The transportation industry’s rapid adoption of digital technology is providing state highway agencies (SHAs) with the opportunity to transform their project delivery practices.
Digital project delivery provides an opportunity to leverage data for more than one application of highway construction. But what is digital project delivery?
To put it simply, it is the effective use of digital data to design, construct, inspect and record as-built conditions during the delivery of a construction project. Typical technology used for digital project delivery include 3D surveys (light detection and ranging, also known as “LiDAR”), 3D engineered models, automated machine guided construction equipment, mobile devices and GIS applications, paperless workflows, and most recently unmanned aircraft systems (UAS) more commonly known as “drones.” The same technology used to design the project can be used for building and inspecting the work.
Following are highlights of some notable practices and examples of how digital data may be leveraged for project delivery of highway construction.
Roadway and Bridge Models for Visualization and Public Outreach
The most commonly known use of digital project delivery is production of visualization models for public information. These models are typically developed for large, complex or high profile projects; and the visual quality is photorealistic.
These models are characterized by their 3D components being textured with materials, and having defined lighting conditions and camera locations. These models are rendered to produce still images and videos to give the viewer a virtual representation of the project, but the model itself is not suitable for automated machine guided (AMG) construction equipment.
3D Survey Data Collection
Being able to collect existing site conditions quickly and accurately represented in three dimensions can be achieved with remote sensing technology, such as with the use of terrestrial or airborne equipment, including UASs.
LiDAR is a geospatial technology that allows the rapid and geospatially accurate acquisition of roadway asset data by using a sensor to scan the project area, resulting in what is known as a point cloud. This cloud is composed of billions of points that depict the existing conditions almost as clear as a photograph. UAS, which is a geospatial data delivery platform, uses low-altitude aerial photography or LiDAR to create similar point clouds.
Both technologies rely on global navigational satellite systems (GNSS) to pinpoint a location in the world. The main benefit of these two technologies is that, when captured to the necessary degree of resolution, data can be collected once, but used many times for different purposes because the accuracy and integration of the information is such that when planned properly, it can meet survey design accuracies as well as general positioning.
According to a 2017 Oregon State University Study, the investment of a mobile LiDAR mapping system is recovered within one year of collecting information for multiple applications. For example, the Oregon Department of Transportation invested over $1 million to deploy one mobile mapping system, resulting in a savings of almost $5 million over a five-year period.
While a nearly 250 percent return-on-investment is impressive, having the 3D survey information readily available to support 3D design projects, asset management inventory, bridge vertical clearances, and maintenance preventive work is the real value of this mature technology.
Roadway Models for Contract Plans and Construction Applications
Starting with an accurate model of the existing conditions—such as through use of a LiDAR model—a roadway designer can produce a 3D design model as part of the process to develop contract plan-sheets.
The designer uses civil modeling tools to generate traditional deliverables for highway construction. This 3D design model is geometrically and geospatially correct, and depicts a visual representation of the design intent. The primary use of this digital design data is to produce contract plan-sheets, but it is often delivered as a reference information document for construction applications.
Contractors use this data to prepare estimates for bidding the project, and files to import to the AMG equipment to do grading and paving. Then the same design data can be used by the construction inspector to verify locations and elevations of items being constructed, provided they have the appropriate modern surveying equipment.
While technology is available to create 3D-engineered models for bridges, it is not a standard practice. There are many efforts to bring awareness to the maturing capabilities of commercially available software.
Digital As-Built Records
Perhaps the most underutilized technology based on the market maturity, collection of digital as-builts offers the most benefits to an SHA. The practice of collecting digital as-built records refers to the process to capture information about the installation and characteristics of a feature either directly from the field using smart forms tied to a geospatial database, or by extracting features after the assets are built from a LiDAR point cloud.
In either case, the information stored in the database typically includes GPS coordinates to locate the position of each type of asset (e.g. guardrail and culverts), as well as other characteristics, such as type of asset, dimensions, manufacturer, and date of installment that can be cataloged in a GIS database.
Digital project delivery technology has been driven by the contracting industry over the last decade, and now SHAs are adopting many of these modern practices to streamline processes, enable innovation, manage risk and capture data about their transportation assets for future data-driven decisions. WSP has been working at the national level with the Federal Highway Administration and some SHAs to develop guidance for adopting digital project delivery technology.
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