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51 5 Conclusions and Recommendations The conclusions and recommendations in this chapter respond to the four tasks in the committeeâs Statement of Task: 1. Analysis of the performance of bridges that received Innovative Bridge Research and Construction (IBRC) funding in meeting the goals of the program. 2. Analysis of the utility of the innovative materials and technologies used in IBRC projects in meeting needs for a sustainable and low life-cycle cost transportation system. 3. Recommendations to Congress on how the installed and life-cycle costs of bridges could be reduced through the use of innovative materials and technologies, including, as appropriate, any changes in the design and construction of bridges needed to maximize the cost reductions. 4. A summary of any additional research that may be needed to fur- ther evaluate innovative approaches to reducing the installed and life-cycle costs of highway bridges. The first three sections in this chapter present the committeeâs conclu- sions on the extent to which the IBRC projects met the goals of the pro- gram, the utility of the technologies, and opportunities to reduce life-cycle costs of bridges through programs to foster innovation and through devel- opment and evaluation of specific technologies. The final section presents recommendations for federal and state actions to promote cost-saving in- novation through an incentive grant program and through research.
52 PERFORMANCE OF BRIDGES PERFORMANCE OF THE IBRC PROJECTS IN MEETING THE GOALS OF THE PROGRAM The legislatively defined goals of the IBRC program were: 1. Development of new, cost-effective, innovative materials for high- way bridge applications. 2. Reduction of maintenance costs and life-cycle costs of bridges, including the costs of new construction, replacement, or rehabilita- tion of deficient bridges. 3. Development of construction techniques to increase safety and reduce construction time and traffic congestion. 4. Development of engineering design criteria for innovative products and materials for use in highway bridges and structures. 5. Development of cost-effective and innovative techniques to sepa- rate vehicle and pedestrian traffic from railroad traffic. 6. Development of highway bridges and structures that will withstand natural disasters, including alternative processes for the seismic retrofit of bridges. 7. Development of new nondestructive bridge evaluation technologies and techniques. As described in the following section, the committee identified projects that were successful in advancing most of these goals, as well as projects that attempted to fulfill the goals but fell short. Some of the goals received little attention in the program. 1. Development of new, cost-effective, innovative materials for highway bridge applications. IBRC contributed most significantly to promoting the application for high- way bridges of four innovative materials: advanced concrete materials, fiber-reinforced polymer (FRP) composites, corrosion-resistant steel rebar, and high-performance steel (HPS). These materials were available and in use in other applications before the IBRC program, but had been used rarely or not at all in highway bridges. Use of these materials probably would have grown in the absence of the program, but it is likely that the experience that the state highway agencies gained from IBRC projects sub- stantially accelerated their adoption. Advanced Concrete Materials High-performance concrete (HPC) for use in all bridge elements was de- veloped under the first Strategic Highway Research Program (SHRP) in
CONCLUSIONS AND RECOMMENDATIONS 53 the early 1990s (Halladay 1998). The Federal Highway Administration (FHWA) undertook a program in 1993 to promote use of HPC in highway bridges, which included a series of âshowcaseâ workshops for bridge design and construction professionals and construction of demonstration bridges (Russell et al. 2006, 1). At the time of the first HPC showcase in Texas in 1996, six HPC bridges were under construction in the United States (FHWA 1996). The IBRC program provided funding to approximately 81 HPC proj- ects, 12 self-consolidating concrete (SCC) projects, and 4 ultra-high perfor- mance concrete (UHPC) projects, located in 37 states. The program thus was instrumental in introducing states to the material and significantly advanced HPC implementation. Use of HPC has become standard practice in most states today. Two- thirds of the states that responded to the American Association of State Highway and Transportation Officials (AASHTO) Committee on Bridges and Structures survey reported using HPC and SCC, with most following state-developed specifications. Nearly half of the states that responded re- ported using UHPC (see Table 3-3). The AASHTO survey did not determine the extent or characteristics of use of UHPC by these states. FRP Composites The feasibility of the use of FRP composites in construction of new bridges and rehabilitation of existing bridges was demonstrated in the 1980s and early 1990s in projects outside of the United States. By the 1990s, a few U.S. states were experimenting with this technology in bridge projects. To compare U.S. polymer composite bridge technology with the state of the technology abroad, FHWA organized a tour of 23 project sites in Europe and Japan for U.S. government and industry representatives and re- searchers. The tour report concluded that U.S. composite bridge technology was not lagging behind the technology implemented in the visited countries, but that all countries lacked comprehensive design standards and specifica- tions as well as programs for detailed long-term monitoring and evaluation (Hooks et al. 1997). Also in response to the interest in FRP composite mate- rials in the 1990s, AASHTO established Technical Committee T-6, Fiber Reinforced Polymer Composites, to develop specifications, standards, and guidance for bridge owners. The other IBRC technologies were advanced by existing AASHTO technical committees. The initiation of the IBRC program in 1998 coincided with the growing interest in the technology. Trials of FRP materials were a major interest of IBRC participants. Approximately 161 projects in 30 states involving use of FRP materials received funding. These included 41 projects in 23 states that used externally bonded FRP reinforcement. More than 40 percent of IBRC grant funds went to projects that used FRP materials (see Table 2-2).
54 PERFORMANCE OF BRIDGES Today most state highway agencies use externally bonded FRP rein- forcement and nearly half of those that responded to the 2018 AASHTO survey use FRP rebar. However, few of the states that responded to the survey use or have specifications for FRP deck elements, FRP superstruc- ture elements, or FRP prestressing tendons (strand or bar) (see Table 3-3). Most states had little or no prior experience with these materials and IBRC helped fund large numbers of FRP applications in the majority of states. Therefore, it is likely that the experience of the IBRC program influenced state practices today, including the popularity of externally bonded FRP reinforcement as well as the hesitance of many states to use the other FRP technologies. Corrosion-Resistant Steel Rebar To protect bridge deck reinforcement from corrosion, the standard prac- tice for bridge deck construction for many years was to provide two levels of corrosion protection by using sufficient concrete cover and the use of epoxy-coated rebar. In the early 1990s, several state departments of trans- portation began research on alternative reinforcement materials to increase the service life of bridge decks. IBRC grants provided opportunities for states to evaluate alternative rebar materials. Alternative metallic reinforcement materials used in IBRC projects were solid stainless steel and stainless steel clad rebar, low chromium steel rebar, and galvanized rebar. The IBRC program included approximately 51 projects that used these materials in 30 states. IBRC projects also used FRP rebar. According to the AASHTO Committee on Bridges and Structures 2018 survey of state highway agencies, 22 states currently use stainless steel rebar in projects, with 9 states also indicating that they use both galvanized and low-chromium steel. Although standards and specifications are available for these materials, there may be some concerns about product availability in certain areas of the country and the initial cost of the products. HPS HPS for highway bridges was developed through a cooperative research program formed in 1994 by FHWA, the Office of Naval Research (ONR), and the American Iron and Steel Institute (AISI). The HPS Steering Com- mittee was formed to guide the research and support adoption of HPS (Lwin 2002, 4). The first U.S. HPS highway bridge opened in December 1997 (FHWA 2002). By 2002, 30 HPS bridges were in service in 10 states (FHWA 2002); by 2003, 46 bridges in 14 states were in service and 65 were under construction in 17 states (Mistry 2003, 6). In 2018, about 500 HPS bridges are in service in 47 states (AISI 2018; SMDI 2017).
CONCLUSIONS AND RECOMMENDATIONS 55 The creation of the IBRC program in 1998 was a timely complement to the FHWAâONRâAISI initiative. The first five grants for HPS projects were awarded in 1999. From 1999 to 2005, 47 IBRC projects in 29 states dem- onstrated use of HPS in bridges. IBRC funding reinforced the governmentâ industry initiative by providing an incentive for states to build HPS bridges, probably earlier than many would have done so without the program. 2. Reduction of maintenance costs and life-cycle costs of bridges, including the costs of new construction, replacement, or rehabilitation of deficient bridges. New technologies can reduce life-cycle costs in several ways: through re- duced initial construction cost (provided the reduction is not offset by lost service life or higher maintenance costs), longer service life, lower maintenance costs, or lower user costs. As described in Chapter 4, the data available to the committee on the IBRC projects does not contain the information needed to compare life-cycle costs of alternative technologies. Direct comparison of life-cycle costs of two alternative technologies would require data on construction costs, maintenance and rehabilitation costs over a period of decades, and expected service lives for bridges that use the alternative technologies and that are similar with respect to traffic and climate. Examples of life-cycle cost comparisons from sources other than the IBRC projects are cited in Chapter 4. The available comparisons are projec- tions that depend on assumptions about performance of materials over long periods, rather than empirical observations of cost differences. Published studies cited in Chapter 4 provide evidence that HPC bridge decks, low- chromium and stainless steel rebar, HPS girders, and ABC reduce bridge life-cycle costs when used in appropriate applications. In most of these com- parisons, cost savings from improved performance (or from reduced user costs in the case of ABC) are projected to offset somewhat higher highway agency initial construction costs, although initial cost savings in some ap- plications are also reported. The evidence available from published studies is incomplete, and economic comparisons are especially scarce. In spite of these limitations of the documented evidence on cost and field performance, the physical properties of certain of the IBRC technolo- gies provide grounds for expecting that their use can provide life-cycle cost savings. In addition, the extent of acceptance that some of these technolo- gies have gained with the state highway agencies in recent decades is evi- dence that the agencies are experiencing performance that provides savings or that they expect savings. On the basis of these kinds of evidenceâthe physical properties of materials, published cost comparisons, and growing acceptance in state highway programsâthe committee concludes that it is likely that the IBRC
56 PERFORMANCE OF BRIDGES program contributed to the reduction of costs through promotion of use of the following materials: â¢ HPC: Use of HPC in bridge construction can reduce life-cycle cost because the durability of the material extends bridge service life and because of savings attainable in construction cost. Properties of HPC allow bridges to be constructed more quickly and with less material, compared with conventional concrete. For example, use of high-strength HPC allows for shallower girder cross-sections, reducing the required height of approach spans and also reducing earthwork requirements. Alternatively, longer girders can be con- structed with high-strength HPC, reducing the number of supports required. â¢ HPS: Use of HPS can reduce bridge construction costs because its greater strength allows the bridge to be constructed with less mate- rial, compared with construction that uses conventional materials. Additional savings can be realized in transporting material, erec- tion, constructing foundations, and earthwork. â¢ Corrosion-resistant steel rebar: Use of this material in bridge decks can reduce life-cycle cost by delaying rebar corrosion, thus extend- ing service life. Avoiding deck repairs also avoids the user cost of delay during repair work. â¢ Externally bonded FRP reinforcement: This lightweight material is used for repairing bridges that have experienced deterioration or for strengthening bridges to increase their load-carrying capacity. Repairs can be carried out faster and at lower initial cost than with alternative technologies. Use of new technologies other than materials can also reduce initial and maintenance costs and extend service life. Such technologies demon- strated in IBRC projects include accelerated bridge construction (ABC), cathodic protection systems to control corrosion, and monitoring and instrumentation. ABC reduces life-cycle costs primarily by reducing user costs during construction (motorist delays at construction sites) and also reduces ini- tial construction costs for some projects, although current ABC projects typically have somewhat higher initial construction costs. In addition, the off-site or near-site fabrication of elements and systems away from traf- fic (and if elements are constructed in fabrication plants, also away from weather constraints) allows enhanced quality control that can improve material quality and product durability, thereby producing longer-lasting performance with reduced maintenance cost. Other benefits include reduced environmental impacts and improved site constructability. These multiple benefits result in reduced life-cycle costs for ABC projects.
CONCLUSIONS AND RECOMMENDATIONS 57 Corrosion control reduces maintenance and rehabilitation needs and extends the service life of the bridge. A properly designed monitoring program can reduce costs by alerting the highway agency to incipient problems, allowing more efficient planning of maintenance and rehabilitation. Long-term monitoring of performance is needed to verify cost savings from the IBRC technologies in highway bridge applications and to identify the applications in which the technologies are most beneficial. The bridge innovation program proposed below would provide an opportunity for monitoring and evaluation. 3. Development of construction techniques to increase safety and reduce construction time and traffic congestion. ABC is the most significant IBRC technology for reducing the duration of traffic disruptions necessitated by bridge construction. The motivation for most ABC projects is to reduce on-site construction time and traffic con- gestion. In addition, because ABC reduces the duration of highway work zones, it increases safety for construction crews and travelers. These time savings are achieved in large part through off-site or near-site fabrication of bridge elements (such as pier caps) and systems (such as superstructure spans), with quick on-site installation. Use of materials demonstrated in IBRC projects can also reduce con- struction time and increase safety. Use of SCC in place of conventional concrete in appropriate applications (primarily for the purpose of improv- ing consolidation and quality) can reduce concrete placement labor re- quirements, leading to improved worksite safety and reduced construction time. Use of prefabricated FRP decks can reduce construction time. Use of more durable materials such as HPC reduces traffic delay over the life of the bridge by reducing the frequency of maintenance and extending the life of the deck and substructure. IBRC materials (particularly HPC and FRP) were used in the prefabricated elements of approximately three-quarters of the ABC IBRC projects for which details were available to the committee. With materials that reduce the cost of bridge strengthening and rehabilita- tion, such as externally bonded FRP reinforcement, states can afford to upgrade more load-restricted bridges, eliminating the user delay costs of load restrictions. 4. Development of engineering design criteria for innovative products and materials for use in highway bridges and structures. The majority of the states that responded to the AASHTO survey on IBRC technologies today have special provisions or specifications established for HPC, SCC, UHPC, externally bonded FRP reinforcement, stainless steel
58 PERFORMANCE OF BRIDGES rebar, metallizing, cathodic protection, HPS, and ABC (see Table 3-3). The timing of the IBRC program was a stimulus for developing standards, specifications, and other forms of guidance for the new bridge materials and technologies that were coming into use beginning in the 1990s. New Hampshireâs Mill Street Bridge in the town of Epping is an ex- ample of how IBRC projects supported the development of standards and specifications. The bridge was replaced in 2004 with an ABC bridge that included HPC elements, following a 2002 IBRC award. The abutment footing, abutment stem, and mechanical connector details developed in this project were the origin of the precast concrete cantilever abutment details included in the first edition of the Precast/Prestressed Concrete In- stitute Northeastâs (PCINEâs) PCINE Guidelines for ABC Using Precast/ Prestressed Concrete Components. These guidelines were subsequently up- dated with additional research and have been implemented in the northeast region of the country (PCINE 2014). The updated details are also included in the FHWA ABC manual (Culmo 2011). Similarly, certain of the guide- lines are included in the AASHTO Guide Specifications for ABC Design and Construction (AASHTO 2018a). In a similar case, IBRC program funding motivated the development of new welding procedures for HPS. The Pennsylvania Department of Transportation constructed two HPS bridges with IBRC funding. Weld- ing procedures developed during the research for these projects have been adopted nationwide. As previously described, IBRC was the catalyst that stimulated state interest in use of FRP for bridge construction. In response to that inter- est, AASHTO established a standing technical committee (T-6, Techni- cal Committee on Fiber-Reinforced Composites) to develop specifications, standards, and guidance. AASHTO has adopted five guide specifications (AASHTO 2008, 2009, 2012a, 2012b, 2018a) and a standard specifica- tion (AASHTO 2013) for design of bridges and bridge elements using FRP materials. The AASHTO Committee on Bridges and Structures continues to develop standards and specifications to support use of FRP. Inspection and evaluation of structures that use FRP is an area that remains in need of standards or guidance. 5. Development of cost-effective and innovative techniques to separate vehicle and pedestrian traffic from railroad traffic. No IBRC project for which the committee had information appears to have had development of innovative techniques for separation of pedestrian and vehicle traffic from railroad traffic as a primary objective. Seven IBRC projects were identified in the project documentation avail- able to the committee as involving construction or strengthening of highway
CONCLUSIONS AND RECOMMENDATIONS 59 overpasses over railroads. The technologies applied were FRP decks, FRP rebar, externally bonded FRP reinforcement, SCC girders, HPC in a deck and girders, and hybrid steel girders. 6. Development of highway bridges and structures that will withstand natural disasters, including alternative processes for the seismic retrofit of bridges. IBRC technologies valuable for the construction or retrofit of bridges to re- sist earthquakes and floods include HPC, externally bonded FRP reinforce- ment, and HPS. In one IBRC project, use of HPC allowed construction of a longer span, eliminating the need for a pier in a streambed and reducing the risk of scour damage. Externally bonded FRP reinforcement is commonly used to strengthen existing bridges to reduce risk of disaster damage. Six IBRC projects involved seismic retrofit or seismic protection on new bridges, according to the project documentation available to the committee. The technologies involved were installation of monitoring instrumentation for evaluation of the performance of seismic bearings, replacement of seis- mic bearings on an existing bridge, installation of seismic bearings on a new bridge, installation of instrumentation to monitor response to seismic loads on a new bridge, construction of an HPC deck slab on a new bridge to re- duce dead load and thus ease design of the substructure to meet seismic load requirements, and replacement of a bridge using ABC in a high seismic area. 7. Development of new nondestructive bridge evaluation technologies and techniques. No IBRC project for which the committee had information appears to have had development of nondestructive evaluation techniques as a primary ob- jective. The records available to the committee indicate eight projects that included installation of sensors on bridges for monitoring of stress, defor- mation, rate of rebar corrosion, scour, or chloride ingress. As was the case with ABC, the FHWA instructions to the states encouraged applications demonstrating monitoring only in the later years of the program. Costs of monitoring technologies have declined substantially in recent years, limiting the relevance of the IBRC experience. Summary: Performance of the IBRC Projects in Meeting the Goals of the Program The projects completed under the IBRC program contributed substantially to fulfillment of at least five of the programâs goals. The program was pri- marily valuable for motivating state highway agencies nationwide to gain
60 PERFORMANCE OF BRIDGES experience with several technologies that had reached an advanced stage of development but had not yet been adopted for highway bridge construc- tion in the United States. However, the programâs contributions could have been greater if it had stronger provisions for in-service evaluation of the technologies demonstrated and for dissemination of project results. Grant recipients were not required to systematically monitor the performance in service of the innovative components of their projects. Records of projects were not systematically maintained and cost implications of new technolo- gies were not documented. Consequently, performance over time of the projects cannot readily be evaluated and opportunities are reduced for agencies to learn from the IBRC experiences of others. UTILITY OF THE IBRC TECHNOLOGIES The committeeâs Statement of Task asks it to analyze the utility, compared with conventional materials and technologies, of each of the innovative ma- terials and technologies used in the IBRC projects in meeting the need for a sustainable and low life-cycle cost transportation system. The committee considered that the materials and technologies that have greatest utility are those that provide substantial cost savings, are widely applicable, and are readily available to highway agencies. Conclusions about the utility of the IBRC technologies are presented in the following section for three groups of technologies: technologies that have been proven to be highly useful for reducing life-cycle costs and are of broad applicability; promising technologies that are at an advanced stage of development and have been applied but are not yet generally accepted and may require additional research, evaluation, or standards and specifications development; and technologies at a less advanced stage of development or those for which the utility is still uncertain. Technologies of Proven High Utility and Wide Applicability The IBRC technologies in this group are HPC and other advanced concrete materials (SCC and UHPC), externally bonded FRP reinforcement, HPS, and ABC. The technologies in this group share the following characteristics: â¢ The life-cycle cost reductions achievable with the technology, com- pared with older alternative materials or methods, are generally recognized and have been demonstrated in a large number of proj- ects. The forms of cost reduction are: â reduced initial construction costs (attainable with HPC, exter- nally bonded FRP reinforcement, HPS, and ABC);
CONCLUSIONS AND RECOMMENDATIONS 61 â increased durability that extends service life and reduces main- tenance and rehabilitation needs (HPC); and â reduced user costs through faster construction or reduced maintenance frequency (ABC). â¢ The technology is readily accessible to highway agencies. Materi- als suppliers and experienced contractors are available. Standards, specifications, and guidelines are established; most states that re- sponded to the AASHTO 2018 state bridge engineers survey have developed specifications or standards for their use (see Table 3-3). â¢ The technology has become fundamental to highway bridge con- struction (or is becoming so), with applicability in many kinds of projects throughout the United States. Each of the technologies is used today by the large majority of states that responded to the AASHTO state bridge engineers survey, with the exception of UHPC, a relatively new material (see Table 3-3). Contributing to the application of these important technologies was a major accomplishment of the IBRC program. Efforts to apply the technolo- gies to highway bridges were under way before the IBRC program began; however, the program accelerated their development and adoption. Ap- plications of these technologies made up a large portion of the program in terms of funding, numbers of projects, and numbers of states with projects (see Table 2-2). Promising Technologies at an Advanced Stage But Requiring Further Development or Demonstration The IBRC technologies in this group are FRP (other than externally bonded FRP reinforcement) and corrosion-resistant concrete reinforcement (low- carbon chromium steel, galvanized steel, and stainless steel rebar). These technologies have demonstrated potential for reducing the life-cycle costs of bridges, but their application has been more limited than for the technolo- gies in the first group. Solid or clad stainless steel rebar was used in approximately 29 IBRC projects, and a majority of states that responded to the AASHTO bridge engineers survey reported that the material is in use and that they have specifications for the material today (see Tables 2-2 and 3-3). However, galvanized and low-chromium steel rebar were used in few projects and few states report using these materials today. Life-cycle cost estimates cited in Chapter 3 suggest that use of these materials in place of conventional ma- terials would result in savings. Obstacles to their greater use may be initial cost, lack of availability, and lack of awareness of the potential benefits of
62 PERFORMANCE OF BRIDGES these rebar materials. Promotion activities would increase awareness and could lead to increased use and increased availability. Projects featuring use of FRP materials for a variety of applications made up a major portion of the IBRC program (see Table 2-2). Today, externally bonded FRP reinforcement is used by nearly all of the states that responded to the AASHTO 2018 bridge engineers survey, and FRP rebar is used by nearly half of them (see Table 3-3). However, FRP deck elements, used in approximately 65 IBRC projects in 23 states, are used in fewer than one-quarter of states that responded to the AASHTO survey. Similarly, FRP prestressing tendons (strand or bar) and FRP superstructure elements, both demonstrated in multiple IBRC projects, are little used today (see Table 3-3). Obstacles to fully realizing the potential benefits of these FRP tech- nologies have included lack of standards or specifications, higher cost or limited availability of materials, lack of evaluations that document benefits, highway agency and contractor inexperience, negative impressions formed by unsuccessful results in early trials, and unresolved technical problems. A program of research, evaluation, standards and specifications development, and technology transfer to determine appropriate applications and attain greater benefit from the use of FRP in bridge applications is outlined later in this chapter. Promising Technologies at a Less Advanced Stage The IBRC technologies in this group include monitoring and instrumenta- tion and corrosion control technologies other than the corrosion-resistant concrete reinforcement materials (including cathodic protection anodes, galvanic protection, electrochemical chloride extraction, metallizing, paint systems, and deck coatings). These technologies are promising as means of reducing life-cycle costs and some of them may become increasingly important in the future. However, at the time of IBRC, they attracted little attention from the states, and few projects that used them were funded (see Table 2-2). The utility of cathodic protection systems, electrochemical chloride extraction, galvanic protection, and metallizing is to extend the service life of existing structures. These techniques were not new at the time of IBRC. SHRP had developed and evaluated cathodic protection and electro- chemical chloride extraction methods for steel-reinforced concrete bridges. Presumably, these technologies were not among the highest priorities of bridge engineers at the time of the IBRC program. Research to demonstrate performance over time may be necessary to gain greater acceptance for these technologies. Metallizing technology has advanced since IBRC. AASHTO and the National Steel Bridge Alliance (NSBA) collaborated with industry to
CONCLUSIONS AND RECOMMENDATIONS 63 develop a specification for thermal spray coating for steel beams that was adopted in 2017 (AASHTO/NSBA 2017). The use of this specification will help standardize metallizing methods across the nation, thus helping to achieve quality and value in the application of metallic thermal sprayed coating systems. Monitoring technology costs have declined and capabilities have in- creased since the time of the IBRC program. Opportunities for reducing bridge life-cycle costs through improvement and application of monitoring are identified later in this chapter. Summary: Utility of the IBRC Technologies Certain applications in every category of IBRC technologies (HPC and other advanced concrete materials, FRP composites, corrosion control tech- nologies, HPS, and ABC) showed high utility in the IBRC program for reducing bridge life-cycle costs. Several have achieved general acceptance in state highway bridge programs (including HPC, HPS, stainless steel rebar, and externally bonded FRP reinforcement). Others (including ABC and monitoring technology) could produce much greater savings if used more widely. Certain IBRC technologies (for example, FRP deck and superstruc- ture elements) remain promising but will require further development or more systematic evaluation before their optimum use and full potential can be determined. OPPORTUNITIES TO REDUCE INSTALLED AND LIFE-CYCLE COSTS OF BRIDGES THROUGH INNOVATION Conclusions are presented in the following section on three topics: the im- portance of federal incentives for innovation, the importance of highway agency asset management and evaluation practices in fostering cost-saving innovation, and specific technological opportunities to reduce the installed and life-cycle costs of highway bridges. Importance of Federal Incentives as Stimulus for Innovation in Highway Bridges As described in Chapter 3, the evidence is strong that the IBRC program increased the use of innovative technology in highway bridges nationwide. The funds provided by the program mitigated the risk of innovation and motivated the use of new technologies. The greatest impact was through providing incentives for highway agencies to apply technologies that were already well developed and of proven benefit but had not become standard practice (for example, HPC and HPS). The program was less successful at increasing the application of technologies that were at earlier stages of
64 PERFORMANCE OF BRIDGES development (for example, nondestructive evaluation and FRP deck and superstructure elements). The structure of the IBRC program did not have the features that would be required to advance such technologies toward implementation: planning to define specific objectives, a process to allocate funds consistent with objectives, coordination across multiple projects, and a provision for systematic monitoring and evaluation. A new federal incentive grant program for innovative bridge technology could continue the success of IBRC in accelerating the adoption of proven technologies that have not yet gained wide acceptance, and also contribute to advancing less developed technologies, by supporting state highway agency bridge projects that were coordinated as elements of research and evaluation studies. Long-term monitoring of the performance and costs of new materials is an urgent evaluation research need that could be organized through a new federal grant program. The recommendations in this chapter include a proposal for the structure of such a program. Importance of Management and Evaluation Practices That Support Innovation The methods that a highway agency uses to design its bridges and man- age its bridge system are the primary factors that determine the agencyâs success in controlling costs and maximizing the public benefits of bridge investments. A bridge management system that identifies maintenance and rehabilitation needs and helps optimize maintenance spending will highlight the value of cost-saving innovations for carrying out repairs or avoiding the need for repairs. Agencies that use life-cycle costing to compare bridge design alternatives and have bridge management systems to help guide maintenance and rehabilitation decisions are more likely to recognize the benefits of innovative materials and technologies. Life-cycle cost analysis is necessary to evaluate technology that extends the service life of a structure or reduces the frequency of maintenance or rehabilitation, but has a higher initial cost than alternatives. Life-cycle costing that takes user costs into account is also necessary to assess the full value of technologies that reduce travel delays from construction and maintenance. FHWA provides training courses, software, case studies, and an intro- ductory guide for life-cycle cost analysis of highway projects, including bridges (FHWA 2017). The National Cooperative Highway Research P rogarm (NCHRP) has produced a manual for bridge life-cycle cost analy- sis (Hawk 2003). A new federal innovation incentive grant program could contribute in two ways to advancing highway agency management practices. First, the program could support projects that would provide data on the perfor- mance of alternative materials and technologies. Life-cycle costing is useful
CONCLUSIONS AND RECOMMENDATIONS 65 for guiding decisions only if reliable data on long-term performance are available. Second, highway agency trials of state-of-the-art management systems and evaluation methods, or upgrades of existing systems, could be designated eligible projects to receive grants. Eligible practices would include asset management, life-cycle costing, and service life design. As with all projects in the innovation incentive grant program, projects involving management systems and evaluation methods would be required to include periodic reporting in a standard format of experience, costs, and benefits. Specific Technology Opportunities to Reduce Installed and Life-Cycle Costs The committee reviewed the status of the technologies demonstrated in the IBRC projects and innovations that have emerged since the program to identify opportunities to reduce installed and life-cycle costs and thereby improve bridge performance. These are described in the following section. The technologies are at various stages of development. Well-developed technologies may be in need of promotion to expand awareness and ap- plication. For less-developed technologies, there may be a need for research to fully develop the technology, standards and specifications development, or evaluation research to verify and demonstrate benefits. The interviews with state highway agencies conducted for the commit- tee identified a variety of obstacles that may slow or block highway agency adoption of a potentially cost-saving new technology: â¢ The technology may not yet be fully developed and technical prob- lems remain to be resolved. â¢ The technology may have high cost because economies of scale have not yet been attained. â¢ Cost savings may not be sufficiently documented to justify a trial of the technology. â¢ Standards and specifications necessary for guiding use of the tech- nology may be lacking. â¢ Agency or contractor staff may lack experience or training in the use of the technology. â¢ The agency does not regularly apply life-cycle cost as the basis for design decisions, and so a technology with higher initial cost than alternatives, offset by long-term savings, will not be accepted. Technology emphasis areas in a new federal innovation incentive grant pro- gram could be chosen from the following technology opportunities. Such a program would select projects targeting the specific obstacles facing each tech- nology to advance the technology toward full development and application.
66 PERFORMANCE OF BRIDGES Concrete HPC was one of the most frequently used innovative materials in IBRC projects; 34 states received IBRC grants for projects featuring HPC, UHPC, or SCC. HPC is today in general use for highway bridges throughout the United States. Opportunities exist to increase the benefits of these advanced concrete materials by developing designs and applications that take full advantage of their special properties: â¢ UHPC is being used for deck closure connections and is a promis- ing material for use as an overlay. The material has essentially zero permeability and therefore prevents penetration of materials that cause corrosion of steel reinforcement. â¢ Adoption of design standards that optimize use of advanced con- crete materials could allow lower-cost construction and lead to greater use of the innovative materials. Design standards in some cases do not take into account the improved performance charac- teristics of these materials. The consequence may be that structures designed according to the standards do not make the most eco- nomical use of the material, or that the innovative material is not used because the cost of a design according to the standard would not be justifiable. â¢ Similarly, adoption of bridge rating standards that give proper credit for the properties of innovative materials would encourage appropriate use of the materials. â¢ SCC has not been used for bridge decks because of its high flow- ability property, although the material could be useful for decks on high-capacity bridges. SCC has lower permeability than con- ventional concrete (Trezos et al. 2010) and thus could provide extended service life. Technologies that have become of interest since the end of the IBRC pro- gram also hold promise for cost-saving applications. These include: â¢ Alternative cementitious materials to reduce the carbon footprint of cement manufacture. (Environmental costs may be regarded as components of life-cycle costs.) â¢ Fiber reinforcement in concrete decks to control cracking and in- crease durability. â¢ Use of high-strength steel reinforcement, particularly in earthquake- resistant concrete structures, and to reduce rebar congestion. â¢ Concrete-filled steel tubes, in which structural concrete is placed inside a structural steel shell. Properly designed concrete-filled steel
CONCLUSIONS AND RECOMMENDATIONS 67 tubes are inherently stronger and stiffer than their conventional reinforced concrete counterparts; these are valuable qualities for bridges in seismically active regions on sites with soft liquefiable soils (WSDT 2018, 7-101). Steel As with HPC, HPS was a frequently used material in IBRC projects and today is in general use by most state highway agencies for bridge applica- tions. Current opportunities for achieving life-cycle cost savings through improved steel materials include the following: â¢ Development and adoption of design standards and practices that take full advantage of the properties of HPS. â¢ Evaluation of the performance of innovative applications of steel such as corrugated webs and folded plate girders. â¢ Development of design criteria and material specifications for tu- bular member design. â¢ Advancement of improved grades of stainless and conventional steel for bridge construction. â¢ Evaluation of shape memory alloys for use as prestressing materi- als in reinforced concrete structures and for strengthening existing structures (Shahverdi et al. 2018). â¢ Development of appropriate applications of weathering steel. A method for determining corrosion rate would aid in design of bridges with this material. FRP and Other Composite Materials FRP materials were the most common category of innovative material in the IBRC projects, with 161 projects in 30 states. Today, externally bonded FRP reinforcement is used by most state highway agencies and the use of FRP rebar in concrete bridge decks is growing. However, there is infrequent use of several other FRP applications demonstrated in IBRC projects, includ- ing FRP deck elements, FRP superstructure elements, and FRP prestressing tendons (strand or bar). The obstacles to greater use of FRP include initial cost, perceptions gained in early unsuccessful projects, lack of standards or guidance for inspection and evaluation of the materials, possible lack of awareness of existing AASHTO bridge specifications and guidelines for FRP, present limited availability of experienced fabricators (concomitant with the limited market for bridge elements), and incompleteness or incon- sistency of available design and construction standards and specifications for certain applications.
68 PERFORMANCE OF BRIDGES Needs for advancing FRP applications include the following: â¢ Data on durability and service life. â¢ Filling gaps in existing standards, specifications, and guidelines for design, use, and inspection. â¢ Accumulation of more field experience in projects with systematic follow-up evaluation. Properly designed projects in a new federal innovation incentive grant program could meet some of these needs. Significant advancement has occurred in the standardization of glass fiber-reinforced polymer (GFRP) rebar, including development of a standard specification (ASTM International 2017). The AASHTO LRFD Bridge Design Guide Specifications for GFRP Reinforced Concrete, Second Edi- tion (AASHTO 2018b) expands the use of GFRP rebar from the limitation to decks and rails imposed by the first Load and Resistance Factor Design (LRFD) guide edition to all appropriate elements of the bridge. A pro- gram of bridge deck construction with GFRP rebar is needed to determine whether the composites industry can consistently supply quality material to multiple projects. A current NCHRP project1 is developing a GFRP tendon made up of one or more strands. Substructure applications for GFRP prestressing strands in foundation piling should be explored. Bridge applications that use advanced materials such as engineered cementitious composites are under development. These advanced materials have properties that could potentially allow fundamental change, such as three-dimensional (3-D) printing, to current fabrication methods. Corrosion Control Projects that use corrosion-resistant concrete reinforcement materials were popular in IBRC, and two of the materials demonstrated in the program, stainless steel rebar and FRP rebar, are used in many states today. However, few IBRC projects featured cathodic protection, galvanic protection, or coatings for corrosion control, and the program appears to have had little impact on advancing these technologies. These latter technologies may hold great promise for extending the service life of existing bridges, but there is a lack of rigorous research documenting their benefits. Galvanized steel for bridge superstructures is an existing technology 1 NCHRP IDEA 20-30, Project 207, MILDGLASS: GFRP Strand for Resilient Mild Prestressed Concrete, http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=4654.
CONCLUSIONS AND RECOMMENDATIONS 69 that is not widely used but that may merit evaluation and trials to assess its potential. ABC As FHWA encouraged applications for ABC projects late in the IBRC program, only about a dozen states received funding for projects that highlighted ABC as a primary innovation. Other projects included ABC practices, for example, FRP bridge deck projects in which the deck was fab- ricated offsite. Today, most states conduct ABC projects only infrequently, and ABC generally is not regarded as a standard practice or considered as an option in most bridge projects. Opportunities to increase cost savings from ABC include the following: â¢ Expanding use of ABC to all bridges for which the practice would be cost effective. If ABC were routinely evaluated as an option for all bridge projects on the basis of life-cycle cost, it is likely that it would be found to be beneficial in many more projects than those for which it is now used. â¢ Expanding use of life-cycle cost analysis, with inclusion of direct and indirect agency costs and with realistic accounting for user costs of construction delays, as the basis for comparing bridge design and construction alternatives. â¢ Developing bridge designs that take full advantage of the time- saving potential of prefabricated elements. Designs of prefabricated elements today are often based on designs of conventional cast-in- place structures. â¢ Expanding use in bridge construction of bridge move equipment (self-propelled modular transporters or lateral slides). Use of these technologies to move prefabricated systems minimizes traffic disruption. Monitoring and Evaluation Methods and applications for monitoring and evaluation of bridges did not receive emphasis in the IBRC program. Important opportunities exist to reduce bridge life-cycle costs by improving evaluation and monitoring. The following are examples: â¢ Advancement of building information modeling (BIM) for bridges and structures as a framework for maintaining and sharing data during design and construction and throughout the service life of the bridge.
70 PERFORMANCE OF BRIDGES â¢ Integration of data from weight-in-motion installations with the National Bridge Inventory (NBI) data system to measure the rela- tionship of traffic to deterioration and to support improved esti- mates of service life and replacement needs. â¢ Artificial intelligence applications to make full use of bridge moni- toring and evaluation data in bridge management systems to guide maintenance and rehabilitation decisions. â¢ Application of low-cost, low-maintenance sensors for detecting the initiation of reinforcing steel corrosion. â¢ Use of unmanned aerial vehicles to increase the efficiency of bridge inspections. â¢ Development and application of improved nondestructive bridge evaluation technologies and techniques to allow for more precise and reliable assessment of bridge performance. â¢ Use of visualization, 3-D modeling, and virtual reality technologies in ABC and conventional projects. â¢ Methods for maintaining and updating current infrastructure to be more effectively used with upcoming new transportation technolo- gies, such as autonomous vehicle, web base sensing, communica- tion technologies, and real-time traffic data. RECOMMENDATIONS Recommendations of the committee are presented in the following section on three topics: a new federal program to provide incentives for innovation in bridge construction, research needs to develop and evaluate innovative approaches to reducing the installed and life-cycle costs of highway bridges, and other actions to encourage innovation to reduce life-cycle costs of bridges. New Federal Program to Provide Incentives for Innovation in Bridge Construction The preceding section described numerous technologies at various stages of development that hold promise for improving bridge performance and reducing life-cycle cost. However, most require further development, evalu- ation, or promotion to increase awareness of their potential among bridge owners. Congress should create a new federal bridge innovation incentive program, administered by FHWA, to advance such technologies and to promote their use in U.S. highways. As was stated at the beginning of this chapter, the IBRC program in- creased use of cost-saving innovative technology in U.S. highway bridges, but had limited impact in advancing technologies at earlier stages of devel- opment toward application. The new federal program can be modeled on
CONCLUSIONS AND RECOMMENDATIONS 71 IBRC, but with features to improve on the results of the earlier program. The new program should incorporate the provisions described in the fol- lowing paragraphs. Program Plan The program should be guided by a plan that defines the objectives, allo- cates funds in accordance with the objectives, and specifies procedures that FHWA will follow for selecting projects that contribute to the objectives. The plan should specify the division of funds between projects for which the primary objective is to gain widespread use of proven technologies and projects for development and evaluation of earlier-stage technologies. The terms of grants in the program should allow states adequate time for project development and flexibility in implementing technologies (for example, the possibility of substituting sites for a project). This flexibility was an important feature of the IBRC program. The grant program should award funds early in the project process, so that the availability of funds is known when decisions on the scope of work are being made and there is sufficient time to provide information and preparation to the project team and contractors. FHWA should develop the plan in consultation with the state highway agencies. Advice should be solicited from industry and from researchers. Definition of Objectives Objectives for the program should be specifically defined with respect to (1) the technologies to be developed, demonstrated, or evaluated; (2) the specific improvements in bridge performance to be obtained with each tech- nology; and (3) the contribution of the projects funded in the program to advancing each technology. The objective for a particular technology will depend on its state of development. For technologies of proven value that are not yet generally adopted, the objective may be to expand use by pro- viding incentives for states to gain experience with them. For technologies at earlier stages, the objective may be to conduct trials to develop or evalu- ate the technology or to support standards and specifications development. Recordkeeping FHWA should have in place at the beginning of the program a project recordkeeping system that maintains comprehensive, current, and accurate information on each grant awarded. The record should include the location and NBI number of each involved bridge, a detailed description of the full scope of the project of which the grant-funded activities or features are a part, data on funds awarded and expended and total project costs, and a
72 PERFORMANCE OF BRIDGES description of monitoring and evaluation provisions. The record system should track projects through completion and through follow-up evalua- tion activities. The record system should record any changes in the location, scope, or technologies involved in a project made after award of a grant. Dissemination FHWA should establish, at the initiation of the program, arrangements to disseminate to highway agencies, researchers, and the public information on projects under way, assessments of completed projects, and data and results from long-term monitoring. Monitoring Performance of Technologies For all technologies that require long-term monitoring for evaluation, the program should include funding and specific standard requirements for monitoring. FHWA should maintain a repository of monitoring data from projects in the program. Monitoring should follow two tracks: â¢ Every project that receives a grant (including projects for which the primary objective is to promote wider use of proven technolo- gies) should be subject to a minimum standardized monitoring and reporting requirement, appropriate for the specific technology dem- onstrated in the project, for a period of years after the completion of the construction phase of the project. Required data collection would be simple and practical. â¢ Projects for which the objective is development, testing, or evalua- tion of a technology should have additional requirements, includ- ing an evaluation research design that specifies data collection. These projects may involve installation of monitoring technology. Requirements may include monitoring the performance of control bridges for comparison purposes. Grant amounts for projects with primary research or evaluation objectives would cover data collec- tion costs. Evaluations conducted in conjunction with bridge projects funded by the program would be complementary to FHWAâs Long-Term Bridge Perfor- mance (LTBP) Program. The two programs would not duplicate efforts because the proposed program would concentrate on evaluating a specific group of innovative materials and technologies that would be unlikely to receive focused attention in the LTBP Program.
CONCLUSIONS AND RECOMMENDATIONS 73 Emphasis Areas Emphasis areas for project selection should be determined by the federalâ state consultative process previously recommended. The committee recom- mends that consideration be given to the following areas: â¢ Projects that contribute to development and evaluation of designs, standards, and specifications that take full advantage of the perfor- mance qualities of advanced materials. â¢ ABC projects that allow highway agencies to gain experience with technologies for bridge system moves in addition to bridge element installations such as prefabricated substructures. â¢ FRP projects that are coordinated with a program of FRP evalu- ation research, such as the research program recommended in the following section. â¢ Projects with provision for systematic long-term monitoring of the performance of materials and technologies. â¢ Projects to develop and evaluate corrosion control methods for existing structures. â¢ Projects to determine the circumstances that warrant installation of structural health monitoring instrumentation in new and existing bridges. â¢ Projects to develop, demonstrate, or evaluate management systems and decision tools that support cost-saving innovation, including bridge management systems, life-cycle cost assessment, and service life design. Research Needs The U.S. Department of Transportation (USDOT) and the state departments of transportation should consider sponsoring research with the objectives identified below, which address the development and evaluation of innova- tive approaches to reducing the installed and life-cycle costs of highway bridges. Research projects on these topics should have sharply defined prob- lem statements and objectives and valid research designs. These research projects could be carried out in conjunction with projects funded by the federal innovation incentive grant program previously recommended; that is, construction, rehabilitation, or monitoring projects that receive grants could be planned as experiments or as data sources for purposes of the research. Research on these topics could also be conducted independently of the incentive grant program. The recommended research objectives are:
74 PERFORMANCE OF BRIDGES â¢ Development and validation of models for projecting service life and deterioration rates for use in bridge management and life-cycle cost analysis. â¢ Long-term monitoring of the durability, performance, and costs of materials and technologies: Highway agencies will hesitate to adopt unfamiliar but potentially cost-saving technologies without strong evidence of performance over time. If bridge owners waited for re- sults of long-term monitoring evaluations before deciding whether to adopt a technology, innovation would be greatly slowed. Evi- dence from laboratory measurements and accelerated testing, the experience of construction of early projects, and short-term moni- toring (e.g., 4 to 10 years) of the performance of early projects can identify technologies that are likely to provide long-term cost savings. Data from long-term monitoring are necessary to validate expectations and to determine the practices that maximize the benefits of the new technology. Evidence of long-term performance is especially important to justify a technology with higher initial cost than alternatives in a life-cycle costs comparison. Systematic long-term performance data are lacking or inadequate for the ma- terials demonstrated in the IBRC program. Standard procedures for inspecting the materials could be developed in conjunction with monitoring studies. â¢ New nondestructive bridge evaluation technologies and techniques: Improved capability for quantitative measurement of bridge con- dition and for efficient inspection of bridges will allow highway agencies to choose maintenance, rehabilitation, and replacement strategies that reduce the life-cycle costs of their bridges. The in- formation from evaluations will also lead to design improvements that reduce life-cycle cost. â¢ Optimized designs and standardization for materials: Development is needed of designs and design standards that maximize the cost savings attained from advanced materials and that specify use of these materials in applications for which their properties are most valuable. Bridge rating standards are needed that properly account for the performance of these materials. â¢ Development of advanced materials such as engineered cementi- tious composites for bridge elements and optimization of their use in bridge applications. â¢ Optimized design for ABC: Design methods are needed that take full advantage of the economies attainable from prefabrication of bridge elements and systems. A NCHRP report on research to develop the ABC design and construction guide specifications that were subsequently adopted by AASHTO lists more than 30 ABC
CONCLUSIONS AND RECOMMENDATIONS 75 knowledge gaps and identifies research needed to fill certain gaps (Culmo et al. 2017, 25â48). â¢ Methods of maintaining and updating existing infrastructure to accommodate truck platooning (operation of two or more trucks in a convoy with close spacing maintained by an advanced driver assistance system) and other upcoming transportation technologies. These research objectives parallel the objectives previously suggested for the proposed new federal innovation incentive grant program. Problem statements for specific research projects could be developed as part of the planning for the grant program. FRP Bridge Applications Evaluation Use of FRP composites in bridges was a major emphasis area of the IBRC program. Externally bonded FRP reinforcement and FRP rebar, two ap- plications demonstrated in IBRC projects, have gained substantial use by highway agencies. However, FRP deck elements, superstructure elements, and prestressing tendons (strand or bar), which together were demonstrated in more than 100 IBRC projects, are used by few states today, according to the 2018 AASHTO state bridge engineers survey. Apparently, the experi- ence of the IBRC program either did not resolve uncertainties about the performance and appropriate applications of these technologies or did not overcome highway agenciesâ resistance to change. FHWA, in cooperation with the state highway agencies, could deter- mine the potential for greater use and benefit from FRP materials in bridge construction through a research and technology transfer program that includes the activities listed below. FHWA and the states should consider undertaking such a program in light of their overall innovation objectives and available resources. â¢ Develop a material qualification and certification program that identifies suitable FRP materials for bridge construction. â¢ Conduct material durability studies and create a materials database that is accessible to highway agencies and engineering professionals to enable improved quality and safe designs and construction. â¢ Conduct demonstration projects to collect cost and long-term per- formance data for cost-benefit and life-cycle cost analysis, and develop a materials cost database to support analyses. â¢ Harmonize and refine the currently available AASHTO FRP speci- fications and guides to ensure their consistency and uniformity. â¢ Conduct trial design and construction projects to test ease of use and reasonableness of the standards and specifications. Projects
76 PERFORMANCE OF BRIDGES should take place in several states and involve several bridge engi- neering firms. â¢ Develop inspection, repair, and rating procedures for bridge com- ponents and systems that use FRP materials consistent with stan- dard practice for concrete, steel, and timber bridges. â¢ Conduct education and training programs that provide bridge structural design, bridge maintenance and inspection, and bridge materials research and test engineers in the federal and state gov- ernments and the private sector with knowledge, tools, and tech- niques for the effective use of these materials. These activities could be organized as an emphasis area within the innova- tion incentive grant program previously recommended. Other Actions to Encourage Innovation Professional Interchange In the interviews conducted for this study, state highway agency staff emphasized that interaction with engineers in other states is a key source of information about innovations and commonly influences decisions to try new technology. Interactions occur at professional events organized by AASHTO and others as well as informally. Interactions in regional working groups established to promote technical interchange can lead to cooperation in developing standards and specifications. State engineers identified the Bridge Preservation Partnerships, supported by the AASHTO Transportation System Preservation Technical Services Program, as an effec- tive resource for technical interchange. Opportunities for highway agency engineers to interact with researchers and with industry representatives are also valuable. Virtual meetings via the Internet are becoming increasingly effective tools for technology transfer of innovative products. However, person-to- person events continue to be the most effective means for streamlining the successful implementation of innovation. Project demonstration showcases allow potential users to come together to witness firsthand a new product being built in the field. Showcases include presentations by the experts who designed, fabricated, and constructed a bridge that incorporates the focus innovation, followed by a tour of the bridge, preferably during its construc- tion. Potential users not only hear about the new technology, but also talk with the experts and see it being implemented in the field. The state highway agencies should recognize the essential role of pro- fessional interactions among engineers for the dissemination of technical advances, support the establishment of activities that provide opportunities
CONCLUSIONS AND RECOMMENDATIONS 77 for technical exchange, and support participation of their engineers in these activities. Existing Federal Highway Innovation Programs Congress should continue to provide funding and direction in future federal aid program authorizations for the existing innovation programs admin- istered by the FHWA Center for Accelerating Innovation. These programs are important in encouraging state highway agencies to use innovative technologies and methods and have accelerated the process of adoption. The new bridge innovation incentive program previously recommended is not intended as a substitute for the existing programs. Dissemination and Implementation of Research Results All federal highway research and innovation programs should incorporate formal provisions and sufficient resources for implementation, dissemina- tion, and long-term monitoring of in-service performance of new technolo- gies. Strengthening federal implementation activities will greatly magnify the value of research. State highway agencies hesitate to implement new technologies without evidence of performance.