Barrier work on the A702 at Brownsbank Cattle Creep originally due to finish in March, will now continue until the end of June.
The essential maintenance to install a new vehicle restraint system (VRS) on the A702, 500m north of Candymill, Biggar, began in November.
Originally work to replace a damaged section of the existing barrier was intended to be complete by the end of March 2017, but geotechnical investigations - to determine the condition of the carriageway and supporting ground – have revealed that more extensive works are required.
A new barrier system is needed, with work to provide more substantial foundations for it.
Since November temporary traffic lights have been in place to slow down traffic and reduce the risk of a vehicle striking the weakened barrier at this location.
Stuart Wallace, Bridges Manager for Amey, the company responsible for managing the roads network, said: “The extent of soil erosion at this site has convinced us that the establishment of new foundations, and installation of a new state-of-the-art vehicle restraint system, is required.
"We are considering the use of steel sheet piling to install a reinforced concrete ground beam that will provide a more substantial foundation for the new barrier.
“We apologise for any inconvenience caused by extending this essential maintenance scheme, but the safety of the travelling public remains our primary concern. We would like to thank road users for their continued patience and support.”
This work has been planned in consultation with Transport Scotland, Traffic Scotland, the emergency services, local bus operating companies, adjacent landowners and South Lanarkshire Council.
Further updates on the progress of this scheme are available online at: https://scottishtrunkroadsse.amey.co.uk/a702-brownsbank-cattle-creep/