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5 C H A P T E R 2 The framework for the PMDb system developed under this project was designed to capture the factors that influence the performance of maintenance treatments, including climate condi- tions, traffic levels, existing pavement conditions, material properties, and workmanship, or the factors pertaining to pavement performance, and establish a common framework that is com- patible with the many existing maintenance data collection practices at state DOTs. A review of the existing practices examined the type and scope of activities in pavement maintenance and identified areas where data collection practices exist to populate a national framework. Scope of Pavement Maintenance Pavement maintenance can be defined in terms of DOT policy, budget allocations, and a vari- ety of maintenance activities performed by highway agencies to preserve highway pavements. Major rehabilitation and new construction of pavements tend to be fairly well documented in terms of design, location, construction, and performance. In contrast, maintenance activities, such as routine, reactive, and preventive, are not as well documented. Although highway agen- cies document information pertaining to maintenance actions, such as methods, rates, bases of measurement, costs, performance, and other related factors, as part of their MMS. Pavement-Maintenance Practices State highway agencies are placing increasing importance on pavement maintenance. There is a significant change in practice from the âworst-firstâ approach in which pavements were allowed to deteriorate to highly distressed conditions before any major (and more intrusive) rehabilitation was performed to an approach that considers the performance and cost-effectiveness of preventive maintenance. In order for agencies to make the best use of maintenance and preservation treatments, it is important to collect, store, and analyze performance data that captures the effect of the treat- ment on performance. The particular issue of cost-effectiveness has been studied by many agen- cies, including Michigan (Bausano, Chatti, and Williams, 2004; Galehouse, 2002; and Ram and Peshkin, 2013); Texas (Chang, Chen, and Hung, 2005; Chen, Lin, and Luo, 2003); Indiana (Labi et al., 2005; Labi et al., 2006; and Labi et al., 2007); Arizona (Peshkin, 2006; Smith et al., 2005); Ontario (Wei and Tighe, 2004); and Utah (Romero and Anderson, 2005). Several studies have analyzed different aspects of maintenance treatment cost-effectiveness, including case studies (Baladi et al., 2002; Hicks, Seeds, and Peshkin, 2000), a synthesis of preventive maintenance treatment practice (Cuelho, Mokwa, and Akin, 2006), cost-effective preventive maintenance (Geoffroy, 1996), optimization of pavement preservation (Mamlouk and Zaniewski, 2001), SPS-3 Background on Pavement- Maintenance Practices
6 Framework for a Pavement-Maintenance Database System and SPS-4 studies (Morian, Epps, and Gibson, 1997), and optimal timing (Peshkin, Hoerner, and Zimmerman, 2004). However, the importance of being able to determine treatment impacts is not restricted to preventive maintenance; both routine and reactive maintenance are important practices of every highway agency and, as such, there should be an inherent interest in identifying the treatments or pavement-maintenance activities that provide the greatest return at any time in the life of a pavement. The ability to carry out the analysis that would support the determination of cost- effectiveness hinges on the availability of data on the treatments, the conditions under which the treatments were used, and their subsequent performances. Especially where maintenance is concerned, these data are rarely available. While there is an extensive body of literature on the performance and benefits of pavement- maintenance treatments, published information on issues associated with data collection, man- agement, and analysis, particularly related to maintenance treatments, is limited. Pavement Maintenance and Pavement Preservation A recent trend at state DOTs is the emergence and growth of pavement-preservation programs, whose philosophy is succinctly captured in the term âkeeping good roads in good conditionâ in order to prolong pavement service life. Many state highway agencies have been using PMSs to analyze system performance and demonstrate to legislators the benefits of pavement preservation as opposed to the âaddress the worst-firstâ strategy to sustain and/or improve the overall condi- tion of the pavement network (Zimmerman and Peshkin, 2003). Figure 1 is a schematic of how pavement preservation may help extend the life of the pavement, delaying the need for major rehabilitation activities. Pavement-Maintenance Terms This section presents a set of commonly used pavement-maintenance data terms and defini- tions that were identified for evaluating the performance and effectiveness of the different types of maintenance treatments. Pavement sections are defined as a specific section of an established, defined route, which may require maintenance. An operation describes the type of maintenance work being performed (routine, reactive, or preventive) on the pavement section, and a main- tenance activity is a specific treatment (e.g., crack sealing, asphalt patching, dowel bar retrofit, Figure 1. Potential effect of pavement preservation on pavement condition.
Background on Pavement-Maintenance Practices 7 diamond grinding) applied during the operation. An event describes the accomplishment of an operation using a specific maintenance activity. The dates, quantity of work, and resources used are described as a part of an event. Table 1 describes these terms in further detail. Pavement-Maintenance Operations Pavement-maintenance operations are categorized by highway agencies in several different ways to quantify the purpose and desired outcome. Table 2 describes the types of operations most commonly identified as a part of an agencyâs maintenance program (FHWA, 2002). Pavement-Maintenance Activities Pavement-maintenance activities are those specific pavement treatments that are conducted to fulfill the maintenance operations goal. Treatment types vary across the United States depend- ing on traffic, climate, local practices, and desired outcome. Sometimes maintenance operations may include two or more combined activities (e.g., an asphalt pavement that receives an asphalt patching activity, prior to a thin asphalt overlay activity). This section describes and defines the various pavement-maintenance activities most commonly performed by highway agencies for different pavement types. Asphalt-Surfaced Pavements Asphalt-surfaced pavements are pavements surfaced with an asphalt material, whether hot-mix asphalt (HMA), warm-mix asphalt (WMA), or an asphalt-based surface treatment. Although these are different pavement types, the applicable maintenance and preservation activities are very similar. Table 3 provides a summary of various maintenance and preservation treatments used for asphalt-surfaced pavements. Table 1. Pavement-maintenance terms. Term Description Pavement section Specific portion of a road that encompasses the pavement-maintenance treatment operation and activity. Operation Type of maintenance work being performed: routine, reactive, or preventive maintenance. Activity Specific maintenance action being performed and supporting information describing the action. Event Time and location of a particular maintenance activity. This is described further in Chapter 2. Contracting mechanism Method of contracting to perform the activity: whether in-house or by a contractor, including warranty specifications, if any. Table 2. Pavement-maintenance operations. Operation Type Description Routine maintenance Planned work that is performed on a regular basis to maintain and preserve the condition of the highway system or respond to specific conditions and events that restore the highway system to an adequate level of service. Reactive maintenance Actions that are performed in response to sudden, acute problems that must be corrected to address safety issues and restore normal traffic operations. Preventive maintenance Planned strategy of cost-effective treatments applied to an existing roadway system and its appurtenances that preserves the system, retards future deterioration, maintains or improves the functional condition of the system, and extends the life of the existing pavement (without increasing the structural capacity).
8 Framework for a Pavement-Maintenance Database System Table 3. Maintenance treatments for asphalt-surfaced pavements. Treatment Definition Asphalt patching It is used to treat localized distresses. These repairs address surface distresses and full-depth patches address structural distresses (Peshkin et al., 2011). Chip seal Sprayed application of asphalt (usually emulsion, although heated asphalt cement and cutbacks are also used) followed by aggregate chips rolled to achieve 50% to 70% embedment. Different types of chip seals are obtained by varying the binder, the aggregate, or by placing multiple courses (Gransberg and James, 2005). Chip seals enhance surface characteristics and seal the underlying pavement structure. Cold-in-place recycling Milling and sizing reclaimed asphalt pavement (RAP) and mixing in-place with recycling additive and new aggregate. This is then re-laid and compacted as a new base course. Cold-in-place recycling requires that a new surface be placed over it, usually an asphalt overlay or other surface treatments (ARRA, 2001). Crack filling Placement of adhesive material into and over non-working cracks; minimal crack preparation, lower-quality materials used (Decker, 2014). Crack sealing Placement of adhesive material into and over working cracks; good crack preparation, high-quality materials used (Decker, 2014). Fog seal/rejuvenator Very light application of asphalt emulsion on pavement surface. Fog seals apply additional asphalt to seal the existing asphalt surface, while the composition of rejuvenators allows them to penetrate slightly into the surface and reduce the stiffness of the pavement at its surface (Peshkin et al., 2011). Hot-in-place recycling The removal and replacement of a portion of the surface of an existing asphalt pavement to correct surface distresses within the top 2 in. (51 mm). The pavement surface is softened by heat, mechanically loosened, picked up, and mixed with recycling agent, aggregate, rejuvenators, and/or virgin asphalt, and then relayed (ARRA, 2001). Microsurfacing Mix of crushed, well-graded aggregate, mineral filler, and latex-modified emulsified asphalt. Microsurfacing can seal non-working cracks, restore desirables surface characteristics, fill ruts, and seal off the pavement structure. This is usually delivered with specialized mixing and placement equipment (ISSA, 2010). Milling Process of removing pavement material from the surface of the pavement to either prepare the surface to receive overlays (by removing rutting and surface irregularities), restore pavement cross slopes and profile, or re- establish the pavementâs surface friction characteristics (micromilling). Retrofitted edge drains Devices added to a pavement after it is in service to facilitate the removal of subsurface water. These devices usually consist of a drainage feature that is placed between the edge of the pavement and the shoulder. This technique is used to collect water that has infiltrated into the pavement structure and to discharge it to the ditches through regularly spaced outlet drains (Smith, Hoerner, and Peshkin, 2008). Slurry seal Mixture of quick- or slow-setting emulsified asphalt, well-graded fine aggregate, mineral filler, and water. It is used to fill cracks and seal areas or the entire surface of asphalt pavements (ISSA, 2010). Thin and ultra-thin overlays Asphalt binder (may be polymerized or rubber-modified) and dense-graded, gap-graded, or open-graded aggregate combined in central mixing placement and placed with paver in thickness ranging from 0.625 in. to 0.75 in. (16 mm to 19 mm) for ultra-thin and 0.75 in. to 1.5 in. (19 mm to 38 mm) for thin overlays. Costs and performance depend on the binder type and whether milling has been performed prior to treatment placement (Newcomb, 2009). Ultra-thin bonded wearing course Bituminous layer placed on top of an existing pavement and bonded with a thick, polymer-modified asphalt emulsion tack to improve the functional or surface characteristics of pavements, including enhancing friction and reducing noise. Consists of open-graded or gap-graded aggregates and rubber or polymer-modified asphalt layers 0.4 in. to 0.8 in. (10 mm to 20 mm) thick, well bonded to the pavement surface (Newcomb, 2009). Bonded concrete resurfacing Thin, 2 in. to 5 in. (50 mm to 125 mm), Portland cement concrete overlay of an existing HMA pavement. The overlay provides a stable surface that is resistant to deformation from static, slow moving, and turning loads (Smith, Hoerner, and Peshkin, 2008).
Background on Pavement-Maintenance Practices 9 Concrete-Surface Pavements Concrete-surface pavements are pavements surfaced with concrete, and include jointed plain concrete pavements (JPCP), jointed reinforced concrete pavements (JRCP), and continuously reinforced concrete pavements (CRCP). In general, these pavements consist of a concrete sur- face on one or more granular or bound layers and also include various concrete overlays that can be placed on existing concrete pavements (unbonded and bonded concrete overlays) or on existing asphalt pavements (conventional whitetopping, thin, and ultra-thin whitetopping). However, the maintenance and preservation activities for these different pavement types are largely identical (although there are some variations in how the treatment is executed depend- ing on whether the pavement is jointed or a CRCP). Table 4 provides a summary of the various maintenance and preservation treatments applied to concrete-surfaced pavements. Table 4. Maintenance treatments for concrete-surfaced pavements. Treatment Definition Crack sealing Placement of an adhesive material into and over working cracks. Often characterized by good crack preparation and use of high-quality sealant materials (Smith, Hoerner, and Peshkin, 2008). Cross stitching Technique used to maintain load transfer across non-working longitudinal cracks in co (Smith, Hoerner, and Peshkin, 2008) ncrete pavements that are in relatively good condition Diamond grinding Removal of a thin concrete layer, 0.12 in. to 0.25 in. (3 mm to 6 mm), from the pavement surface using special equipment outfitted with diamond-tipped saw blades (Smith, Hoerner, and Peshkin, 2008). Diamond grooving Cutting narrow, discrete grooves (typically longitudinal) into the pavement surface to increase tire-pavement contact when the surface is wet and to reduce noise (Smith, Hoerner, and Peshkin, 2008). Full-depth repair Removal and replacement of deteriorated concrete through the full depth of the slab; may be cast-in-place or precast (Smith, Hoerner, and Peshkin, 2008). Joint resealing Removal of existing longitudinal/transverse joint sealants and preparation and installation of new sealant material (Smith, Hoerner, and Peshkin, 2008). Load transfer retrofit Installation of dowel bars or other mechanical devices at transverse joints or cracks in order to effectively transfer wheel loads across slabs and reduce deflections (Peshkin et al., 2011). Partial-depth repair Localized removal and replacement of deteriorated concrete (most often in the vicinity of joints) in the upper third of the slab (Peshkin et al., 2011). Retrofitted edge drains Devices added to a pavement after it has been in service to facilitate the removal of subsurface water. These devices usually consist of a drainage feature that is placed between the edge of the pavement and the shoulder. This technique is used to collect water that has infiltrated into the pavement structure and to discharge it to the ditches through regularly spaced outlet drains (Smith, Hoerner, and Peshkin, 2008). Slab stabilization Restoration of support beneath concrete slabs by filling voids and thereby reducing deflections. Slab stabilization involves raising slabs to their desired elevation by pressure and inserting material beneath settled slabs (Smith, Hoerner, and Peshkin, 2008). Thin and ultra-thin overlay Asphalt binder (may be polymerized) and dense-graded, gap-graded, or open- graded aggregate combined in central mixing placement and placed with paver in thickness ranging from 0.625 in. to 0.75 in. (16 mm to 19 mm) for ultra-thin and 0.75 in. to 1.5 in. (19 mm to 38 mm) for thin overlays. Costs and performance depend in part on binder type and whether milling has been performed prior to treatment placement (Newcomb, 2009). Ultra-thin bonded wearing course Bituminous layer placed on top of an existing concrete pavement to improve the functional or surface characteristics of the pavement, including enhancing friction and reducing noise. Consists of open-graded or gap-graded aggregates and rubberized or polymer-modified asphalt layers 0.4 in. to 0.8 in. (10 mm to 20 mm) thick well bonded to the concrete surface (Newcomb, 2009).
10 Framework for a Pavement-Maintenance Database System Composite Pavements Composite pavements are pavement structures consisting of a combination of asphalt and concrete layers. Most commonly these are asphalt overlays of concrete pavements (concrete overlays of asphalt pavements are discussed in the section on concrete pavements). For mainte- nance purposes, the same treatments applied to asphalt-surfaced pavements apply to composite pavements. However, two forms of deteriorationâdelamination and reflection crackingâmay trigger the need for maintenance that is not typically covered for the two primary pavement types. Sawing and sealing joints in the HMA overlay and the use of membranes or interlayers are techniques used to mitigate reflection cracking in composite pavements. Otherwise mainte- nance activities for composite pavements are the same as to those described for asphalt-surfaced or concrete-surfaced pavements. Pavement-Maintenance Costs A review of pavement-maintenance activity practices by state DOTs showed a variety of terms and boundaries to describe pavement-maintenance costs. Maintenance costs are computed from the use of resources that include labor, equipment, and materials. Cost calculations also require pay items, quantities, and bid prices. Maintenance accomplishments include quantity of main- tenance work performed, which may be expressed in units specific to maintenance operations or as quantities of a specific maintenance activity. Eventually, these items are used to develop the unit costs associated with a particular operation or activity. Often there is a difference in these costs that is based on whether the work is performed in-house by state forces or contracted out. When the work is performed by a contractor, depending on the terms of the contract, the costs of the various elements can be identified fairly easily. However, if the work is performed in-house, practices for calculating the true cost of the various elements of the work or the overall activ- ity vary substantially and the disparities between the calculated costs associated with different methods of completing the work should be considered. Table 5 describes each of the cost terms. Pavement-Maintenance Data Current practices for maintenance data management vary dramatically among state highway agencies as no single predominant system is available or in use. One common trend among DOTs is the use of an MMS to store pavement-maintenance construction information. Most Term Description Labor Labor hours and unit rates to perform maintenance work (in-house and by contractors); sum product of hours and unit rates Equipment Cost of equipment (rental or purchase); sum product of usage hours and unit costs Materials Materials and quantities used in the maintenance activity; sum product of material quantities and unit costs Pay item List of pay items and unit costs; sum product of pay items used and unit costs Traffic mobilization Cost to provide traffic control to perform maintenance work Overhead/other Cost elements that may be included within cost such as administrative or non- activity related costs that were assigned to the maintenance project Accomplishment Quantity of maintenance work performed, in units of length or area, related to the sum of labor, equipment, material, traffic mobilization, and overhead costs to develop the unit cost of treatment Table 5. Pavement-maintenance costs.
Background on Pavement-Maintenance Practices 11 commonly, maintenance activity data is stored centrally within the agency, although many detailed aspects of the maintenance operation, activity, and cost remains decentralized in dis- tricts or regional offices. The following sections highlight some of the state DOT practices related to pavement-maintenance data collection. Data Collection Methods The use of mobile data collection has becoming increasingly popular in pavement manage- ment implementations. The North Carolina DOT conducted a study on the feasibility of using personal data assistants (PDAs) to collect employee and equipment time, work accomplishments, and work locations (using GPS) for input into their MMS (Edgerton, Pilson, and Whitley, 2009). This study found that smaller, rugged PDAs improved productivity and the GPS locations were very accurate in locating the sites (95% of the time the locations were within 50 feet of a mapped roadway centerline and 80% of the time the locations were within 10 feet). Based on this study, the North Carolina DOT decided to make mobile pavement-maintenance data collection a regu- lar practice. The Texas DOT recently conducted the pilot implementation of a web-based GIS system to provide information for pavement-maintenance decision making (Zhang and Murphy, 2013). The system provides historical data on pavement conditions and performance and other pavement inventory that enables the user to develop performance trends based on a family of pavement sections. Australia has also recognized the need to establish centralized databases for analyzing the effectiveness of pavement-maintenance treatments. A nationwide PMDb covering a range of roadways from various states in Australia was established by the Australian Road Research Board (Martin, Byrne, and Aguiar, 2011). The database includes information on pavement-condition data, roughness, rutting, texture, traffic, maintenance-related expenditures, and routine, periodic, and other rehabilitation activities. Data Collection Practices Types of Data Collected Pavement-maintenance data collected by most agencies include: ⢠Material type and quantity, ⢠Labor, ⢠Equipment, ⢠Cost, ⢠Maintenance method and activity, ⢠General location (between markers or mileposts), and ⢠Construction data. Pavement-maintenance data not collected by most highway agencies include: ⢠Precise location (using GPS), ⢠Pavement condition at time of maintenance, ⢠Weather at time of maintenance, and ⢠Periodic performance after construction. A survey was conducted to identify various existing pavement-maintenance data collec- tion practices (see Appendix A). In response to the survey, many state DOTs reported that some pavement-maintenance data related to labor and equipment are typically not tracked if the maintenance work is done thorough contract. They also noted that, in general, there are
12 Framework for a Pavement-Maintenance Database System significant differences in the type of information collected and the level of details reported if the work is done by contract or in-house. Regarding cost data, while reporting a single unit cost may appear to be straightforward, agen- cies do not use a consistent unit measure for any given treatment. For example, some agencies pay for crack sealing by the pound and some by the linear foot. In addition, the survey identified that cost data can be highly variable, depending on such factors as the location of the job, the size of the job, the contracting method, the ancillary activities included in the treatment placement, and the condition of the pavement. Pavement-Maintenance Work Done by Contractors Most of the state DOTs that responded to the survey indicated that they use contractors to provide pavement-maintenance services and noted that approximately 55% of the pavement- maintenance work was done by in-house agency forces (including other public agencies acting on the agencyâs behalf) and 45% of the pavement-maintenance needs were done by the contrac- tors. Surface treatments (e.g., chip seals, slurry seals, microsurfacing) are typically performed by contractors. The patching and crack sealing work is shared almost equally between contractors and the in-house agency forces. Many state DOTs indicated that no general reporting require- ments are placed on contractors hired for pavement-maintenance work; a few required hard copies, electronic data, or tabular summaries of the work performed. Use of Data Collected Pavement-Maintenance Data Survey responses indicate that pavement-maintenance data is used primarily to: ⢠Develop budgets, ⢠Track labor use, ⢠Schedule future maintenance work, ⢠Compare work accomplished versus planned work, ⢠Track material and equipment usage, ⢠Track pavement performance, ⢠Identify the most suitable maintenance actions based on pavement condition, ⢠Select cost-effective treatment strategies, ⢠Develop treatment performance models, and ⢠Validate performance of specific treatments. Pavement-Maintenance Treatments The selection of appropriate treatments must consider relevant factors, including the follow- ing (Hicks, Seeds, and Peshkin, 2000): ⢠Existing pavement type, ⢠Type and extent of distress, ⢠Climate, ⢠Cost of treatment, ⢠Availability of qualified contractors, ⢠Time of year of placement, ⢠Facility downtime, ⢠Traffic loading, ⢠Expected life, ⢠Availability of quality materials, ⢠Pavement noise and surface friction,
Background on Pavement-Maintenance Practices 13 ⢠Anticipated level of service, and ⢠Other project-specific requirements. Many of these factors must be collected in order to make appropriate pavement-maintenance decisions. Thus, a national database of maintenance treatments and effectiveness is needed to support the decisions. An example of a sequential approach for evaluating possible preservation treatments and the data required to make decisions for an existing pavement and identifying the preferred one is shown in Figure 2 (Peshkin et al., 2011). Figure 2. Process of selecting the preferred preservation treatment. NOTE: MPD = mean profile depth, MTD = mean texture depth, IFI = International Friction Index.
14 Framework for a Pavement-Maintenance Database System Pavement Inventory Terms Pavement is defined as the structure constructed above the existing subgrade soil, typically placed in distinct layers and including compacted/natural subgrade, subbase, base, and the riding surface (Figure 3). Broadly, this encompasses pavement structures in a number of different facility types, such as highways, streets, roads, shoulders, and parking areas, but the focus of this project is on pavement structures used in mainline paving of highways/roadways. To describe the existing pavements on which maintenance operations may be performed, DOTs commonly classify their pavement inventory. The data elements and definitions related to pavement data are summarized in Table 6. Pavement-Condition Terms Maintenance treatments generally have some effect on the condition of pavements. Different performance measures are used by highway agencies to evaluate the effectiveness of maintenance actions; not all measures are applicable to study the effectiveness of every maintenance action [e.g., the International Roughness Index (IRI) is not a good measure for the effectiveness of crack sealing treatments, especially in the short term]. Overall performance measures (compos- ite condition indices computed using raw distress data quantities) are among the most widely Figure 3. Basic components of a typical pavement system. Table 6. Pavement inventory data elements. Data Element Description Functional classification Process by which streets and highways are grouped into classes or systems, according to the character of traffic service that they are intended to provide. The highway performance monitoring system (HPMS) classification codes are commonly used. Climatic zone Classification of the general climate conditions in which the pavement- maintenance activities are performed. The HPMS and long-term pavement performance (LTPP) climatic zones are commonly used. Traffic loading Characteristics of the traffic operating on pavements, in terms of parameters such as equivalent single axle load (ESAL), average annual daily traffic (AADT), percentage of truck traffic, and growth rates of traffic. Pavement surface Classification of the existing surface material (asphalt, concrete, existing preservation treatment) and thickness. Pavement layer(s) Characteristics of pavement layer(s) in the maintenance section including materials (aggregate type/gradation, binder, additives, other proprietary products etc.), thickness, and overall function of the layer (base, structural, wearing, repair). Pavement subgrade Characteristics of the soil and subgrade material and stiffness. Subsurface drainage Longitudinal, lateral, or other features designed to move subsurface moisture away from the pavement structure.
Background on Pavement-Maintenance Practices 15 used. Levels of service are also frequently used by maintenance. In addition to the maintenance activities performed to improve the service life of the pavements and delay major rehabilitation activities, some treatments may be applied to address safety issues, reduce noise, and improve the overall ride quality. Table 7 summarizes the measures that describe pavement-maintenance treatment performance. Pavement-Condition Data Most agencies use PMS as the primary data source to track and report the performance of pavement-maintenance treatments over time. The use of PMS has grown considerably since its initial implementation by state highway agencies beginning in the late 1970s. A relatively recent trend is the emergence and growth of pavement preventive maintenance and preserva- tion programs. Pavement-Performance Parameters Most states collect individual distress data (e.g., cracking, rutting, faulting), composite pavement-condition indices [e.g., Pavement Condition Index (PCI), Pavement Condition Rating (PCR), or Pavement Serviceability Index (PSI)], and ride indices [e.g., IRI, Ride Condi- tion Index (RCI)]. Very few states use subjective indices (e.g., good, fair, poor) to supplement the other data collected. Data Collection Frequency and Methods Performance data on the National Highway System (NHS) routes and other primary routes are generally collected every year. Performance data on other functional classes are typically conducted every two years. The frequency of collection also varies in terms of coverage. Most states collect performance data on a single representative lane within the given pavement route while others collect multiple lanes of information. State highway agencies are making conscious efforts to embrace state-of-the-art technologies to collect data related to pavement maintenance. Pavement-performance data are currently col- lected through both manual and automated surveys as a part of the PMS program. Automated surveys are more common, although manual surveys are still conducted. Only a small percent- age of the respondents to the survey noted that they used handheld devices or computers in the field to collect and report data. Thus many pavement-maintenance data elements are not captured digitally during initial data collection processes. Table 7. Pavement-performance measures. Performance Measure Description Individual distresses Distress types, severities, and quantities noted based on pavement-condition surveys Overall condition indicator Composite indices used to describe pavement surface conditions using raw distressed data collected (e.g., PCI, PCR) Pavement service life extension Effectiveness of the treatment in addressing distresses and slowing down the rate of deterioration; may be computed based on individual distresses or overall condition indicators Safety Effectiveness of the treatment in improving safety-related characteristics (e.g., friction, texture) Ride quality Effectiveness of the treatment in improving the overall smoothness and ride quality of the surface (e.g., IRI, profile index) Noise Effectiveness of the treatment in reducing the noise due to tire-pavement interaction
16 Framework for a Pavement-Maintenance Database System Integrating Pavement Management and Pavement Maintenance The integration of pavement maintenance into pavement management requires a concen- trated effort on the part of transportation agencies to re-evaluate their existing data collection activities, to revise and update performance modeling approaches, and to improve overall pro- gram development activities. The desired outcome is that the need for pavement-maintenance treatments, the timing of application, and their performance (and effectiveness) be identified within an agencyâs PMS, and that the benefits realized from the application of the treatments be accounted for in the systemâs optimization analysis. Pavement-Condition Data Practices Most highway agencies use some form of an overall pavement condition indicator (e.g., PCI, PCR) to assess the general performance of pavements. However, the overall pavement condition indicator may not capture the true performance of some maintenance treatments. Maintenance treatments may be applied primarily to seal the pavement, to improve safety characteristics, to improve the general ride quality, or to address pavement-tire noise. While appropriate measures to determine if such treatments are effective may be available through the PMS used by the state highway agencies, some relevant information may not be available. Recent studies have evaluated agency-wide pavement-maintenance and pavement-preservation treatments (Ram and Peshkin, 2013; Peshkin, Ram, and Wolters, 2012), and considered the fol- lowing items: ⢠Purpose of the treatment application (e.g., whether it was applied to address noise or friction, seal the pavement, or stopgap), ⢠Cost of the treatment on a project-by-project basis, ⢠Equipment used to perform the maintenance activity, ⢠Materials data (e.g., aggregate gradation, binder details) and the quantities used, ⢠Condition of the pavement prior to the placement of the preservation treatment, and ⢠Accuracy of recording the location of the maintenance treatment and the ability to link the location to the details stored in the PMS. Two recent studies observed a lack of consistency in identifying treatments in PMDb (Ram and Peshkin, 2013; Peshkin, Ram, and Wolters, 2012). A single type of treatment was noted to have several names, which made it difficult for agencies to determine if the treatments are actu- ally the same when modeling and comparing performance. Also, in some cases, only the year of treatment application and pavement condition data collection were noted; the specific date of the treatment was not recorded. This causes problems when analyzing the data if the pavement collection and its treatment application occur in the same year. If the date of a treatment applica- tion and pavement-condition data collection is not available, it is not possible to determine with complete confidence if the pavement-condition data collection was performed prior to or after the application of the treatment. Therefore, it is important to establish a database structure that captures the critical elements of PMS and MMS and highlights the performance associated with pavement-maintenance treatments. Summary of Pavement Maintenance Pavement-maintenance programs vary across the United States. While highway agencies may perform many of the same maintenance activities, there is wide variation in how these activities are identified, recorded, and reported. The use of a uniform or standardized database framework and consistent definitions and measures for recording maintenance activities will facilitate the evaluation of the effectiveness of maintenance and preservation treatments and decisions regard- ing the use of the treatments.
