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Hazel McDonald is chief bridge engineer at Transport Scotland

This network is also highly diverse. Parts of it are relatively conventional motorways, but there are also large lengths of rural routes and routes with no diversions, including routes to ports and vital connections for islands.

This means that maintenance and renewal of increasingly ageing assets entail complex processes. Adding to the complexity, significant attention has to be paid to the tourism season, with some local economies highly dependent on tourist access at key times of the year. All of this makes for some notable challenges.

Transport Scotland chief bridge engineer Hazel McDonald explains: “One solution to bridge replacements is that we use temporary bridging where we’ve not got a diversion route, but that means probably twice as much work. You’ve designed your new structure, but you’re also having to design your foundations and do all your environmental assessment for your temporary bridge. You need to get that in, and then later reinstate nature at the end. So, it’s almost like doing two bridge replacements.

“And then there are land issues, because we don’t own a lot of the land that the road sits on. We have to negotiate with landowners or purchase land, which can take a long time. There’s also a lot of stakeholder engagement with local landowners, local businesses, MSPs, MPs, local councillors and others.”

All of this creates an understandable pressure to get decisions right and make them well ahead of time so communities know what is coming.

Inspections across assets can feed into prioritisation throughout the network, but this can be complicated by somewhat subjective inspection outcomes, with two inspectors perhaps concluding different prioritisations when they inspect a structure. And of course, there are emergencies to deal with too.

“Transport Scotland is a thin client,” says McDonald, going on to explain what that means. “We have a small team that manage the structures on behalf of Scottish Ministers by using four operating companies to deliver the works on the ground. Our [supplier] operating companies have significant inspection, design, environmental and road safety staff and they procure contractors to do physical works on our behalf.

“One growing problem as the structures have aged on the motorway stock is that we have a lot of half joints, post-tensioning, potential for concrete spalling and so on. So, we need more proactive inspections of specific risks, and that includes inspecting for risks that are worsened by climate change, such as ensuring culverts haven’t become blocked by debris or bridge supports scoured.

“While we aim to be proactive and plan ahead, emergencies that occur can be highly variable. We might have no bridge strikes one year and then have two in relatively quick succession, or have several scour issues to deal with at once.

“That takes a lot of resource and focus for staff, which holds back planned works as you deal with an emergency. All of this makes for a complex picture just in terms of the assets, before we even address the existence of different organisational approaches.”

Many highland and island communities have no diversion routes for maintenance and upgrade works, necessitating complex solutions such as temporary bridges

Organisational differences

The nature of bridge inspections, while very formally structured in one sense, has often involved some degree of informality in others, with different organisations using different regimes for inspections. This represents an added risk for an asset owner.

McDonald explains: “It puts a client at risk if you don’t have confidence in your inspection reports and different authorities have different procedures. At Transport Scotland we follow the Design Manual for Roads and Bridges (DMRB) process. The inspector does the inspection and the operating company inspection manager will review that before it comes to us. Then our unit managers will review all the inspections that come across their desk and the results feed into our work prioritisation.

“Other authorities may not have as many staff or don’t have staff with sufficient knowledge and experience of structural issues, and so perhaps don’t follow that review process. That makes them very reliant on the people that do the inspections, which makes it very important that the inspectors can demonstrate their experience and proficiency.”

This can be particularly problematic when something goes wrong.

“If you’re basing a decision on inspection information and it turns out to be inaccurate, then there’s a question about where that leaves you as an owner, bridge manager or chief executive in a small authority if your inspector doesn’t have the necessary knowledge and skills.”

Subjective outcomes

Inspections have traditionally been very dependent on visual assessment, which isn’t always easy with some assets, and can only tell engineers so much about what is really happening with a structure. It can also lead to some anomalous results, depending on who does the inspection and when they do it.

“If it is a visual inspection, it can be a bit subjective,” says McDonald. “One of the things that is mandated to do before you go to do an inspection is to review the previous one. Now, if it’s a different inspector, they might have a slightly different view on the severity or the priority of a particular defect that they’ve gone out to look at. One way around that is to use digital image correlation.

“Visual imaging is getting better and if you’ve got the capacity to be able to store inspections in that format, then you can track the change in condition over time. That is really the most valuable thing. But not everybody’s got the capability to undertake those kind of inspections or interrogate that kind of dataset, or even store that kind of data.

“Obviously, working for a government department, we’re restricted in terms of what we are can do with IT systems for good reasons that include security and cost, but there is definitely merit in exploring what can be done.

“This should reflect priorities. I would suggest perhaps technologies such as digital image correlation aren’t necessary for every structure. That said, there have been examples of somebody going out to do another inspection and the new report suggests a structure has improved since the last inspection. That is something that should be picked up by whoever’s reviewing it from the operator.

“Then, when it comes to us at Transport Scotland, our unit managers can have a look at it and go, ‘Wait a minute, you said last time it was something else, can you just put a little commentary around why you think it’s in better condition than previously thought?’”

“All of this matters because the outcome of an inspection feeds into our forward work priorities, not just the defects but the rate of change. That’s the bit that we’re really interested in, the rate of deterioration.”

Certification of inspectors

Long-standing concerns about the subjective nature of inspections have led to attempts to better quantify the experience and knowledge of inspectors.

Some years ago, this led to the UK Bridges Board undertaking a quality review of inspection reports that found quality wanting. That led the board to work with the UK’s Department for Transport (DfT) to introduce certification. Unfortunately, when this was put out to tender by the DfT, there was no interest from the market in developing and running a scheme.

That did not stop the UK Bridges Board seeking to make it happen. McDonald explains: “There was still a desire to do it, because it was incompatible that a person would rightly need certification to check a domestic gas boiler, but not to inspect a major highways structure.”

The UK Bridges Board began working with Lantra, an awarding body that already provided National Highway Sector Schemes for the Highways Agency (which later became Highways England and then National Highways) on the development and assessment of competence, leading to the Bridge Inspection Certification Scheme (Bics).

“They worked closely with Lantra but the first scheme launched required candidates to inspect all material and structure types and it quickly became apparent that it needed to be more manageable,” says McDonald. “So, we divided it into modules with mandatory skills and then materials skills. If you only inspect masonry, why should you need to demonstrate knowledge and experience of concrete?”

“The independent assessors found it very time-consuming to assess candidates and it was difficult for candidates to decide what information should go into the e-portfolio, so submissions were often very large. As a result, we set about simplifying this by introducing a knowledge-based test like the Construction Industry Training Board (CITB) Construction Skills Certification Scheme (CSCS) test.

“That has helped and allowed the scheme to award a new associate inspector level certification, as well as inspector and senior inspector levels.”

Implementation of Bics has been predominantly client-led. Transport Scotland has mandated it, as have others, although smaller authorities have had to phase this in for staff as it would have mean changing terms of employment for embedded staff. There has also been some lag, as procurement of inspection services by local authorities were tendered with certification written into requirements, but then found a lack of certified people available.

Some organisations also feel that cost is another challenge of the scheme, although McDonald points out that the price tag comes from having a robust scheme.

“The scheme is independently assessed to ensure it is fair and comprehensive. Lantra appoints independent assessors and we have to pay for their time to review the portfolios, make a recommendation for an interview and then undertake an interview. The interview process is important to ensure the assessment is robust, and partly to check that submissions are the candidate’s own work, which it turns out on a couple of occasions not to have been.”

For those who have mandated certification, McDonald suggests the impact is worth it. “We mandated this at Transport Scotland and I think what we have is a lot more comfort that we have confidence in the competency of staff that are being put forward. Previously it was up to our operating companies to ensure that they had suitably qualified and experienced staff to do this, but there was no formal process.

“I think from a client point of view we’ve got a bit more comfort, knowing that somebody has independently assessed the professionals involved. We also have an independent audit group that has looked at inspection quality, as well as our unit managers who review all the inspections that come across their desks, and the quality is improving.

“I wouldn’t say that quality improvement was all down to Bics. It probably results from a multi-pronged approach to improvement, but it certainly gives us more comfort as we make asset management and investment decisions based on inspection reports.”

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