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28 costs are primarily comprised of the costs of human fatali- computations. A somewhat simplified approach for comput- ties, nonfatal injuries, and accompanying property damage. ing work zone time-delay costs is presented in NCHRP Report · Discomfort costs. Costs associated with driving in congested 523 (Peshkin et al. 2004). The OPTime spreadsheet program traffic or on rough roads. developed as part of that study on optimal timing of preventive · Environmental costs. Costs associated with traffic noise and maintenance can be used to perform the computations. Fol- with the operation of construction equipment in work zones. lowing are brief descriptions of how user costs can be incorpo- rated into the EAC and BCR methods of cost-effectiveness Additionally, user costs can be incurred during the estab- analysis: lishment of a work zone or during normal (nonrestricted) highway operating conditions: · In the EAC method, two aspects of user costs can be con- sidered. The first aspect is the work zone user costs asso- · Work zone costs. This category of user costs deals with costs ciated with each alternative preservation treatment. brought about by the establishment of a work zone. A work Since the work zone characteristics of each alternative zone is defined as an area of a highway where maintenance, will vary based on application rates, material setting/ rehabilitation, or construction operations are taking place, curing times, and other construction factors, the delays which impinge on the number of lanes available to mov- experienced as a result of the different work zone require- ing traffic or affect the operational characteristics of traffic ments will also vary. flowing through the area (Walls and Smith 1998). A work · The second aspect is the work zone user costs associated zone disrupts normal traffic flow, drastically reduces the with the timing of an assumed future rehabilitation at the capacity of the roadway, and leads to specific changes in end of the preservation treatment's expected life. A preser- roadway use patterns that affect the nature of user costs. vation treatment with a longer forecasted life results in a · Normal operating condition costs. In between work zone delay in the timing of the assumed rehabilitation. When periods, user costs are still incurred during normal operat- discounted to present-day costs, the work zone user costs ing conditions. These include highway user costs associated associated with the rehabilitation will be lower than the with using a facility during periods free of construction, same rehabilitation work zone user costs associated with a repair, rehabilitation, or any work zone activity that restricts shorter life-preservation treatment. This is illustrated in the capacity of the facility. Figure 3.4. · In the BCR method, the user costs of all future preserva- The inclusion of user costs as part of any economic analysis tion and rehabilitation treatments associated with each of pavements is a controversial issue. While there is general preservation strategy can be computed as part of the agreement that traffic delays increase user costs, the actual LCCA. Although the user cost NPV results may be com- costs can be difficult to quantify and often overwhelm the bined with the agency cost NPV results, it is generally rec- direct agency costs, particularly for high-volume facilities ommended that they be examined separately because of (Peshkin et al. 2004). the possibility that they will overwhelm the agency costs. Current FHWA-recommended practice is to consider including in the economic analysis only the time-delay and Selection of the Preferred vehicle operating cost components associated with work Preservation Treatment zones. These components can be estimated reasonably well and make up a large portion of the total user costs. Other Although treatment cost-effectiveness is a major consideration work zone user cost components are too difficult to collect or in the selection of the preferred treatment, it is not the final reasonably quantify, or they do not factor to an appreciable answer in the process. The reality of the decision-making amount. Furthermore, for most pavement facilities in fair or process is that many other factors (economic and noneco- good condition (e.g., pavements with a PSR of 2.5 or greater), nomic) must be considered along with cost-effectiveness. user costs during normal operating conditions are minimal Some of these factors may have been previously considered as (Peshkin et al. 2004). part of the steps to identify feasible treatments, yet may also For projects in which time-delay and VOC work zone user be desired for consideration in the final selection. Examples costs are likely to occur as a result of performing preservation include the availability of qualified (and properly equipped) and/or rehabilitation activities, consideration should be given contractors and quality materials, the anticipated level of traf- to evaluating these costs as part of the selected cost-effectiveness fic disruption, and surface characteristics issues. analysis method. Detailed procedures for computing them Upon completion of the cost-effectiveness analysis, it may are provided in the FHWA's Interim Technical Bulletin on be desirable to eliminate certain treatment alternatives on the LCCA in Pavement Design (Walls and Smith 1998), and the basis of not being able to meet key financial goals. Such elim- RealCost spreadsheet program can be used to perform the ination criteria might include the following:
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29 Pavement Condition Preservation Treatment 1 (PT1) Preservation Treatment 2 (PT2) Condition Threshold (Trigger for Rehabilitation) LifePT2 LifePT1 Time, years UCRehab UCRehab Discount future UCRehab user costs to NPV present day (PT2) UCRehab NPV (PT1) TPT2 TPT1 Time, years Figure 3.4. Effect of preservation treatment life on discounted rehabilitation user costs. · Substantially lower cost-effectiveness compared with that which can also be assigned weights as part of a decision of other treatment alternatives (e.g., EAC greater than 10% matrix: higher than the EACs of the alternatives, B/C ratios greater than 10% less than the ratios of the alternatives); · Economic attributes: · Initial cost greater than available funding, resulting in neg- Initial cost; ative impact on network-level budgeting; and Cost-effectiveness (EAC or B/C); · Excessive user costs that would have serious negative impact Agency cost; and on roadway users. User cost. · Construction/materials attributes: Availability of qualified (and properly equipped) con- Alternatively, these economic factors can be combined tractors; with several noneconomic factors, as described below. Availability of quality materials; A useful mechanism to systematically and rationally Conservation of materials/energy; and evaluate the different factors and identify the preferred Weather limitations. treatment is the treatment decision matrix. In a treatment · Customer satisfaction attributes: decision matrix, various selection factors are identified for Traffic disruption; consideration and each factor is assigned a weight. The Safety issues (friction, splash/spray, reflectivity/visibil- weights are then multiplied by rating scores given to each ity); and treatment alternative, based on how well the treatment sat- Ride quality and noise issues. isfies each of the selection factors. The weighted scores of · Agency policy/preference attributes: each treatment alternative are then summed and compared Continuity of adjacent pavements; with the weighted scores of the other treatments. The treat- Continuity of adjacent lanes; and ment with the highest score is then recognized as the pre- Local preference. ferred treatment. A fairly complete list of factors that are appropriate for A decision matrix that incorporates these factors and illus- inclusion in the final selection process is provided below. trates the assignment of weights and the basis for rating scores The factors are grouped according to different attributes, is provided in Table 3.6.
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30 Table 3.6. Example of Preservation Treatment Decision Matrix Treatment 1 Treatment 2 Attribute Factor Combined Rating Weighted Rating Weighted Attribute and Selection Factor Weight Weight Weight Score Score Score Score Economic 40 Initial cost 30 12.0 Cost-effectiveness 30 12.0 Agency cost 10 4.0 User cost 30 12.0 Total 100 Construction/materials 25 Availability of qualified contractors 20 5.0 Availability of quality materials 20 5.0 Conservation of materials/energy 30 7.5 Weather limitations 30 7.5 Total 100 Customer satisfaction 25 Traffic disruption 40 10.0 Safety issues 40 10.0 Ride quality and noise issues 20 5.0 Total 100 Agency policy/preference 10 Continuity of adjacent pavements 20 2.0 Continuity of adjacent lanes 20 2.0 Local preference 60 6.0 Total 100 Cumulative Weighted Score Note: Basis for treatment rating scores (1-to-5 scale); initial cost: 1 = highest, 5=lowest; cost-effectiveness: 1 = least cost effective, 5 = most cost-effective; agency cost: 1 = highest, 5 = lowest; user cost: 1 = highest, 5 = lowest; availability of qualified contractors: 1 = low/none, 5 = high; availability of quality materials: 1 = low/none, 5 = high; conservation of materials/energy: 1 = low, 5 = high; weather limitations: 1 = major, 5 = low/none; traffic disruption: 1 = major, 5 = low/none; safety issues: 1 = serious, 5 = none; ride quality and noise issues: 1 = serious, 5 = none; continuity of adjacent pavements: 1 = does not match at either end, 5 = matches at both ends; continuity of adjacent lanes: 1 = does not match, 5 = matches; local preference: 1 = inconsistent with preference, 5 = consistent with preference.