Evaluating Pavement Strategies and Barriers for Noise Mitigation (2013)

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40 To further illustrate the approach for evaluating barriers and pavement strategies for highway noise abatement, projects from three state highway agencies (California, North Carolina, and Arizona) were analyzed. In each case, the OBSI data used was measured previously by the research team for pavements found in that state. Pavement options representing state practices were considered (these options may have been used in the original agency design and analysis). The TNM models were obtained either from the state agency or their contractors. Example A: I-580 Lane Addition The project consists of the addition of high-occupancy vehicle (HOV) lanes to 13.1 mi of the eight-lane I-580 between Dublin and Livermore, California. It was assumed that both eastbound and westbound HOV lanes were to be added as a single project. All eight lanes of the existing pavement are aged PCC with longitudinal tines. The additional lanes will incorporate a portion of the existing shoulder and a newly constructed pavement to provide the added lane and shoul- der; the lanes are to be re-striped. The following construction options were considered for the added lane: 1. PCC pavement (as are the existing four lanes in each direction). 2. HMA pavement and overlay of all lanes with a quieter fric- tion course. The following pavement alternatives were considered for the LCCA: 1. Construct added HOV lanes and shoulders with PCC. The PCC of the added lanes will be longitudinally tined similar to the surface texture of the existing pavement. The exist- ing pavement is in good condition and does not require rehabilitation at this time. Diamond grind all lanes (for noise and other considerations) 10 years after the addition of the HOV lanes and every 20 years thereafter. 2. Construct added HOV lanes and shoulders with PCC and diamond grind all lanes to reduce the tire–pavement noise levels. Diamond grind all lanes on a 20-year cycle thereafter. 3. Construct added HOV lanes and shoulders with PCC and overlay all lanes and shoulders with a 1 in. RAC(O) over- lay. Mill the RAC(O) overlay and replace it every 9 years for noise performance. 4. Construct added HOV lanes and shoulders with HMA and overlay all lanes and shoulders with a 1 in. RAC(O) overlay. Mill the RAC(O) overlay and replace it every 9 years for noise performance. 5. Construct added HOV lanes and shoulders with HMA and overlay existing lanes and shoulders with a 5 in. HMA overlay. Mill 2 in. of the HMA overlay and overlay it on a 12-year cycle. Details of the LCCA for these cases of pavement alterna- tives (with no barriers) are presented in Appendix F. Table 22 lists the NPV for the five pavement alternatives on a cost-per- mile basis. Only the three alternatives with the lowest NPV were considered for further analysis because they provide acoustically unique alternatives that have the low cost. Alter- native 5 (all HMA) is the most expensive; it was not consid- ered further. Alternative 4 [HMA with RAC(O) overlay] was also not considered further because it provides acoustic per- formance similar to that of Alternative 3, but at a higher cost. Out of the 13.1 mi project, three smaller segments were considered, each with several potential barrier locations. For each segment, TNM was used to predict traffic noise levels for the three different pavement alternatives. For this analysis, the existing PCC pavement was used as the reference pavement. Alternative 1 (the existing eight lanes and two HOV lanes added with no further modification) provides the lowest cost. Alternative 5 (all HMA) would provide the closest acoustic performance to that of the TNM Average Pavement, but its cost would always be greater than any of the other alternatives. As shown previously in the LCCA for the six-lane example, the C H A P T E R 5 State Project-Based Examples

41 performance of the LT PCC and TNM Average Pavement was nearly identical, but for this example, the levels for the exist- ing LT PCC pavement are about 1 dB greater than TNM Aver- age Pavement. Barrier and pavement analysis for each of the three segments is presented in this section. The NPV costs are the barrier LCCA costs based on $51.61/ft2 (scaled to height and length as needed) plus the pavement NPV costs listed in Table 22. The analysis considers Caltrans policy as of May 2011 as described in the previous examples. The acoustic perfor- mance of the LT PCC, ground PCC, and RAC(O) pavement is also the same as that used previously. Barrier heights ranging from 12 to 16 ft were considered because 12 ft was determined to be sufficient to block the line of sight to truck exhaust stacks and 16 ft is generally the maximum allowed height. Segment 1 Cases Segment 1 is the 1 mi section located between the free- way intersections at 1st Street and Vasco Road as shown in Figure 20. In this segment, five barriers were analyzed. Three of these barriers—SWWB6, SWEB9, and SWEB10—are new, and two are existing barriers to which height would be added to reduce noise levels at sensitive receptors to levels below the NAC. Existing barriers SWWB7 and SWWB8 are 14 ft and 12 ft high, respectively. These barriers shield two relatively densely built-up subdivisions; the other proposed barriers would shield fewer receptors (Table 23). Results of the feasibility, reasonableness, effectiveness, and cost analyses are summarized in Table 24 for the SWWB6 bar- rier. The predicted levels for the existing baseline PCC pavement range from below the Caltrans NAC of 66 dBA to 80 dBA. Of 23 identified impacted receptors, 12 would be at the 80 dBA level. For this case, all three alternatives with barriers meet the feasible and reasonable criteria and are nearly equal in terms of effectiveness with only 1 dB difference among them. With respect to cost, the PCC with 14 ft barrier and RAC(O) with 12 ft barrier are quite close ($10,000 difference), while the ground PCC with 12 ft barrier is more than $100,000 higher than either of the other two. The user NPV for either of the two PCC with barrier alternatives is significantly lower than the RAC(O) alternative (see Appendix G), which could be a consideration in alternative selection. The two quieter pave- ment options without barriers [ground PCC and RAC(O)] do not provide enough reduction to meet the 5 dB acoustic fea- sibility criterion [RAC(O) provides reductions of up to 4 dB]. Summaries of the analysis results for the SWWB7 and SWWB8 barriers are shown in Tables 25 and 26, respectively. The results of these cases are similar with none of the alternatives found to meet the feasibility requirements, cost- reasonableness requirements, or the design goal. In these cases, increasing the barrier height to the maximum height of 16 ft was considered, but it increased the insertion loss of only 1 dB to 2 dB and increased noise reduction when combined with quieter pavements by 1 to 4 dB. The higher existing bar- rier SWWB7 together with the quieter pavements produced reductions of no more than 1 dB while the reductions for the SWWB8 were 2 to 3 dB. The analyses for the SWEB9 and SWEB10 barriers were essentially the same as shown in Tables 27 and 28, respec- tively. For these cases, the alternatives with barriers produced feasible reductions and achieved the design goal, except for the PCC with 14 ft SWEB10 barrier. However, with only two receptors in each case, sufficient allowance was not generated to allow any of the alternatives to be cost reasonable. For the Table 22. Summary of NPV results per mile for Example A. Alternative Agency NPV Cost ($000) No. Description 1 Added PCC Lanes Only 3,691 2 Added PCC Lanes—All Lanes Ground 5,060 3 Added PCC Lanes—RAC(O) Overlay 4,668 4 Added HMA Lanes—RAC(O) Overlay 5,353 5 Added HMA Lanes—All HMA 5,466 Figure 20. Aerial photograph of Segment 1 of an HOV lane addition project on I-580 near Livermore, California. SWWB6 SWWB7 SWWB8 SWEB9 SWEB10 Source: Google Earth © 2011 Google Table 23. Description and properties of proposed barriers for Example A. Barrier Designation Current Height (ft) Proposed Height (ft) Length (ft) No. of Impacted ReceptorsLT PCC Grd PCC/ RAC(O) SWWB6 0 14 12 800 23 SWWB7 14 16 16 1,375 38 SWWB8 12 16 16 2,150 31 SWEB9 0 14 12 800 2 SWEB10 0 14 12 1,100 2

42 Table 24. Summary of analysis results for the SWWB6 barrier. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 65–80 0 559 – – 14 PCC + 14 ft 17 62–67 1–13 1,206 646 935 Y Y Y 1 PCC + Grinding 0 63–77 2–3 767 207 – N N N 11 PCC + Grinding + 12 ft 18 60–66 3–14 1,321 761 990 Y Y Y 0 PCC + RAC(O) 0 62–76 3–4 707 148 – N N N 10 PCC + RAC(O) + 12 ft 18 59–66 3–12 1,216 656 990 Y Y Y 0 Table 25. Summary of analysis results for the existing 14 ft barrier SWWB7. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC + 0 ft 0 63–68 0 961 – – 1 PCC + 2 ft 0 63–67 0–1 1,120 159 – N N N 0 PCC + Grinding 0 63–68 0–1 1,318 357 – N N N 1 PCC + Grinding + 12 ft 0 63–68 0–2 1,476 515 – N N N 1 PCC + RAC(O) + 0 ft 0 63–67 0–1 1,216 254 – N N N 0 PCC + RAC(O) + 2 ft 0 62–67 1–2 1,374 413 – N N N 0 Table 26. Summary of analysis results for the existing 12 ft barrier SWWB8. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC + 0 ft 0 63–70 0 1,503 – – 3 PCC + 4 ft 0 61–67 1–4 1,999 496 – N N N 0 PCC + Grinding + 0 ft 0 62–69 1–2 2,060 557 – N N N 2 PCC + Grinding + 4 ft 0 61–67 1–4 2,557 1,054 – N N N 0 PCC + RAC(O) + 0 ft 0 61–68 1–3 1,901 398 – N N N 1 PCC + RAC(O) + 4 ft 0 61–67 1–4 2,397 894 – N N N 0 quieter pavement alternatives, 3 and 4 dB reductions were predicted. However, these reductions do not meet feasibility requirements and, therefore, do not generate allowances. Considering the entire segment, the use of the quieter RAC(O) pavement along the entire 1 mi distance between interchanges would produce reductions of 1 to 4 dB that would likely be noticeable at some of the receptor locations. However, it would increase the NPV of the project by about $1,000,000 in comparison with the existing PCC alternative (see Table 22) and does not appear to be a reasonable cost. However, if some form of rehabilitation of the existing pave- ment (e.g., grinding) was considered as part of the overall project, the RAC(O) alternative would produce slightly lower noise levels with an NPV savings of about $400,000. Segment 2 Cases The second segment extends from the newly built inter- section with Isabel Avenue to just east of Portola Avenue as shown in Figure 21. Two barrier options SWEB6 and SWEB7

43 Table 27. Summary of analysis results for the SWEB9 barrier. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 77–80 0 559 – – 16 PCC + 14 ft 2 71 6–9 1,206 646 110 Y N Y 3 PCC + Grinding 0 74–77 3 767 207 – N N N 9 PCC + Grinding + 12 ft 2 69 8–11 1,321 761 110 Y N Y 1 PCC + RAC(O) 0 73–76 4 707 148 – N N N 8 PCC + RAC(O) + 12 ft 2 68 9–12 1,261 702 110 Y N Y 0 Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 74 0 769 – – 16 PCC + 14 ft 2 68–69 5–6 1,658 889 110 Y N N 3 PCC + Grinding 0 71 3 1,054 285 – N N N 9 PCC + Grinding + 12 ft 2 67–68 7–8 1,816 1,047 110 Y N Y 1 PCC + RAC(O) 0 70 4 973 204 – N N N 8 PCC + RAC(O) + 12 ft 2 64–65 9–10 1,861 1,092 110 Y N Y 0 Table 28. Summary of analysis results for the SWEB10 barrier. Figure 21. Aerial photograph of Segment 2 of an HOV lane addition project on I-580 near Livermore, California. SWEB6 SWEB6p SWEB7 Source: Google Earth © 2011 Google

44 were analyzed. The SWEB6 barrier is proposed in two lengths: 4,875 ft (the full barrier) and 2,200 ft (the partial bar- rier designated “SWEB6p”). The full barrier shields only an additional 2 residences beyond the 60 shielded by the partial barrier. The level predicted for these two receptors is about 69 dBA, which is above the Caltrans NAC. The second barrier, SWEB7, would shield 15 multi-family residential impacted receptors. Details of these barriers are given in Table 29. A summary of the analysis results for the SWEB6 barrier is provided in Table 30. The predicted levels for the recep- tors range from 66 to 78 dBA (i.e., at the Caltrans threshold for impact to 12 dB above it). All of the alternatives, except the PCC with grinding only option, provide an acoustically feasible noise reduction. Of these alternatives, only RAC(O) without a barrier is cost reasonable, but it does not meet the 7 dB design criterion. If Caltrans’s criteria are applied, none of these alternatives would be considered further. A summary of the results for the partial length SWEB6 barrier is provided in Table 31. These results indicate that all alternatives with the barrier are cost reasonable and meet the design criterion and that the RAC(O) with 12 ft barrier is most effective (by 1 or 2 dB). To provide some benefit to the two receptors that do not benefit from the SWEB6p barrier, a combined alternative may be considered that uses the RAC(O) with 12 ft high SWEB6p and the RAC(O)-only alternative for the remaining 2,675 ft that the full SWEB6 barrier would cover if used. The two receptors would both receive acoustically feasible reduc- tions of 5 and 6 dB that qualify for cost allowance. The NPV for extending the RAC(O) would be $495,000; the total NPV cost for abatement would be $2,680,000 [$2,185,000 for the RAC(O) with a partial length, 12 ft high SWEB6p barrier and $495,000 for extending the RAC(O)]. However, the combined allowance for this alternative would be $3,410,000 (62 ben- efited receptors). Thus, this alternative would be feasible and cost reasonable, meet the design criteria, and provide a more Table 29. Description and properties of proposed barriers for Segment 2. Barrier Designation Current Height (ft) Proposed Height (ft) Length (ft) No. of Impacted ReceptorsLT PCC Grd PCC/ RAC(O) SWEB6 0 14 12 4,875 62 SWEB6p 0 14 12 2,200 60 SWEB7 0 14 12 1,375 15 Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 66–78 3,408 – – 12 PCC + 14 ft 49 61–68 4–11 7,347 3,939 2,695 Y N Y 1 PCC + Grinding 0 63–74 2–4 4,672 1,264 – N N N 8 PCC + Grinding + 12 ft 62 60–67 5–11 8,048 4,640 3,410 Y N Y 1 PCC + RAC(O) 47 63–72 3–6 4,310 902 2,585 Y Y N 6 PCC + RAC(O) + 12 ft 62 59–66 6–12 7,686 4,278 3,410 Y N Y 0 Table 30. Summary of analysis results for the SWEB6 barrier (full length). Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 66–78 1,538 – – 12 PCC + 14 ft 49 61–68 4–11 3,315 1,778 2,695 Y Y Y 2 PCC + Grinding 0 63–74 2–4 2,108 570 – N N N 8 PCC + Grinding + 12 ft 60 60–67 5–11 3,886 2,348 3,300 Y Y Y 1 PCC + RAC(O) 47 63–72 3–6 1,945 407 2,585 Y Y N 6 PCC + RAC(O) + 12 ft 60 59–66 6–12 3,723 2,185 3,300 Y Y Y 0 Table 31. Summary of analysis results for the SWEB6p barrier (partial length).

45 Table 32. Summary of analysis results for the SWEB7 barrier. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 69 961 – – 9 PCC + 14 ft 15 63 6 1,913 952 825 Y N N 3 PCC + Grinding 0 65–66 3–4 1,318 357 – N N N 6 PCC + Grinding + 12 ft 15 60–61 8–9 2,270 1,309 825 Y N Y 1 PCC + RAC(O) 15 64 5 1,216 254 825 Y Y N 4 PCC + RAC(O) + 12 ft 15 59–60 3–12 2,168 1,207 825 Y N Y 0 SWWB10 SWWB11 SWEB11 Source: Google Earth © 2011 Google Figure 22. Aerial photograph of Segment 3. effective solution for at least two more receptors in addition to those benefiting from the partial version of SWEB6. A summary of the analysis results for the SWEB7 barrier is presented in Table 32. As in the case of the full version of SWEB6, SWEB7 is acoustically feasible for all alternatives except the ground PCC without a barrier but attained rea- sonable cost only for RAC(O) without a barrier. Thus, none of the alternatives meet all the criteria and no abatement would be considered. If the 7 dB design goal requirement is not considered, only the RAC(O) meets the other feasible and reasonable criteria. As in the previous barrier case, a hybrid alternative can be considered for SWEB7. This alternative uses RAC(O) from the western end of the SWEB6 barrier to the eastern end of SWEB7 (a total distance of 6,450 ft). The total NPV would be $1,392,000 [composed of the NPV of the additional 200 ft of RAC(O), the NPV for the RAC(O)-only alternative in the SWBE7 analysis, and the NPV for the SWBE7 barrier], compared to the original $1,207,000. Thus, the NPV cost of the additional abatement would be $185,000, and the total NPV cost of abatement for this second hybrid case would be $2,865,000 [$2,680,000 for abatement for the first hybrid alternative and $185,000 for additional RAC(O) from the end of SWEB6 to SWEB7]. The allowance for the 77 benefited receptors would be $4,235,000. As before, this second hybrid alternative is feasible and cost reasonable, meets the design criteria, and provides a more effective solution for 17 more receptors in areas where barriers were not reasonable. It also provides the most effective alternative for those shielded by the partial version of SWEB6. Segment 3 Cases The third segment considered extends from the Vasco Road overpass for about 0.5 mi to the east and is shown in Figure 22. In this segment, three barriers are proposed: two barriers on

46 the westbound side, SWWB10 and SWWB11, and one barrier on the eastbound side, SWEB11. Because the existing subdivi- sion barriers provide some noise reduction resulting in levels slightly below the NAC threshold, the residences shielded by the SWWB11 barrier do not count as impacted receptors. SWWB11 is actually proposed because a nearby park is currently not shielded and receives a predicted level of 78 dBA. However, some of the alternatives considered produce enough noise reduction to result in benefit to some of the residential receptors. Informa- tion on the proposed barriers is provided in Table 33. A summary of analysis results for Barrier SWWB10 is pro- vided in Table 34. Without a barrier, the traffic noise levels are predicted to range from 68 to 77 dBA, or 2 to 11 dB above the NAC. As in some of the other cases, all abatement alternatives are acoustically feasible except for the ground PCC without a barrier, and only the RAC(O) without a barrier is reason- able for cost. Therefore, none of these alternatives would be considered and no abatement is proposed. Without SWWB11, the predicted levels range up to 78 dBA. As shown in Table 35, the three alternatives that include bar- riers are acoustically feasible and meet the design goal of 7 dB but only the ground PCC with a 12 ft barrier and the RAC(O) with a 12 ft barrier are reasonable for cost. The 14 ft barrier used with the existing PCC is not cost reasonable because of the low number of benefited receptors. A 16 ft barrier was also analyzed for this alternative and found not to benefit any more receptors. Thus, only two 12 ft barri- ers with either of the quieter pavements meet the feasible and reasonable criteria. These two alternatives are nearly equal in effectiveness and NPV for abatement with the RAC(O) with a 12 ft barrier alternative having a small advantage. The summary of the analysis results for Barrier SWEB11, provided in Table 36, indicates levels for the existing pave- ment (without any barrier) ranging from 69 to 81 dBA or 3 Table 33. Description and properties of proposed barriers for Segment 3. Barrier Designation Current Height (ft) Proposed Height (ft) Length (ft) No. of Impacted ReceptorsLT PCC Grd PCC/ RAC(O) SWWB10 0 12 12 800 4 SWWB11 0* 14 12 900 13 SWEB11 0 12 12 900 16 *Excludes existing subdivision sound walls near residences Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 68–77 0 559 – – 13 PCC + 12 ft 3 66–68 2–9 1,113 554 165 Y N Y 4 PCC + Grinding 0 65–74 3 767 207 – N N N 10 PCC + Grinding + 12 ft 4 63–67 5–10 1,321 761 220 Y N Y 3 PCC + RAC(O) 4 62–71 6 707 148 220 Y Y N 7 PCC + RAC(O) + 12 ft 4 62–64 5–13 1,261 632 220 Y N Y 0 Table 34. Summary of analysis results for the SWWB10 barrier. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 64–78 0 629 – – 9 PCC + 14 ft 3 61–70 3–8 1,356 727 165 Y N Y 3 PCC + Grinding 0 62–75 2–3 863 233 – N N N 8 PCC + Grinding + 12 ft 20 59–68 4–10 1,486 857 1,100 Y Y Y 1 PCC + RAC(O) 0 61–74 2–4 796 167 – N N N 7 PCC + RAC(O) + 12 ft 20 59–67 4–11 1,419 790 1,100 Y Y Y 0 Table 35. Summary of analysis results for the SWWB11 barrier.

47 to 15 dB above the NAC. Also, all three alternatives with a bar- rier meet the feasible and reasonable criteria. Another consid- eration is using one of the two viable options for SWWB11 that include a quieter pavement (Table 35) directly opposite the SWEB11 barrier. In this case, the addition of the SWEB11 barrier would increase the abatement NPV by only $623,000 as the cost of the quieter pavement is already included in the SWWB11 barrier cost. An additional benefit for some receptors would be achieved by extending the SWWB10 barrier to the east end of the SWEB11 barrier for a total pavement length of 2,275 ft. In this case, the total abatement cost would be $1,667,000 [$421,000 for the cost of the RAC(O) plus $623,000 for each of the two 12 ft barriers SWWB11 and SWEB11]. The allowance for the total 40 benefited receptors would be $2,200,000. This hybrid alternative is feasible and cost rea- sonable, meets the design criteria, provides benefit for four more receptors in the area, and is the most effective alterna- tive for those shielded by the SWWB11 and SWEB11 barriers. Observations from California Lane Addition (Example A) Cases Several observations can be made from the cases examined in Example A for the HOV lane addition. For the six-lane ide- alized LCCA cases, quieter pavement alone was found not to meet a design goal of 7 dB. Noise reductions meeting acous- tic feasibility requirements of 5 to 6 dB were achieved some- times, but typical reductions were on the order of 3 to 4 dB. Additions to existing barriers were found not to be feasible or reasonable for all the considered cases even when height was extended to the maximum of 16 ft. Quieter pavements com- bined with low-height barriers were found to be effective at reducing noise by 1 to 3 dB. Finally, combining quieter pave- ment with individual barrier alternatives can provide feasible and reasonable noise reduction for highway segments where individual barriers alone would not be feasible and reason- able. Such hybrid solutions were also found in some cases to result in reduced cost and provide lower noise levels for more receptors. Example B: Lane Addition Projects on I-40 and I-485 Two more example case studies were developed based on highway widening projects in North Carolina. For these examples, a variety of different pavement types and tex- tures were considered: transversely tined PCC, S9.5 HMA, and diamond grind. The OBSI one-third octave spectra for these pavements are shown in Figure 23 (OBSI testing was conducted in North Carolina in September 2010 using the SRTT (64). The range of levels for these pavements is suffi- cient to identify quieter and noisier options for potential use in this project. LCCA was completed for each of these proj- ects using construction costs supplied by the North Carolina DOT (NCDOT); the results are summarized in this section (details are provided in Appendix H). The TNM results were generated using models supplied by NCDOT but re-run with the specific OBSI adjustments as done in the previous examples. The results of abatement analysis for each case were com- pared to NCDOT criteria (65) except in examination of cost reasonableness. NCDOT uses a threshold level for noise impact of 66 dBA approaching the federal NAC of 67 dBA. Acoustically feasible options must achieve a noise reduction of 5 dB for at least one impacted receptor. Benefited recep- tors for use in reasonableness determination are receptors that receive a reduction of 5 dB regardless of impact deter- mination. The design goal is 7 dB for at least one front row receptor. NCDOT cost reasonableness is calculated on an allowed square foot of barrier area per benefited receptor up to a maximum of 2,500 ft2 per each receptor. Similar to the MassDOT policy, this method of determining reasonableness cannot be directly applied in the LCCA in which the cost of Table 36. Summary of analysis results for the SWEB11 barrier. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l R an ge (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 69–81 0 629 – – 12 PCC + 12 ft 10 66–71 3–10 1,252 623 550 Y Y Y 2 PCC + Grinding 0 67–79 2 863 233 – N N N 10 PCC + Grinding + 12 ft 16 64–69 5–12 1,486 857 880 Y Y Y 0 PCC + RAC(O) 6 65–76 4–5 796 167 330 Y Y N 7 PCC + RAC(O) + 12 ft 16 62–69 7–12 1,419 790 880 Y Y Y 0

48 barriers is combined with and compared to pavement costs. An average barrier cost of $35/ft2 and allowance of $37,500 per benefited receptor was used for this analysis. I-40 Widening Project The existing highway on I-40 near Raleigh has three lanes of travel in both directions and is constructed of PCC with a semi-random transversely tined texture. In this project, two additional travel lanes are to be added in the median, one in each direction of travel. The project includes the new lanes of travel and new shoulders on the median. Barriers NSA02 SB and NSA02 NB were proposed along the south and north sides of the highway, respectively, to shield primarily residen- tial receptors. An aerial photograph of the project showing the receptors and proposed barrier locations is shown in Fig- ure 24. Another barrier, NSA01, along a two-lane ramp that connects westbound I-40 to eastbound I-440 was evaluated as part of the project (Figure 25). Although this ramp was not altered in the project, a barrier to shield residences to the east and south of the ramp was considered. For the widening project, the following three scenarios were considered: 1. Construction of new lanes and shoulders with PCC (trans- versely tined); future rehabilitation includes diamond grind- ing of all lanes on a 20-year cycle. 2. Construction of new lanes and shoulders with PCC, which is then diamond ground together with the existing lanes; future rehabilitation includes diamond grinding of all lanes on a 20-year cycle. 3. Construction of new lanes and shoulders with PCC and overlay of all lanes with 1 in. S9.5 mm HMA; future rehabil- itation includes mill and overlay all lanes with 1 in. S9.5 mm HMA every 9 years. 70 75 80 85 90 95 100 105 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 1/3 Octave Band Center Frequency, Hz So un d In te ns ity L ev el , d BA I-40 Transverse Tine PCC - 105.2 dBA I-77 S9.5 Asphalt - 98.7 dBA I-77 Diamond Grind - 101.6 dBA Figure 23. SRTT OBSI one-third octave band spectra for pavements used in Example B. NSA02 SB NSA02 NB Source: Google Earth © 2011 Google Figure 24. Location of barriers on I-40 highway widening project near Raleigh, North Carolina.

49 A summary of the costs for these options is provided in Table 37 and details of the barriers and abatement alterna- tives considered for the eastbound and westbound directions are given in Table 38. Details of the LCCA are provided in Appendix G. NSA02 SB Barrier Considering the existing transversely tined PCC as the base- line pavement, the information needed to evaluate feasibility, reasonableness, effectiveness, and costs of the NSA02 SB bar- rier are presented in Table 39. For this case, all of the alterna- tives, except for the ground PCC without a barrier, produce a feasible reduction of 5 dB or more in noise level. To assess cost reasonableness, a $525/dB increase over the existing, current level (typically, 2 dB) per impacted recep- tor was added to the allowance generated by the number of benefited receptors times $37,500 (according to the NCDOT policy). In this manner, cost reasonableness was confirmed for four alternatives: PCC with a 16 ft barrier, ground PCC with a 12 ft barrier, S9.5 HMA with no barrier, and S9.5 HMA with a 12 ft barrier. For the existing PCC with 14 ft barrier alternative, the added height over the 12 ft barriers used for the quieter pavements does not result in a sufficient number of benefited receptors to generate the required allowance. Only the alternatives with barriers meet the design goal reductions of 7 dB or more although the S9.5 HMA without a barrier provides reductions of up to 6 dB. The maximum and average levels for each alternative are shown in Table 39. For this example, effectiveness in Table 39 refers to the maximum predicted levels relative to the low- est maximum level. Three alternatives meet all of the criteria: ground PCC with a 12 ft barrier, S9.5 HMA with a 12 ft bar- rier, and the existing PCC with a 16 ft barrier. Of these alterna- tives, the S9.5 HMA with a 12 ft barrier is 3 dB more effective than the ground PCC with a 12 ft barrier and 6 dB more effec- tive than the PCC with a 16 ft barrier. The S9.5 HMA with a 12 ft barrier produces about twice the benefited receptors as any other option. However, the NPV for the S9.5 HMA with a 12 ft barrier alternative is higher than the NPV for ground PCC with a 12 ft barrier and the PCC with a 16 ft barrier by $151,000 and $273,000, respectively. NSA02 NB Barrier Results of the analysis for the NSA02 NB barrier are shown in Table 40. All of the alternatives, except for the ground PCC without a barrier, are acoustically feasible and all alterna- tives with barriers, except the PCC with a 14 ft barrier, meet the criterion for cost reasonableness. The S9.5 HMA without a barrier is under the allowance and is cost reasonable, but it does not meet the design goal requirement. The S9.5 HMA with the 12 ft barrier is most effective by 3 dB or more but it has the highest NPV cost. Quieter Pavements with Barrier(s) In considering the alternatives that use quieter pavements in combination with both barriers—the ground PCC and the S9.5 HMA with 12 ft barriers—the cost of the quieter pave- ment is common to both barrier alternatives. To analyze these alternatives, the cost of the pavement for the greatest length (3,738 ft for the NSA02 NB barrier) is added to the cost of the two barriers to produce the NPVs shown in Table 41. NSA01 Source: Google Earth © 2011 Google Figure 25. Location of barriers for widening project on I-40 to I-440 ramp near Raleigh, North Carolina. Alternative Agency NPV Cost ($000) No. Description 1 Added PCC Lane Only 4,186 2 Added PCC Lane—All Lanes Ground 5,427 3 Added PCC Lane—S9.5 HMA Overlay 5,942 Table 37. Summary of NPV results for I-40 lane additions. Table 38. Description and properties of proposed barriers for different pavement alternatives for I-40 lane additions. Barrier Designation Current Height (ft) Proposed Height (ft) Length (ft) No. of Impacted Receptors Trans. Tine PCC Grd PCC/ S9.5 HMA NSA02 SB 0 14 & 16 12 1,553 43 NSA02 NB 0 14 & 16 12 3,738 52

50 Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l M ax / A vg (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 77/67 0 1,231 – – 9 PCC + 14 ft 21 74/64 3–9 2,082 851 810 Y N Y 6 PCC + 16 ft 29 74/63 4–11 2,203 972 1,110 Y Y Y 6 PCC + Grinding 0 74/64 3 1,596 365 – N N N 6 PCC + Grinding + 12 ft 38 71/62 5–10 2,325 1,094 1,448 Y Y Y 3 PCC + S9.5 HMA 35 71/62 4–6 1,747 516 1,335 Y Y N 3 PCC + S9.5 HMA + 12 ft 70 68/60 7–12 2,476 1,245 2,648 Y Y Y 0 Table 39. Summary of analysis results for the NSA02 SB barrier. Table 40. Summary of analysis results for the NSA02 NB barrier. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l M ax / A vg (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 76/66 0 2,962 – – 11 PCC + 14 ft 51 70/61 5–10 5,010 2,048 1,940 Y N Y 5 PCC + 16 ft 62 70/60 5–11 5,303 2,340 2,352 Y Y Y 5 PCC + Grinding 0 73/64 2–3 3,841 878 – N N N 8 PCC + Grinding + 12 ft 90 68/59 7–11 5,596 2,633 3,402 Y Y Y 3 PCC + S9.5 HMA 33 70/61 4–5 4,205 1,243 1,265 Y Y N 5 PCC + S9.5 HMA + 12 ft 98 65/58 8–12 5,960 2,998 3,702 Y Y Y 0 Table 41. Cost and allowance results for analysis of combined pavement and barrier alternatives considering both sides of the highway. Abatement Abatement NPV Costs ($000) Benefited Receptors PPC + 16 ft Grd PCC + 12 ft S9.5 HMA + 12 ft PPC + 16 ft Grd PCC + 12 ft S9.5 HMA + 12 ft Pavement – 878 1,243 Barrier NSA02 SB 972 729 729 29 38 70 Barrier NSA02 NB 2,340 1,755 1,755 62 90 98 Total 3,312 3,362 3,727 91 128 168 Cost/Benefited Receptor 36 26 22

51 These costs account for the barriers and the pavement (with the quieter pavement included only once) as it affects recep- tors on both sides of the highway. The total NPV cost for the alternatives using ground PCC and S9.5 HMA are close to the NPV of the PCC with 16 ft barriers. For the S9.5 HMA with 12 ft barriers, the combined NPV costs from Tables 39 and 40 are $4,243,000 compared to $3,727,000 in Table 41. The total number of benefited receptors for the PCC, ground PCC, and S9.5 HMA alternatives is determined from the numbers reported in Tables 39 and 40; the results are shown in Table 41. Therefore, the cost per benefited receptor is lowest for the S9.5 HMA with 12 ft barriers. Consideration of the cost per benefited receptor may be useful in comparing abatement alternatives that have relatively close NPV costs and noise reduction performance. Another alternative to consider would be building the NSA02 NB barrier and using the S9.5 HMA pavement with- out the NSA02 SB barrier. The S9.5 HMA without a bar- rier will produce 35 benefited receptors (Table 39) and the NSA02 NB barrier will produce another 98 for a total of 133 benefited receptors for a total cost of $2,998,000 ($1,243,000 + $1,755,000). This alternative meets all criteria, has the lowest NPV, and has a cost per benefited receptor of $23,000. NSA01 Barrier For the NSA01 barrier (located along the ramp between I-40 and I-440), the NPV costs reflect only the cost of noise abatement as the existing pavement is considered the baseline. The NPV costs for the pavement options, shown in Table 42, consider the future rehabilitation cycle. Two barrier heights (10 and 12 ft), each 1,500 ft long, were considered for this seg- ment. The existing PCC pavement with barrier heights of 10 and 12 ft and the ground PCC with a 12 ft high barrier were evaluated. For the S9.5 HMA, no barriers were evaluated as the levels with this pavement did not produce any impacted receptors. Barrier options were considered for the existing PCC pavement to shield 10 impacted residential receptors and for the ground PCC pavement to shield 3 impacted receptors. The results of the analysis for various alternatives are shown in Table 43. All options except the ground PCC with- out a barrier are acoustically feasible, but only the S9.5 HMA and ground PCC with a 12 ft barrier are reasonable for cost. The ground PCC with a 12 ft barrier alternative achieves the design goal of a 7 dB reduction; the S9.5 HMA pavement does not. However, there are no noise impacts associated with the S9.5 HMA pavement. At a higher cost, the ground PCC with the 12 ft barrier is the most effective alternative in terms of level and number of benefited receptors, and the lowest cost per benefited receptor at $28,750. The S9.5 HMA without a barrier is the second most effective alternative and produces the second highest number of benefited receptors. I-485 Widening Project This case study involves the expansion of an Interstate in North Carolina from four lanes of travel and auxiliary lanes into six lanes of travel. As in the previous case, the new travel lanes will be added to the median on existing shoulders with new shoulders to be added to the inside. The existing roadway is an aged HMA. However, this case study will consider the existing pavement and an assumed existing old PCC pave- ment with transverse texture. An aerial photograph of the project area is shown in Figure 26 with the location of a pro- posed single barrier on the east of the highway. Table 42. Summary of NPV results for pavements on the North Carolina I-40/I-440 ramp. Alternative Agency NPV Cost ($000) No. Description 1 Retain Existing PCC (later rehabs) 346 2 PCC—All Lanes Ground 1,105 3 All Lanes 1 in. S9.5 HMA Overlay 876 Table 43. Summary of analysis results for the NSA01 barrier of the I-40/I-440 ramp. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l M ax / A vg (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 70/59 0 98 – – 8 PCC + 10 ft 12 67/57 2–8 685 587 455 Y N Y 5 PCC + 12 ft 15 65/56 2–9 803 705 568 Y N Y 3 PCC + Grinding 0 67/57 2–4 314 216 – N N N 5 PCC + Grinding + 12 ft 32 62/54 4–12 1,018 920 1,205 Y Y Y 0 PCC + S9.5 HMA 23 64/56 3–6 876 778 868 Y Y N 2

52 For the project, the following five pavement alternatives are considered (two for the existing HMA and three for the assumed PCC pavement): 1. HMA—Construct new lanes and shoulders with HMA. Future rehabilitation includes mill and overlay of all lanes with 1.5 in. of HMA every 12 years. 2. HMA—Construct new lanes and shoulders with HMA and overlay all lanes with 1 in. S9.5 mm wearing surface. The wearing surface will be milled and replaced every 9 years to provide noise performance. 3. PCC—Construct new lanes with PCC (transversely tined) and the shoulders with HMA. Future rehabilitation includes mill and overlay of right two lanes with 1.5 in. of HMA every 12 years and diamond grinding of the left lane on a 20-year cycle. 4. PCC—Construct new lanes with PCC and the shoulders with HMA, and overlay all lanes with 1.5 inches of HMA. Future rehabilitation includes mill and overlay all lanes with 1.5 inches of HMA every 12 years. 5. PCC—Construct new lane with PCC and the shoulder with HMA, and overlay all lanes with S9.5 mm wearing surface. The wearing surface is milled and replaced every 9 years for noise performance. An LCCA was performed for these pavements (details are provided in Appendix G) and a summary of the estimated NPV costs are presented in Table 44. The acoustic perfor- mance of the 1.5 in. HMA overlay and the existing HMA pavement was assumed to be that of TNM Average Pavement. HMA pavement noise levels were measured on NC State Route 268. Two barrier designs of the same length were evalu- ated: one design with a constant height of 25 ft and another with a varied height to provide a constant elevation for the top of the barrier; details are provided in Table 45. Table 46 provides the results for the abatement analysis for the HMA pavement with and without barriers. Only the Figure 26. Location of barrier for widening project on I-485 near Charlotte, North Carolina. Barrier Source: Google Earth © 2011 Google Table 44. NPV results for North Carolina I-485 lane additions. Alternative Agency NPV Cost ($000) No. Description 1 Added HMA Lanes Only 4,035 2 Added HMA Lanes—1 in. S9.5 Overlay 5,080 3 Added PCC Lanes Only 5,093 4 Added PCC Lanes—1.5 in. HMA Overlay 5,884 5 Added PCC Lanes—1 in. S9.5 Overlay 6,197 Table 45. Proposed barriers for North Carolina I-485 lane additions. Barrier Designation Barrier Height (ft) Barrier Length (ft) Barrier Area (ft2) No of Impacted Receptors 25 ft Constant 25 2,698 67,455 HMA - 17 Varied Height Varies 2,698 36,538 PCC - 31 Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l M ax / A vg (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) HMA 0 72/64 0 2,062 – – 13 HMA + 25 ft 38 62/57 7–13 4,423 2,361 1,434 Y N Y 3 HMA + Varied Height 19 69/62 4–9 3,341 1,279 721 Y N Y 10 HMA + S9.5 0 69/62 2–3 2,596 534 – N N N 10 HMA + S9.5 + 25 ft 46 59/55 9–16 4,957 2,895 1,734 Y N Y 0 HMA + S9.5 + Varied Height 41 62/57 7–11 3,875 1,813 1,546 Y N Y 3 Table 46. Summary of analysis results of I-485 for the existing HMA pavement.

53 alternatives that include a barrier meet both the 5 dB acous- tic feasibility criterion and the 7 dB design goal. None of the alternatives meet the cost-reasonableness criterion based on the dollar allowance per benefited receptor, but all bar- rier options meet the reasonableness criterion based on the barrier square feet per benefited receptor. Assuming the cost reasonableness is met using the latter calculation method, the alternative of S9.5 HMA overlay with the 25 ft barrier would provide the most effective acoustic performance based on lowest absolute level and number of benefited receptors, although it has the highest cost. The alternative of S9.5 overlay with the varied height barrier is 3 dB less effec- tive, provides five fewer benefited receptors, and has a lower NPV cost than the same pavement with the 25 ft barrier by $1,082,000. The HMA with a varied height barrier alterna- tive has a lower NPV cost, but it is less effective (by 7 dB) and benefits less than half of the number of receptors. The cost per benefited receptor for all the alternatives with barriers is essentially the same (within $300 of each other) but the S9.5 overlay with 25 ft barrier alternative has the lowest cost per benefited receptor. In cases where several options have similar cost and effectiveness, other considerations may be applied for the selection process. The results for the assumed existing PCC construction with and without barriers are provided in Table 47. The S9.5 overlay without a barrier option is feasible and cost reasonable, but it falls 1 dB short of the design goal and is 10 dB less effective than the most effective alternative (S9.5 with the 25 ft barrier). All barrier alternatives meet the rea- sonableness criterion based on the square feet per benefited receptor and have nearly equal costs per benefited receptor. Of these alternatives, the S9.5 overlay with the 25 ft barrier provides a slightly lower cost per benefited receptor than the HMA overlay with the 25 ft barrier. As for the HMA case, other considerations may be applied for the selection process. Observations from the North Carolina Lane Addition (Example B) Cases In these case studies, the quieter HMA without barrier alter- natives were sometimes found to be feasible and cost rea- sonable; other barrier options were not. In some cases, the effectiveness was found to be within 3 to 5 dB of the lowest absolute level provided by the barrier alternative. Compared to the barrier alternatives, the quieter pavement without a bar- rier had considerable cost advantage although it did not meet a 7 dB design goal for any of the cases. When barriers were eval- uated on both sides of the highway, quieter pavements served both sides of the highway and improved cost-reasonableness considerations. In some situations, quieter pavement benefits receptors on both sides of a highway, which contributes to the barriers’ cost reasonableness because of the lower combined pavement–barrier cost or the increased number of benefited receptors. In some of the cases, several alternatives with dif- ferent NPV costs and effectiveness would meet all criteria. For such cases, a rational approach for trading off NPV cost and effectiveness needs to be considered. The cost per benefited receptor may be an appropriate criterion for comparing alter- natives involving different numbers of benefited receptors. Example C: New Highway Constructions and Realignments For this example case, two projects in Arizona were consid- ered, each involving new construction. One project is a com- pletely new eight-lane highway and the second project is a realignment of an existing four-lane highway. PCC and HMA alternatives are considered for both cases. For PCC alternatives, the final texture is longitudinally tined or the pavement is over- laid with ARFC. The HMA alternative uses an ARFC overlay as a wearing surface. The Goodyear Aquatred OBSI data shown in Figure 27 was used. The pavement and barrier NPV costs Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l M ax / A vg (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 74/66 0 2,602 – – 15 PCC + 25 ft 40 64/59 3–9 4,963 2,361 1,516 Y N Y 5 PCC + Varied Height 21 66/62 4–11 3,881 1,279 804 Y N Y 7 PCC + HMA 0 74/64 2–3 3,007 405 – N N N 15 PCC + HMA + 25 ft 46 62/57 9–15 5,368 2,766 1,741 Y N Y 3 PCC + HMA + Varied Height 39 65/60 6–11 4,285 1,683 1,479 Y N Y 6 PCC + S9.5 23 69/62 5–6 3,167 565 879 Y Y N 10 PCC + S9.5 + 25 ft 48 59/55 11–18 5,527 2,925 1,816 Y N Y 0 PCC + S9.5 + Varied Height 41 62/57 9–13 4,445 1,843 1,554 Y N Y 3 Table 47. Summary of analysis results of I-485 for the assumed PCC pavement.

54 were scaled from the LCCA of the six-lane highway scenario discussed in Chapter 4 (see Table 6). The NPV costs for the pavement (without a barrier) were multiplied by 1.333 for the eight-lane case and by 0.6667 for the four-lane case. The costs for the ARFC overlay were the same as for the RAC(O). Barrier NPV costs were scaled by height relative to the 12 ft high and $27/ft2 barrier used in the earlier example. For the noise-level predictions, TNM results were generated by models provided by ADOT and re-run with the specific OBSI adjustments. The analysis of each alternative for the two cases was compared to ADOT policy (66). ADOT defines “approach- ing” the NAC as 3 dB below 67 dBA or 64 dBA. For acous- tic feasibility, at least half of the impacted receptors must receive a 5 dB reduction. To determine cost reasonableness, benefited receptors are allowed up to $49,000 in costs for noise abatement with the cost of barriers set at $35/ft2 for barriers on grade. To meet the design goal, at least half of the benefited receptors in the first row should receive a 7 dB reduction. New Construction: New Eight-Lane Highway In this project, an existing uncontrolled access, four-lane section of state highway will be completely replaced with an eight-lane access-controlled freeway as an extension of an existing freeway. Currently, one side of the right-of-way contains a relatively high density of residential receptors in several subdivisions. This segment extends about 13,500 ft and a barrier is considered for this entire length. The oppo- site side of the proposed freeway does not have residential receptors, but it has a recreational use area that is consid- ered a sensitive receptor. For this receptor, a barrier with a length of 2,632 ft parallel to the barrier on the opposite side is considered. The following pavement alternatives are considered: 1. Construct all new lanes and shoulders with PCC (longi- tudinally tined). Future rehabilitation includes diamond grinding of all lanes on a 20-year cycle. 2. Construct all new lanes and shoulders with PCC and over- lay all travel lanes with 1 in. thick ARFC. Future rehabili- tation includes mill and overlay of all lanes with 3/4 in. ARFC every 9 years. 3. Construct all new lanes and shoulders with HMA and overlay all travel lanes with 1 in. thick ARFC. Future reha- bilitation includes mill and overlay of all lanes with 3/4 in. ARFC every 9 years. The NPV costs for the 13,500 ft long pavement alternatives of the project are given in Table 48. For noise abatement, barriers with heights of 16 and 10 ft on both sides of the freeway are considered. With one barrier being much shorter than the other, no accounting for the quieter pavement affecting both sides is considered as there is 70 75 80 85 90 95 100 105 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 1/3 Octave Band Center Frequency, Hz So un d In te ni st y Le ve l, dB A ADOT ARFC - 97.0 dBA Long. Tine PCC - 103.3 dBA Figure 27. OBSI one-third octave band spectra for ARFC and longitudinally tined PCC pavements used in Example C.

55 little impact on the cost analysis. The total number of impacted receptors is 249 when both sides are counted. For the analy- sis, new longitudinally tined PCC pavement that produces predicted levels about 1.5 dB higher than TNM Average Pave- ment is considered as the acoustic baseline. The results when compared to ADOT criteria are provided in Table 49. The acoustic performance of the ARFC on either the PCC or the HMA pavement is the same, but the NPV of the HMA is lower than the PCC alternative. Alternatives that include a barrier meet the acoustic feasibility criterion. For the ARFC overlay without a barrier alternatives, the feasibility criterion is not met because a 5 dB reduction is achieved for only 120 receptors (125 required). For cost reasonableness, only three alternatives—the PCC with a 16 ft barrier, the PCC with a 10 ft barrier, and the HMA with ARFC overlay and 10 ft barrier—are below the cost allowance. Thus, only these three alternatives are viable under the ADOT policies. Of these, the PCC with a 16 ft barrier is most acoustically effective and the PCC with a 10 ft barrier is the least effective, but it has the low- est NPV costs. The PCC with a 10 ft barrier alternative provides the lowest cost per benefited receptor because the number of benefited receptors does not change with the decreased bar- rier height although the effectiveness is reduced by 5 dB. The alternative of HMA and ARFC with a 10 ft barrier comes in between the PCC alternatives in terms of cost and effec- Alternative Agency NPV Cost ($000) No. Description 1 New Construction of PCC 27,013 2 PCC & Added 1 in. Overlay of ARFC—9-Year Cycle 34,471 3 HMA & Added 1 in. Overlay of ARFC—9-Year Cycle 30,627 Table 48. Summary of NPV results for the new eight-lane highway construction. Table 49. Summary of analysis results for the eight-lane new highway construction. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l M ax / A vg (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 80/75 0 27,013 – – 16 PCC + 10 ft 224 72/68 10/7 33,326 6,313 10,976 Y Y Y 8 PCC + 16 ft 224 67/65 13/10 37,114 10,101 10,976 Y Y Y 3 PCC + ARFC 120 75/71 5/4 34,471 7,458 5,880 N N N 11 PCC + ARFC + 10 ft 249 69/66 13/9 40,784 13,771 12,201 Y N Y 5 PCC + ARFC + 16 ft 249 64/62 16/13 44,572 17,559 12,201 Y N Y 0 HMA + ARFC 120 75/71 5/4 30,627 3,614 5,880 N Y N 11 HMA + ARFC + 10 ft 249 69/66 13/9 36,940 9,927 12,201 Y Y Y 5 HMA + ARFC + 16 ft 249 64/62 16/13 40,728 13,715 12,201 Y N Y 0 tiveness, but it produces the highest number of benefited receptors. New Construction: Four-Lane Highway Realignment In this project, the existing four-lane highway is being realigned around an existing land use and on/off ramps are being added for an existing intersecting roadway. The high- way remains four lanes and pavement construction alterna- tives are the same as for the previous case. The project length is 9,700 ft. The resulting LCCA NPV costs for the pavements are given in Table 50. Proposed barriers are considered along one side of the roadway for the entire length of the project. Only one barrier height of 12 ft is considered for the PCC and HMA pavements. Eighty-nine impacted receptors could potentially be benefited by these barriers. The results of the analysis are shown in Table 51. For this case, only the alternatives with barriers meet the 5 dB acous- tic feasibility criterion (the maximum reduction provided by the ARFC without a barrier is 4 dB). None of the alternatives meet the cost-reasonableness criteria and only the barrier alternatives achieve the design criterion. The most effective alternatives are the PCC/HMA and ARFC with the 12 ft bar- rier, although they do not meet all criteria. The ARFC overlay

56 on HMA alternative has the lowest NPV cost, but it meets none of the criteria. None of the abatement options meet the criteria largely because of the low density of the receptors over the length of the project. With only 89 impacted receptors over almost 2 mi, insufficient cost allowance is generated even though all receptors would receive a 5 dB benefit or more for all of the barrier cases. This case also presents an example in which a quieter pavement alone could provide an effective solution with a 3 to 4 dB reduction. Observations from New Construction and Realignment (Example C) Cases For the eight-lane new construction, viable alternatives with different barrier heights and pavements were produced, but none of these alternatives meet all required criteria. For example, the design goal of 7 dB cannot be met with the ARFC overlay alone. If the uniform transversely tined texture that was previously used by the agency is considered as the Alternative Agency NPV Cost ($000) No. Description 1 New Construction of PCC 9,715 2 PCC & Added 1 in. Overlay of ARFC—9-Year Cycle 12,397 3 HMA & Added 1 in. Overlay of ARFC—9-Year Cycle 11,015 Table 50. Summary of NPV results per mile for the new four- lane highway realignment. Pavement Type and Barrier Height R ec ep to rs B en ef ite d Pr ed ic te d Le ve l M ax / A vg (d BA ) N oi se R ed uc tio n R an ge (d B) To ta l P ro jec t N PV ($0 00 ) N PV fo r N oi se A ba te m en t ( $0 00 ) R ea so na bl en es s A llo w an ce ($ 00 0) Fe as ib le Co st Re as on ab le D es ig n G oa l Ef fe ct iv en es s ( dB ) PCC 0 72/69 0 9,715 – – 10 PCC + 12 ft 89 66/63 7/5 14,275 4,560 4,361 Y N Y 4 PCC + ARFC 0 68/66 4/3 12,397 2,682 – N N N 6 PCC + ARFC + 12 ft 89 62/60 11/8 16,957 7,242 4,361 Y N Y 0 HMA + ARFC 0 68/66 4/3 11,015 1,300 – N N N 6 HMA + ARFC + 12 ft 89 62/60 11/8 15,575 5,860 4,361 Y N Y 0 Table 51. Summary of analysis of four-lane highway realignment. baseline, the design goal may be met because its OBSI levels are typically 3 to 5 dB higher than for a longitudinally tined PCC pavement (67). ARFC produces reductions of 5 dB but not for 50% of the impacted receptors. The realignment case demonstrates the difficulty of devel- oping any type of noise abatement when the density of the impacted receptors per length of project is low. All three bar- rier alternatives produce the maximum number of benefited receptors; however, none meet all of the criteria. To develop alternatives that meet the criteria, barrier height should be optimized to identify a lower height that would generate the required number of benefited receptors and reduce the NPV costs to make it viable for cost reasonableness. Depending on the concentration of impacted receptors, reducing the length of the barrier or breaking it into multiple shorter segments may also produce viable alternatives. This case also raises the issue of pavement-specific acoustic feasibility and reasonableness crite- ria when no abatement alternative meets a first level of criteria and receptors are impacted at levels well exceeding the NAC.