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5BACKGROUND Modern road transportation systems comprise many physical components, or assets, that enable them to fulfill the publicâs expectations to travel to their destinations safely, conve- niently, in reasonable time, and at reasonable cost. Roadway pavements and bridges are among the most visible and highly valued elements of highways, roads, and streets. These aspects of road links are essential to providing smooth, safe, effi- cient, and cost-effective movement of people and goods. Many other assets in highway, road, and street networks however also play important roles in ensuring the structural integrity as well as the orderly, safe, convenient, and efficient mobility expected in a well-functioning and cost-effective transportation system. These additional assets are located above, below, and alongside the roadway proper; encom- passing items such as signs, signals, lighting, centerline or median barriers, guardrails, crash attenuators, lane and edge striping, and other pavement markings, sidewalks, roadside delineators, pavement subsurface drains, drainage inlets and catch basins, culverts and drainage ditches, retaining walls, and fencing. The importance of these âother assetsâ should not be underestimated. They are critical to an orderly and safe movement of vehicles and people in several ways: ⢠They help guide vehicles (signs, lane striping, and delineators) and avoid conflicts at intersections (signs and traffic signals). ⢠They help prevent collisions with other vehicles (striping and centerline barriers) and with roadway and roadside objects (guardrails, warning signs, and crash attenuators). ⢠They alert motorists to situations requiring heightened attentiveness (warning signs, signals, and pavement markings) and increase overall awareness at night (roadway lighting and retroreflective signs, pavement markings, and delineators). Assets such as drainage structures and pipes, retaining walls, and fences enable roads to serve properly in their nat- ural setting and to protect the public from natural threats such as floods and slides. They help maintain the integrity of the roadway foundation by collecting and diverting water from the road surface and subsurface, and transporting nat- ural watercourses safely along and across the right-of-way (drainage inlets, subsurface drains, culvert pipes, box cul- verts, and ditches). They enable the construction and preser- vation of an optimal road alignment and profile in hilly or mountainous terrain, and in urban areas where open land is scarce (retaining walls and reinforced earth structures), while protecting motorists as well as the natural environ- ment (fallen-rock barriers, gabions, and fish passages). They prevent unwanted incursions within the transportation right- of-way by people and animals (signs, fences, and cattle guards). These types of assets enable highway, road, and street networks to serve several transportation modes simultane- ously, both motorized and nonmotorized. They delineate reserved lanes and loading areas (e.g., for buses, taxis, deliv- ery trucks, and cyclists), separate the traffic streams of different modes (e.g., pedestrian sidewalks, bicycle paths, and lanes), and help organize the movement of conflicting modes where they must cross (e.g., signs, signals, and pavement markings at crosswalks). They provide important warnings and regulatory controls on traffic at critical locations; for example, in school zones, at busy intersec- tions, and near housing for the elderly or people with special needs. Often these assets are used in combination with one another for maximum effectiveness; for example, signs, signals, markings, and lighting. STUDY OBJECTIVES The objectives of this synthesis were to gain a better understanding of the state of practice for managing trans- portation infrastructure assets other than pavements and bridges, to identify best practices, and to document gaps in existing knowledge and needs for further research. The study focused on the assets listed here, although unique or innova- tive management methods for other assets were also included whenever identified. The following six types of assets were the primary subjects of this study, and are referred to in this report as âselected infrastructure assetsâ or simply âselected assetsâ: ⢠Traffic signals, including structural components; ⢠Lighting, including structural components; ⢠Signs, both ground-mounted (or roadside) and over- head, including structural components; ⢠Pavement lane striping and other markings; ⢠Drainage culverts and pipes (but not bridges); and CHAPTER ONE INTRODUCTION
⢠Sidewalks, including the walkway itself, curbs, and corners on urban roads and streets (corner curbs, and curb cuts and ramps if present). The synthesis was designed to address a number of issues related to these selected assets, including: ⢠Agency management approaches for each asset; ⢠Methods to determine condition of the asset; ⢠Methods to determine where an asset is in its life span; ⢠Methods to forecast future resource needs for preserv- ing and/or achieving a service-level objective; ⢠Service-life models or assumptions that are used to forecast maintenance, rehabilitation, and replacement; ⢠Methods and technologies used to collect, analyze, predict, map, and maintain asset information; ⢠Major knowledge gaps and research needed to improve the validity of service-life estimates for the six selected transportation assets; and ⢠Other non-pavement, non-bridge assets for which unique or innovative management approaches have been developed. STUDY APPROACH This synthesis study examined these and other aspects of asset management related to the selected infrastructure assets, including primary sources of technical guidance for management; basic approaches to budgeting for, and conducting, preservation, operation, and maintenance; organizational responsibilities for ongoing maintenance; measurement of asset condition and performance, including methods and frequencies of data collection; estimates of service lives (or deterioration models) for key components of the selected assets, accounting for the different materials used; information technology capabilities available to help agencies manage these selected assets; perceptions of the transportation objectives that are served by maintaining selected assets in good condition; and major gaps in knowl- edge that impede better asset management, with recommen- dations for future research. These data were gathered through a review of U.S. and international literature and a survey of state, provincial, county, and city transportation agencies in the United States and Canada. The survey questionnaire was developed with the advice of the Topic Panel and was presented in seven parts: six related to the six classes of infrastructure assets listed previously, and a seventh that addressed broader issues of asset management and knowledge gaps and needs. The survey questionnaire is included in Appendix A. Follow-up communications with selected survey respondents provided additional information. The survey was distributed to the contact individuals for asset management within each state department of transportation (DOT) or state highway agency (SHA), as identified by AASHTO. The FHWAâs Local 6 Technical Assistance Program network assisted with the distribution to U.S. cities and counties. Distribution to provinces and cities in Canada was facilitated by the Transportation Association of Canada (TAC). A total of 35 state DOTs, SHAs, highway and transportation (H&T) organizations, provincial ministries of transport, and trans- portation or public works departments in cities and counties responded to this questionnaire and are listed in Appendix B. These 35 jurisdictions provided 39 sets of completed ques- tionnaires, as the results for Colorado were submitted indi- vidually by Colorado DOT region. Not all respondents completed all parts of the question- naire. The number of responses with useable data therefore varied by survey part. When subsequent chapters refer to âreporting agenciesâ or âresponding agencies,â the numbers of responses for each asset type are as given by the follow- ing counts: signals (31), lighting (32), signs (36), markings (33), culverts (30), and sidewalks (23). This report discusses the survey findings fully, reflecting the breadth and detail of the questions as posed. Comments and additional information that were provided by survey participants are paraphrased following the graphical and tabular compilations of responses. The report also cites the findings of additional surveys that have been conducted by other researchers in earlier studies. There is a considerable body of literature associated with each of the six selected assets. This synthesis reviews the portions of that literature that most directly explain and illustrate to what degree agencies have applied good asset management practice to the six selected assets. This review includes considerations such as service-life estimation, supporting data collection, applications of information tech- nology, relevant human factors issues, gaps in current knowledge, and needs for research. The number, detail, and types of sources of this literature are not uniform across the six types of assets, however, which has also been observed by other researchers (e.g., Zwahlen et al. 2005). For exam- ple, there are considerable numbers of references addressing the physical and chemical performance of culvert materials and pavement markings, respectively; explanations of how these assets degrade over time are technically complex. Other assets, such as traffic signals and roadway lighting (excluding supports), exhibit performance based on a differ- ent set of organizing principles that are rooted in electrical/ electronic systems and communications rather than physical material abrasion, deformation, and corrosion; the literature related to the asset management of these systems in a trans- portation context is not as extensive. Applications of asset management to roadway lighting and examples of innova- tive lighting technology are prevalent in the international lit- erature. Sidewalk asset management plans are almost exclu- sively in the domain of local governments rather than state DOTs, at least in U.S. practice. These differences are one of the key reasons for addressing the six assets individually in
7chapters two through seven. At the same time, the impor- tance of viewing asset management comprehensively is a major reason for consolidating findings across assets and describing strategic agency management approaches in chapter eight. PRACTICAL ASSESSMENTS OF ASSET MANAGEMENT General Asset management is a strategic approach to managing transportation infrastructure that aims to get the best results or performance in the preservation, improvement, and oper- ation of infrastructure assets given the resources available. According to the AASHTO Transportation Asset Man- agement Guide, good asset management approach is policy- driven and performance-based, considers alternatives or options, evaluates competing projects and services based on cost-effectiveness and the anticipated impact on system per- formance, considers tradeoffs among programs, employs systematic and consistent business processes and decision criteria, and makes good use of quality information and analytic procedures (Cambridge Systematics, Inc. et al. 2002). During the development of the Guide in NCHRP Project 20-24(11), site visits to several DOTs indicated that all agencies likely practice at least some elements of good asset management, but none are likely to have fully imple- mented all potential aspects. Today, asset management is seen as applicable to transportation agencies at all levels of government, and the concept has been applied internation- ally among selected national, provincial, and municipal agencies for many years. Although asset management is a fundamental idea that applies in concept to any significant facility or item of infrastructure, there has been a tendency in the United States until now to associate it most closely with pave- ment and bridge management. One purpose of this syn- thesis is to identify how asset management concepts and techniques have been, or can be, applied to other trans- portation assets such as the six selected assets that are the focus of this study. This objective will first be addressed for each of the six assets individually, considering results from agencies that have participated in the synthesis survey, plus findings of the international literature review. Results across the six selected assets will then be consoli- dated to develop general findings on how agencies man- age their transportation assets other than pavements and bridges. It will also highlight leading efforts by individual agencies to develop improved information-gathering tech- niques, management procedures, and decision-support systems for their non-pavement, non-bridge assets. It will contrast these state-of-the-art examples with the wide range of current practices that now exist within the broader population of transportation agencies at various levels of government worldwide. Maturity of Asset Management Development Although âasset managementâ relates to many facets of an agencyâs business processes and decisions, it is possible to provide brief, descriptive examples that help to identify where an agency is in its asset management development. Table 1 presents such a âmaturity diagramâ for three levels of development. ⢠Basic infrastructure management, which is based not on an initial awareness of asset management, but con- tinuing decision making that is largely focused on indi- vidual assets. Asset management needs are typically addressed by engineering-based solutions. An asset inventory may exist, but, if so, it is not integrated with a corporate data warehouse. ⢠Growing application of asset management, where policy, processes, and staffing are all working to integrate an agencyâs decision making for long-term, mid-term, and immediate needs. ⢠State-of-the-art asset management, which represents a comprehensive application of good practices across assets and programs, and broad organizational buy-in with commitment from top management. The agency adopts positions and decision processes based on fund- ing asset needs in a sustainable manner, subject to resource constraints. Decision making is no longer asset-centric. Data and decisions reflect confidence levels so that communities and stakeholders can knowledgeably weigh in on preferred and affordable levels of services. Asset management is seen as a busi- ness management philosophy, not a program. The information in Table 1 has been developed from several sources: the Transportation Asset Management Guide (Cambridge Systematics, Inc. et al. 2002), the International Infrastructure Management Manual (IIMM, or âI2M2â) issued by the National Asset Management Steering Group (2006), NCHRP Report 551: Performance Measures and Targets for Transportation Asset Man- agement (Cambridge Systematics, Inc. et al. 2006), the FHWA report Roadway Safety Hardware Asset Man- agement Systems: Case Studies (Hensing and Rowshan 2005), and a general knowledge of the evolution of pave- ment management and bridge management, which are often cited as examples of transportation asset management in practice. Points to note are: ⢠Table 1 compares progressive stages of infrastructure asset management development. It is intended as a template. More complete and authoritative information on the concepts and implementation of asset manage- ment is provided in the references cited in the preceding paragraph. ⢠Asset management is really continuous process im- provement and is not developed in discreet stages. The use of three stages of development in Table 1 is
8General Stages of Infrastructure Management Maturity Aspect of Infrastructure Management Basic Infrastructure Management Growing Application of Asset Management State-of-the-Art Asset Management Overall Description of Agency Practice Investment and management decisions reflect current public policy objectives and good standard engineering practice. Thinking and decision making tend to be organized around specific programs, projects, and technologies, with little cross-program interaction. Management is to some degree reactive to current condition and performance. Research and information exchange likewise focus on specific assets or technologies. Business processes and decisions show increasing sophistication and cross- program, cross-disciplinary involvement, and an increasing ability to understand long-term as well as short-term implications of decisions. There is a greater capability to account for factors affecting asset performance, costs, and impacts across a wide range of situations, supported by strengthened analytic tools and data. Better information means that sources and degrees of risks are better understood and better addressed, enabling more proactive approaches. Transportation asset management is aligned with public policies and priorities, agency strategic business plans, transportation long-range plans, and transportation financial and construction program plans. Business processes and decisions reflect principles in the Transportation Asset Management Guide, and represent an integrated, multi- disciplinary, and transparent approach to solving problems. Policy Guidance Agency practices conform to applicable federal, state, and local statutes; local public policy; governing engineering standards and practices; and agency policies and procedures. Public outreach is largely project-specific. Early human-factors research focuses on minimum acceptable asset performance. Preceding capabilities plus: Guidance moves beyond ìwish lists â to provide clear governmental priorities among competing goals, objectives, and initiatives. Agency begins to integrate this guidance within aspects of its investment and management decision- making processes; e.g., in ranking and prioritization criteria, and performance- measure targets. Human factors understanding of asset- performance requirements extends to different population groups. Preceding capabilities plus: Long-range planning, agency strategic planning, and decisions on program funding and resource allocation are fully integrated horizontally (across agency units) and vertically (top management, managerial, and technical levels) under the umbrella of this guidance. Public outreach extends to identifying governmental priorities at a broad program level. Asset Life-Cycle Focus Project engineering decisions tend to focus on selection of materials and technology, initial cost and service life comparisons, and required impacts studies across alternatives. Maintenance and operations management decisions are largely detached from those for design and construction. Agencies apply life-cycle analysis techniques to compare total long-term performance, costs, benefits, and other impacts of project alternatives. Agencies increasingly integrate design and construction, maintenance, and operations considerations when analyzing performance, costs, benefits, and other impacts of project options. Project decisions are based on maximization of life-cycle benefits or minimization of life-cycle costs, plus consideration of other (nonquantitative) impacts. Life-cycle impacts to the public are considered in decisions on management options. The life-cycle framework enables analysis of certain tradeoffs (e.g., capital- maintenance, benefits-to- costs). TABLE 1 ASSET MANAGEMENT MATURITY CRITERIA (continued)
9General Stages of Infrastructure Management MaturityAspect of Infrastructure Management Basic Infrastructure Management Growing Application of Asset Management State-of-the-Art Asset Management Asset Performance and Costs Asset performance is understood in basic terms such as estimated service life and measures of condition and reliability, based largely on historical data, engineering judgment, and manufacturerâs recommendations. Predictive models of asset deterioration are simple (if they exist at all), and causal factors (effects of different operating environments) are imperfectly understood. Causal factors affecting asset deterioration are reasonably well understood based on published research and the agencyâs own experience. This knowledge is captured within predictive deterioration models, which may be joined with life- cycle decision-support methods (e.g., optimization, heuristics, decision trees) in management systems to forecast needs for treatments, associated costs, and improvement in asset condition or extension of service life. Management systems are applied to identify strategies for attaining performance targets within available resources. Preceding capabilities plus: Models yield information on asset performance and cost that can be easily processed or summarized for use by different agency organizational units and levels, as well as for external accountability reporting and public information. Understanding of asset performanceâin terms of current condition, stated objectives and targets, resulting investment needs, and performance trackingâis vertically integrated and understood by the agency, executive, and legislative stakeholders. Impacts of Asset Performance Impacts are understood and communicated in basic, qualitative terms (e.g., high- moderate-low effects). Quantitative information and capability to predict impacts for different investment options are limited. More comprehensive, detailed, quantitative information on impacts of asset performance on mobility, accessibility, safety, preservation of asset investment, etc., is available through research and agency experience. This knowledge is captured within predictive models used in decision support (e.g., management systems). Agency has attained or acquired a body of research on impacts of asset performance in different situations, climates, road classes, etc. Predictive models of impacts are fully incorporated in life-cycle procedures to optimize decisions on construction, rehabilitation, and maintenance. Resource Allocation, Budgeting, and Project Selection Budget development conforms to applicable law, funding eligibility, and agency planning and programming guidelines. Various approaches may be used in setting target program budget amounts; e.g., past yearâs budget plus inflation and other adjustments, percent of total budget designated for each program, percent of inventory addressed annually, and level-of- service-based budgeting. Ranking of projects in each program is based on a defined method; e.g., a scoring approach or a combination of objective and subjective criteria. Preceding capabilities plus: Budget development emphasizes more explicitly the relationship between proposed budget and target level of service or performance, with implications for achieving defined policy objectives. Ranking or prioritization criteria are closely aligned with policy objectives and performance targets. Level of service considers customer needs and perceptions, in addition to other public-policy and agency priorities. Budgeting results and forecast program impacts are communicated to stakeholders and the public. Preceding capabilities plus: Cross-program tradeoffs are explicitly considered, in addition to prioritization of projects within each program. Resource allocation and budgeting process is fully vertically aligned, with project prioritization criteria, tradeoff analyses, and performance measures and targets in full agreement with policy goals and objectives. Devices such as geographic information system-based maps and dashboards are used to communicate budget results and program impacts to stakeholders and the public. TABLE 1 (continued) (continued)
10 General Stages of Infrastructure Manage me nt Maturity Aspect of Infrastructure Management Basic Infrastructure Management Growing Application of Asset Manage me nt State-of-the-Art Asset Manage me nt Organization Decision ma king occurs in silos, and inform ation is not readily accessible across an agency . Awareness of asset ma nage me nt occurs at professional conferences or through literature. Role of asset management is assigned; cross- functional asset ma nage me nt team s exist. Occasional training is attended by asset ma nagers . Cross-functional asset ma nage me nt responsibility exists; briefs top ma nage me nt on status. Recognition and commitment to sustainable ma nage me nt of assets am ong em ployees, ma nage me nt, and elected officials . Hiring for asset ma nager role is explicit and training and asset ma nage me nt training occurs regularly and reaches all em ployees, ma nagers, and elected officials. Succession planning takes into account the role of asset ma nagers. Perform ance Measure me nt Perform ance is understood in basically engineering term s; e.g., asset condition and work outputs. Perform ance m easures ma y include research results on im pacts to road users (e.g., serviceability m easures). Measures ma y co mp rise a mi x of quantitative and qualitative indicators. Agency tracks custom er co mme nts and co mp laints. Previous capabilities plus: Asset perform ance is understood in engineering, econom ic, and customer - oriented term s. There is greater consideration to custom er - oriented outco me s (consistent with greater attention to impacts in other items above), and may be supplem ented by custom er surveys . There is increasing use of quantitative m easures, establishm ent of target values, and application of predictive m odels to evaluate invest me nt options against targets. Body of perform ance me asures is well- established and incorporated in business and decision processes as the basis for accountability reporting internally and externally, and to support policy form ulation, prioritization and tradeoff analyses, resource allocation, and public feedback. Measures are expressed in various form s for different audiences, including reports, trend lines, dashboards, ma ps, and other devices. TABLE 1 (continued) (continued)
11 convenient but arbitrary. For example, the AASHTO Transportation Asset Management Guide gives more detailed examples of state-of-the-art practice and com- pares typical current practices with equivalent prac- tices with good asset management. The IIMM provides two levels of asset management attainment, a âcoreâ level and an âadvancedâ level. The important point is understanding the potential span of improvement that is possible with asset management, rather than the spe- cific number of development levels used to track that improvement. ⢠Entries in Table 1 highlight examples of typical prac- tices at each stage in the U.S. transportation context, and should not be taken too literally for any one agency. Agencies differ in their management ap- proaches and cultures for many reasons, and prac- tices that may be viewed as âbasicâ by one agency may be regarded as âadvancedâ by another. Again, the purpose of Table 1 is to provide broad, general comparisons. ⢠In practice, every transportation agency displays exam- ples of excellent asset management in some aspects of its work, and no agency has a âperfect asset manage- ment scoreââthere is always room for improvement. Any one agency will therefore represent a blend of practices from two or three stages in Table 1. Based on the technical findings for each asset in chapters two through seven, the guidelines in Table 1 will be applied in chapter eight to evaluate how current management General Stages of Infrastructure Manage me nt Maturity Aspect of Infrastructure Management Basic Infrastructure Management Growing Application of Asset Manage me nt State-of-the-Art Asset Manage me nt Inform ation Technology (IT) and Data Collection and Processing Models and engineering relationships discussed in previous item s are incorporated within IT tools such as si mp le progra ms , spreadsheet workbooks, or legacy management systems (typically stand-alone, asset- specific, ma naging own data). Perform ance and im pacts ma y include a mix of objective (quantitative) and subjective (qualitative) data. Asset inspections may be scheduled, periodic, occasional, or on-de ma nd (i.e., following a complaint or asset failure). Data collection tends to be conducted for particular assets and progra ms by individual agency units, with resulting potential duplication of coverage and potentially contradictory values. Preceding capabilities plus: IT tools have evolved to mo re sophisticated ma nage me nt system s, incorporating engineering and econom ic models, life- cycle concepts, and decision-support procedures (e.g., optim ization, heuristics, decision rules, or trees). More refined and controlled data collection protocols are used on defined frequencies of inspection, with an increasing trend toward data integration and sharing throughout the agency and across asset classes. Sa mp ling techniques may also be em ployed. Where appropriate, there is increasing use of automation in data collection and processing (e.g., global positioning system locations, bar code readers, auto ma ted m easuring devices). Preceding capabilities plus: Asset ma nage me nt system s are organized on an integrating platform (e.g., geographic information system or web-based portals) for internal and possibly external access to inform ation. The agency ma intains co mp lete, current, and accurate data on asset inventory, condition, perform ance, cost, and work acco mp lishm ent. Data are updated on a predeterm ined schedule or by established criteria. Data supporting infrastructure asset ma nage me nt are fully integrated within a unified sche me . Techniques such as data warehousing ma y support reporting to various agency levels and stakeholders. There is an appropriate mi x of data collection technology (e.g., visual, physical, and auto ma ted m easure me nt, re mo te sensing) to ensure high- quality data and cost - effective coverage. Inform ation on custom er perceptions is updated regularly through surveys, focus groups, co mp laint tracking, or other met hods. TABLE 1 (continued)
practices for selected assets compare with the benchmarks set for good asset management. The result will be an assess- ment of the range of practices now in use, identification of gaps and potential research needs regarding management of the selected assets, and a focus on those agencies that are âat the front of the curveâ regarding their management of the selected infrastructure assets. Demonstrating the Importance of Selected Assets One of the hallmarks of good asset management practice is to be able to justify asset-related expenditures on the basis of worthwhile investment and value for dollar spent. Pavement management and bridge management systems are often cited as examples of how the principles, decision criteria, and quality of data associated with good asset man- agement can be embodied within practical, well-understood tools for managers. A key issue regarding the six selected assets is the lack of a strong history in quantifying and demonstrating the benefits that these assets provide to the public, and in using that information to identify needs, prioritize projects, and demonstrate accountability for expenditures. The value of a properly functioning set of traffic signals, roadway lights, road signs, pavement mark- ings, drainage culverts, and sidewalks is understood techni- cally during design. Broader impacts of these assets on road users, pedestrians, and the general public can be, and often are, expressed descriptively. However, agenciesâ capabili- ties to manage selected assets with the same level of data availability and analytic sophistication that are now employed for pavement and bridge management vary widely and often fall short of the benchmark set by well- developed pavement and bridge management systems. As an example, one of the questions in the survey con- ducted for this study asked agencies about the quantity of their inventory, and their level of expenditures for new installation and subsequent maintenance and rehabilitation, for each of the six selected assets. The question elicited one of the lowest response rates in the survey, with many partial or blank responses. Moreover, the data that were reported were highly inconsistent. From the results that were received, it was evident that (1) not all agencies maintain inventories of selected assets, and of those that do, agencies structure their inventories quite differently and express them in different units of measure; and (2) data on expenditures for the six selected assets are incomplete and difficult to compare reliably, either among agencies or in compiling annual expenditures for new installations versus those for maintenance and rehabilitation. Limited information on esti- mated expenditures for selected assets is available from other sources, and is cited in the chapters for those assets. As a general statement, however, many agencies do not have a good understanding of the quantity of selected assets that they manage or how much they spend on these assets. 12 Several other themes emerged from this study regarding how agencies manage these assets, and how they view the importance of selected assets: ⢠The wide range in management practices across agen- ciesâThese variations were evident in several areas; for example, in an agenciesâ acquisition of basic infor- mation such as expected service life; methods of data collection and analysis; measures of asset performance and failure; criteria and threshold values for repair, rehabilitation, and replacement; ability to predict asset condition, performance, and life-cycle costs; and ana- lytic methods and tools to help manage these assets. ⢠Different perspectives on the role of selected assetsâ There is a basic question among agencies as to whether the selected assets are indeed âassetsâ or merely âfeaturesâ or âhardwareâ associated with some larger component of infrastructure; for example, are traffic signals or signalized intersections the asset of interest? Decisions on questions such as this play an important role in shaping how selected assets are viewed within an agency and in determining what level of effort will be devoted to gathering and orga- nizing information on their status and cost. ⢠The lack of a perceived problem in current manage- ment of these assetsâAgencies apply a number of management approaches to selected assets, including periodic inspections, programmed replacements, and quick responses to customer complaints. These meth- ods appear to workâso long as no crisis develops. Given existing funding pressures, agencies may resist more frequent and focused attention, more advanced management approaches, and strengthened investment priority for these assets. ⢠Difficulty in demonstrating and communicating the importance of selected assets to the overall public goodâFailures of selected assets can have serious (and in severe cases, catastrophic) consequences to mobility, safety, and public welfare. However, these conse- quences are not widely communicated, and are there- fore poorly recognized and appreciated. Part of the reason is the lack of adequate analytic tools and more comprehensive performance information, which, if they were available, could demonstrate a performance- based relationship between selected asset condition or performance and resulting impacts to the public. Other factors, however, also come into play: â The need to consider operational performance as opposed to just physical condition of assets (e.g., proper signal timing; hydraulic performance of culverts; effect of pavement glare on visibility of pavement markings; and role of human factors in driver perceptions of roadway lighting, traffic signs, and pavement markings). â The need to consider the combined effects of sev- eral selected assets working together; for example, the combined roles of pavement markings, lighting,
13 signs, and signals at intersections and crosswalks; and the combined roles of roadway lighting and pavement marking conditions in ensuring adequate nighttime visibility of centerline, lane, and edge striping. â The need for a system-level view of selected asset performance; for example, the role of signal systems in providing safe, efficient movement of traffic along a length of roadway rather than just through a single intersection; and the ability of traffic signals, road- way lighting, road signs, pavement markings, and sidewalks to serve adequately different segments of the population and different types and configurations of vehicles. â The need for a long-term view of selected asset performance; for example, the ability of signal systems to respond to changes in long-term traffic volume and composition, as well as short-term interruptions in normal traffic patterns; and the ability of a culvert system to provide ongoing pro- tection against flooding given land-use changes and highway expansion that may have occurred after many years. ORGANIZATION OF SYNTHESIS Chapters two through seven discuss the synthesis findings for each of the six selected assets: chapter two, traffic sig- nals; chapter three, roadway lighting; chapter four, road signs; chapter five, pavement markings; chapter six, drainage culverts; and chapter seven, sidewalks. Chapter eight sum- marizes cross-cutting findings and themes among the six selected assets. It presents several examples from agencies in the United States and internationally that have implemented or are now looking at ways to manage selected assets better. Chapter nine presents the conclusions.
