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Publication Number:      Date:  Winter 1995
Issue No: Vol. 59 No. 2
Date: Winter 1995


Robotics in Highway Construction and Maintenance


by Dah-Cheng Woo


When the Office of Advanced Research was established in April 1992 at the Federal Highway Administration's (FHWA) Turner-Fairbank Highway Research Center, robotics -- robot and automation technology -- was made one of the six key areas of research.

Robotics has been used extensively in many fields because it enhances workers' safety, increases production efficiency, and improves the quality of products. It is important to introduce and to encourage use of this technology in highway transportation.

As an ultimate goal, robotics can be used in all phases of highway transportation: production of highway material, construction of highways (including quality control), highway maintenance and operations (including inspection and monitoring), and performance in hazardous and difficult-to-access environments. So far, its use in highway transportation has been limited.

Dr. Woo tries the controls of the Caltrans aerial bridge-inspection system.

Dr. Woo tries the controls of the Caltrans aerial bridge-inspection system.

Although robotics technology can benefit highway transportation in many ways and can result in big savings, it is not cheap, especially for applications in the rugged outdoor environment of highway construction and maintenance. Robotics research is multidisciplinary, involves high technology, and requires special laboratory facilities. Its products are sensitive, complicated, and often expansive machineries that require special training to operate and maintain.

These factors must be considered in a total cost-benefit study of the expected end product. The total cost must include the research cost, the cost for developing the end product, the estimated cost of the end product, the cost of training operators, and the cost of maintenance. The benefit must be measured by enhanced safety, increased productivity, and improved quality. Only by comparing the total costs of the work done in the existing way and in the new way can we avoid undesirable results, such as producing overly expensive equipment or a difficult-to-operate machine.

An operator demonstrates the flying aerial platform for bridge inspections.

An operator demonstrates the flying aerial platform for bridge inspections.


This research program has two major goals:

  1. To improve the existing techniques, equipment, and methods.
  2. To develop new techniques, equipment, and methods.

This is an applied research program based on existing robotics knowledge. The research product must be practical and cost-effective for use in highway construction and maintenance.

This study does not include robotics application to the efficient and safe operation of vehicle traffic on highways. This is covered by FHWA's special program on intelligent transportation systems.

Significant Results Thus Far

The National Institute of Standards and Technology (NIST), under an interagency agreement with FHWA, completed an in-depth study on the application of present robotics knowledge to enhance safety, quality, and productivity of highway construction, maintenance, and operation. The study was conducted by a panel of robotics experts from academia and government. The panel visited the sites of three highway construction and maintenance projects in the field to gain insights on issues and needs by close observation and through discussions with engineers, contractors, supervisors, equipment operators, and material suppliers.

Two workshops were held during this study. The first one was to gather industrial views and to examine requirements and opportunities for automation/robotics in highway transportation. The second one was to exchange technical state of the art and to identify application areas of technology.

From these sources and the literature search, the panel selected six potential research programs for detailed evaluation. They are site integration, automated bridge decking, automated trenching and pipe-laying, automated bridge inspection and maintenance, automated pavement inspection and repair, and temporary bridging.

These proposals were then submitted to the Civil Engineering Research Foundation (CERF) for a study of life-cycle cost-benefits, assuming the technical objectives could be met. Professional engineers in industry, engineering faculty from academic departments, and state departments of transportation engineers participated in the CERF study. Four proposals provided significant, potential economic improvements over current practice. These involved automated pavement inspection and crack-sealing, automated bridge inspection and maintenance, automated bridge deck construction, and site integration.

The CERF study was not a complete cost-benefit study. Nevertheless, the NIST study is a good reference for FHWA in conducting robotics research for highway construction and maintenance. The results of this study are available in the six reports listed as references at the end of this article.

Research in Progress

Site Integration Program

Following the recommendation of the NIST study, FHWA initiated a five_year study of the Site Integration Program. Implementation of this research will provide significant economic benefits over current practices by integrating all activities at the worksite, thus reducing construction time, reducing materials costs by reducing waste, and enhancing safety by monitoring equipment in motion. This will be accomplished by:

Aerial Bridge-Inspection System

In response to NIST's recommended research program on automated bridge inspection and maintenance, a pooled-fund, state planning and research (SP&R) program study was initiated for the development of an aerial bridge-inspection device for more efficient and safer inspections without traffic delay. This study is the second phase of research by the California Department of Transportation (Caltrans) on the "Aerial Platform System for Bridge Inspection."

In the first phase, Caltrans developed a prototype aerial platform equipped with a video inspection camera. This platform is capable of vertical takeoff and landing and can position the inspection camera within 0.6 meters of the location to be inspected. Electric power is supplied to the vehicle through a 30-meter power cable. A fiber-optic cable transmits control signals and video images to and from the aerial platform and the ground-based station.

The video inspection camera is a vision-enhancement system, which is being developed concurrently under another Caltrans research contract. This contract will provide a complete ground-based station with provisions for real-time monitoring of the bridge structure.

In the ongoing second phase of this research -- jointly sponsored by FHWA, California, Connecticut, Indiana, New York, Pennsylvania, and Texas -- efforts will focus on the development of this device for field operation. This includes improving the landing gear, increasing its stability characteristics, operating at remote sites, adding a back-up power and control system, testing light-weight body protection against contact with a bridge structure and foreign objects, and possibly adding other devices to facilitate bridge inspection. Figure 1 shows the general concept of this system.

Figure 1 - Caltrans' concept of the aerial bridge-inspection system.

FHWA Advanced Research Grants in 1993

From the 1993 FHWA Advanced Research Grant Program to develop emerging, advanced, and adaptive technologies having potential for long-range applications to highway transportation, two research studies were awarded under the major area of robots/automation/man_machines.

North Carolina State University (NCSU) is conducting a study on "Robotic Bridge Paint Removal, Field Testing, and Evaluation of Promising Technologies." The use of robotic equipment to apply selected, available methods to remove paint from bridges eliminates a hazardous work environment. The complete containment of removed debris prevents the lead in old paint from polluting the environment. North Carolina Department of Transportation and NCSU researchers jointly determined the available paint-removal methods. Figure 2 shows the general concept of this system.

Figure 2 - NCSU's robotic paint removal system.

The other grant was awarded to the University of Arkansas at Little Rock to develop an "Automated Measurement of Aggregate Indices of Shape" by constructing a second-generation imager, optimized for aggregate analysis. The instrument conveniently samples and acquires images of aggregate (coarse or fine), rapidly extracts the features of the objects in each image, estimates the thickness of each object, constructs a gradation curve for the aggregate (even if multiple samples from different sieves are used), and displays the data in a two-dimensional fashion so that, for example, angularity may be studied as a function of size. The data will be analyzed to determine which features, if any, quantitatively predict pavement performance.

The crane boom to which the robotic paint-removal system is attached.A close-up of the NCSU's robotic paint-removal system in operation.

The crane boom to which the robotic paint-removal system is attached. A close-up of the NCSU's robotic paint-removal system in operation.

Other Current Research

To take advantage of a large-scale manipulator developed by the University of Texas at Austin with the support of the National Science Foundation (NSF), FHWA and NSF are co-sponsoring the second phase of this project, "Development of Large-Scale Manipulator Technology for Construction." It will concentrate on the development of internal and external measurement approaches to handle slop and deflection errors arising from the mass and scale of the manipulator.

The development of the Automatic Pavement Crack-Sealing Machine and the Pothole-Repairing Machine started as part of the Strategic Highway Research Program. These projects are being continued in the Long-Term Pavement Performance Program.

Future Research

In 1994, the only Advanced Research Grant in robots/automation/man-machines was awarded to NCSU to investigate "CAD (Computer-Aided Design)-Integrated Real-Time Control for Robotic Excavation and PipeLaying Development and Field Testing." This study will prove the technical feasibility and effectiveness of laser-based spatial position control of trench excavation under real-world conditions, and researchers will fieldtest an innovative technology for the detection of buried metal obstacles.

A minor development study of a semiautomatic pavement crack sealing machine will be sponsored jointly by the FHWA's Office of Technology Applications, the Texas Department of Transportation, and an equipment manufacturer. This research will advance technology initiated in a Strategic Highway Research Program study.

Further development of the robotic, bridge paint-removal system by NCSU under North Carolina's SP&R program is being considered.

New research is being considered in the automated pavement inspection area to develop accurate means to detect pavement distress at the earliest stage so corrective measures can be taken to prevent a major problem.

Another area of potential research in highway construction and repair involves improving work zone safety and reducing traffic congestion through the use of robotic aids.

Future research is needed for automated, continuous bridge inspection, including underwater inspection of abutment and pier scour and the development of environmentally sound and continuous operations for bridge painting and paint removal.

FHWA is always looking for innovative ideas for better highway transportation.


  1. First Workshop Report -- Automation/Robotics for Road Construction, Maintenance, and Operation, Publication No. FHWA-RD-93-078, Federal Highway Administration, Washington, D.C., December 1992.
  2. Second Workshop Proceedings -- Application of Robotics and Automation to Highway Construction, Maintenance, and Operation: Technical State of the Art, Publication No. FHWA-RD-94-051, Federal Highway Administration, Washington, D.C., April 28, 1993.
  3. Robotics Application to Highway Transportation, Volume I: Final Report, Publication No. FHWA-RD-94-053, Federal Highway Administration, Washington, D.C., expected availability date: February 1995.
  4. Robotics Application to Highway Transportation, Volume II: Literature Search (Resource Materials), Publication No. FHWA_RD-94-054, Federal Highway Administration, Washington, D.C., expected availability date: February 1995.
  5. Robotics Application to Highway Transportation, Volume III: Proposed Research Topics and Cost/Benefit Evaluations (Resource Materials), Publication No. FHWA-RD-94-094, Federal Highway Administration, Washington, D.C., expected availability date: February 1995.
  6. Robotics Application to Highway Transportation. Volume IV: Proposals for Potential Research (Resource Materials), Publication No. FHWA-RD-94-095, Federal Highway Administration, Washington, D.C., expected availability date: February 1995.

Dr. "Charles" Dah-Cheng Woo is a hydraulic engineer with 30 years of research experience in highway drainage and hydrology for FHWA. Currently he is the research manager for robots/automation/man-machines in the Office of Advanced Research, Office of the Associate Administrator for Research and Development at the Turner-Fairbank Highway Research Center in McLean, Va. He is the author of many technical papers and several previous articles in Public Roads.




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