National Academies Press: OpenBook

Guidelines for the Use of Pavement Warranties on Highway Construction Projects (2011)

Chapter: Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements

« Previous: Chapter 2 - Research Findings
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Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
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Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
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Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
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Page 39
Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
×
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Page 40
Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
×
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Page 41
Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
×
Page 41
Page 42
Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
×
Page 42
Page 43
Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
×
Page 43
Page 44
Suggested Citation:"Chapter 3 - Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements." National Academies of Sciences, Engineering, and Medicine. 2011. Guidelines for the Use of Pavement Warranties on Highway Construction Projects. Washington, DC: The National Academies Press. doi: 10.17226/14554.
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36 Chapter 2 summarizes the findings of the comprehensive investigation performed under NCHRP Project 10-68’s Phase I research effort. Task 2 of Phase I required the development of a systematic method or decision process for evaluating candidate pavement warranty projects. The original intent of this task was to develop this decision process based on project- level criteria such as project type and existing conditions. It was determined early in Phase I that few DOTs documented a systematic decision process for identifying candidate warranty projects. It was also determined that many DOTs considered very few variables in their warranty decision processes. Addi- tionally, the research team found that key decision factors were not limited to project-level decision criteria. Rather, the decision process often included broader, programmatic considerations such as contractor familiarity with QA-type specifications and limitations of DOT resources. Finally, it was determined that the decision criteria would vary depending on the type of warranty being applied. Therefore, the decision process for evaluating candidate warranty projects developed under Task 2 is a multilevel tool that enables the user to eval- uate both program-level and project-level criteria in addition to evaluating different types of warranties. Furthermore, the guidelines and model specifications developed under Tasks 5, 6, and 7 must address these multiple levels of decision criteria as well. The following sections discuss the approach that was used to address these multilevel considerations in the development of the warranty decision tool, the guideline document, and the sample provisions. Warranty Decision Tool A systematic decision tool for applying pavement warranties to highway construction projects is presented in Appendix A2. During the Phase I research, several DOTs using pavement warranties indicated through interviews that potential warranty projects were often applied to a limited pool of projects with good existing base and soil conditions. In other words, projects with a high probability of success were often selected as can- didate warranty projects. This tool was designed for selecting warranty projects beyond just the safe projects. Instead it was designed to evaluate various levels of risk based on program- and project-level criteria with respect to warranty type and to include suggested strategies for mitigating risks. During the one-on-one interviews with DOTs that have warranty experience, DOTs were asked to assess whether the application of the warranty resulted in an overall benefit to the DOT. Through these discussions, the research team deter- mined that the single most important factor in determining the measure of a project’s success or failure was the project’s ability to achieve a goal or expectation such as to improve quality or compensate for limited agency resources. Because materials and workmanship warranties are designed to satisfy different expectations than performance warranties, it was determined that the first step of the warranty decision process should be to identify the motivation or objective of using the warranty. The likelihood of success in applying warranties involves choosing the right type of warranty to achieve the stated goals of the project. Success also requires an under- standing of project-level conditions, such as base conditions and ability to predict traffic volumes, and program-level conditions, such as the level of cooperation of industry and the ability to develop performance-based specifications. Figure 13 summarizes the steps in the decision tool contained in Appendix A2. Each of the steps is discussed in the guidelines and the decision tool. The warranty decision tool is composed of three parts to assist DOTs through the decision process identified above. Part 1 asks DOTs to identify their objectives or motivations for using warranties and to weigh those objectives by applying a total of 10 points across various possible objectives, which C H A P T E R 3 Development of a Pavement Warranty Decision Tool, Best Practice Guidelines, and Model Technical Provisions for HMA and PCC Pavements

37 were identified and compiled through the Phase I research and refined by vetting the process using DOTs with warranty experience. Each possible objective in Part 1 has a corresponding list of criteria in Part 2. These criteria focus on the program-level conditions determined to be necessary or desirable for achiev- ing the stated objective for using a warranty as determined by the Task 1 research. All of the criteria listed in Part 2 are structured in the form of statements that, if true, contribute to successful warranty implementation. Users are asked to rate the statements on a scale of 1 to 10, with 10 being extremely true and 1 being very false. The statements are weighted evenly, and the ratings entered by the user for each statement are averaged to determine the average criteria rating. This rating is then combined with the weighting of the objectives in Part 1 to return a percentage score ranging from 0 to 100. DOTs can then use this scoring to evaluate the likelihood of success of the warranty from a programmatic standpoint. DOTs can then identify what program-level conditions, if any, require change or further development before applying a warranty program. The criteria used in Part 2 were revised and refined through the vetting process, which is described in detail in the following section. Part 3 prompts the user to assess the level of risk associated with using different types of warranties based on project-level criteria. Part 3 consists of three different sections of multiple choice questions. Each section pertains to one of the follow- ing types of construction: preservation, rehabilitation, or new construction. It was necessary to separate these sections out because the type of construction can affect the risk associated with applying a warranty. Each answer to the questions in Part 3 carries an associated risk factor for each warranty type. Risk factors are based on an adjectival rating system of low, medium, and high risk. These risk ratings were designed to steer the user to a specific type of warranty based on project-level criteria and were developed and refined though the vetting process described in the following section. Vetting Process The warranty decision tool was sent to several representa- tives with experience using warranties. Representatives were asked to test the tool on actual projects and return comments on the validity of the results and the structure of the tool itself. The following DOT personnel reviewed the warranty decisions tool and participated in the vetting process: Caltrans Lance Brown, Shakir Shatnawi CDOT Jay Goldbaum FDOT David Sadler MNDOT Pat Schafer, Kevin Kennedy, Curtis Bleech WisDOT Irene Battaglia Commentary and results on test run applications of the tool were provided by Lance Brown, Jay Goldbaum, David Sadler, and Irene Battaglia, and a summary of the results follows. Comments on the structure and content of the tool were pro- vided by Lance Brown, Shakir Shatnawi, Pat Schafer, Kevin Kennedy, Curtis Bleech, and Irene Battaglia, and are summa- rized following the results of the test applications. Results on Test Applications of the Tool Caltrans Caltrans tested the tool on a thin blanket overlay project. Caltrans identified and weighted objectives as follows: Prevent early catastrophic failures 6 Promote quality/consistency of the overall network 2 Reduce life-cycle costs 2 After rating the statements in Part 2, the decision tool returned a 74% rating for likelihood of success in achieving Figure 13. Decision process for selecting a warranty project and warranty type.

38 stated objectives. After answering questions in Part 3, the risk matrix results showed an overall low risk rating for a Type 1 warranty and an overall medium risk rating for a Type 2 warranty. Applying a Type 1 warranty to this type of project is consistent with the manner in which Caltrans applies its warranties. CDOT CDOT tested the warranty decision tool on three existing pavement warranty projects to determine if the project pro- duced accurate results. CDOT reported that overall, the tool works well and accurately matches the objectives of the project and the administration in charge at the time these projects were advertised. The first project tested was CDOT’s pilot 10-year PCC warranty project on Interstate 70 in Kit Carson County. The project scope included a 9.1-mile stretch along the four-lane highway. Colorado reported that the tool determined an 85% success rate and a favorable risk matrix output for a Type 2 warranty. The second project tested was CDOT’s 5-year HMA reha- bilitation warranty project on U.S. Highway 36, east of Byers. The project is located in Arapahoe and Adams counties and is 10 miles long. The rehabilitation strategy used was a 4-in. cold recycle overlay. Colorado reported that the tool determined a 90% success rate for a Type 2 warranty. The third project tested was a proposed urban, new con- struction, 5-year HMA pavement project through Denver that is currently in its preliminary design phase. CDOT selected improving performance on a particular project as the primary objective of the warranty. The tool initially returned a low success rate of 52%, causing CDOT to re-evaluate the state- ments in Part 2. Statement 2.E.4 (the agency is willing to consider design–build or to allow the contractor greater flex- ibility in mix design and other areas of control) was rated low since CDOT intended to use design–bid–build contracting. However, CDOT saw that by increasing the rating for this statement, the success rating improved to 80%. FDOT FDOT reported that the decision tool produced acceptable results assuming the typical types of pavement projects implemented by FDOT. Florida applies Type 1 warranties with the objective of preventing premature catastrophic failures. FDOT stated that the risk ratings established under Part 3 were acceptable as drafted, and proposed no changes. WisDOT WisDOT reported that the risk assessment results returned appeared fairly accurate for two project tests, but a few changes in risk determination were noted. These recommended changes were incorporated in the revised tool. Comments Regarding Structure and Content of the Tool Caltrans One of the two reviewers from Caltrans commented that overall the tool is difficult to understand and that the intent of all questions is not clear. The reviewer commented that engineers selecting projects need to fully understand the purpose of each question and understand how these questions fit into the risk matrix. The reviewer agreed that the use of a committee team for selection of a warranty project is a good plan. The second reviewer from Caltrans commented that the report describing the seven-step decisions is well written and easy to follow. Comments about specific sections of the war- ranty selection tool are summarized as follows: Part 1: Caltrans suggested adding the objective of transferring accountability from the agency to the contractor in Part 1. Because this objective was integral to the other objectives, the research team edited the existing Part 2 statements to address the transfer of accountability to the contractor. Part 2: Caltrans suggested that Statement 2.A.1 be divided into two separate statements. Statement 2.A.1 reads: “One or both of the following conditions exist: • A primary goal of the agency is to ensure strict adherence to the standard method specification • There is a need for a technique to act as a counterbalance for time pressures that may affect compliance with the specification.” This statement is aligned with the objective of preventing early, catastrophic failures. The researchers did not divide it into two separate parts because doing so would imply that both conditions are required to be true in order to accomplish the objective. However, in this case, if either condition exists, the application of a warranty is consistent with the objective. Part 3: Caltrans noted that the assigned risk factors for questions on mix design, phasing and traffic management, and project expectation differed in Parts 3A, 3B, and 3C. This was an intentional variation because it was determined that the risk associated with these variables is dependent on both the type of warranty (e.g., Type 1, 2, or 3) and the kind of project (e.g., preservation, rehabilitation, or new construction). Caltrans recommended expanding the question on exist- ing conditions, and they provided a matrix showing guide- lines on existing conditions used to determine excluded areas for warranty projects. Caltrans operates under the premise that good existing base conditions are essential criteria for

warranty projects. The risk assessment of existing conditions is addressed in Part 3 of the tool. The research team decided not to expand this criterion in order to avoid adding more complexity to the tool. Caltrans also commented that traffic control not be shifted to the contractor on its warranty project. Rather, the contractor must conform to the DOT’s traffic management plans. This item was deleted from Section 3A (pavement preservation), but it was not removed from Sections 3B and 3C (rehabilitation and new construction/reconstruction) because it was deter- mined that traffic management responsibility should be con- sidered on these types of projects. Finally, to reduce the complexity of the tool, Caltrans recommended consolidating warranties into two types: 1- to 5-year short-term warranties and 10-year warranties. The reviewer conveyed that in his experience materials and work- manship warranties do not provide benefit and, therefore, should not be used. The reviewer recommended that the tool should focus on performance-based warranties that allow the contractor to make decisions. The reviewer agrees that the level of contractor input may vary depending on the warranty length and that for longer-term projects, the condition of the base condition will play a key role. MNDOT In general, MDOT commented that the tool was very useful as a means of investigating the use of warranties. MNDOT stated that they have streamlined the decision process into qualifying projects categorically (i.e., CPM and R&R) rather than individually. Thus, the warranty design process focuses more heavily on categorizing fixes rather than looking at individual projects, and the design of the project plays a major part in determining the type of warranty that will be applied. Comments to specific sections of the warranty selection tool are summarized as follows: Part 3: MDOT recommended revisions to questions 3.A.2, 3.B.2, and 3.C.2 regarding the scope of the project. The ques- tions on base and foundation conditions were reevaluated based on these comments. MDOT also commented that ESALs should only apply if the warranty includes an ESAL escalation clause, which would imply that the design and performance used for the warranty thresholds has been verified with actual ESALs; also, this would only apply to long-term warranties. MDOT commented that phasing and traffic management control would only be beneficial to shift to the contractor in a Type 3 situation. The research team believes that ESALs and shift- ing phasing and traffic management control can be part of a Type 2 warranty. The research team removed this crite- rion for Type 1 warranties but retained these criteria for Types 2 and 3. Finally, MDOT commented that it does not believe that the manner in which thresholds are established affects the risk rating, regardless of the warranty type. Based on information gathered through literature and interviews, particularly with TxDOT, the research team believes that the level of accuracy of the historical performance data does play a factor in the risk of the warranty. Accuracy of the threshold is deter- mined by the reliability of the historical data and the ability of the DOT to translate the historical data into performance curves. The more accurate the thresholds, the less risk the contractor must build into the bid. However, the research team attempted to clarify the intention of this question in the revised tool. WisDOT WisDOT commented that overall the tool appears to be a useful aid for DOTs looking to start a warranty program. There were no issues taken with Part 1 of the decision tool. Several of the programmatic issues identified in Part 2 are issues that WisDOT considered during the development of its warranty program, but other issues were addressed along the way, and WisDOT continues to address some of the issues today. Therefore, while WisDOT agrees it is important to consider these issues, WisDOT does not believe all these issues have to be resolved before constructing a warranty project. Programmatic issues in Part 2 that WisDOT identified to be of particular importance include • Addressing the learning curve, • Addressing bonding, • Creating the paper trail, and • Managing internal administrative costs. WisDOT suggested adding a section that addresses whether a method to resolve conflicts has been established. While it is agreed that this is an essential aspect of a warranty provision that must be addressed in the development of the warranty specification, the research team does not believe that it is a deciding factor in whether to apply a warranty. However, the establishment of a conflict resolution team is an admin- istrative cost, which can be a deciding factor. Since managing the administrative cost of warranties is addressed in the tool, the research team did not add a question to specifically address dispute resolution. WisDOT noted that a flowchart used to aid project selection focuses entirely on foundation conditions, and there should perhaps be more focus on this in Part 3. WisDOT noted that there is an important distinction in risk between an overlay that is applied directly to an existing concrete pavement versus an overlay applied on a milled asphalt surface. Questions 3.B.2 and 3.C.2 were revised to address this comment. 39

40 WisDOT noted that it has struggled with how to deal with legal and/or undocumented ESAL overloads. WisDOT sug- gested modifying a question or adding an additional question regarding the potential of seasonal or undocumented over- loads in Part 3. The questions on ESALs have been revised to include overloads accordingly. Finally, WisDOT recommended that the tool include commentary on how the risk output matrix is evaluated and what the acceptable range is for L, M, and H ratings when choosing a warranty type. The research team added instructions to the tool in response to this comment. Vetting Summary Reviewers from the four DOTs that provided results on test applications of the tool reported that the results on the type of warranty suggested by the tool were consistent with the type of warranty ultimately applied by the DOT. The majority of comments on the structure of the tool were directed at Part 3 on questions related to foundation conditions, mix-design, traffic management, and ESALs. The following revisions were made to address these comments: • Added the concept of transferring accountability from the DOT to contractors in Part 2; • Revised the multiple-choice answers to questions 3.A.2, 3.B.2, and 3.C.2 related to foundation conditions; • Revised multiple-choice answers to questions on mix-design control; • Deleted questions on traffic control and ESALs under Section 3A on pavement preservation; and • Revised multiple-choice answers to address seasonal/ undocumented overloads in questions on ESALs. Development of Warranty Implementation Guidelines and Model Technical Provisions for HMA and PCC Pavements Chapter 2 used a literature review and workshop and inter- view results to identify and discuss a number of key issues related to the implementation of pavement warranties. Related issues included warranty objectives or rationale, project selection, performance indicators and distress thresholds, warranty durations, bonding practices, and risk allocation in terms of contract type, responsibility for quality control, inspection, testing, remedial work, and exclusions. In the existing literature addressing warranty implementation, recent guidance from FHWA recommended that DOTs, particularly when implementing pavement warranty projects for the first time, engage the industry in the development of specifications and discuss bonding with the surety industry before attempt- ing to implement a warranty to clarify the warranty coverage and roles and responsibilities. It also recommended that DOTs not attempt to implement a warranty program without a mature QA process in place for acceptance of materials and construction (FHWA, 2008). Based on the observations and lessons learned from DOTs that have developed sustained warranty programs, the research team created a framework including seven generic topic ele- ments that should be addressed in steps to successfully develop and implement pavement warranties. These elements are discussed in the following sections and are reflected in the pavement warranty guidelines shown in Appendix A1. Rationale for Warranties The Appendix A1 guidelines start by addressing the com- mon drivers or objectives for using pavement warranties. Regardless of whether the decision to use warranties is driven internally by the DOT or externally, as in a legislative man- date, it is imperative to understand the rationale behind the warranty. The objectives for using a warranty can include improved quality, innovation, reduced inspections, transfer of accountability, and extended service life. Identifying and articulating the objectives must come first because they guide the follow-on decisions of what warranty type to implement and how it should be implemented. For example, the quality objective can mean setting the target acceptance criteria higher than the historic average or based on a lower standard deviation. In one case, the quality goal could be to extend service life. In another, the goal could be to improve contractor consistency and attention to detail when constructing the work. The differences in these will affect what type of warranty to implement and how to implement it. In theory, improved contractor performance leads to improved quality; however, the link between performance and quality is not guaranteed. Therefore, these two objectives should be distinguished when determining the rationale behind warranties. Program Considerations The Appendix A1 guidelines next address various pro- grammatic considerations necessary for successful implemen- tation of pavement warranties. The inclusion of programmatic considerations as a screening step was not part of the initial scope of this research, but it became apparent after obtaining the findings from practitioners that programmatic issues must be addressed as part of the decision tool and guidelines, particularly for the first-time implementation of pavement warranties. Programmatic prerequisites include the need for both owner and industry warranty concept buy-in, some level

of DOT and industry experience with QA specifications, surety support, and reliable historic performance data. The more that these programmatic conditions are ingrained or in place, the greater the likelihood that the implementation of pavement warranties will be successful or that the DOT will be able to transition from materials and workmanship to performance warranties. Project Considerations The next step in the Appendix A1 guidelines is project con- siderations. The DOT must determine whether a specific project is suitable for a warranty and what type of warranty would best serve the goals or needs of the project. Project characteristics to consider that may affect the implementation of a warranty include • Project scope; • Material type, quality, and availability; • Foundation conditions; • Pavement remedial work anticipated; • Structural design; • Contracting method; • Traffic projections; • Construction phasing and work sequence; and • Exclusions. The project-specific considerations shown in Appendix A1 address whether a warranty is appropriate for the project scope, whether existing base or pavement conditions or traffic loads might limit the warranty or trigger exclusions, and what warranty type would be the most appropriate for the project in the context of scope, contracting method, and risk allocation. The last step in the decision process is to assess, based on programmatic and project-specific inputs, whether to imple- ment a warranty and what type to implement. The warranty decision tool described in this chapter and presented in Appendix A2 is integrated with these guidelines. Developing Warranty Provisions If a DOT already has an established pavement warranty program or provisions and is interested in improving exist- ing practices or transitioning to a longer-term performance warranty, then the DOT would focus primarily on project- specific considerations and the contents of warranty provi- sions themselves. Key considerations in the development of warranty provisions are the selection of appropriate perform- ance indicators, establishing appropriate thresholds, and determining the most appropriate monitoring and evaluation plan for the roadway classification and warranty type. Performance Indicators and Thresholds Important to the implementation of warranty provisions are selecting the right performance indicators and setting thresholds that achieve the desired quality or pavement per- formance based on the project objectives. The logical steps in establishing indicators and setting thresholds are 1. Select pavements of target age, 2. Establish evaluation section length, 3. Evaluate PMS or other performance data, and 4. Establish performance indicator threshold values. The research findings indicated that the choice of indicators was derived from a number of sources, but the most reliable basis is historic pavement management data from similar pre- viously constructed pavements. Tables 14 and 15 in Chapter 2 compare common performance indicators and thresholds used in warranty specifications for HMA pavement. In general, the findings suggest that a DOT developing a warranty provision should focus on distresses or functional characteristics that can be measured routinely and objectively (as part of a PMS or other test roadway), directly affect the safety of the facility and the performance of the pavement, and relate to elements of the pavement or the project that are under the control of the contractor. While many performance indicators or measurable distresses have been identified in the literature and affect performance, some indicators are less critical, are subsumed by other indica- tors, or as a practical matter do not justify the resources required to evaluate them on a routine basis. Appendix A1 includes HMA and PCC pavement performance criteria summarizing the range of common indicators, measurements, potential causes, and fixes applicable to pavement warranty types based on the Distress Identification Manual for the Long-Term Pavement Performance Program (Miller and Bellinger, 2003) and other sources (Washington State DOT, 2008 and FHWA, 2001). The guidelines recommend that the DOT should choose distress indicators for HMA and PCC pavements where the cause of distress is relatively straightforward to identify and is related to scope of work under the contractor’s control. The guidelines also recommend that, if practical, DOTs should use high-speed computer-automated evaluations of HMA pavements for ride quality (IRI), rutting, and longitudinal and transverse cracking, and should evaluate other distress indicators only if required. As in the case of performance indicators, it is necessary to set thresholds based on pavement age and expected traffic conditions and determine whether the pavement condition during the warranty period is consistent with the expected distress thresholds for the age and service life of the pave- ment. As discussed in the Appendix A1 guidelines, the key to 41

42 establishing appropriate threshold values lies in consistent, reliable historical performance data gathered through a DOT’s PMS. Figures 6, 7, and 8 in Chapter 2 and the guidelines in Appendix A1 discuss how a DOT might use data output from its PMS to develop thresholds for IRI and rutting for a typical HMA warranty pavement segment. Warranty objectives, warranty duration, and dependability of information derived from historical or model data are important factors that shape how a threshold is structured and established. The evaluation interval or section length will affect the threshold levels. The threshold may also be affected by how the pavement is constructed. For example, the more opportunities to achieve smoothness through constructing multiple pavement layers or surface milling, the tighter the smoothness tolerance could be. Based on existing warranty specifications, distress threshold values vary significantly with geographical region, roadway classification and design standards, materials used, and the warranty objectives. The distress thresholds for cracking among other surface distresses used in some of the warranty specifi- cations define multiple thresholds based on levels of severity of distresses described in the Distress Identification Manual (Miller and Bellinger, 2003). Each level, if exceeded, will trigger different remedial actions. If the objective of the warranty is to dramatically improve quality over the warranty duration, then thresholds should be set tighter than the expected distress values (or dispersion) to achieve this warranty objective. If the objective is to maintain a roadway to a defined level of service for its expected service life or beyond, as in the case of a long-term Type 3 warranty provision, the thresholds may be structured to meet graduated or tiered values based on the age of the pavement or to meet a minimum acceptable standard based on a defined pave- ment age. In some of these cases, particularly for PPP agree- ments or lease agreements, DOTs are also experimenting with pavement hand-back requirements based on a residual life requirement (translated to thresholds) that would be deter- mined at a stage close to the end of the warranty or maintenance period. The model specifications shown in Appendices A3 and A4 include hand-back language to illustrate the current thought process regarding this type of requirement. Monitoring and Evaluation Guidelines and specifications must also address cost- effective approaches to monitoring and evaluating a warranty provision. The type of warranty implemented will factor into how the warranty is monitored and evaluated. Other con- tributing factors will include the performance indicators and thresholds specified in the warranty provisions and the fre- quency of the monitoring effort. Monitoring may occur on a regular interval, at random, or as the result of a trigger or alert flagged during standard PMS inspections, as determined by the warranty specification. Monitoring may be conducted as a formal process or as an informal process. It may be witnessed by a representative of the contractor. Distresses on warranty projects are measured and evaluated as a function of average distress per segment length. The seg- ment length, or lot, must be carefully considered. If evaluation segments are too long, a localized area of poor performance can be diluted. However, segments must be long enough to allow a practical means of data processing. Based on the research findings, typical segment lengths used in the United States range from approximately 300 ft to 500 ft (100 m to 167 m). However, these segments are much different from the segment length, typically 1 mile (1.6 km), used to process network data under the standard pavement management system. Therefore, if using standard network data for comparative purposes to determine the effectiveness of warranties, an appropriate adjustment should be made to thresholds to correlate the warranty and the network data. Considerations for monitoring and evaluation are discussed in the Appendix A1 guidelines and in the commentary included in the model specifications in Appendices A3 and A4. Specification Content In addition to selecting the right indicators and thresholds, remedial actions, and monitoring and evaluation plan, the warranty provisions must address the other key administrative elements of warranty specifications. These include bonding, conflict resolution, exclusions, quality control, measurement and payment, and acceptance. The organization and content of warranty provisions will vary considerably based in part on the choice of warranty (i.e., Type I materials and workmanship versus Type II or III performance) and the contracting strategy (i.e., design–bid–build or design–build). Warranty provisions also may be formatted as stand-alone special provisions or aligned with the standard specifications for flexible and rigid pavements (typically AASHTO Divisions 400 and 500). The recent FHWA guidance for pavement warranties recommends that the specifications address the following core elements for pavement warranty specifications (FHWA, 2008): 1. Description; 2. Warranty bond/guarantee requirements; 3. Conflict resolution team; 4. Permit requirements; 5. Pavement distress indicators, thresholds, and remedial action; 6. Elective/preventive actions; 7. Agency maintenance responsibilities; 8. Method of measurement; 9. Basis of payment;

10. Quality control plans; 11. Verification and evaluation; and 12. Final warranty acceptance. The FHWA guidance also notes that the content of these elements will vary considerably based on whether the DOT is implementing a materials and workmanship or a performance warranty, an HMA or PCC pavement, or is using an alternative contracting method. For example, the responsibility for quality management activities will shift based on the warranty type and contracting method. The performance criteria and thresholds will change based on the pavement type and warranty objectives. The research team compared this suggested approach with current warranty specification content, expanding its content analysis of HMA and PCC specifications to determine what core elements were addressed in the specifications and how they were drafted. The research team compared performance indicators and thresholds for PCC pavement, bonding require- ments, exclusions, conflict resolution, measurement and pay- ment, and acceptance requirements among other elements. The complete list of the warranty specifications reviewed as part of this effort is included in Appendix B. Based on this initial review, the research team selected and compared a representative sample of these warranty specifica- tions representing the range of possible formats and contents. Table 17 includes this comparison of six DOT pavement warranty specifications to determine the most common organizational structure and content of these specifications. Based on the content analysis of these existing specifications, the research team found that the organizational structure was in part dictated by the type and the term of the warranty, which was consistent with the recent FHWA guidance (FHWA, 2008). As noted in Table 17, the sections used in virtually all of the specifications reviewed included the following core elements: • Description, • Warranty bond, • Conflict resolution, • Pavement performance evaluations (distress indicators, thresholds, monitoring, and remedial action), • Warranty work/permit requirements, • Exclusion, • Measurement, and • Payment. The elements that were less-frequently used in the warranty special provisions or included elsewhere in the specifications for a project were • Definitions, • Contractor QC plan, • Initial acceptance, • Elective/preventative action, • Agency maintenance, • Final acceptance, and • Release from warranty. The research team determined that the model warranty specifications shown in Appendices A3 and A4 should at a minimum include the core elements and the less frequently Specification Section PA IN MS FL WI MI Description √ √ √ √ √ √ snoitinifeD √ Warranty (bond/guarantee) √ √ √ √ √ √ Contractor QC plan (Documentation) √ √ √ Initial Acceptance √ Conflict Resolution √ √ √ √ √ √ Pavement performance criteria (distress indicators and thresholds) √ √ √ √ √ √ Warranty evaluations (monitoring, and evaluation of distress) √ √ √ √ √ √ Warranty exclusions √ √ √ √ √ √ Warranty (remedial) work/ permit requirements √ √ √ √ √ √ Elective/preventative action √ √ √ Agency maintenance/emergency repairs √ √ Measurement √ √ √ √ √ √ Payment √ √ √ √ √ √ Payment adjustments √ Final (inspection) acceptance √ Release from warranty √ Table 17. Comparison of warranty specification sections. 43

44 used agency maintenance and final acceptance language. The DOT could then add optional language depending on agency practices and whether the specification was a Type 1 (materials and workmanship) warranty or a Type 2 or 3 (performance) warranty. For example, for a Type 2 or 3 per- formance warranty, the specification may include respon- sibility for planned maintenance and the contractor may be required to submit a QC plan. Suggested language for the content of these elements was adapted from the representa- tive sample of warranty specifications and edited to achieve a consistent style and format. The research team decided that the model specifications shown in Appendices A3 and A4 would be most useful struc- tured as special provisions/standard supplements to Divi- sions 400 and 500, but could also be drafted as stand-alone AASHTO-formatted standard pavement specifications. This would allow the flexibility to modify the model warranty specifications based on agency practices, whether the warranty is a Type 1 materials and workmanship or a Type 2 or 3 perfor- mance warranty and whether it is written as a special provi- sion or as a standard specification. Recommended inserts or optional language, based on the specification structure or type of warranty (materials and workmanship versus performance), are noted in the commentary in italics as appropriate. Where applicable, standard language was adopted from the AASHTO Guide Specifications for Highway Construction. Some sections of the model specifications are written in a manner to appear as absolute or definite. This was not intended to be the only approach to the content of the section but provides examples based on current practices. Bracketed items are suggested options or suggested values and should be changed as needed to meet the specific requirements of the project or program.

Next: Chapter 4 - Conclusions and Recommendations »
Guidelines for the Use of Pavement Warranties on Highway Construction Projects Get This Book
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 699: Guidelines for the Use of Pavement Warranties on Highway Construction Projects is designed to help guide state departments of transportation (DOTs) in establishing pavement warranty programs.

The guide identifies programmatic and project-level decision criteria that DOTs should consider when implementing and sustaining a program. The guide presents strategies to mitigate project-specific risks and also includes model warranty specification provisions.

The guide also includes a decision tool to help identify program-level issues and project-specific risks. The tool is included on a CD-ROM that is packaged with the printed version of the report.

The CD-ROM is also available for download from TRB’s website as an ISO image. Links to the ISO image and instructions for burning a CD-ROM from an ISO image are provided below.

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CD-ROM Disclaimer - This software is offered as is, without warranty or promise of support of any kind either expressed or implied. Under no circumstance will the National Academy of Sciences or the Transportation Research Board (collectively “TRB’) be liable for any loss or damage caused by the installation or operation of this product. TRB makes no representation or warranty of any kind, expressed or implied, in fact or in law, including without limitation, the warranty of merchantability or the warranty of fitness for a particular purpose, and shall not in any case be liable for any consequential or special damages.

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