches Evans Bay, the targeted transmission upgrades will be complete across the whole island.

"This will be the last segment of trenching for the project."

She added: "I encourage everyone to drive safely around open trenches and working crews.

"This project has many benefits for the consumer and will be the last time we need to trench roads to replace major grid infrastructure for the foreseeable future."

Ms Leman thanked the public for their patience.

Details on the upgrade can be found on the Belco website.

Major roadworks for electricity supply planned at West End