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22 Table 3.3. Feasibility Matrix for Preliminary Identification of Candidate Preservation Treatments for PCC-Surfaced Pavements Distress Types and Severity Levels (L Low, M Medium, H High) Surface Distress Window of Map Opportunity Crack/Scale Water Polish (Non-ASR) D-Crack Popouts Bleed/Pump PCI/ Age Preservation Treatment PCR (yr) -- -- L/M/H -- -- Concrete joint resealing 7590 510 Concrete crack sealing 7090 512 Diamond grinding 7090 512 Í Diamond grooving 7090 512 Partial-depth concrete patching 6585 615 Í Full-depth concrete patching 6585 615 Í b Í Dowel bar retrofitting 6585 615 Í Ultra-thin bonded wearing course 7090 512 Í Í Thin HMA overlay 7090 512 Í Í Note: = Highly Recommended; Í = Generally Recommended; = Provisionally Recommended; = Not Recommended. a May be appropriate in conjunction with partial- and/or full-depth repairs to ensure smooth profile. b Isolated incidences of D-cracking only. c Isolated incidences of faulting only. d Likely needed in conjunction with diamond grinding. (continued on next page) provided in Tables 3.4 and 3.5, factors such as the time of year of time) using analysis procedures that range from detailed of treatment construction, availability of quality materials and and complex to less detailed and simple. In simple terms, the qualified contractors, roadway geometrics (e.g., horizontal and/ alternative that provides the greatest benefits for the least or vertical curves, intersections, pavement markings/striping, costs is the "best." curb-and-gutter), traffic accommodation and safety issues, This section presents two different approaches that can and environmental considerations (e.g., emissions and air be used to evaluate the cost-effectiveness of preservation quality, recycling and sustainability issues), should be prop- treatments. These approaches are the equivalent annual cost erly considered. This process should result in a final list of fea- (EAC) and the benefit-cost ratio (BCR). The first approach, sible treatments that can be analyzed for cost-effectiveness, EAC, is the simplest to perform and requires only basic infor- leading to a selection of the preferred treatment. mation regarding cost and performance. It measures cost- Appendix B provides two example illustrations for using effectiveness in the short term for alternatives that are assumed the feasibility matrices in Tables 3.2 through 3.5 to identify to provide similar benefit (e.g., a chip seal and a slurry seal final treatment candidates. One example is for treatment of that are both applied to improve surface texture). The sec- an HMA-surfaced pavement, while the other is for treatment ond approach, BCR, requires much more data and compu- of a PCC-surfaced pavement. tational effort and measures cost-effectiveness in the long term. It is appropriate for evaluating treatments that do not necessarily provide the same benefit, such as crack sealing Treatment Cost-Effectiveness Analysis and a chip seal. Cost-effectiveness analysis is an economic evaluation tech- Each approach requires reliable, up-to-date estimates of the nique for comparing that which is sacrificed (cost) to that cost and performance of the treatments to be analyzed. Histor- which is gained (performance benefit) for the purpose of eval- ical bid price data are an excellent source for developing treat- uating alternatives (Lamptey et al. 2005). Cost-effectiveness ment cost estimates, but these data must be adjusted to current can be measured in the short term (i.e., for one or more treat- values to account for the effects of inflation. To the extent pos- ments administered at a given time) or in the long term (i.e., sible, care should be exercised in developing estimated costs for several treatments carried out over an extended period so that they account for project-specific factors, such as size
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23 Table 3.3. (continued) Distress Types and Severity Levels Surface Characteristics Joint Distress Cracking Distress Deformation Distress Issues Joint Seal Joint Long/ Ride Damage Spall Corner Trans Faulting Patches Quality Friction Noise Preservation Treatment L/M/H L/M/H L/M/H L/M/H L/M/H L/M/H -- -- -- Concrete joint resealing Í Concrete crack sealing Í Í Diamond grinding a ÍÍ ÍÍ Í Diamond grooving Í Partial-depth concrete patching Í Í Í Full-depth concrete patching Í Í Í c Í Í Dowel bar retrofitting Í d Ultra-thin bonded wearing course Í Í ÍÍ Í Thin HMA overlay Í Í ÍÍ (quantity of treatment needed), site-specific surface prepara- modeling techniques (i.e., time-series trends of overall con- tion requirements (such as material removal, patching, and dition, serviceability, and/or individual distress development). cleaning), special traffic control requirements, and various And, since pretreatment pavement condition can have a sig- contingencies (e.g., striping and pavement marker removal/ nificant impact on treatment performance, the analysis should replacement and associated shoulder work), that may have be limited to projects with pretreatment condition levels that impacted the documented treatment costs. Also, to ensure a fair are similar to the proposed project. cost comparison of all treatment options, the final estimated If historical performance data are not available or are insuf- costs should be based on a common unit of measure, such as ficient for analysis, then performance information should be $/yd2 or $/lane-mi. sought from other sources. These may include agencies that Obtaining meaningful estimates of treatment performance have utilized the candidate treatments in similar conditions is more complicated. Ideally these are developed using data or from practitioners knowledgeable of the performance of from the PMS database and the pavement history database (if the candidate treatments. separate from the PMS database). However, few PMS data- bases include information on preservation treatment per- Equivalent Annual Cost formance or are able to discern the issue of greatest interest: when the treatment stopped being effective. In any analysis of The EAC method of cost-effectiveness is an inverse measure available data, care should be taken to ensure that the data of the proverbial "bang for the buck." It involves a simple cal- analyzed are from projects with characteristics (e.g., existing culation of the treatment unit cost divided by the expected pavement type and conditions, traffic loadings, and climatic treatment performance, as shown below. conditions) that are similar to those of the proposed project. This is sometimes referred to as the pavement "family" con- Treatment Unit Cost EAC = (1) cept. Although pavement survival analysis techniques (i.e., Expected Performance, years time until treatment failure or until a specific threshold condi- tion is reached) can be used, estimates of treatment perfor- In this analysis method, the expected treatment perfor- mance are more easily achieved using pavement performance mance is the extension in service life of the pavement generated
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Table 3.4. Feasibility Matrix for Final Identification of Candidate Preservation Treatments for HMA-Surfaced Pavements Treatment Durability Rural Roads Urban Roads Work Zone Duration Restrictions Expected Climatic Zone Climatic Zone High High Overnight Performance on Preservation Traffic ADT Deep Moderate Traffic ADT Deep Moderate or Single High-Volume Relative Treatment >5,000 vpd Freeze Freeze Nonfreeze >10,000 vpd Freeze Freeze Nonfreeze Shift Weekend Longer Facility (yr) Cost Crack fill 23 $ Crack seal 26 $ Slurry seal Í Í Í Í 35 $$ (Type III) Microsurfacing: Í Í Í Í Í Í 35 $$ Single Microsurfacing: Í Í Í Í Í Í 46 $$/$$$ Double Chip Seal: Single Conventional Í Í Í Í Í Í Í 46 $$ Polymer $$$ modified Chip Seal: Double Conventional Í Í Í Í Í Í Í 68 $$/$$$ Polymer $$$ modified Ultra-thin bonded Í Í Í Í Í Í 58 $$$ wearing course Ultra-thin HMAOL Í Í Í 47 $$ Thin HMAOL Í Í 510 $$$ Cold milling and Í 611 $$$ thin HMAOL Hot in-place recycling Surf recycle 58 $$$ and HMAOL Remixing Í 612 $$$ and HMAOL Repaving 612 $$$ Cold in-place Í Í Í Í Í Í Í 511 $$$ recycling and HMAOL Profile milling Í Í Í Í Í 24 $ Ultra-thin whitetopping Í Í NA $$$$ Note: = Highly Recommended; Í = Generally Recommended; = Provisionally Recommended; = Not Recommended. $ (lowest relative cost) $$$$ (highest relative cost).
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Table 3.5. Feasibility Matrix for Final Identification of Candidate Preservation Treatments for PCC-Surfaced Pavements Treatment Durability Rural Roads Urban Roads Work Zone Duration Restrictions Expected Climatic Zone Climatic Zone High High Overnight Performance on Preservation Traffic ADT Deep Moderate Traffic ADT Deep Moderate or Single High-Volume Relative Treatment >5,000 vpd Freeze Freeze Nonfreeze >10,000 vpd Freeze Freeze Nonfreeze Shift Weekend Longer Facility (yr) Cost Concrete joint Í 47 $ resealing Concrete crack Í Í 46 $ sealing Diamond grinding Í Í 612 $$ Diamond grooving Í Í Í Í 612 $$ Partial-depth Í Í a a 515 $$/$$$ patching Full-depth patching a a 1015 $$/$$$ Dowel bar retrofitting Í Í Í Í a a 1015 $$$ Ultra-thin bonded Í Í Í Í Í 57 $$$ wearing course Thin HMA overlay Í Í Í 58 $$$ Note: = Highly Recommended; Í = Generally Recommended; = Provisionally Recommended; = Not Recommended. $ (lowest relative cost) $$$$ (highest relative cost). a Use of high early strength or fast-track proprietary materials make these treatments suitable options for overnight, single-shift, and weekend closures. Use of conventional PCC repair materials generally requires "longer" closures.
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26 Approach A: Life Pavement extension based on Condition pretreatment condition levels Preservation Treatment Condition Threshold Approach B: Life extension based on specified condition threshold levels Time, years Figure 3.2. Estimation of preservation treatment performance using two approaches to pavement life extension. by the preservation treatment. Although this extension may the expected timings of future preservation and rehabilitation be easily identified as (a) the time taken for the pavement con- treatments and the corresponding jumps and subsequent dition or serviceability/smoothness to return to the level it deterioration in condition or serviceability/smoothness. The was at immediately prior to the treatment, a more discerning expected timings are determined from service life analyses of appraisal uses (b) the difference between the time taken for the the existing pavement and the specific rehabilitation treat- treated pavement to deteriorate to a certain threshold level ments, and from the service life extensions estimated for the and the time taken for the untreated pavement to deteriorate preservation treatment. to the same threshold level. Both approaches are illustrated in The top portion of Figure 3.3 illustrates the assessment Figure 3.2. of benefits using the area-under-the-performance-curve approach. A treatment alternative with more area under Benefit-Cost Ratio the curve yields greater benefit through higher levels of condition or serviceability/smoothness provided to the high- The BCR method of cost-effectiveness combines the results way users. of individual evaluations of treatment benefits and treatment The costs associated with a particular preservation strategy costs to generate a benefit-to-cost (B/C) ratio. The B/C ratios are evaluated using life-cycle cost analysis (LCCA) techniques. of alternative preservation treatments (and, if desired, a "no The LCCA must use the same analysis period and the same treatment" option) are then compared and the treatment timings of preservation and rehabilitation treatments as those with the highest ratio is deemed the most cost-effective. used previously in computing benefits. A specified discount Since the analysis is performed over a long period covering rate (typically 3% to 5%) is used to convert the costs of the the life cycle of a pavement, the costs and performance char- future projected preservation and rehabilitation treatments acteristics of the existing pavement (whether the original (and any salvage value at the end of the analysis period) to structure or the last significant rehabilitation treatment) and present-day costs. These costs are then summed together with all future projected preservation and rehabilitation treat- the cost of the existing pavement (again, either the original ments associated with a given preservation strategy must be structure or the last significant rehabilitation) to generate the estimated. total life-cycle cost (expressed as net present value [NPV]) In the BCR method, the benefits associated with a particu- associated with the preservation strategy. The computational lar preservation strategy are evaluated from the standpoint of formula used in this process is as follows. benefits accrued to the highway user over a selected analysis period (usually 25 to 40 years, beginning from the original n AP k 1 j 1 construction). They are quantified by computing the area NPV = IC + M&R j × - SV × (2) under the pavement performance curve, which is defined by j =1 1 + idis 1 + idis
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27 Pavement Total Benefit = B0 + BP1 + BOL1 + BOL2 Condition New Pavement Construction Preservation Overlay 1 Overlay 2 Treatment 1 B0 BP1 BOL1 BOL2 Lower Benefit Limit Time, years Analysis Period C0 COL1 COL2 CP1 S Figure 3.3. Illustration of benefits and costs associated with a pavement preservation treatment strategy. where obtained from the area-under-the-performance-curve analy- NPV = Net present value, $; sis by the "cost" obtained from the LCCA: IC = Present cost of initial construction activity, $; k = Number of future preservation/rehabilitation B C = Benefit NPV (3) activities; M&Rj = Cost of jth future preservation/rehabilitation activ- As stated previously, the treatment with the highest B/C ity in terms of present costs (i.e., constant/real ratio is deemed the most cost-effective. dollars), $; idis = Discount rate; Consideration of User Costs nj = Number of years from the present of the jth future M&R (maintenance and rehabilitation) activity; User costs are defined as nonagency costs that are borne by SV = Salvage value, $; and the users of a pavement facility (Peshkin et al. 2004). User AP = Analysis period length, years. costs can be incurred through various mechanisms and at any time over the life of a project. Overall, there are five primary The bottom portion of Figure 3.3 illustrates the stream of mechanisms of user costs: costs included in the LCCA. These costs occur in accordance with the preservation and rehabilitation treatment timings · Time-delay costs. Opportunity costs incurred as a result of established and used in the analysis of benefits. They represent additional time spent completing a journey because of the costs paid by the agency to construct the existing pave- work zones (i.e., lane restrictions, road closures) associated ment and apply the subsequent preservation and rehabilita- with construction, maintenance, or rehabilitation activi- tion treatments. ties. The opportunity cost represents the value associated Although most state highway agencies have a standardized with other activities that cannot be completed because of procedure for conducting LCCA, state-of-the-practice guid- the extra time that is normally spent completing a journey. ance has been developed and made available by the FHWA · Vehicle operating costs (VOCs). Costs associated with fuel through the Interim Technical Bulletin on LCCA in Pavement and oil consumption, tire wear, emissions, maintenance Design (Walls and Smith 1998). A companion LCCA spread- and repair, and depreciation due to work zone traffic flow sheet program, RealCost, has also been developed and is disruptions and/or significantly rough roads. VOCs typi- available for public use at www.fhwa.dot.gov/infrastructure/ cally involve the out-of-pocket expenses associated with asstmgmt/lccasoft.cfm. owning, operating, and maintaining a vehicle. In the final step of the BCR method, the B/C ratio for each · Crash costs. Costs associated with additional crashes brought preservation strategy is computed by dividing the "benefit" about by work zones or by rough or slippery roads. Crash