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19 The provisional recommendations given in the evalua- possible. The forecasted conditions can be developed using tion matrices suggest that engineering judgment is needed to the historical performance data (overall indicator, individual account for other site-specific factors/conditions and for distress types and severities, smoothness, friction, and so on) specific agency practices. Ideally, multiple treatment options collected for the subject pavement and projecting their trends should be identified, such that each option is shown to be to the time in which the preservation activity will occur. at least generally recommended () for all of the identified Depending on the time gap and the historical trends, this distresses and surface characteristics. In some instances, it could greatly affect the types of preservation treatments iden- may be appropriate to consider combining treatments (e.g., tified as being feasible. crack sealing with chip sealing) to increase the number of feasible options. What constitutes a surface characteristic issue depends in Final Identification of Feasible large part on agency policy and the characteristics and demands Preservation Treatments of the project. Generally speaking, the higher the traffic volume Once a preliminary list of feasible treatments has been devel- for a given roadway facility, the lower the maximum accept- oped, further evaluation is needed to determine which of the able threshold for roughness. Also, the more difficult the treatments largely satisfies the needs and constraints of the driving environment (e.g., higher traffic volume, higher speed, project. The evaluation matrices in Tables 3.4 and 3.5 can be more curves and intersections), the higher the minimum used for this purpose. The information presented serves as acceptable threshold for friction. In rural areas, pavementtire a guide with respect to the treatments most commonly and noise is usually not considered an issue, whereas in urban res- successfully used by highway agencies on high-traffic-volume idential areas, the contribution of pavementtire noise (i.e., roadways (subdivided by rural and urban settings) located in at-the-source noise) to overall wayside noise can be an impor- different climatic regions. tant issue. This is particularly true where sound walls do not In these matrices, the appropriateness of a treatment is des- exist, traffic levels and speeds are high, and residences are in ignated by the same series of symbols used in Tables 3.2 and close proximity to the roadway. 3.3 ( for highly recommended down to for not recom- For high-traffic-volume roadways, international roughness mended). In addition to identifying work zone duration index (IRI) values above 100 to 110 in/mi may be perceived as restrictions (i.e., the time period needed following the place- an issue to be addressed by the preservation treatment. IRI val- ment of a treatment until the treated pavement can be opened ues greater than 150 to 200 in/mi may be more indicative of the need for major rehabilitation. For high-speed (50 mph), to traffic) associated with each treatment, these matrices also high-traffic-volume roadways, smooth-tire 40-mph friction provide expected treatment performance ranges and relative number (FN40S) values below 30 to 32 may be perceived as treatment cost information. The expected performance ranges marginal or too low, prompting the need for a restoration are based on high-traffic-volume application, but do not take treatment. Good practice dictates that this need be confirmed into account the effects of existing pavement condition, cli- by examining wet-weather accident rates along the project mate, and construction quality risk. To account for these fac- length. Although there is no nationally recognized require- tors on each candidate treatment, it is suggested that values ment for the maximum level of noise (either at the source or near the lower limit of the performance range be used for at a point on the wayside) that can be generated by a highway pavements in fair condition and located in a severe climate pavement, it should be pointed out that the quietest pave- (i.e., deep-freeze climate zone). On the flip side, it is suggested ments generate on-board sound intensity (OBSI) levels (at-the- that values near the upper limit of the range be used for pave- source noise) between 96 and 102 dB(A), whereas the loudest ments in good condition and located in a mild climate (i.e., pavements generate OBSI levels in the 108 to 112 dB(A) range. nonfreeze climatic zone). Depending on the characteristics of a project located in a noise- A logical, systematic way of accounting for construction sensitive environment, OBSI values above 106 to 108 dB(A) quality risk is to apply a confidence factor to the expected per- may be perceived as an issue to be addressed by the preserva- formance range, with a factor of 1.0 representing 100% con- tion treatment. fidence, 0.75 representing 75% confidence, and so on. Thus, Finally, although the current age and conditions can be if the expected performance of a treatment ranges from 4.0 used to identify feasible treatments, it is important to con- to 6.0 years and the level of confidence is 75% (reflecting sider when the preservation activity is expected or scheduled some shortcomings in agency/contractor experience and/ to occur. If there is a significant gap (1 year) between the or materials quality), then the range would be reduced to time the latest condition data were collected and the time the between 3.0 to 4.5 years. treatment is likely to be constructed, then it is recommended In addition to the treatment performance and relative cost that treatment selection be based on forecasted conditions, if information (which could be impacted by funding constraints)

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20 Table 3.2. Feasibility Matrix for Preliminary Identification of Candidate Preservation Treatments for HMA-Surfaced Pavements Distress Types and Severity Levels (L Low, M Medium, H High) Surface Distress Cracking Distress Window of Water Fatigue/ Opportunity Ravel/ Bleed/ Segre- Bleed/ Long WP/ Trans Joint Long/ Weather Flush Polish gation Pumpa Slippage Block Therm Reflect Edge Preservation PCI/ Age Treatment PCR (yr) L/M/H -- -- L/M/H -- L/M/H L/M/H L/M/H L/M/H L/M/H Crack fill 7590 36d Crack seal 8095 25 d Slurry seal (Type III) 7085 58 Microsurfacing: Single 7085 58 Microsurfacing: Double 7085 58 Chip seal: Single Conventional 7085 58 Polymer modified 7085 58 Chip seal: Double Conventional 7085 58 Polymer modified 7085 58 Ultra-thin bonded 6585 510 wearing course Ultra-thin HMAOL 6585 510 Thin HMAOL 6080 612 Cold milling and 6075 712 thin HMAOL Hot in-place recycling Surf recycle/HMAOL 7085 58 Remixing/HMAOL 6075 712 Repaving 6075 712 Cold in-place recycling 6075 712 and HMAOL Profile milling 8090 36 Ultra-thin whitetopping 6080 612 Note: = Highly Recommended; = Generally Recommended; = Provisionally Recommended; = Not Recommended. a Porous surface mix problem. b Rutting primarily confined to HMA surface layer and largely continuous in extent. c Corrugation/shoving primarily HMA surface layer mix problem and frequent in extent. d For composite AC/PCC pavements, a more probable window of opportunity is 24 years for crack filling and 13 years for crack sealing. e Localized application in the case of bumps. (continued on next page)

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21 Table 3.2. (continued) Distress Types and Severity Levels Surface Deformation Distress Characteristics Issues Wear/ Stable Corrug/ Bumps/ Ride Ruttingb Shovec Sags Patches Quality Friction Noise Preservation Treatment L/M/H L/M/H L/M/H L/M/H -- -- -- Crack fill Crack seal Slurry seal (Type III) Microsurfacing: Single Microsurfacing: Double Chip seal: Single Conventional Polymer modified Chip seal: Double Conventional Polymer modified Ultra-thin bonded wearing course Ultra-thin HMAOL Thin HMAOL Cold milling and thin HMAOL Hot in-place recycling Surf recycle/HMAOL Remixing/HMAOL Repaving Cold in-place recycling and HMAOL Profile milling e e Ultra-thin whitetopping