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Highway Infrastructure Inspection Practices for the Digital Age (2022)

Chapter: Chapter 3 - Survey of the State of the Practice

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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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Suggested Citation:"Chapter 3 - Survey of the State of the Practice." National Academies of Sciences, Engineering, and Medicine. 2022. Highway Infrastructure Inspection Practices for the Digital Age. Washington, DC: The National Academies Press. doi: 10.17226/26592.
×
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33   C H A P T E R   3 Introduction This chapter presents current state DOT practices in the use of technologies for highway infrastructure inspection. To collect the most updated information on highway infrastructure inspection during the digital age, a web-based survey was distributed to the voting members of the AASHTO Committee on Construction, which includes DOT representatives from 50 states and the District of Columbia. The purpose of the survey was to identify technologies currently in use by state DOTs for inspection of new and existing highway infrastructure assets and to document different methods used to assess the viability, efficiencies, and return on investment (ROI) of inspection technologies. In addition, the survey results helped determine which state DOTs would be contacted for case examples, as detailed in Chapter 4. Appendix A includes the survey questionnaire while Appendix B contains individual DOT responses to each question in the survey. The findings presented in this chapter are a result of the responses of the 42 state DOTs that completed the survey, representing an 82% response rate. As discussed in Chapter 1, the survey was designed to collect relevant information within four main technology areas: • Geospatial technologies, • Remote sensing and monitoring technologies, • Mobile devices and software applications, and • Nondestructive evaluation methods. The chapter begins with a report of the general findings on the use of technologies for high- way inspection. It then discusses the current practice of each of the aforementioned technology areas. Finally, the chapter summarizes key findings about the different methods used to assess the viability, efficiencies, and ROI of inspection technologies. It is important to note that the 42 state DOT respondents were not required to respond to all of the questions in the survey. As a result, the sample size (n) of the questions can vary. In addition, several questions in the survey have a “Not Sure” option for respondents to select if they are not confident about the information requested. The following sections discuss the key findings from the survey in detail. General Findings State DOTs are currently using various technologies for inspection of their highway infra- structure during construction or maintenance of assets. Table 3.1 presents the 42 state DOTs that responded to the survey. Out of 42 state DOTs, 19 (45%) reported that they have used all four technology areas studied in this synthesis (geospatial technologies, remote sensing and moni- toring technologies, mobile devices and software applications, and nondestructive evaluation Survey of the State of the Practice

34 Highway Infrastructure Inspection Practices for the Digital Age State DOT Geospatial Technologies Remote Sensing and Monitoring Technologies Mobile Devices and Software Applications Nondestructive Evaluation Methods Alabama Arkansas California Colorado Connecticut Delaware Florida Georgia Hawaii Illinois Indiana Iowa Kansas Kentucky Maryland Massachusetts Minnesota Mississippi Missouri Montana Nebraska New Hampshire New Jersey New Mexico New York North Carolina North Dakota Oklahoma Oregon Pennsylvania Rhode Island South Carolina South Dakota Tennessee Texas Utah Vermont Virginia Washington West Virginia Wisconsin Wyoming Table 3.1. Reported technology implementation for highway infrastructure inspection. methods). Five state DOTs, including Maryland, Mississippi, New Hampshire, Oklahoma, and Wyoming, indicated that they have implemented one technology area for inspection of their highway infrastructure during construction or maintenance of assets. A total of 18 state DOTs (43%) stated that they have implemented two or three technology areas for their highway infra- structure inspection. It is important to note that some state DOTs may not have selected one of these four technology areas if that technology area was not being used for highway infrastructure during construction or maintenance of assets. Figure 3.1 shows that 41 out of 42 responding state DOTs (98%) indicated that they have used mobile devices and software applications for inspection of their highway infrastructure during

Survey of the State of the Practice 35   construction or maintenance of assets. Thirty-two state DOTs (76%) reported that they used geospatial technologies for highway infrastructure inspection. Similarly, two-thirds of respond- ing state DOTs (28 responses or 67%) mentioned that they used remote sensing and monitoring technologies or nondestructive evaluation methods for inspection of their highway infrastruc- ture during construction or maintenance of assets. Figure 3.2 shows the application of the four technologies (geospatial technologies, remote sensing and monitoring technologies, mobile devices and software applications, and non- destructive evaluation methods) associated with different types of highway infrastructure, including roadways, signage or roadsides, earthwork or grading, bridges, drainage systems, and non-bridge structures. More than 70% of the 42 responding state DOTs indicated that they have used mobile devices and software applications for inspection of all infrastructure types. Similarly, more than 50% of the 42 responding state DOTs have used geospatial tech- nologies for inspection of roadways, signage or roadsides, and earthwork or grading. Approxi- mately 50% of the responding state DOTs have used geospatial technologies for inspection of bridges and drainage systems. Remote sensing and monitoring technologies are typically used for inspection of roadways (45%), bridges (45%), and earthwork or grading (19%). Four state DOTs (10%) indicated that they have used remote sensing and monitoring technolo- gies for inspection of non-bridge structures. Approximately 75% of the 42 responding state DOTs indicated that they have used nondestructive evaluation technologies for inspection of roadways and bridges. Figure 3.3 shows that most state DOTs have provided training to their staff regarding the use of technologies for highway inspection. There are a variety of training approaches that state DOTs have used to help their staff better implement inspection technologies. Specifically, more than 60% of the 42 state DOT responses have used hands-on/field-based training, peer training, online training, or classroom-based training. Additionally, 19 state DOTs have used vendor demonstrations and 16 state DOTs have used workshops to train their staff to use technologies for highway inspection. To further identify how technologies are used for inspection of new and existing highway infrastructure assets, the following sections present the current state of practice in using the 67% 67% 76% 98% 0 10 20 30 40 50 Nondestructive Evaluation Methods Remote Sensing & Monitoring Technologies Geospatial Technologies Mobile Devices & Software Applications Number of state DOT responses (n=42) Figure 3.1. Technologies used by state DOTs for highway infrastructure inspection.

36 Highway Infrastructure Inspection Practices for the Digital Age 2% 10% 38% 45% 62% 62% 67% 69% 0 10 20 30 40 50 No training provided Only provided reference materials (hardcopy or electronic) Workshop Vendor demonstration Classroom based training Online training Peer training Hands on/ eld-based training Number of state DOT responses (n=42) Figure 3.3. Methods of training for using technologies for highway infrastructure inspection. Figure 3.2. Use of technologies for highway infrastructure inspection. 31% 21% 76% 24% 17% 74% 74% 71% 83% 79% 76% 88% 10% 0% 45% 19% 5% 45% 43% 48% 50% 52% 52% 67% 0 10 20 30 40 Non-bridge structures Drainage systems Bridges Earthwork/grading Signage/roadside Roadways Number of state DOT responses (n=42) Geospatial Tech. Remote Sensing & Monitoring Mobile Devices & Software Nondestructive Evaluation

Survey of the State of the Practice 37   four technology areas (geospatial technologies, remote sensing and monitoring technologies, mobile devices and software applications, and nondestructive evaluation methods) based on the responses of the 42 state DOTs. Geospatial Technologies The survey respondents were asked to indicate the number of years that their state DOTs have been using geospatial technologies for inspection of highway infrastructure during construction or maintenance of assets. Figure 3.4 summarizes the results of this question. Out of 32 responses, 13 state DOTs (41%) have used geospatial technologies for 2 to 5 years. Seventeen state DOTs (53%) have used geospatial technologies for more than 5 years. Two state DOTs (6%) indicated that they have used geospatial technologies for less than 2 years. Application for Highway Construction Inspection Figure 3.5 shows the main geospatial technologies used for highway infrastructure inspection during construction. Twenty-six state DOTs (81%) have used GNSS/GPS, 19 state DOTs (59%) have used e-ticketing technologies, and nine state DOTs (28%) have used terrestrial photogram- metry (TP) for inspection of their highway infrastructure during construction. Figure 3.5 also indicates that approximately 50% of the 32 responding DOTs have used UASs, RTSs, and GIS for inspection of their highway infrastructure during construction. Table 3.2 summarizes the application of each geospatial technology associated with common inspection activities during construction of highway projects. Table 3.2 indicates that the GNSS/ GPS technology is primarily used for earthwork inspection and quantities, UASs are dominantly used for monitoring construction and creating site photos and videos, and e-ticketing is domi- nantly used for tracking the position of bulk materials (e.g., concrete, asphalt, aggregate loads). For the implementation of the GNSS/GPS technology (Table 3.2), the top inspection activities during construction of highway projects based on the responses from 26 DOTs include: • Earthwork inspection and quantities (17 DOTs, 65%), • Collecting as-built information/developing 3D as-built models (13 DOTs, 50%), 6% 41% 19% 34% 0 5 10 15 20 < 2 years 2-5 years 5-10 years >10 years Number of state DOT responses (n=32) Figure 3.4. Experience in using geospatial technologies for highway infrastructure inspection.

38 Highway Infrastructure Inspection Practices for the Digital Age 28% 47% 47% 50% 59% 81% 0 10 20 30 40 Terrestrial Photogrammetry (TP) Geographic Information Systems (GIS) Robotic Total Stations (RTS) Unmanned Aircraft Systems (UAS) (Note: UAS is also a remote sensing technology) e-Ticketing Global Navigation Satellite Systems (GNSS)/ Global Positioning System (GPS) Number of state DOT responses (n=32) Figure 3.5. Types of geospatial technologies used for highway infrastructure inspection during construction. Typical Inspection Activities GNSS/ GPS (n=26) GIS (n=15) UAS (n=16) RTS (n=15) TP (n=9) e-Ticketing (n=19) Not Sure Tracking position of bulk material (concrete, asphalt, aggregate loads) 6(*) 1 1 2 0 13 3 Tracking finished materials and inventory (pipe, rebar, etc.) 5 2 0 2 0 0 6 Measurement of material strength and temperature (concrete, base course, etc.) 3 2 0 0 0 0 7 Measurement of pavement thickness 4 1 0 2 0 1 8 Earthwork inspection and quantities 17 1 8 9 4 1 3 Structural inspection and quantities 8 3 6 2 2 1 4 Monitoring construction progress 11 4 14 6 4 1 2 Verification and documentation of work completed for payment 13 3 2 6 1 6 2 Locating underground utilities and underground assets 7 3 0 3 0 0 8 Collecting as-built info/developing 3D as-built models 13 5 3 6 3 0 5 Quality control/quality assurance 10 2 2 6 1 3 4 Erosion control inspection 4 2 3 0 1 1 6 Site photos and videos 5 4 12 0 3 0 4 (*): The numbers in the cells indicate the number of DOT responses. Table 3.2. Applications of geospatial technologies for highway infrastructure inspection during construction.

Survey of the State of the Practice 39   • Verification and documentation of work completed for payment (13 DOTs, 50%), • Monitoring construction progress (11 DOTs, 42%), and • Quality control and quality assurance activities (10 DOTs, 38%). For the implementation of GIS (Table 3.2), the top inspection activities during construction of highway projects based on the responses from 15 state DOTs include: • Collecting as-built information/developing 3D as-built models (five DOTs, 33%), • Site photos and videos (four DOTs, 27%), • Monitoring construction progress (four DOTs, 27%), • Locating underground utilities and underground assets (three DOTs, 20%), • Verification and documentation of work completed for payment (three DOTs, 20%), and • Structural inspection and quantities (three DOTs, 20%). For the implementation of UASs (Table 3.2), the top inspection activities during construction of highway projects based on the responses from 16 state DOTs include: • Monitoring construction progress (14 DOTs, 88%), • Site photos and videos (12 DOTs, 75%), • Earthwork inspection and quantities (eight DOTs, 50%), and • Structural inspection and quantities (six DOTs, 38%). For the implementation of RTSs (Table 3.2), the top inspection activities during construction of highway projects based on the responses from 15 state DOTs include: • Earthwork inspection and quantities (nine DOTs, 60%), • General quality control and quality assurance activities (six DOTs, 40%), • Collecting as-built information/developing 3D as-built models (six DOTs, 40%), • Verification and documentation of work completed for payment (six DOTs, 40%), and • Monitoring construction progress (six DOTs, 40%). For the implementation of the TP technology (Table 3.2), the top inspection activities during construction of highway projects based on the responses from nine state DOTs include: • Monitoring construction progress (four DOTs, 44%), • Earthwork inspection and quantities (four DOTs, 44%), • Site photos and videos (three DOTs, 33%), and • Collecting as-built information/developing 3D as-built models (three DOTs, 33%). Finally, for the implementation of the e-ticketing technology (Table 3.2), the top inspection activities during construction of highway projects based on the responses from 19 state DOTs include: • Tracking the position of bulk material such as concrete, asphalt, aggregate loads (13 DOTs, 68%); • Verification and documentation of work completed for payment (six DOTs, 32%); and • Quality control and quality assurance (three DOTs, 16%). Application for Inspection of Highway Infrastructure Assets Figure 3.6 shows the main geospatial technologies used for highway infrastructure inspection during maintenance of assets. Out of 32 responses, 19 state DOTs (59%) have used GIS, 12 state DOTs (38%) have used GNSS/GPS, 10 state DOTs (31%) have used UASs, six state DOTs (19%) have used TP, and four state DOTs (13%) have used RTSs for inspection of their highway infrastructure during maintenance of assets. Table 3.3 summarizes the application of each geospatial technology associated with typical inspection activities during maintenance or asset management of highway infrastructure.

40 Highway Infrastructure Inspection Practices for the Digital Age Figure 3.6. Types of geospatial technologies used for highway infrastructure inspection during maintenance of assets. Relevant Inspection Activities GNSS/ GPS (n=12) GIS (n=19) UAS (n=10) RTS (n=4) TP (n=6) Not Sure Location of pavement/material placement for performance tracking 6(*) 6 0 1 1 11 Signage, culvert, guardrail, and other asset inventories and inspection 10 16 3 1 1 7 Sharing asset information between different functional units 7 15 1 1 1 8 Pavement crack and defect detection 6 3 1 1 1 12 Structural inspection 6 4 10 3 1 8 Slope stability and landslide assessment 3 4 5 2 2 12 Location of voids/buried assets 0 3 0 2 0 13 (*): Number of DOT responses. Table 3.3. Applications of geospatial technologies for highway infrastructure inspection during maintenance of assets. Table 3.3 indicates that the GNSS/GPS and GIS technology are dominantly used for signage, culvert, guardrail, and other asset inventories and inspection; the GIS technology is also dom- inantly used for sharing asset information between different functional units; and UASs are dominantly used for structural inspection. For the implementation of the GNSS/GPS technology (Table 3.3), the top inspection activities during maintenance of highway assets based on the responses from 12 DOTs include: • Signage, culvert, guardrail, and other asset inventories and inspection (10 DOTs, 83%); • Sharing asset information between different functional units (seven DOTs, 58%); • Structural inspections (six DOTs, 50%); • Pavement crack and defect detection (six DOTs, 50%); and • Location of pavement/material placement for performance tracking (six DOTs, 50%). 13% 19% 31% 38% 59% 0 10 20 30 Number of state DOT responses (n=32) Robotic Total Stations (RTS) Terrestrial Photogrammetry (TP) Unmanned Aircraft Systems (UAS) (Note: UAS is also a remote sensing technology) Global Navigation Satellite Systems (GNSS)/Global Positioning System (GPS) Geographic Information Systems (GIS)

Survey of the State of the Practice 41   For the implementation of GIS (Table 3.3), the top inspection activities during maintenance of highway assets based on the responses from 19 DOTs include: • Signage, culvert, guardrail, and other asset inventories and inspection (16 DOTs, 84%); • Sharing asset information between different functional units (15 DOTs, 79%); • Location of pavement/material placement for performance tracking (six DOTs, 32%); • Slope stability and landslide assessment (four DOTs, 21%); and • Structural inspection (four DOTs, 21%). For the implementation of UASs (Table 3.3), the top inspection activities during maintenance of highway assets based on the responses from 10 DOTs include: • Structural inspection (10 DOTs, 100%); • Slope stability and landslide assessment (five DOTs, 50%); and • Signage, culvert, guardrail, and other asset inventories and inspection (three DOTs, 30%). For the implementation of RTSs (Table 3.3), the top inspection activities during maintenance of highway assets based on the responses from four DOTs include: • Structural inspection (three DOTs including Oregon, Massachusetts, and Nebraska, 75%), • Location of voids/buried assets (two DOTs including Oregon and Massachusetts, 50%), and • Slope stability and landslide assessment (two DOTs including Oregon and Massachusetts, 50%). Finally, as shown in Table 3.3, only a limited number of state DOTs have used TP technology for highway infrastructure inspection during maintenance or asset management. For example, the Pennsylvania and Arkansas DOTs have used TP for slope stability and landslide assessment. The North Carolina DOT has used TP for pavement crack and defect detection. The West Virginia DOT has used TP for sharing asset information between different functional units and for the location of pavement/material placement for performance tracking. Challenges in Implementation The survey respondents were asked to identify the main factors that impede the use of geo- spatial technologies for highway infrastructure inspection during construction and maintenance of assets. Figure 3.7 summarizes the main challenges on the basis of the responses from 32 state DOTs. The top five challenges in the implementation of geospatial technologies for highway infrastructure inspection during construction and maintenance of assets are: • Lack of training, knowledge, and skills to use technologies; • Lack of reliable internet connection in remote locations; • Cost issues; • Lack of standard contract specifications; and • Device maintenance and user support. Remote Sensing and Monitoring Technologies The survey respondents were asked to indicate the number of years that their state DOTs have been using remote sensing and monitoring technologies for inspection of highway infrastructure during construction or maintenance of assets. Figure 3.8 summarizes the results of this question. Out of 28 responses, 10 state DOTs (36%) have used remote sensing and monitoring technologies for highway infrastructure inspection for more than 10 years. Six state DOTs (21%) have used remote sensing and monitoring technologies for 5 to 10 years. Three state DOTs (11%) indicated that they have used remote sensing and monitoring technologies for less than 2 years.

42 Highway Infrastructure Inspection Practices for the Digital Age 10% 13% 16% 23% 26% 29% 42% 45% 48% 52% 55% 74% 0 5 10 15 20 25 Access, privacy, or security concerns Incompatibility with (or restricted by) legal, regulatory, or policy requirement Quality of data collected Incompatibility with existing hardware Lack of technical results/case studies demonstrating accuracy Insufficient agency network levels, IT infrastructure/cellular service Resistance to change Device maintenance and user support Lack of standard contract specifications Cost issues Lack of reliable internet connection in remote locations Lack of training, knowledge, and skills to use technologies Number of state DOT responses (n=32) Figure 3.7. Challenges in using geospatial technologies for highway infrastructure inspection during construction or asset management. 11% 32% 21% 36% 0 5 10 15 < 2 years 2-5 years 5-10 years >10 years Number of state DOT responses (n=28) Figure 3.8. Experience in using remote sensing and monitoring technologies for highway infrastructure inspection.

Survey of the State of the Practice 43   Application for Highway Construction Inspection Figure 3.9 shows the main types of remote sensing and monitoring technologies used for high- way infrastructure inspection during construction. Out of 28 responses, 21 DOTs (75%) have used remote sensors (e.g., accelerometers, maturity meter sensors, or strain gauges); 15 DOTs (54%) have used remote cameras; 14 DOTs (50%) have used both IC and LiDAR/3D laser scan- ning; and 13 DOTs (46%) have used infrared sensors (e.g., thermal, motion detectors, object detection, thermal profiling) for inspection of their highway infrastructure during construction. Figure 3.9 also indicates that four DOTs (14%) have used barcodes and readers and three DOTs (11%) have used RFID for inspection of their highway infrastructure during construction. Table 3.4 summarizes the application of each remote sensing and monitoring technology associated with typical inspection activities during construction of a highway project. Table 3.4 indicates that the LiDAR/3D laser scanning technology is typically used for collecting as-built information/developing 3D as-built models as well as structural inspection and quantities, intel- ligent compaction is typically used for quality control and quality assurance activities, remote sensors and infrared sensors are dominantly used for measurement of material strength and temperature (e.g., concrete, base course), and remote cameras are dominantly used for monitor- ing construction progress and capturing site photos and videos. The following sections present in more detail the results of using each remote sensing and monitoring technology for inspec- tion of highway infrastructure during construction. For the implementation of the LiDAR/3D laser scanning technology (Table 3.4), the top inspection activities during construction of highway projects based on the responses from 14 state DOTs include: • Collecting as-built information/developing 3D as-built models (five DOTs, 36%), • Structural inspection and quantities (four DOTs, 29%), and • Earthwork inspection and quantities (three DOTs, 21%). Figure 3.9. Types of remote sensing and monitoring technologies used for highway infrastructure inspection during construction. 11% 14% 46% 50% 50% 54% 75% 0 10 20 30 Radio-Frequency Identification (RFID) Barcodes & Readers (B&R) Infrared Sensors (e.g., thermal, motion detectors, object detection, thermal profiling) (IS) Light Detection and Ranging (LIDAR)/3D Laser Scanning Intelligent Compaction (IC) Remote Cameras (RC) Remote Sensors (e.g., accelerometers, maturity meter sensors, strain gauges, etc.) (RS) Number of state DOT responses (n=28)

44 Highway Infrastructure Inspection Practices for the Digital Age For the implementation of intelligent compaction (Table 3.4), the top inspection activities during construction of highway projects based on the responses from 14 state DOTs include: • Quality control and quality assurance (six DOTs, 43%), • Earthwork inspection and quantities (three DOTs, 21%), and • Measurement of pavement thickness (three DOTs, 21%). For the implementation of remote sensors (Table 3.4), the top inspection activities during construction of highway projects based on the responses from 21 state DOTs include: • Measurement of material strength and temperature (seven DOTs, 33%), • Quality control and quality assurance (six DOTs, 29%), and • Measurement of pavement thickness (three DOTs, 14%). For the implementation of infrared sensors (Table 3.4), the top inspection activities during construction of highway projects based on the responses from 13 state DOTs include: • Measurement of material strength and temperature (10 DOTs, 77%), and • Locating underground utilities and underground assets (two DOTs, 15%). For the implementation of remote cameras (Table 3.4), the top inspection activities during construction of highway projects based on the responses from 15 state DOTs include: • Capturing site photos and videos (12 DOTs, 80%), • Monitoring construction progress (10 DOTs, 67%), and • Tracking the position of bulk material loads (three DOTs, 20%). (*): Number of DOT responses. Typical Inspection Activities LiDAR/3D Laser Scanning (n=14) Intelligent Compaction (n=14) Remote Sensors (n=21) Infrared Sensors (n=13) Remote Cameras (n=15) Barcodes and Readers (n=4) RFID (n=3) Not Sure Tracking the position of bulk material (concrete, asphalt, aggregate loads) 0 (*) 0 0 1 3 0 1 4 Tracking finished materials and inventory (pipe, rebar, etc.) 0 0 2 1 1 0 1 5 Measurement of material strength and temperature (concrete, base course, etc.) 0 2 7 10 0 0 1 2 Measurement of pavement thickness 0 3 3 0 0 0 0 5 Earthwork inspection and quantities 3 3 1 0 0 0 0 3 Structural inspection and quantities 4 1 1 0 2 0 0 4 Monitoring construction progress 2 1 1 0 10 0 0 4 Verification and documentation of work completed for payment 2 1 2 0 0 0 0 4 Locating underground utilities and underground assets 1 0 2 2 0 0 0 5 Collecting as-built information/developing 3D as-built models 5 0 1 0 0 0 0 4 Quality control/quality assurance 2 6 6 1 1 2 1 1 Erosion control inspection 0 0 1 1 0 0 0 5 Site photos and videos 1 0 1 0 12 1 0 4 Monitoring ground acceleration during pile driving 0 0 1 0 0 0 0 0 Traffic monitoring (queue detection) 0 0 1 0 1 0 0 0 Table 3.4. Applications of remote sensing and monitoring technologies for highway inspection during construction.

Survey of the State of the Practice 45   Finally, as shown in Table 3.4, a limited number of state DOTs have used RFID and bar- code and reader technologies for highway infrastructure inspection during construction. For example, the Indiana DOT mentioned that it has used RFID technology for measure- ment of material strength and temperature and for managing quality control and quality assurance activities. The North Carolina DOT has used RFID technology for tracking the position of bulk concrete, asphalt, and aggregate loads, and for tracking finished materials and inventory such as pipe and rebar. Similarly, the Indiana and South Carolina DOTs mentioned that they have used barcodes and readers for managing quality control and qual- ity assurance activities. The Missouri DOT has used barcodes and readers for capturing site photos and videos. Application for Inspection of Highway Infrastructure Assets Figure 3.10 shows the typical remote sensing and monitoring technologies used for highway infrastructure inspection during maintenance of assets. Out of 28 responses, 10 state DOTs (36%) have used remote cameras; nine state DOTs (32%) have used LiDAR/3D laser scanning tech- nologies; seven state DOTs (25%) have used remote sensors; three state DOTs (11%) including Kentucky, South Carolina, and Nebraska have used barcodes and readers; and three state DOTs (11%) including Wisconsin, Florida, and Nebraska have used infrared sensors. The Virginia DOT mentioned that it has used RFID for inspection of its highway infrastructure during maintenance of assets. Table 3.5 summarizes the applications of remote sensing and monitoring technologies associ- ated with common inspection activities during maintenance of assets. As shown in Table 3.5, the majority of state DOTs indicated that they are unsure of how remote sensing and monitor- ing technologies are used for highway infrastructure inspection during maintenance of assets. LiDAR/3D laser scanning technology is the most dominant remote sensing technology that is used for highway infrastructure inspection during asset management. Specifically, four DOTs (Oregon, Indiana, Kentucky, and Nebraska) mentioned that they have used LiDAR/3D laser scanning technology for pavement crack and defect detection. Three DOTs (Oregon, Kentucky, and Washington) indicated that they have used LiDAR/3D laser scanning for slope stability Figure 3.10. Types of remote sensing and monitoring technologies used for highway infrastructure inspection during maintenance of assets. 4% 11% 11% 25% 32% 36% 0 5 10 15 Radio-Frequency Identification (RFID) Infrared Sensors (e.g., thermal, motion detectors, object detection, thermal profiling) (IS) Barcodes & Readers (B&R) Remote Sensors (e.g., accelerometers, maturity meter sensors, strain gauges, etc.) (RS) Light Detection and Ranging (LiDAR)/3D Laser Scanning Remote Cameras (RC) Number of state DOT responses (n=28)

46 Highway Infrastructure Inspection Practices for the Digital Age and landslide assessment. The Oregon and South Carolina DOTs indicated that they have used LiDAR/3D laser scanning for the location of pavement/material placement for performance tracking. The Oregon DOT has also used LiDAR/3D laser scanning for signage, culvert, and guardrail inventories and inspection and for sharing asset information between different func- tional units. The Pennsylvania DOT has used LiDAR/3D laser scanning for structural inspection of existing infrastructure assets. Similarly, three DOTs (Virginia, Wisconsin, and South Carolina) indicated that they have used remote sensors for structural inspection during asset management. The Oregon and Washington DOTs have used remote sensors for slope stability and landslide assessment. The Wisconsin DOT indicated that it has used remote sensors for pavement crack and defect detection; inventories and inspection of signage, culverts, guardrails, and other assets; the location of pavement/material placement for performance tracking; and the location of voids/buried assets. The Nebraska DOT has used remote sensors, remote cameras, and infrared sensors for inspection of road conditions and anti-icing systems. Intelligent compaction is not used for highway infrastructure inspection during asset management as this technology is only applied to paving operations during construction. Challenges in Implementation The survey respondents were asked to identify the main factors that impede the use of remote sensing and monitoring technologies for highway infrastructure inspection during construc- tion or asset management. Figure 3.11 summarizes these main challenges on the basis of the responses from 28 state DOTs. The top challenges in using remote sensing and monitoring technologies for highway infra- structure inspection during construction or asset management include the following: • Cost issues; • Lack of training, knowledge, and skills to use technologies; • Device maintenance and user support; • Lack of reliable internet connection in remote locations; • Lack of standard contract specifications; and • Resistance to change. Typical Inspection Activities LiDAR/3D Laser Scanning (n=9) Remote Sensors (n=7) Infrared Sensors (n=3) Remote Cameras (n=10) Barcodes and Readers (n=3) RFID (n=1) Not Sure Location of pavement/material placement for performance tracking 2(*) 1 0 0 0 0 7 Signage, culvert, guardrail, and other asset inventories and inspection 1 1 0 1 2 0 8 Sharing asset information between different functional units 1 0 0 1 0 0 8 Pavement crack and defect detection 4 1 0 0 0 0 8 Structural inspection 1 3 0 1 0 0 7 Slope stability and landslide assessment 3 2 0 0 0 0 7 Location of voids/buried assets 0 1 1 0 0 1 7 (*): The number of DOT responses. Table 3.5. Applications of remote sensing and monitoring technologies for infrastructure inspection during maintenance of assets.

Survey of the State of the Practice 47   7% 11% 21% 21% 21% 29% 32% 32% 43% 46% 54% 68% 0 5 10 15 20 Incompatibility with (or restricted by) legal, regulatory, or policy requirement Access, privacy, or security concerns Incompatibility with existing hardware Lack of technical results/case studies demonstrating accuracy Quality of data collected Insufficient agency network levels, IT infrastructure/cellular service Lack of standard contract specifications Resistance to change Lack of reliable internet connection in remote locations Device maintenance and user support Lack of training, knowledge, and skills to use technologies Cost issues Number of state DOT responses (n=28) Figure 3.11. Challenges in using remote sensing and monitoring technologies for highway infrastructure inspection during construction or asset management. Mobile Devices and Software Applications Figure 3.12 summarizes the number of years that state DOTs have been using mobile devices and software applications for inspection of highway infrastructure during con- struction or maintenance of assets. Out of 41 responses, eight state DOTs (20%) have used mobile devices and software applications for highway infrastructure inspection for more than 10 years, 12 state DOTs (29%) have used them from 5 to 10 years, and 15 state DOTs (37%) have used them for highway infrastructure inspection from 2 to 5 years. Six state DOTs (15%) indicated that they have used mobile devices and software applications for less than 2 years. Application for Highway Construction Inspection Figure 3.13 indicates the typical mobile devices and software applications that DOTs use for highway infrastructure inspection during construction. Out of 41 responses, 37 DOTs (90%) have used tablet computers and smartphones (TSs); 22 DOTs (54%) have used hand- held data collectors (HDCs) such as Real-Time Kinematics (RTK) or Trimble Yuma; and 17 DOTs (41%) have used automated machine guidance (AMG) and 3D engineered models/ BIM (3D models) for inspection of their highway infrastructure during construction. Figure 3.13 also indicates that two DOTs (California and Connecticut) have used virtual reality/augmented reality (VR/AR) for inspection of their highway infrastructure during construction.

48 Highway Infrastructure Inspection Practices for the Digital Age 15% 37% 29% 20% 0 5 10 15 20 < 2 years 2-5 years 5-10 years >10 years Number of state DOT responses (n=41) Figure 3.12. Experience in using mobile devices and software applications for highway infrastructure inspection. Figure 3.13. Types of mobile devices and software applications used for highway infrastructure inspection during construction. Table 3.6 summarizes the use of mobile devices and software applications associated with typical inspection activities during construction of a highway project. Table 3.6 indicates that 3D models and AMG are typically used for earthwork inspection and quantities. TSs are used for a number of inspection activities during construction such as verification and documenta- tion of work completed for payment, monitoring construction progress, site photos and videos, and 3D as-built models. HDCs are typically used for monitoring construction progress, earth- work inspection and quantities, and quality control/quality assurance activities. Only the California DOT has used VR/AR for earthwork inspection and quantities during construction. The following 5% 41% 41% 54% 0 10 20 30 40 Virtual Reality/Augmented Reality (VR/AR) 3D Engineered Models/BIM (3D) Automated Machine Guidance (AMG) Handheld data collectors (e.g., Real-Time Kinematics (RTK), Trimble Yuma) (HDC) Tablet computers/smartphones (TS) Number of state DOT responses (n=41) 90%

Survey of the State of the Practice 49   sections present in more detail the uses of mobile devices and software applications for inspec- tion of highway infrastructure during construction. For the implementation of 3D models (Table 3.6), the top inspection activities during con- struction of highway projects based on the responses from 17 state DOTs include: • Earthwork inspection and quantities (10 DOTs, 59%), • Collecting as-built information/developing 3D as-built models (five DOTs, 29%), • Monitoring construction progress (three DOTs, 18%), • Verification and documentation of work completed for payment (two DOTs, 12%), and • Measurement of pavement thickness (two DOTs, 12%). For the implementation of AMG (Table 3.6), the top inspection activities during construction of highway projects based on the responses from 17 state DOTs include: • Earthwork inspection and quantities (seven DOTs, 41%), • Monitoring construction progress (four DOTs, 24%), • Quality control/quality assurance (two DOTs, 12%), • Tracking finished materials and inventory (pipe, rebar, etc.) (two DOTs, 12%), and • Tracking the position of bulk material (concrete, asphalt, aggregate loads) (two DOTs, 12%). For the implementation of TSs (Table 3.6), the top inspection activities during construction of highway projects based on the responses from 37 state DOTs include: • Verification and documentation of work completed for payment (33 DOTs, 89%), • Monitoring construction progress (32 DOTs, 87%), • Site photos and videos (26 DOTs, 70%), • Quality control/quality assurance (24 DOTs, 65%), and • Erosion control inspection (22 DOTs, 59%). (*): The number of DOT responses. Typical Inspection Activities Tracking the position of bulk material (concrete, asphalt, aggregate loads) 0(*) 2 13 6 0 4 Tracking finished materials and inventory (pipe, rebar, etc.) 1 2 20 2 0 4 Measurement of material strength and temperature (concrete, base course, etc.) 1 1 6 4 0 7 Measurement of pavement thickness 2 1 5 3 0 5 Earthwork inspection and quantities 10 7 17 9 1 4 Structural inspection and quantities 1 0 17 3 0 6 Monitoring construction progress 3 4 32 12 0 2 Verification and documentation of work completed for payment 2 0 33 6 0 1 Locating underground utilities and underground assets 0 0 1 1 0 10 Collecting as-built information/developing 3D as-built models 5 1 11 5 0 5 Quality control/quality assurance 1 2 24 9 0 3 Erosion control inspection 0 0 22 3 0 4 Site photos and videos 0 0 26 5 0 3 3D Models (n=17) AMG (n=17) TSs (n=37) HDCs (n=22) VR/AR (n=2) Not Sure Table 3.6. Applications of mobile devices and software for highway inspection during construction.

50 Highway Infrastructure Inspection Practices for the Digital Age For the implementation of HDCs (Table 3.6), the top inspection activities during construc- tion of highway projects based on the responses from 22 state DOTs include: • Monitoring construction progress (12 DOTs, 55%), • Quality control/quality assurance (nine DOTs, 41%), • Earthwork inspection and quantities (nine DOTs, 41%), • Verification and documentation of work completed for payment (six DOTs, 27%), and • Tracking the position of bulk material (concrete, asphalt, aggregate loads) (six DOTs, 27%). Application for Inspection of Highway Infrastructure Assets Figure 3.14 shows the typical mobile devices and software applications used for highway infrastructure inspection during maintenance of assets. Out of 41 responses, 16 state DOTs (39%) have used TSs and seven state DOTs (17%) have used HDCs such as Real-Time Kinematics (RTK) or Trimble Yuma. The Florida DOT was the only responding DOT that has used 3D models for inspection of its highway infrastructure during maintenance of assets. Table 3.7 summarizes the application of mobile devices and software associated with typi- cal inspection activities during maintenance of assets. Out of 41 DOT responses, two state DOTs, Oregon and Florida, have used 3D models during maintenance of assets. The Oregon DOT has used 3D models for pavement crack and defect detection, while the Florida DOT has used 3D models for structural inspections. As shown in Table 3.7, the majority of state DOTs indicated that they have used TSs for the following inspection activities during maintenance of assets: • Signage, culvert, guardrail, and other asset inventories and inspection (16 responses or 100%); • Sharing asset information between different functional units (14 responses or 87.5%); • Structural inspection (10 responses or 62.5%); • Location of pavement/material placement for performance tracking (six responses or 37.5%); and • Slope stability and landslide assessment (six responses or 37.5%). Additionally, Table 3.7 indicates that four DOTs (Iowa, Nebraska, New York, and South Dakota) have used HDCs for inventories and inspection of signage, culverts, guardrails, and other assets. The South Dakota and Iowa DOTs have used HDCs for sharing asset information between different functional units. Furthermore, the South Dakota and Tennessee DOTs have Figure 3.14. Types of mobile devices and software applications used for highway infrastructure inspection during maintenance of assets. 2% 17% 39% 0 5 10 15 20 3D engineered models/BIM (3D) Handheld data collectors (e.g., Real-Time Kinematics (RTK), Trimble Yuma) (HDC) Tablet computers/smartphones (TS) Number of state DOT responses (n=41)

Survey of the State of the Practice 51   (*): The number of DOT responses. Typical Inspection Activities 3D Models (n=1) TSs (n=16) HDCs (n=7) Not Sure Location of pavement/material placement for performance tracking 0(*) 6 0 13 Signage, culvert, guardrail, and other asset inventories and inspection 0 16 4 12 Sharing asset information between different functional units 0 14 2 11 Pavement crack and defect detection 1 3 1 16 Structural inspection 1 10 0 13 Slope stability and landslide assessment 0 6 2 13 Location of voids/buried assets 0 1 0 15 Table 3.7. Applications of mobile devices and software for highway inspection during maintenance of assets. used HDCs for slope stability and landslide assessment. The Wisconsin DOT has used HDCs for pavement crack and defect detection. Challenges in Implementation The survey respondents were asked to identify the main factors holding back the use of mobile devices and software applications for highway infrastructure inspection during construction or asset management. Figure 3.15 summarizes the main challenges in the implementation of mobile devices and software applications for highway infrastructure inspection on the basis of 39 responses. The top challenges in using mobile devices and software applications for highway infrastruc- ture inspection during construction or maintenance of assets include: • Lack of reliable internet connection in remote locations; • Lack of training, knowledge, and skills to use technologies; • Cost issues; • Device maintenance and user support; and • Resistance to change. Nondestructive Evaluation Methods State DOTs have used nondestructive evaluation technologies for many years. Figure 3.16 displays the experience of state DOTs in the use of nondestructive evaluation technologies for highway infrastructure inspection. Twenty-five out of 28 DOT responses indicated that they have used nondestructive evaluation methods for highway infrastructure inspection during construction or maintenance of assets for more than 10 years. Application for Highway Construction Inspection Applications of nondestructive evaluation methods include the use of a variety of technolo- gies for construction inspections and asset management of highway infrastructure, as shown in

52 Highway Infrastructure Inspection Practices for the Digital Age 5% 13% 13% 13% 21% 26% 28% 41% 41% 46% 49% 54% 0 5 10 15 20 25 Incompatibility with (or restricted by) legal, regulatory, or policy requirement Access, privacy, or security concerns Lack of technical results/case studies demonstrating accuracy Quality of data collected Lack of standard contract specifications Incompatibility with existing hardware Insufficient agency network levels, IT infrastructure/cellular service Device maintenance and user support Resistance to change Cost issues Lack of training, knowledge, and skills to use technologies Lack of reliable internet connection in remote locations Number of state DOT responses (n=39) Figure 3.15. Challenges in using mobile devices and software applications for highway infrastructure inspection during construction or maintenance of assets. 4% 4% 4% 89% 0 5 10 15 20 25 30 < 2 years 2-5 years 5-10 years >10 years Number of state DOT responses (n=28) Figure 3.16. Experience in using nondestructive evaluation methods for highway infrastructure inspection.

Survey of the State of the Practice 53   Figure 3.17. More than half of 28 DOT responses indicated that they have used the following nondestructive evaluation methods for highway inspection during construction: • Nuclear density gauges (26 DOTs, 93%), • Dynamic test loading for piles (24 DOTs, 86%), • Cross-hole sonic logging for drilled shafts (21 DOTs, 75%), • Surface profile measuring systems (20 DOTs, 71%), • Ground-penetrating radar (GPR) (18 DOTs, 64%), and • Ultrasonic testing (16 DOTs, 57%). The less common nondestructive evaluation methods used by state DOTs during construc- tion for highway inspection include: • Thermal integrity testing (12 DOTs, 43%), • Infrared thermography (11 DOTs, 39%), • Magnetic imaging tools (11 DOTs, 39%), and • Acoustic emission (5 DOTs, 18%). Figure 3.18 shows the common applications of nondestructive evaluation technologies for highway infrastructure inspection during construction based on 28 DOT responses. The top inspec- tion activities that are suitable for using nondestructive evaluation methods include: • Quality control/quality assurance (24 DOTs, 86%), • In-situ material characterization (density, modulus, presence of defects) (22 DOTs, 79%), • Foundation investigation tools—assessing new drilled-shaft integrity (21 DOTs, 75%), • Structural inspection (19 DOTs, 68%), and • Identification and cause characterization of bridge deck deterioration (15 DOTs, 54%). Application for Inspection of Highway Infrastructure Assets Figure 3.19 shows the typical nondestructive evaluation methods and techniques used for highway infrastructure inspection during maintenance of assets. Based on the responses from 18% 39% 39% 43% 50% 57% 64% 71% 75% 86% 93% 0 5 10 15 20 25 30 Acoustic emission Infrared thermography Magnetic imaging tools (MIT) Thermal integrity testing Falling weight deflectometers Ultrasonic testing Ground penetrating radar (GPR) Surface profile measuring systems Cross-hole sonic logging for drilled shafts Dynamic test loading for piles Nuclear density gauges Number of state DOT responses (n=28) Figure 3.17. Types of nondestructive evaluation methods used for highway infrastructure inspection during construction.

54 Highway Infrastructure Inspection Practices for the Digital Age Figure 3.18. Application of nondestructive evaluation methods for highway infrastructure inspection during construction. 4% 4% 4% 4% 7% 7% 14% 21% 25% 29% 39% 0 5 10 15 Dynamic test loading for piles Thermal integrity testing Cross-hole sonic logging for drilled shafts Infrared thermography Magnetic imaging tools (MIT) Acoustic emission Nuclear density gauges Ultrasonic testing Falling weight deflectometers Surface profile measuring systems Ground penetrating radar (GPR) Number of state DOT responses (n=28) Figure 3.19. Types of nondestructive evaluation methods/techniques used for highway infrastructure inspection during maintenance of assets. 25% 29% 32% 39% 39% 54% 68% 75% 79% 86% 0 5 10 15 20 25 Early detection of concrete deterioration mechanisms Measurement friction and noise properties for pavements Measurement of pavement thickness Identification of fatigue and fracture damage Determination of extent and severity of steel corrosion Identification and cause characterization of bridge deck deterioration Structural inspection Foundation investigation tools—assessing new drilled-shaft integrity In-situ material characterization (density, modulus, presence of defects) Quality control/Quality assurance Number of state DOT responses (n=28)

Survey of the State of the Practice 55   28 DOTs, the top nondestructive evaluation methods and techniques used by state DOTs for highway inspection during maintenance of assets include: • Ground-penetrating radar (11 DOTs, 39%), • Surface profile measuring systems (eight DOTs, 29%), • Falling weight deflectometers (seven DOTs, 25%), • Ultrasonic testing (six DOTs, 21%), and • Nuclear density gauges (four DOTs, 14%). Figure 3.20 summarizes the common applications of nondestructive evaluation technologies for highway infrastructure inspection during maintenance of assets. Based on the responses from 28 state DOTs, the top inspection activities that are suitable for using nondestructive eval- uation technologies include: • Structural inspection (11 DOTs, 39%), • Determination of the extent and severity of steel corrosion (10 DOTs, 36%), • Real-time automated pavement distress measurements (nine DOTs, 32%), • Identification of fatigue and fracture damage (nine DOTs, 32%), • Measurements of existing scour and scour potential (seven DOTs, 25%), and • Improved methods for measuring profiles (seven DOTs, 25%). Challenges in Implementation The survey respondents were asked to identify the main factors that limit the use of non- destructive evaluation technologies for highway infrastructure inspection during construction or asset management. Figure 3.21 summarizes the main challenges in implementation of non- destructive evaluation methods for highway infrastructure inspection based on the responses 7% 7% 14% 18% 21% 25% 25% 32% 32% 36% 39% 0 5 10 15 Measurement of pavement interlayer bonding Detection of problem areas at bridge approaches Mapping of voids, bonding, and moisture behind retaining walls Early detection of concrete deterioration mechanisms Sharing asset information between different functional units Measurements of existing scour and scour potential Improved methods for measuring profiles Real-time automated pavement distress measurements Identification of fatigue and fracture damage Determination of extent and severity of steel corrosion Structural inspection Number of state DOT responses (n=28) Figure 3.20. Application of nondestructive evaluation methods for highway infrastructure inspection during maintenance or asset management.

56 Highway Infrastructure Inspection Practices for the Digital Age from 21 DOTs. The top challenges in using nondestructive evaluation methods for highway infrastructure inspection during construction or asset management include: • Lack of training, knowledge, and skills to use technologies, • Cost issues, • Resistance to change, • Device maintenance and user support, and • Lack of reliable internet connection in remote locations. Viability and Efficiency of Inspection Technologies The survey respondents were asked to identify the performance metrics that their state DOTs use to evaluate the implementation of technologies for highway infrastructure inspection. Fig- ure 3.22 summarizes the result of this question. The four metrics used by more than two-thirds of the 42 responding DOTs include (1) efficiencies gained when using technologies, (2) increase in quality of a project, (3) overcoming limited inspection resources, and (4) cost–benefit analysis. It is important to note that the cost–benefit analysis performance shown in Figure 3.22 is based on either a specific case project or the perception of the user. Specifically, when the survey respondents were asked to identify the overall return on investment (ROI) from using the technologies for highway infrastructure inspection, most state DOTs stated that the information required to calculate the ROI is not available (see Table 3.8). The survey results also indicated that most state DOTs currently do not track the cost- effectiveness of implementing technologies for highway inspection during construction and Figure 3.21. Challenges in using nondestructive evaluation methods for highway infrastructure inspection during construction or asset management. 14% 5% 10% 14% 19% 29% 29% 33% 38% 38% 48% 48% 0 2 4 6 8 10 12 Other, please specify: Incompatibility with existing hardware Insufficient agency network levels, IT infrastructure/cellular service Access, privacy, or security concerns Lack of technical results/case studies demonstrating accuracy Lack of standard contract specifications Quality of data collected Lack of reliable internet connection in remote locations Device maintenance and user support Resistance to change Cost issues Lack of training, knowledge, and skills to use technologies Number of state DOT responses (n=21)

Survey of the State of the Practice 57   maintenance of assets. Figure 3.23 indicates that 53% of the 42 responding DOTs do not track the cost-effectiveness of implementing technologies. Six state DOTs (14%) (California, New York, New Mexico, Oregon, Pennsylvania, and Wisconsin) mentioned that they have tracked the cost-effectiveness of implementing technolo- gies for highway inspections. Specifically, the Oregon DOT indicated that independent studies were conducted to evaluate and track the cost-effectiveness of implementing technologies. The Oregon DOT also indicated that the ROI of geospatial technologies, remote sensing and monitor- ing technologies, and mobile devices and software applications are greater than 100%. The Pennsylvania DOT mentioned that ROI is analyzed for proposed technologies on the basis of the cost to develop and incorporate efficiency gains or quality improvements. The Pennsylvania DOT indicated that the ROI for geospatial technologies and remote sensing and monitoring technologies is approximately 50–100%, the ROI for mobile devices and software applications is greater than 100%, and the ROI for nondestructive evaluation methods is 20–50%. The Wisconsin DOT indicated that it tracks savings during pilot projects but the ongoing implementation is not tracked. The Wisconsin DOT estimated that the ROI of geospatial tech- nologies, remote sensing and monitoring technologies, and mobile devices and software appli- cations is greater than 100%. 5% 38% 48% 55% 57% 69% 69% 76% 86% 0 10 20 30 40 Others Agility/flexibility for desired tasks Durability and maintenance of devices/technology Advancement in technology End user approval Cost-benefit analysis Overcoming limited inspection resources Increase in quality Efficiencies gained Number of state DOT responses (n=42) Figure 3.22. Performance metrics to evaluate the use of technologies for inspection. Technologies < 0% 0- 10% 10%- 20% 20%- 50% 50%- 100% > 100% Unsure/Information Is Not Available Geospatial technologies 0 0 0 2 1 3 32 Remote sensing and monitoring technologies 0 0 1 1 1 2 33 Mobile devices and software applications 0 0 2 1 2 3 33 Nondestructive evaluation methods 0 0 1 2 2 0 34 Table 3.8. Overall return on investment (ROI) from using the technologies for highway infrastructure inspection (n = 42).

58 Highway Infrastructure Inspection Practices for the Digital Age The California DOT mentioned that it has tracked the cost-effectiveness of implementing technologies by comparing costs of using conventional methods versus using inspection tech- nologies. The California DOT estimated that the ROI of geospatial technologies, remote sensing and monitoring technologies, mobile devices and software applications, and nondestructive evaluation methods is approximately 20–50%. The New Mexico DOT stated that it has tracked the cost-effectiveness of implementing mobile devices and software applications by comparing time spent in the field versus time spent going back to the office to enter quantities for payment and daily work reports. The New Mexico DOT estimated that the ROI of implementing mobile devices and software applications is approxi- mately 10–20%. Finally, to further identify different methods used to assess the viability and efficiencies of inspection technologies, the survey respondents were asked to determine the primary drivers for selecting the technologies. Figure 3.24 shows the results of this question based on the responses from 42 state DOTs. Figure 3.24 shows that more than 70% of the 42 responding DOTs indicated that the main driving factors for using mobile devices and software applications are to (1) enhance the safety of inspectors, (2) improve efficiency, and (3) enhance staffing (using mobile devices and software applications reduces the need for inspection staff). Similarly, more than half of the 42 DOTs responded that the main driving factors of using geospatial technologies are to (1) improve effi- ciency, (2) promote e-construction, and (3) enhance the safety of inspectors. Figure 3.24 also indicates that the main driver of using remote sensing and monitoring technologies and non- destructive evaluation methods is to enhance the safety of inspectors. Summary This chapter presents the survey results associated with four main areas of technologies for highway inspections: geospatial technologies, remote sensing and monitoring technologies, mobile devices and software applications, and nondestructive evaluation methods. Out of 42 responses, 32 state DOTs have used geospatial technologies; 28 state DOTs have used remote sensing and monitoring technologies; 41 state DOTs have used mobile devices and software Yes 14% Unsure 33% No 53% Figure 3.23. DOTs tracking the cost-effectiveness of implementing technologies (n = 42).

Survey of the State of the Practice 59   applications; and 28 state DOTs have used nondestructive evaluation methods. In addition, more than 70% of the 42 responding state DOTs have used mobile devices and soware applica- tions for inspection of various infrastructure types, including roadways, signage and roadsides, bridges, earthwork and grading, drainage systems, and non-bridge structures. Approximately 75% of the 42 responding state DOTs have used nondestructive evaluation technologies for inspection of roadways and bridges. More than 50% of the 42 responding state DOTs have used geospatial technologies for inspection of roadways, signage and roadsides, and earthwork and grading. Approximately 50% of the 42 responding state DOTs have used remote sensing and monitoring technologies for inspection of roadways and bridges. e main applications and chal- lenges of each technology for highway inspection during construction and maintenance of assets are also presented. Furthermore, more than 28 state DOTs responded that the main performance metrics used to evaluate the implementation of technologies for highway infrastructure inspection include eciencies gained, increase in quality, overcoming limited inspection resources, and cost–benet analysis. Finally, 32 out of 42 responding DOTs indicated that the information required to calculate the ROI is not available. Figure 3.24. Primary drivers for selecting technologies for highway inspection. 31% 55% 31% 14% 71% 88% 64% 81% 31% 50% 33% 36% 50% 52% 55% 64% 0 10 20 30 40 Enhance Staffing Enhance Safety of Inspectors Promote E- Construction Improve Effi ency Number of state DOT responses (n=42) Geospatial Tech. Remote Sens ng & Mon tor ng Mob e Dev ces & Software Nondestructive Evaluation

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Historically, state departments of transportation (DOTs) have employed on-site workforces to execute infrastructure inspection using traditional inspection methods.

The TRB National Cooperative Highway Research Program's NCHRP Synthesis 582: Highway Infrastructure Inspection Practices for the Digital Age documents the various technologies - such as unmanned aircraft systems (UASs), embedded and remote sensors, intelligent machines, mobile devices, and new software applications - used by DOTs to inspect highway infrastructure during construction and maintenance of assets.

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