Looking forward to the next half-century of the split-level M5 Wynhol Viaduct, National Highways recently took a journey back in time to learn more about the construction of the South West's iconic motorway section.

The M5 Wynhol Viaduct is celebrating its 50th anniversary this year and to mark the occasion, and share some working knowledge of the iconic structure and surrounding rock slopes, National Highways' geotechnical and structures engineers reached out to 84-year-old Neil Manners, who played a part in the landmark's construction.

The retired engineer has always held a personal interest in the split-level motorway, between junctions 19 and 20 in North Somerset, and recently got the chance to learn more about the current maintenance regime carried out by the company responsible for England's motorways and major A roads.

Following an invitation to National Highways' operational base at Aztec West, near Bristol, Neil discovered the modern, digital methods employed to carry out surveys and maintain the structure.

He said: "As an engineer, I worked on a number of road infrastructure projects across the world and I certainly have some interest in the South West of England, having been involved in construction of the M5 Wynhol Viaduct and the Almondsbury Interchange.

"It was great to get together with the team looking after all these structures in the South West and to learn about the current engineering methods.

"Built into the slopes of the Wynhol cuttings, the M5 viaduct was a real feat of engineering and it was really interesting to see how it's being maintained today."

Caption: Above, Neil Manners meets up with, left, National Highways' South West Engineering Team Manager Terry Robinson and, right, Jon Durnell, Principal Geologist and Engineer for National Highways' Geotechnical Asset Management Team; below, Neil during construction of the split-level motorway

Neil was also treated to an up-close and personal visit to the structure, and Jon Durnell, Principal Engineer and Geologist for National Highways' Geotechnical Asset Management team, said: "As current guardians of the rock cuttings and viaduct, it was fantastic to meet up with Neil and fascinating to learn a little more about the construction and engineering methods and the history of this iconic landmark.

"The Wynhol Cuttings and Viaduct represents a landmark structure across the Strategic Road Network. As with all our structures, we carry out a regular maintenance regime to ensure it stands the test of time, and in car maintenance terms, we carried out its 100,000-mile service earlier this year.

"Working with our contractors BAM Ritchies, a team of abseiling engineers were deployed to work on the rock slopes high above the carriageway, and a state-of-the-art drone survey was carried out to capture high-level geotechnical detail – at over two miles (3.5km) the longest drone overflight of live motorway in the country.

"Given the age of the viaduct, we're going to need to do more work on the slopes and structures of the motorway in the coming years, and that's something we're looking at and preparing for now.

"We presented a lot of design material to Neil, and it was really nice to share all the latest innovations and methods as we look forward to the next 50 years."

Terry Robinson, National Highways' South West Engineering Team Manager, added: "A lot of our bridges and structures are reaching the same age along the M5, in fact next year marks the 50th anniversary of the Avonmouth Bridge.

"We have a robust inspection regime and examine all our bridges and other structures in line with the published guidance in the Design Manual for Roads and Bridges. This includes general visual inspection every two years and more detailed principal inspection every six years, which identifies and records defects in reinforced concrete, steelwork and other construction materials. 

Caption: Abseiling engineers from BAM Ritchies carrying out survey and maintenance work above the M5 Wynhol carriageway earlier this year

"Through a programme of structural inspections, investigations and assessments we ensure that substandard and potentially vulnerable structures are identified, safeguarding measures adopted, and like the Wynhol Viaduct, are fully maintained for many years to come."

National Highways is responsible for nearly 50,000 geotechnical assets on its strategic road network.

And in the South West, the company maintains a total of:

• 2,176 structures, including the two Severn Bridges, the Avonmouth Bridge, structures forming the Almondsbury Interchange, the Saltash Tunnel, Wynhol, Exe and Exminster Viaducts along the M5, together with a whole host of overbridges, underbridges, drainage channels and culverts;
• 6,219 earthworks assets, including embankments and cuttings such as Wynhol
• 9,200 square miles of road, 615 miles long, comprising 70% A road and 30% motorway, in a combination of urban and rural settings.