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6C H A P T E R 2 2.1 Introduction Although each highway asset group has unique characteristics that must be addressed in any asset management methodology, commonalities exist that allow a generalization of the approaches proposed in this work. Figure 1 shows a generic framework that has been considered when developing asset management procedures (FHWA 2010a). Within the asset management framework, common components (e.g., goals, inventory, condi- tion assessment, and evaluation of alternatives) must be addressed in the development of specific procedures. Goals and policies are needed to establish objectives and define criteria for highway preservation programs. Asset inventories with up-to-date condition assessment records and per- formance models are required to forecast the condition over time and determine preservation and budget needs. Evaluation of treatment alternatives is necessary to assess the effect of differing scenarios to select candidate projects to be considered in program implementation. This study pro- poses a general, three-step framework to serve as a guideline in developing procedures to quantify the consequences of delaying maintenance of highway assets, as follows: Step 1. Define the asset preservation policy: 1.1. Identify the types of maintenance, 1.2. Establish performance objectives, and 1.3. Formulate decision criteria for maintenance activities. Step 2. Determine maintenance and budget needs: 2.1. Assess condition or remaining service life, 2.2. Select performance models to forecast condition and/or remaining service life, and 2.3. Perform a needs analysis to identify maintenance activities to meet the established objectives. Step 3. Conduct analyses of delayed maintenance scenarios: 3.1. Formulate delayed maintenance scenarios, 3.2. For each scenario, perform the delayed maintenance scenario analysis, and 3.3. Determine the effects of delayed maintenance and report the consequences. The information required to apply application of the framework to specific asset groups also is addressed in this report. Procedures are described for using the framework for pavements, bridges, culverts, guardrails, lighting, pavement markings, and signs. These procedures primarily address the effects of delaying maintenance, and the main focus is on evaluation of alternatives; however, asset inventory, condition assessment, and performance modeling are necessary to support the evaluation of alternatives. The delayed maintenance scenario analysis results should be considered when making strategic-level funding decisions because âmaintenance is a critical component of an agencyâs asset management planâ (FHWA 2016a). Framework for Quantifying Delayed Maintenance of Highway Assets
Framework for Quantifying Delayed Maintenance of Highway Assets 7 This chapter introduces the fundamental principles on which the general framework was developed. It provides an overview of the asset management process and the information needed to support the three-step asset management framework. Next, the chapter briefly explains how each component is further developed to quantify the consequences of delayed maintenance. Pre- liminary discussion of concepts and issues relevant to applying the framework to individual asset groups is provided as an introduction to the subsequent chapters. Examples include condition assessment, performance measures, models, scenarios analyses, and reports to show the conse- quences of delayed maintenance. 2.2 Preservation Goals and Policies for Maintenance Preservation policies describe actions or procedures adopted and pursued by the responsible agency regarding preservation-related maintenance practices. Preservation goals often are devel- oped in coordination with funding authorities to define the results or achievements expected from policy implementation. Consequently, highway maintenance programs are formulated in accordance with the established policies and goals of the agency. Step 1 of the general framework addresses preservation goals and policies by defining the asset preservation policy. Performance-based preservation policies focus on the timely appli- cation of maintenance activities. FHWA includes preventive maintenance as a major compo- nent of highway preservation programs and defines preservation as âwork that is planned and performed to improve or sustain the condition of the transportation facility in a state of good repair. Preservation activities, generally, do not add capacity or structural value, but do restore Figure 1. Asset management framework. Condition Assessment and Performance Modeling Asset Inventory Goals and Policies Alternatives Evaluation and Program Optimization Short- and Long-Range Plans (Project Selection) Program Implementation Performance Monitoring Budget/ AllocationFeedback Source: FHWA (2010a)
8 Consequences of Delayed Maintenance of Highway Assets the overall condition of the transportation facilityâ (FHWA 2016a). FHWA defines the types of maintenance as follows: â¢ Maintenance âdescribes work that is performed to maintain the condition of the transporta- tion system or to respond to specific conditions or events that restore the highway system to a functional state of operationâ; â¢ Routine maintenance âencompasses work that is performed in reaction to an event, season, or over all deterioration of the transportation asset. This work requires regular reoccurring attentionâ; and â¢ Preventive maintenance âis a cost-effective means of extending the useful life of the federal- aid highwayâ and is further described as âa proactive approach to extend the useful life of the highwayâ (FHWA 2016a). 2.3 Asset Inventory Preservation goals and policies influence the database structure of the asset inventory. The AASHTO Transportation Asset Management Guide: A Focus on Implementation (TAM Guide) defines an asset inventory as a âdatabase that identifies individual assets and their elements, with physical, operational, and administrative characteristics required for developing mainte- nance and rehabilitation strategies and budgetsâ (AASHTO 2011). The TAM Guide emphasizes the need for an asset management system to integrate information to better support decision- making and business processes. The advantages of integrated databases include: â¢ Availability/accessibility; â¢ Timeliness; â¢ Accuracy, correctness, and integrity; â¢ Consistency and clarity; â¢ Completeness; â¢ Reduced duplication; â¢ Faster processing and turnaround time; â¢ Lower data acquisition and storage costs; â¢ Informed and defensible decisions; and â¢ Integrated decision-making (FHWA 2010a). Several state highway agencies have prepared plans for data integration for asset management, and general recommendations are available in both the Data Integration Primer (U.S.DOT 2001) and the TAM Guide. Most agencies, however, are constrained by their past and current infor- mation technology systems and by available resources. Therefore, the main challenges to data integration include: â¢ Heterogeneous data, â¢ Bad data, â¢ Unanticipated costs, and â¢ Lack of data management expertise (FHWA 2010a). The Asset Management Data Collection Guide (AASHTO-AGC-ARTBA 2006) describes the functional characteristics of pavements, bridges, culverts, guardrails, and drainage structures. The guide references data that are regularly collected about the asset; data collection methods; equip- ment and/or technology needed to obtain the data; formats and standards applied to transferring and storing the data; how the data are used for condition assessment; and suggested performance and condition standards. Selected information is essential to support analysis of the effects of applying and delaying maintenance applications. This report describes the essential information needed to support the
Framework for Quantifying Delayed Maintenance of Highway Assets 9 analyses applied in the framework, provides a precautionary discussion about insufficient data and information, and suggests approaches usable to begin the analyses with limited data. 2.4 Condition Assessment, Service Life, and Performance Measures Step 2 of the general framework involves determining maintenance and budget needs. Ele- ments of this step include examining the asset condition and/or remaining service life (RSL) and using performance models to forecast the asset group condition and maintenance needs over time. This section addresses condition assessment and RSL, and introduces performance measures. 2.4.1 Condition Assessment All assets deteriorate over time, so their condition must be assessed periodically. Condition assessment surveys (CASs) are scheduled and conducted to refresh the information available on the condition of an asset. CAS results are used to identify maintenance needs, especially routine or corrective maintenance. These results are combined with performance models and decision criteria to identify the type and timing of needed maintenance. CASs are relatively technical, and they vary significantly among asset groups and across agen- cies. The assessment intervals also vary among asset groups and are influenced by maintenance policies, expected rates of deterioration, environmental conditions, and the importance of the facility. Interstate pavements generally are inspected annually. Pavements on the National High- way System (NHS) and non-NHS roads typically are inspected annually or every 2 years, and pavements on lower volume and local roads and streets may be inspected only once every 3 to 4 years. The National Bridge Inspection Standards (NBIS) recommend that bridges be assessed at least once every 2 years (FHWA 2016d). Some agencies report inspecting signs every year, but others select longer intervals such as once every 3 to 4 years (Re and Carlson 2012). Assess- ment intervals for the other asset groups have not been established by many agencies; however, they are under development in a number of agencies. For example, the Minnesota Department of Transportation (Minnesota DOT) has established an assessment interval of 1 to 2 years for culverts (Minnesota DOT 2011). Additionally, the occurrence of other maintenance or assess- ment activities may trigger an assessment. For example, the Texas Department of Transporta- tion (Texas DOT) recommends inspecting lighting âevery time the lamps are changed or the ring is lowered for any reasonâ (Lopez 2003). Time-sequenced asset condition assessment results are essential for developing and validating performance models. In some highway asset groups, the assessment focuses on detecting when the level of service (LOS) falls below a desired level, establishing a need for routine or reactive maintenance. For example, guardrails are constructed using various materials that have differing support systems and end treatments. Each major component will have a unique deterioration rate that is a func- tion of the properties of the materials used in its construction and the environment in which it provides service. Asset failure affects all preservation programs. In the case of guardrails, how- ever, damage and failure may result from vehicle effects, and no amount of condition assessment will predict when or where an effect will occur. An effective maintenance management system that records when and where effects have occurred together with information on the type and amount of damage, can provide information not only about the need for routine maintenance but also information useful for planning corrective maintenance after such events have occurred. This type of assessment may be part of a formal timed inspection but more often is completed informally, by local maintenance supervisors making regular driving trips throughout their area of responsibility. Incident reports often are used to trigger a damage assessment.
10 Consequences of Delayed Maintenance of Highway Assets Condition assessment for an asset group generally includes individual distress measures, con- dition indices, and other performance measures to evaluate the current condition of the assets in that group. Reporting requirements related to asset condition and performance measures at the national level include the following: â¢ Specific pavement and bridge performance measures must be reported on the NHS as a part of the National Highway Performance Program (NHPP), Title 23 CFR Part 490 (FHWA 2016b). â¢ The Federal Aid Policy Guide, Title 23 CFR 650C, describes inspection procedures, frequency of inspections, and qualifications of inspection personnel. Agencies must report inspection information annually to FHWA for all bridges and culverts with spans greater than 20 feet (FHWA 2016c). â¢ FHWA Report NHI 05-036, Guidelines for the Installation, Inspection, Maintenance and Repair of Structural Supports for Highway Signs, Luminaires, and Traffic Signals, identifies five types of inspections for structural supports, initial, routine, in-depth, interim, and damage. While acknowledging that âinspection of ancillary structures is not required by federal regulations, nor are there any requirements for those personnel who conduct such inspections,â the authors recommend that those completing the inspection meet qualification requirements similar to those found in the NBIS (Garlich and Thorkildsen 2005). 2.4.2 Service Life A complete physical assessment of some asset groups can be costly. For these assets, asset service life can be used as an alternative approach to physical condition assessment. Likewise, the projected service life of assets that are subject to vehicle effect damage can be used to project the percentage of such assets that are likely to need routine or corrective maintenance within a selected time period. However, asset service life varies considerably among asset groups due to different environmental conditions, expected rates of deterioration, importance of the facility for which they provide service, and maintenance practices. Asset service life generally is described as the time between the date the asset was constructed (or put in service) and the date at which it no longer provides acceptable service. For an indi- vidual item (e.g., a single luminaire lighting device), asset life is easy to define. In the case of the luminaire, it is the time between when the fixture was placed in service until it no longer provides light. For many highway assets, however, the definition of acceptable service often is established arbitrarily. RSL generally is described as the time between the current date and the date at which an asset is no longer expected to provide acceptable service. Elkins et al. (2013) detail the issues that arise in establishing end of life and service life of pavements. Thompson et al. (2012) provide con- siderable detail on these issues for pavements, bridges, culverts, signs, and pavement markings. Although Thompson et al. (2012) focus primarily on end-of-life models, they recognize that other intervention times can be identified in analysis models using asset life or RSL. Table 1 shows the service life expectancy and inspection intervals of various assets according to best practices recommended by AASHTO and FHWA (Thompson et al. 2012; FHWA 2007a; Migletz and Graham 2002). 2.4.3 Performance Measures Performance measures facilitate the asset management process because they are used to estab- lish goals, characterize the asset group condition, and monitor the results of the preservation programs. Table 2 provides examples of performance measures for pavement condition, bridge condition, safety, highway system performance, congestion mitigation, and air quality.
Framework for Quantifying Delayed Maintenance of Highway Assets 11 Delaying maintenance affects the asset condition, decreases the LOS, and increases the costs. Agencies commonly measure the increase in maintenance and rehabilitation or reconstruction costs required to preserve the highway system at some designated LOS; however, delaying main- tenance of highway assets has consequences that affect more than just agency costs. Cambridge Systematics et al. (2006) provide an extensive discussion of performance measures for transpor- tation assets and guidelines for selecting performance measures, many of which go well beyond assessing asset condition or looking at service life. Social and environmental consequences also can result from maintenance delays. For exam- ple, highway assets that perform below the expected LOS have been perceived to generate user discomfort, increase exposure to accidents, increase fuel usage, and increase damage to vehicles (Setyawan et al. 2015). Environmentally, air pollution increases with greater traffic congestion. Furthermore, poorer pavement condition can affect vehicle fuel emissions (e.g., CO, CO2, HC, NOx) (Chang et al. 2016). Also, without proper maintenance, materials deterioration also can affect the environment negatively (Setyawan et al. 2015). Agenciesâ performance measures could be broadened to include user costs and safety-related factors (e.g., crash frequency, severity, and the proportion of people injured in collisions) and environmental effects. 2.5 Performance Models Step 2 of the general framework also involves selecting performance models to forecast the asset condition or RSL. Models are needed that relate performance measures to the assetâs service life with and without specific maintenance activities, helping to determine maintenance and budget needs over an analysis period. This section describes performance modeling approaches and provides general guidelines for selecting a performance model to conduct the needs and other analyses. 2.5.1 Performance Models and Maintenance To analyze the effects of delaying maintenance, models are used to project asset performance with and without the application of the proposed maintenance treatments. Models also can show the effects of applying various maintenance treatments to assets at varying levels of asset condi- tion or stages of service life over an analysis period. The effects analyzed may include immediate changes in condition, changes in the rate of deterioration, or both. lavretnInoitcepsnIefiLecivreStessA Pavement 40 years PCC 3 1 year 1 Bridge 50 years 1 1â2 years 1 Culvert 30â50 years 1 Span > 10 ft. 1â2 years 2, Concrete box 4 years 2 Sign Sheeting 5â20 years, posts 10â27.5 years, structures 30â50 years1 1â2 years 1 Pavement Marking 1â2 years waterborne paints, 4â5 years thermoplastic paints 1 Twice a year 3 PCC = Portland cement concrete Sources: 1 Thompson et al. (2012), 2 FHWA (2007a), 3 Migletz and Graham (2002) Table 1. Service life and inspection intervals for condition assessment of highway assets.
12 Consequences of Delayed Maintenance of Highway Assets Category Performance Measure Definition Pavement Condition Interstate pavement in good, fair and poor condition based on the International Roughness Index (IRI) âPercentage of 0.1-mi. segments of Interstate pavement mileage in good, fair and poor condition based on the following criteria: good if IRI <95, fair if IRI is between 95 and 170, and poor if IRI is greater than 170.â Non-Interstate NHS pavement in good, fair and poor condition based on the IRI âPercentage of 0.1-mi. segments of non-Interstate NHS pavement mileage in good, fair and poor condition based on the following criteria: good if IRI < 95, fair if IRI is between 95 and 170, and poor if IRI > 170.â Pavement Structural Health Index âPercentage of pavement which meet minimum criteria for pavement faulting, rutting and cracking.â Bridge Condition Percentage of deck area on structurally deficient bridges âNHS bridge deck area on structurally deficient bridges as a percentage of total NHS bridge deck area.â NHS bridges in good, fair and poor condition based on deck area âPercentage of National Highway System bridges in good, fair, and poor condition, weighted by deck area.â Safety Number of fatalities âFive-year moving average of the count of the number of fatalities on all public roads for a calendar year.â Fatality rate âFive-year moving average of the number of fatalities divided by the vehicle-miles traveled (VMT) for a calendar year.â Number of serious injuries âFive-year moving average of the count of the number of serious injuries on all public roads for a calendar year.â Serious injury rate âFive-year moving average of the number of serious injuries divided by the vehicle-miles traveled (VMT) for a calendar year.â System Performance Annual hrs. of delay (AHD) âTravel time above a congestion threshold (defined by state DOTs and MPOs) in units of vehicle-hours of delay on Interstate and NHS corridors.â Reliability Index (RI80) âThe Reliability Index is defined as the ratio of the 80th percentile travel time to the agency-determined threshold travel time.â Congestion Mitigation and Air Quality (CMAQ) Criteria pollutant emissions âDaily kg. of on-road, mobile source criteria air pollutants (VOC, NOx, PM, CO) reduced by the latest annual program of CMAQ projects.â Annual hrs. of delay (AHD) âTravel time above a congestion threshold (defined by state DOTs and MPOs) in units of vehicle-hours of delay reduced by the latest annual program of CMAQ projects.â MPOs = metropolitan planning organizations VOC = volatile organic compounds; NOx = nitrogen oxides, PM = particulate matter, CO = carbon monoxide Source: AASHTO (2012a) Table 2. Examples of performance measures for highway asset groups.
Framework for Quantifying Delayed Maintenance of Highway Assets 13 For highway assets that exhibit a predictable reduction in condition over time, models are typically developed to predict that condition change over time. Generally, condition data from field assessments are used with statistical methods to develop such models. Expert opinion may be used when field data are not available, but in these cases the models should be updated with observed condition data as it is collected over time. Maintenance effects generally are shown as improvements in condition and/or reductions in rate of deterioration at the time of the treatment. The amount of the change is a function of the type of treatment applied, the properties of the asset to which it is applied, and the condition of the asset at the time of application. Condition assessment data collected immediately before and after the application of a treatment can be used to incorporate the effect of the treatment into the model. Expert opinion may be used when these data are not available, but they should be updated with observed data as it is collected over time. Most pavement and bridge management systems have performance models for predicting deterioration with and without treatments to evaluate the effects of reconstruction, major reha- bilitation, and minor rehabilitation; some systems also have models that include preventive maintenance and routine maintenance treatments. Cyclical preventive maintenance activities, condition-based preventive maintenance, and repairs to restore structural integrity often are found in bridge management systems. For asset groups lacking field measurements or reliable maintenance records, expected asset life can be used as a surrogate for condition assessment and maintenance information. The asset life may be based on manufacturersâ supplied information (e.g., expected life of luminaires). It could also be based on historical records of the typical age at which a maintenance activity was needed on similar assets. The expert opinion of knowledgeable maintenance personnel also can be used to establish initial life estimates. If no other information is available, straight-line dete- rioration models for predicting condition based on expected service life is a simplified modeling option, but expert opinion is required to establish whether the expected shape of the deterioration versus time relationship should be concave, convex, or sigmoidal. Maintenance activities for some asset groups (e.g., guardrails, sign supports, and light supports) are affected by single, unpredictable events such as vehicle crashes. Developing performance models to predict when maintenance will be needed for specific components is challenging for these asset groups. Based on maintenance history records and expert opinion, however, probabilistic models can be developed to predict the percentage or number of similar assets in an asset group in a similar environment that will need routine or corrective maintenance over a specified time period. 2.5.2 Selection of Performance Modeling Approach Generally, performance models employ either a family modeling or site-specific modeling approach. The family modeling approach groups individual assets with similar characteristics (e.g., material type, traffic and climate conditions) and generates performance models based on changes in the family data set. The site-specific modeling approach uses condition assessments based on characteristics specific to individual components of the asset group. The family model- ing approach reduces data demands because the number of variables and data specificity are reduced as compared to the site-specific modeling approach (AASHTO 2012b). The type of performance model selected varies depending on the mode of deterioration of the asset group and other factors identified in the previous section. At the network-management level, the more common performance models include: â¢ Deterministic performance models developed from observed condition data using statistical analyses to formulate mathematical equations that predict the asset condition (or another
14 Consequences of Delayed Maintenance of Highway Assets performance measure) based on age, usage, environmental factors, and asset properties. The most commonly used deterministic performance model forms include linear, polynomial, and power functions. â¢ Probabilistic performance models that predict a range of values, often as a percentage of a group of assets in selected condition states with and without treatment. Generally, the predicted range of values is a function of the same factors used in deterministic models, but it may also be based on expert opinion. Probabilistic performance models include survivor curves and Markov or semi-Markov transition processes. Survivor curves graphically represent probabilities of asset condition over time. The Markov approach incorporates the current condition and assumes that the probability of changing from one asset condition state (or other performance measure state) to another is independent of time. The Markov approach requires less frequent data col- lection; however, because the models only depend on the current state, they exclude the effects of other variables (e.g., traffic or climate). The semi-Markov approach removes the assumption of independence of time. â¢ Bayesian performance models that combine historical or objective data with subjective infor- mation from experts. â¢ Expert-based performance models that rely on subjective data or expertise. Typically, these models are used to supplement the other modeling approaches when historical data is limited or unavailable. The following factors should be considered in selecting the modeling approach: â¢ Adequacy of dataâModel type selection should be based on the availability of adequate historical data. â¢ Significance of variablesâThe most significant variables affecting asset performance (e.g., climate, traffic, materials) should be selected. â¢ Functional formâThe selected model form should fit the data and reflect the typical deterio- ration pattern (e.g., condition will not improve over time unless a treatment is applied and cannot either exceed the maximum value or be less than the minimum value). â¢ Precision and accuracyâThe model should provide reasonable estimates of changes in asset condition over time. Statistical methods to determine model reliability can be evaluated to ensure that reasonable model estimates are used. Following a performance-based approach to moni- toring the results of the preservation program provides feedback that can be used to evaluate if the modelsâ estimates are validated in practice and provide information for improving the accuracy of the models over time. The performance model(s) selected must be able to predict changes in asset condition, service life, or performance measures as needed to identify whether the agency is achieving its goals. 2.6 Needs Analysis The third element of Step 2 in the general framework involves conducting needs analysis to identify the maintenance activities needed to meet the established goals. This analysis should be based on applying the right treatment to the right asset at the right time; in other words, it should reflect applying the best engineering practices related to preservation maintenance treatments for the highway asset group being analyzed. Performance models are used to predict changes in condition, or other parameters, over time. That information is combined with decision criteria to identify when a treatment is needed and what type of treatment is needed. This information is then combined with treatment cost data, and inflation if appropriate, to estimate budget needs over a period of analysis. The decision-support tools must connect the changes in condition or other relevant measures not only to the application of treatments, but also to the cost of applying these treatments.
Framework for Quantifying Delayed Maintenance of Highway Assets 15 For asset groups whose performance models predict deterioration for individual asset segments or groups of asset segments, the change in condition or asset performance may be used to identify when the segment or group of segments will reach a pointâoften called a trigger valueâat which preventive maintenance is needed. When the preventive or condition trigger value is approached or reached, the analysis module can identify the candidate segment or group of segments for appli- cation of maintenance. The trigger value can be used in any of the modeling approaches described in Section 2.5. Over time when repeated treatments are applied, the repeated analysis of asset performance can show the changes in asset condition or performance attributed to the treatments, and identify the asset for maintenance each time it approaches or reaches its trigger value. Figure 2 shows the timely and repeated application of pavement preventive maintenance activities beginning at an early stage in the pavementâs life, when it is still in good structural and functional condition. For comparison, the figure also shows a scenario in which the pavement is allowed to reach failure and is then rehabilitated or reconstructed. For some highway asset groups, little change in condition occurs when preventive maintenance treatments are applied; only a reduction in the rate of deterioration results. For those highway assets, a trigger value can be established that identifies the condition at which preventive main- tenance will no longer be effective. For this situation, the preventive maintenance treatment is generally scheduled on a time-based cycle (e.g., at the end of every 7 years of a 12-year cycle). For highway asset groups that are subject to single, unpredictable events (e.g., guardrails, signs), models are used to predict the percentage or number of similar assets in an asset group that will need routine or corrective maintenance within a specific time period. Generally, the prediction is presented as the percentage or number of similar assets that will need maintenance activities each year. Assets for which field measurements or reliable maintenance records are unavailable can be modeled using expected asset life to predict when individual asset segments or groups of asset segments will reach the end of their useful life or some other condition level established as a maintenance trigger. For repeated maintenance activities, the change in remaining life is adjusted for each treatment application, and the projection is repeated. Funds needed to apply the needed maintenance can be calculated based on unit costs appro- priate for the asset group for the number of treatments needed at designated periods throughout the analysis periods. Cost data are then accumulated for individual asset segments or groups of asset segments over the analysis periods. The analysis periods generally correspond to a funding Source: Galehouse et al. (2006) Figure 2. Concept of maintenance timing applied to pavements.
16 Consequences of Delayed Maintenance of Highway Assets cycle (or a sequence of funding cycles), and often are related to the agencyâs fiscal year; however, other periods may be used. The funding needs estimated from these analyses are considered baseline budgets for the analysis of other scenarios. 2.7 Alternatives Evaluation This section describes scenarios and methods that can be used with analytical tools for alter- natives evaluation. 2.7.1 Formulate Delayed Maintenance Scenarios The first element of Step 3 in the general framework involves formulating delayed maintenance scenarios. Most agencies recognize the importance of proactive preservation (i.e., programs that include timely, appropriate application of preventive and routine maintenance activities), but delayed maintenance is a common issue. The causes of such delays vary among highway asset groups and agencies; however, delays often result from a combination of factors, such as: â¢ Insufficient funds to address the maintenance needs of the highway asset groups, â¢ Agency policies for investment priorities that result in restricted maintenance activities, â¢ Short-term planning perspectives that tend to overlook maintenance needs, â¢ Lack of practical methods to quantify the consequences of delayed maintenance, and â¢ Lack of reports that are targeted at the right decision-making levels. Other causes of delayed maintenance that have been identified in agency surveys and telephone interviews include complex procurement and project approval processes, asset management sys- tems with limited capabilities to conduct scenario analysis, and accessibility and mobility concerns. For example, in certain areas, the need to keep roads and bridges open to traffic makes scheduling traffic control for maintenance activities problematic. In such cases, maintenance activities often are delayed until accessibility concerns are addressed. In brief, preventive and routine maintenance activities may be delayed to a future budget cycle, or until funds become available. Safety and liability issues also may affect the budget allocation process, resulting in delayed maintenance. In the evaluation of alternatives, the treatments scheduled from the needs analysis, along with the associated treatment costs, are included as the baseline scenario to which all other scenarios will be compared. The primary alternative maintenance scenarios considered in this study can be grouped in three categories: â¢ Do nothing (i.e., no maintenance is applied over the analysis period); â¢ Delayed maintenance (i.e., maintenance is delayed by a specified time period, which likely varies for each highway asset group considering the assetsâ expected service life, the agencyâs decision criteria, and the consequences of postponing maintenance activities); and â¢ Budget-driven maintenance (i.e., the limited funds available for maintenance activities drive the scheduling and application of maintenance activities). The delayed maintenance scenarios may include sub-scenarios, depending on the decision context and the methods used by the agency. Alternative scenarios also may be considered to address special situations that are specific to a certain asset group or analysis need. 2.7.2 Perform the Delayed Maintenance Scenario Analysis The second element of Step 3 in the general framework is to perform an analysis of each delayed maintenance scenario. In these analyses, decision-support tools are used to determine the effect
Framework for Quantifying Delayed Maintenance of Highway Assets 17 of delayed maintenance. Analytical tools currently employed by highway agencies are at different maturity levels, as shown in Figure 3 (Rose et al. 2014). These tools also vary in the amount and types of data, performance models, and methods used for alternatives evaluation. To be effec- tive, the tools must relate the maintenance treatment-related change in asset condition (or other defined parameters) to the funds required to apply those treatments. Most agencies have relatively complete data inventories for some asset groups (e.g., pave- ments and bridges), limited data for some highway asset groups (e.g., culverts, signs, guardrail), and inadequate data for other asset groups (e.g., lighting, striping) to support analysis of main- tenance effects. Most highway agencies use pavement management system (PMS) and bridge management system (BMS) decision-support software as tools to analyze maintenance scenarios. PMS and BMS generally include the best toolsets for projecting asset condition or other perfor- mance measures, and have tools to support decision analysis. A few agencies have complete data and decision-support tools to analyze all highway asset groups; for many agencies, however, such analyses tend to be limited to inventories and database management systems. For culverts, lighting, guardrails, pavement markings, and highway signs, maintenance needs typically are determined from field survey inspections, and adjustments to previous budgets are made when developing their preservation programs. The general framework to quantify the consequences of delayed maintenance can be adopted independently from the maturity level of the asset management system, and this report describes analytical tools that agencies can use to conduct scenario analyses. The consequences generally include changes in condition, service life, performance measures, or other consequences needed to identify if the agency is achieving its goals as related to the funds expected to achieve these changes. The results of the scenario analyses should be interpreted considering the capabilities and limitations of the analytical tools used by the agency. 2.7.3 Determine the Effects of Delayed Maintenance The third element in Step 3 of the general framework is basically an investment analysis that involves determining the effect of delayed maintenance and reporting the consequences. It Figure 3. Maturity levels for asset management systems adopted by agencies. Source: Rose et al. (2014)
18 Consequences of Delayed Maintenance of Highway Assets identifies differences in results for (1) investing different amounts of funding, or (2) investing funds at a time different from that identified based on âbest engineeringâ practices in the needs analysis. The results of the needs analysis are considered the baseline scenario. When the delayed maintenance scenarios are run through the analysis tools, the results of each scenario can then be compared to those of the needs analysis. Agencies will likely analyze alternative scenarios reflect- ing their currently prescribed or preferred maintenance policies. The differences in results can be compared to determine the effects of delaying maintenance. Differences generally involve one or more performance measures (e.g., condition, service life); funds required; or other consequences used by the agency to identify if goals are being achieved. Detailed descriptions, along with exam- ples of the maintenance scenarios analyses, are presented for each highway asset group in the appendices to this report, which are accessible online from the NCHRP Project 14-20A webpage. 2.7.4 Report the Consequences of Delayed Maintenance To affect funding allocations and reduce negative effects from delaying maintenance, the results of these analyses must be communicated in an understandable and convincing way to agency decision makers at various management levels. Asset management documents gener- ally identify three major management levels involved in funding-related decision-making: (1) strategic, (2) network, and (3) project management. Decisions related to an agencyâs policies and funding allocations across asset groups generally are made at the strategic level (AASHTO 2012b). Decisions about funding of maintenance and rehabilitation programs for individual asset groups (e.g., pavements, bridges) generally are made at the network level. Decisions about the most cost-effective treatments for individual components of an asset group often are made at the project level. At the project level, engineering staff and information technologists often are heavily involved in conducting the analyses discussed in this report. These groups tend to rely on technical vocab- ulary, complex analysis models, and tables of data (Hobbs 1987). Standard reports with tables of data are extremely useful for detailed analyses and often are prepared by and for the engineer- ing staff. When the results produced in these analyses are presented to the next higher level of management, however, less detail is needed. Presentations must be prepared to address a specific audience (FHWA 1991). Often, well- designed graphics are much more effective communicators than words or tables of numbers (Mouaket and Lucy 1987 and Tufte 1983). For a presentation to management, information generally should be structured in a more graphical format that presents the essence of the analy- sis results without getting lost in details. Experience shows that reports will be read if they are concise, to the point, and contain information the decision makers need to support their posi- tions (Mouaket and Lucy 1987). In summary, reports with condition and asset life information generally are more useful at the project and network-management levels. Information on agency costs is applicable to all levels; however, agency total costs, changes in backlog costs, and asset value are generally most relevant to decision makers at the network and strategic management level. The modeling approach and analytical tools adopted by an agency will affect the set of performance measurements selected to quantify and report the consequences of delayed maintenance. At present, reporting all per- formance measures described in this report may not be required by, or feasible for, some state highway agencies. Nonetheless, it is important that the reports used include the information needed to determine if the highway agency is achieving its established goals, and if not, what would be needed to reach them. The procedures described in Chapter 3 include guidelines to overcome some of these reporting limitations, and more details and examples are provided in the appendices.