Mobile mapping provides essential element of end-to-end digital workflows
Managing and maintaining roadways across hundreds of miles is a challenge for any transportation agency, requiring multiple site visits, testing, mostly paper-based historical documentation, considerable experience and long memories.
National Highways, the highway transportation agency responsible for England’s Strategic Road Network (motorways and major A roads), set out to modernize these conventional practices. The organization established the 20-year Legacy Concrete Roads Programme to replace end of design life and design load pavement, and the Centre of Excellence was set up to help identify, test, and deploy new technologies, tools, and processes to streamline road management.
"We sought a digital representation—a living digital twin—of our concrete roads from which we can simulate asset behavior with an emphasis on safety, community and environmental outcomes."
That quest emphasized the need for a single source of truth.
Michael Ambrose, technical lead for the Concrete Roads Programme, calls the solution the "golden thread" of success. "We sought a digital representation—a living digital twin—of our concrete roads from which we can simulate asset behavior with an emphasis on safety, community and environmental outcomes," he explained. "The idea is to leverage real-world and real-time data to drive preemptive interventions, resulting in improved asset resilience, increased asset life and a safer, smoother running network."
It's an end-to-end solution that begins with as-built data collection, continues through analysis and work package release to contractors and concludes with field work data capture and upload back into the digital twin for future analysis.
Now three years into the program, and three comprehensive mobile surveys, that vision has become reality—and it's impressive. The capabilities and continued advancements are upending conventional practices, making way for more effective, efficient and unexpected maintenance opportunities that simply aren’t possible using more traditional methods.
Mapped and Modeled
Legacy concrete roads make up around 206 miles across 72 sites, or 4%, of England's motorway and long-distance A-road network. As these all lead to England's major ports, there is a vital need to keep them open to keep the UK economy open for business. When repairing concrete roads, repairs are typically isolated to localized sections of the road. Early in the program, the Concrete Roads team recognized that there were challenges with identifying where repairs were required due to the location accuracy of traditional survey and repair design methods and the reduced visibility afforded by night working. This resulted in aborted work, meaning additional cost, time, and disruption to delivery schemes.
Beginning in 2019, the Concrete Roads team focused on data collection on every concrete road to create a model of existing conditions. The goal was to capture as much data on the designated roads quickly with as much detail and accuracy as possible with the least amount of disruption to the public. Mobile laser scanning was a clear choice.
Ambrose and his team first evaluated various mobile mapping solutions that could meet the specifications, which included panoramic images and point clouds to an accuracy of 10mm or better. They ultimately selected the Trimble® MX9 field-to-finish mobile mapping system, not just for its mobile mapping collection capabilities but also for the software interfaces that support point cloud registration and post-processing.
Trimble distribution partner KOREC Group equipped a vehicle with the dual laser Trimble MX9, which includes three 12MP cameras (two side and one down-facing). With its tightly coupled GNSS and IMU, the MX9 is capable of collecting at a speed of 500 scans per second with accuracies to 5mm.
© KOREC Group
Over the course of 5 weeks, the team surveyed 1,700 lane km of concrete roads and evolved roads (concrete overlaid with asphalt) spread, in every lane, across 172 different schemes all over the UK, mapping features and identifiable defects. They gathered two million points per second and thousands of high resolution panoramic images.
Data was gathered to a relative accuracy of 5mm and absolute accuracy of 10mm when adjusted to ground control points and then processed in Trimble Business Center. Mark Reid, UK Sales Director with KOREC Group, said, "The multi echo return was so good that the point cloud even provided excellent vegetation penetration. With the point cloud data, we are able to generate topographic drawings of defect areas that can be interrogated directly within the portal."
That road surface imagery would become the foundation for extracting road defects and then the basis of a repair design.
The Defect Effect
Once the point cloud data was post-processed, the Concrete Roads team worked with KOREC to evaluate the data. The 2021 survey data was provided to the team at Mott McDonald to develop an AI-enabled routine that could quickly identify defects from down facing imagery. This algorithm was able to identify 10 different defect types, such as spalling, transverse cracks, corner cracks, potholes, failed repair, diagonal cracks, good condition repair, longitudinal cracks, scaling and raveling. Further, AECOM, a multinational infrastructure consulting firm, conducted an independent review of the results that Mott McDonald produced and also delivered a report on the efficiencies of the program.
KOREC is now working with AECOM to develop an improved AI model that will be run on the 2023 dataset, which will identify more defect types. The condition data will then be used to inform the investment requirements for the next phase of concrete road repair and renewal.
For instance, Ambrose and his team recently prepared a plan to repair potholes along a 22,000-meter stretch of concrete road. With help from the AI-enabled routine, they knew immediately where those defects were located, the amount of material required to repair and the associated costs.
"On average, we repair about 40% of the documented defects," Ambrose said. "Some of the defects are too small to repair or will cost too much to repair for very little benefit. We extract that 40% out of the database and upload to a custom designed, cloud-based asset management portal with tools that allow us to prepare a bill of material, total cost and even the carbon content of the anticipated repairs—all in a matter of minutes. Now we have an effective repair strategy."
The KOREC cloud-based portal is the home for the concrete roadway digital twin and its purpose and potential is directly driven by what happens in the field. Not only does the portal provide a resource for assessing maintenance actions, but asset managers are also able to issue work packages directly to contractor partners and contractor partners can share data with asset managers.
As part of its vision for an end-to-end assess-repair-and-track digital workflow, the Concrete Roads team equipped its contractors with field collection solutions. In this case, each contractor was provided a Trimble DA2 GNSS receiver with Trimble Catalyst GNSS positioning service, with the KOREC Capture field collection app that runs on Android or IOS devices.
With the Trimble DA2, contractors document the location and repair work as it is completed, and then upload the information to the portal in near real-time, automatically populating shift reports. Asset and environmental condition data are also embedded in the process.
When asked how contractors have responded, Ambrose said, "Every contractor and designer we've worked with so far has absolutely loved the field technology. They've said it's very easy to use, and that they can fully understand it very quickly. And all the geospatial people that are using it certainly appreciate the fact that they can get quick designs out of it as well."
One of the advantages for contractors has been the ability to see design details in the field. "If the contractor sees an anomaly, or a slightly different or worsening defect, the contractor can record and report it back for review. We have a complete record of that decision-making process," Ambrose added.
Concrete roads require multiple interventions, big and small, across the lifecycle of the asset. "With the highway portal, we will have both current and historical data. We’ll know with the click of a few buttons if we’re repairing a new patch of road or re-fixing the same patch, for instance. That’s intel that would have required considerable research previously," he continued.
While the Concrete Roads end-to-end workflow is still in its relative infancy, the ROI is readily clear.
"Every time we use the end-to-end digital solution, we save money just by having quality and comprehensive digital asset management data that can be fed into our analysis and deterioration modeling solutions."
A critical part of this digital twin development is the ability to track performance. The mobile mapping is repeated annually, which allows the asset managers to assess the degradation of defects that weren’t fixed in the previous year, and prioritize based on the budget.
Ambrose said, "We just completed the third mobile mapping survey of the concrete roads earlier this year. When we overlap these with the previous surveys, we see how the pavements have moved."
It's also ideal for detailed analysis of new means and methods. For instance, the Concrete Roads team documented 3,800 repairs with new innovative materials with one failure in three years. "With this highly accurate digital twin, we can see where and why things are doing well and where they’re not," Ambrose said. "In this case, the failure was a combination of factors, not just material choice. That comprehensive and detailed perspective is not something we’ve ever had. The digital twin allows us to keep learning and documenting concrete road behavior, which then becomes a benchmark for future decisions."
The team has also developed embedded sensors in the concrete to measure water runoff quantities, temperature, moisture, dew points and CO2. Ambrose added, "With that information embedded in our model, we can analyze the direct effect of these external factors on concrete behavior that we've never been able to consider. This helps plan ahead for climate change and how the asset is responding to this."
"Or, if a contractor is tasked with making a repair using a material that’s not available because of a supply shortage, we have the means and methods to automatically choose the next-best option to keep that project moving forward,” he continued. "Choosing materials is going to be increasingly important as we respond to the carbon agenda and the changing environment. It’s all about having the right data to make informed decisions in a timely manner."
When asked about time savings, Ambrose noted: "Using the digital platform, we save £29,000 every time we work on a simple scheme and £154,000 on every major scheme compared to previous efforts."
More Work Ahead on Digital Twin
To further build the database, the Concrete Roads team is planning some targeted new mobile mapping schemes with the MX9 later this year to assess the accuracy of the deterioration modeling and provide up-to-date information for future repair and renewal schemes.
The Concrete Roads team is also looking to add more data to its concrete roads database from sources such as high definition imagery, ground-penetrating radar and drone footage as well as thermal, noise and carbon sensors.
"The idea is to collect a big pool of data that will allow us to analyze things we've never considered before that cause the concrete to move," Ambrose continued.
For instance, a heatwave in 2022 drove some concrete pavements into compression, creating a slab heave condition, which allowed the rebar to come through.
"We need to be able to better prepare for these conditions before they affect our roads. A new sealant we’re testing changes color and provides a clear visual indication that something is going on—we would definitely see that in a mobile scan," Ambrose explained. "If we know how small factors contribute to the deterioration of slabs, such as temperature variations, then we can start to engineer appropriate solutions. Perhaps we don't need a crack repair, but instead a slab replacement—those are the answers our digital twin can help provide."
But there’s more work to be done on the development of this dynamic digital twin, according to Ambrose. In particular, he would like to see more automation of the planning and design process. For instance, he’d like to have the ability to see the costs, materials and carbon value of a defect repair with the push of a button. And then, with a few more clicks, see some alternative options with different materials. More automation is in the works amongst KOREC, Trimble and research partner Cambridge University.
"We've developed our golden thread, our live digital twin, which connects data in ways that allow us to see opportunities to do a range of analysis at different stages that we’ve never considered. Already, it’s driving better decision-making — and we’re just getting started."