The additional time is needed for safety reasons following an “HGV incursion”

Roadworks on a stretch of motorway through South Lanarkshire have been extended for a second time, with an extra six weeks of restrictions now being scheduled for safety reasons following a recent lorry incident.

The bridge refurbishment project at Nethan Viaduct, between junctions nine and 11 of the M74, is now set to run until early August compared to the previous anticipated end date in late June – itself a two-month extension to original plans for completion this month.

A fourth phase of work is getting underway this week, with an overnight closure taking place tonight (Monday, April 7) from 8pm to 6am with traffic being diverted onto the B7078 through Lesmahagow for the duration.

Roadworks including lane closures and contraflows have been in place since last October as improvements including waterproofing, concrete repair, resurfacing, expansion joint replacement, edge beam strengthening and barrier upgrading are carried out, with a 30mph limits and average speed cameras in place.

Contractor Amey announced this week: “Unfortunately, following an HGV incursion and other vehicle-related safety issues, existing traffic management arrangements have had to be reassessed to ensure roadworker and public safety.”

A spokesperson said: “The safety of our workforce and the travelling public is paramount when planning and delivering roadworks. This recent incursion incident highlights the importance of the speed restrictions currently in place on the M74 for everyone’s protection.

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“Over 1800 incursions have taken place at our sites since 2024 due to vehicles breaching safety barriers, ignoring red lights, or violating temporary speed restrictions.

“These incursions not only put lives at risk, but also impact the programme of our works, meaning those that do follow the restrictions are inconvenienced by further delays. We thank road users for their continued patience and understanding while these vital improvements are completed.”

It means the “necessary alterations” to the traffic safety arrangements “will result in an extension of the current programme with completion now projected to be Friday August 8” and continue the roadworks throughout the school summer holidays – compared to the originally-planned April 30 finish and then the first extension date of June 26 following adverse weather delays.

Three phases of work have now been completed so far on the northbound carriageway and central reservation, and the overnight closure is required for to conclude the latest phase and begin the remaining work on the southbound section of the route.

Monday night’s closure – starting at 8pm and finishing at 6am on Tuesday, April 8 – will see northbound traffic diverted off the motorway between junctions 12 and 10, and southbound between junctions nine and 12, with both using the B7078 as a diversion route.

The next four months of work will see two lanes running in each direction with contraflows in place; and Amey add that the average speed cameras will remain in operation between junctions nine and 11, saying: “Traffic speed [is] reduced from 70mph to 30mph. This is necessary to ensure the safety of personnel and members of the public given the use of narrow lanes, while also considering the high volume of HGV traffic on this route.”

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Amey is carrying out the major bridge refurbishment work on behalf of Transport Scotland, centered on Nethan Viaduct south of junction 10 and which will “benefit vehicles using this route by improving the safety and condition of the carriageway and the associated structure”.

They noted earlier in the project that the 30mph speed limit is needed due to the roadworks’ location at the bottom of a hill on a high-speed road which carries a large number of lorries, along with the four-lane set-up meaning staff are working on the same carriageway as running traffic segregated by a temporary barrier., were all factors in implementing the 30mph speed limit.

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