Short-Term Effect of Pavement Surface Aging on Tire Pavement Noise Measured with Onboard Sound Intensity Methodology

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1 Short-Term Effect of Pavement Surface Aging on Tire Pavement Noise Measured with Onboard Sound Intensity Methodology Daniel E. Mogrovejo, Gerardo W. Flintsch, Edgar D. de León Izeppi, Kevin K. McGhee, and Ricardo A. Burdisso This paper compares the potential short-term noise reduction generated by the use of two quiet concrete technologies [Next Generation Concrete Surface (NGCS) and conventional diamond grind] and three quiet asphalt surfaces (porous friction course surfaces with and without rubber and different maximum-sized aggregates) with control pavement sections (conventional transverse-tined portland cement concrete pavement and stone matrix asphalt pavement surface). The potentially quiet pavement surfaces were placed along five demonstration projects in Virginia. This paper investigates the susceptibility of the proposed surfaces to external factors, such as aging (four seasons were involved) and air temperature differentials. The statistical analysis of the collected data showed that all proposed surfaces presented benefits in terms of noise reduction; the NGCS exhibited noise reduction potential as high as 5 db(a) when compared with the control section. For the asphalt surfaces, the sections with higher amounts of voids showed the lowest noise levels. In addition, the rubber-modified mixes showed an improved noise reduction potential. Air temperature normalization was performed, and air temperature was found to have a significant influence on the noise measurements, especially during the first months of use. porous friction course (PFC) mixes (different thicknesses, different aggregate sizes, and one rubberized); the concrete technologies were conventional diamond grind (CDG) and Next Generation Concrete Surface (NGCS). These proposed quiet overlays (or technologies) were compared with the following control sections: (a) a stone matrix asphalt (SMA) pavement surface (1.5 in. thick; maximum aggregate size of 9.5 mm) with a PG binder, and (b) a conventional transverse-tined surface (1). The word quiet used throughout this paper to define the proposed overlays does not represent bias. Objective The objective of this paper is to assess the short-term performance of the quiet pavement surfaces in terms of noise reduction when compared with that of the typical asphalt and concrete surfaces used in Virginia. The paper investigates the rate of change in noise levels attributable to external factors, such as environmental effects and air temperature differentials. This paper presents a practical application of the onboard sound intensity (OBSI) methodology used to determine the change in the noise levels of pavement surfaces over time. The initial effects of the environment on tire pavement noise, as measured on different pavement surfaces, are investigated. Four sets of seasonal tests were performed on five projects located in the state of Virginia to determine the rate of change in noise measurements over a longer time frame. Three asphalt surfaces and two concrete surfaces were constructed along five strategic projects to compare their performance in terms of noise reduction against that of the asphalt or concrete (as applicable) control sections. The asphalt surfaces comprised three D. E. Mogrovejo, Charles Via, Jr., Department of Civil and Environmental Engineering, and G. W. Flintsch and E. D. de León Izeppi, Center for Sustainable Transportation Infrastructure, Virginia Tech Transportation Institute, Virginia Polytechnic Institute and State University, 3500 Transportation Research Plaza, Blacksburg, VA K. K. McGhee, Virginia Center for Transportation Innovation and Research, 530 Edgemont Road, Charlottesville, VA R. A. Burdisso, Acoustical and Vibrations Engineering Consultants; Mechanical Engineering Department, 153 Durham Hall, Virginia Polytechnic Institute and State University, Blacksburg, VA Corresponding author: D. E. Mogrovejo, danielmc@vt.edu. Transportation Research Record: Journal of the Transportation Research Board, No. 2403, Transportation Research Board of the National Academies, Washington, D.C., 2014, pp DOI: / Background Recent research has shown a strong relationship between pavement texture and noise (in terms of A-weighted decibels), particularly in those spectra that contribute most to the overall sound intensity level (IL), as measured with the OBSI method (2). For the tire pavement noise to be minimized, the texture of a pavement surface should be small (i.e., depths of less than 5 mm) and negative (i.e., a flat surface with no spikes). Increased megatexture (a wavelength of 50 to 500 mm) generates more low-frequency noise because of the increased tire vibrations. Porous surfaces tend to reduce noise in the higher frequency range and, therefore, provide overall noise reduction. Moreover, macrotexture (a wavelength of 0.5 to 50 mm) appears to be the primary geometric aspect in the achievement of noise reduction. Microtexture (a wavelength of less than 0.5 mm), megatexture, porosity, and structural response are secondary (3). NCHRP Synthesis of Highway Practice 268 summarizes a significant number of studies that have examined the relationship between different pavement textures and noise levels. Some of the findings show that portland cement concrete pavements are generally noisier than asphaltic surfaces and that transverse tining is typically noisier than longitudinal tining or asphaltic surfaces; a 1-in. separation in transverse tines has been shown to be the most annoying surface in terms of noise (4). 17

2 18 Transportation Research Record 2403 One alternative that may reduce noise is the use of mixes with high porosity. Porosity helps with noise absorption and reduces the tire pavement contact area, especially when porosity exceeds 20%. Pavement stiffness is another characteristic that can impact noise, and it has been demonstrated that a decrease in pavement stiffness decreases the noise generated on the pavement. Pavements that have stiffness characteristics approaching that of a tire can be quieter than those constructed with typical asphalt and concrete (5), and research has shown that rubber can help to lower the stiffness (6). Open-graded asphalt has been reported to be the quietest asphalt surface, on the basis of research conducted worldwide, but it is important that the porosity stay high (greater than 20%) over time (4). Another study showed that all porous pavements produced additional sound attenuation when compared to nonporous pavements and that the depth of the porous layer was an important factor for additional attenuation (7). This depth was effective up to a certain degree, but declining benefits then occurred. The literature also suggests that the effect of temperature is different when measured across different surfaces. The temperature effect is comparatively larger for a rough-textured surface than for a smooth-textured surface (8). Researchers at Purdue University found that, for concrete surfaces, different pavement finishes have different impacts on tire pavement noise [as cited by McGhee et al. (1)]. The study found that the quietest concrete surface that had so far been investigated was the NGCS. The NGCS is the result of various steps involving CDG followed by a flush-grind operation and a longitudinal grooving step (1). Researchers have noted that NGCS is promoted by the concrete paving and grooving and grinding industries as the quiet concrete pavement finish (1). Because of the standardized construction process, NGCS pavements represent a consistent, predictable, and quiet nonporous concrete texture. Expected noise levels across these surfaces are generally 99 db(a) (at 60 mph) at the time of construction and increase by several A-weighted decibels over time. NGCSs have been shown to facilitate improved lateral stability and better hydroplaning resistance and therefore provide benefits beyond noise reduction (9). The NGCS also enables the collection of consistent noise measurements from different locations as a result of its systematic construction process (10). Complete specifications and details about the NGCS can be found in Scofield (9). Finally, in terms of the motivation of this study (the finding of quieter pavements as a potential alternative for traffic noise mitigation and its performance over time), to reduce overall traffic noise, it appears to be more effective to aim for quieter roads than quieter tires or engines. The potential for traffic noise reduction with increasing speed proved to be more significantly influenced by the road than by the tire or the engine. For example, the reduction potential at 60 mph (97 km/h) for the road is approximately 10 db; the potential reductions for the tire and the engine are only 4 and 2 db, respectively (11). There is no information yet available about noise reduction properties over time for the surfaces evaluated in this study (a situation that also motivates the study); the potential for traffic noise mitigation over the long term is critical to defining the real performance of these proposed surfaces. Methodology and Description of Test Parameters Tire pavement noise was measured by following AASHTO TP The Virginia Tech Transportation Institute OBSI equipment (shown in Figure 1a) was used during the test (12). The schematic model of the system is shown in Figure 1b (full OBSI system model, Acoustical and Vibrations Engineering Consultants, Inc., 2012). (a) (b) FIGURE 1 Virginia Tech Transportation Institute OBSI system (12): (a) equipment and (b) schematic.

3 Mogrovejo, Flintsch, de León Izeppi, McGhee, and Burdisso 19 FIGURE 2 Locations of five projects for Virginia Quiet Pavement Implementation Program (13) (A 5 asphalt; C 5 concrete). Test Equipment The test equipment comprised The Virginia Tech Transportation Institute OBSI system, which included Acoustic measurement instrumentation [one sound calibrator; four 0.5-in. microphone preamplifiers, two pairs of 0.5-in. condenser microphones for sound intensity, four 10-m extension cables, two spherical windscreens (90 mm in size) for 0.5-in. microphones, one microphone power module with four channels, and the physical parts for assembly] and OBSI software, Versions 1.00 and 1.43, licensed to the Virginia Tech Transportation Institute (Copyright, 2007 to 2011, Acoustical and Vibrations Engineering Consultants, Inc.); A 2011 sedan with a gross vehicle weight rating of 2,064 kg (4,549 lb); the sedan was used for all OBSI measurements; A P225/60R16 97S radial standard reference test tire (SRTT), which was used for all OBSI measurements (the tire was selected according to ASTM F 2493); A Type A durometer, which was used for the hardness measurements performed on the SRTT before every set of OBSI testing [the durometer was chosen according to Section X1(Durometer Selection Guide) of ASTM D (2010)]; A pocket weather tracker, which was used to calculate air temperature, wind speed, barometric pressure, air density, and relative humidity for all OBSI measurements; and A Class 2 laser thermometer, which was used for pavement temperature measurements. All the measurements were taken in the outer lane. The speeds and time frames [60 mph (96.6 km/h) and 440 ft (134 m), respectively] were constant for all runs, in accordance with AASHTO TP Each set of runs was conducted in a time frame during which the environmental conditions were considered the same or within an acceptable 5 F range of variability. The tire inflation pressure was 30 ± 2 psi ( ± kpa). The wind speed measurements, the hardness of the SRTT rubber, the pavement temperature, the barometric pressure, and the air density were also recorded for each set of runs. Sites Five strategic sites were selected within the state of Virginia. Figure 2 depicts the locations of the sites. The latest traffic data for the projects (2011) are presented in Table 1. A detailed layout of the projects and sections can be seen in Figure 3, and a description of the pavement surfaces for each of the projects is provided in Figure 4. All the sections were around 1 mi long (a length of more than 440 ft was required according to standard requirements for section lengths). Results The results presented correspond to the measurements taken during fall 2011, spring 2012, fall 2012, and spring 2013 for the five demonstration projects. The results are reported as overall A-weighted Test Procedure The test procedure for each of the five projects was as follows: The equipment was calibrated in accordance with the manufacturer s specifications before the actual experiments. Measurements were taken in complete loops that covered both directions of all the proposed surfaces and the control surfaces. The number of loops made was relative to the minimum number of valid runs that needed to be recorded for all sections; a minimum of three valid runs for each section (and each direction) were recorded. TABLE 1 Average Daily Traffic and Four-Tire Percentage for All Projects Project ADT Four Tire (%) Project ADT Four Tire (%) SR-7 56, I , SR , SR-76 28, SR , Note: The four-tire percentage refers to light vehicles. ADT = average daily traffic.

4 20 Transportation Research Record 2403 FIGURE 3 Section configurations for all projects (AR 5 asphalt rubber; VA 5 Virginia; trans. tined PCCP 5 transverse-tined portland cement concrete pavement).

5 Mogrovejo, Flintsch, de León Izeppi, McGhee, and Burdisso 21 Asphalt control section (a) (b) (c) (d) Concrete control section (e) (f) (g) FIGURE 4 Pavement surfaces for all projects: (a) SMA 9.5: PG , NMSA mm, VTM ~ 3.95%, 1.5 in. thick, 180 lb/yd 2 in SR-7, 165 lb/yd 2 in SR-199 and SR-288; (b) AR-PFC 9.5: 1 in. thick, NMSA mm, VTM % 17.10%, 95 lb/yd 2 in SR-7, 90 lb/yd 2 in SR-199 and SR-288; (c) PFC 9.5: PG , 1 in. thick, NMSA mm, VTM % 17.10%, 95 lb/yd 2 in SR-7, 90 lb/yd 2 in SR-199 and SR-288; (d) PFC 12.5: PG , 2 in. thick in SR-7, 1.5 in. thick in SR-199 and SR-288, NMSA mm, VTM % 17.5%, 190 lb/yd 2 in SR-7, 180 lb/yd 2 in SR-199, 135 lb/yd 2 in SR-288; (e) trans. tined PCCP; (f) NGCS; and (g) CDG (VTM 5 voids in total mix; NMSA 5 nominal maximum size of aggregate). sound ILs and were calculated through the use of A-weighted, one-third octave band levels. (A-weighting is the filter most commonly used to make overall noise measurements. The attenuation of the sound with an A-weighted filter corresponds to the fact that the human ear is not as sensitive to the sound of lower frequencies as it is to the sound of higher frequencies.) Validation For only valid runs to be used during the analysis of the field data, AASHTO TP was used to meet the following criteria: Coherence. The coherence of sound pressure between the two microphones of the sound intensity probe shall be equal to or greater than 0.8 for each one-third octave band with a center frequency between 400 and 4000 Hz and equal to or greater than 0.5 for the one-third octave band with a center frequency of 5000 Hz (AASHTO TP 76-12). Pressure intensity index. The [pressure intensity] index shall be less than 5.0 db in each one-third octave band with a center frequency between 400 and 5000 Hz (AASHTO TP 76-12). Direction of the sound intensity vector. [M]ust be positive for each one-third octave band with a center frequency between 400 and 5000 Hz (AASHTO TP 76-12).

6 22 Transportation Research Record 2403 Standard deviation. The standard deviation of the overall ILs from the multiple valid runs shall be no greater than 0.6 dba.... The standard deviation of the ILs from the multiple valid runs within any one-third octave band with a center frequency between 400 and 5000 Hz shall be no greater than 1.2 dba (AASHTO TP 76-12). Data Reporting AASHTO TP was used to report the following data: For a single run, the results were reported as A-weighted sound ILs (A-weighted decibels referenced to 1 pw/m 2 ) for each frequency defined on the one-third octave band scale (hertz). For each set of valid runs, the average overall sound IL (A-weighted decibels referenced to 1 pw/m 2 ) was reported. Measurements Table 2 presents the meteorological and tire conditions for the four periods of the field experiments. For all five projects, a minimum of two valid runs was taken for each section in each direction. In most of the cases, three to seven valid runs were averaged to find the overall ILs in A-weighted decibels. The results of the average overall ILs (in A-weighted decibels) for all the seasonal sets of runs are summarized in Tables 3 and 4. TABLE 2 Test Conditions for All Periods Project Condition SR-7 SR-199 SR-288 I-64 SR-76 Fall 2011 Date 2/17/ /19/ /20/ /19/ /20/2011 Time 10:39 14:10 10:30 10:25 13:04 Air temperature ( F) Pavement temperature ( F) Barometric pressure (inhg) Air density (lb/ft 3 ) Wind speed (mph) Durometer reading Spring 2012 Date 4/9/2012 4/12/2012 4/11/2012 4/11/2012 4/10/2012 Time 15:52 10:30 10:35 16:40 15:30 Air temperature ( F) Pavement temperature ( F) Barometric pressure (inhg) Air density (lb/ft 3 ) Wind speed (mph) Durometer reading Fall 2012 Date 10/23/ /14/ /14/ /15/ /14/2012 Time 13:02 14:25 9:23 10:00 11:30 Air temperature ( F) Pavement temperature ( F) Barometric pressure (inhg) Air density (lb/ft 3 ) Wind speed (mph) Durometer reading Spring 2013 Date 4/1/2013 4/3/2013 4/2/2013 4/3/2013 4/2/2013 Time 12:18 10:30 13:30 14:00 12:05 Air temperature ( F) Pavement temperature ( F) Barometric pressure (inhg) Air density (lb/ft 3 ) Wind speed (mph) Durometer reading Note: inhg = inches of mercury.

7 Mogrovejo, Flintsch, de León Izeppi, McGhee, and Burdisso 23 TABLE 3 Average Overall IL for All Periods: SR-7, SR-199, I-64, and SR-76 Average Overall IL Measured [db(a)], by Season and Direction Fall 2011 Spring 2012 Fall 2012 Spring 2013 Project East West East West East West East West SR-7 1. SMA AR-PFC PFC PFC SR SMA AR-PFC PFC PFC SMA I NGCS CDG Trans. tined PCCP SR NGCS CDG Trans. tined PCCP Note: = different surface treatment had been applied to this section; therefore, noise measurements were not taken. TABLE 4 Average Overall IL for All Periods, SR-288 Average Overall IL Measured [db(a)], by Season and Direction Fall 2011 Spring 2012 Fall 2012 Spring 2013 Section North South North South North South North South 1. SMA AR-PFC PFC PFC SMA The actual air temperature at the time of the testing was used in the calculation of these results. Analysis Noise Reduction Performance The information presented in Table 3 was analyzed statistically, and the results are presented in Figure 5. (Figure 5, a to d, depicts the noise results for fall 2011, spring 2012, fall 2012, and spring 2013, respectively.) The analysis sorted the data by surface type or pavement technology in the linear scale. Equation 1 was used to convert the IL values in the logarithmic scale into linear data; those IL values were then transformed back to the logarithmic scale with Equation 2. IL IL = 10 log scale 10 (1) linearscale IL = 10 p log IL (2) log scale 10 linearscale The performance of the studied surfaces follows a consistent and somewhat expected trend. For the concrete sections, the two proposed surfaces (CDG and NGCS) are quieter than the control section (transverse-tined portland cement concrete pavement); there is a measurable average decrease in noise of 2 db(a) for the CDG and a measurable and noticeable decrease of more than 5 db(a) for the NGCS. The NGCS is therefore a significantly better technology for concrete projects designed to decrease noise. Another advantage is that the NGCS seems to be the most reliable in terms of noise variability between different locations. Given the potential for improved lateral stability and the better hydroplaning resistance benefits of the NGCS, it is reasonable to conclude that this technology represents an attractive option as a quiet surface for concrete pavement projects. The reduced variability shown for transversally tined portland cement concrete pavement in the fall 2012 measurements probably resulted from the smaller sample after the control section on I-64 was rehabilitated. For the asphalt surfaces, the variability in the data is appreciably larger. However, some clear trends can be found. For all the seasons, the tendency shows that all the candidate quiet porous sections are quieter than the asphalt control section. The addition of rubber also

8 24 Transportation Research Record 2403 Overall IL [db(a) Ref. 1 pw/m 2 ] Overall IL [db(a) Ref. 1 pw/m 2 ] Overall IL [db(a) Ref. 1 pw/m 2 ] Overall IL [db(a) Ref. 1 pw/m 2 ] (a) (b) (c) seems to have a positive effect on noise reduction. The single quietest measurement of noise corresponds to the rubberized surface. These trends confirm the results found in the literature that more voids and less stiffness in the pavement surface create noticeable reductions in noise for asphalt sections. Susceptibility to Air Temperature To compare ILs during different seasons (with and without the influence of air temperature variability), the data for all the tests (each individual value before averaging) were normalized to a standard air temperature of 68 F (20 C) with Equation 3. IL normalized = IL measured + [ α ( measured airtemperature standard airtemperature )] (3) IL normalized and IL measured are given in A-weighted decibels, the correction factor α is given in A-weighted decibels per degree Fahrenheit, and the measured and standard air temperatures are in given in degrees Fahrenheit. The standard air temperature of 68 F (20 C) was chosen in accordance with AASHTO TP (draft standard). The standard also recommends a value of α = 0.04 db(a)/ F for Equation 3. However, experiments conducted on a Virginia surface have suggested that a correction parameter of α = 0.05 db(a)/ F may be more appropriate for the state (12). Therefore, this latter value of α was used in the formula, as shown in Equation 4: measured [ ( ) [ ( ) ( )]] IL ( db( A) ) = IL ( dba ( )) db( A ) F normalized airtemperature F 68 F (4) Figure 6 summarizes the average performance for all the surfaces investigated. Figure 6a presents the average overall ILs (or noise levels) in A-weighted decibels for data without normalization (and shows the influence of external factors such as air temperature). Figure 6b depicts the same noise levels but with the normalized data (without air temperature influence). A comparison of Figure 6, a and b, shows that air temperature has an influence on the data and that normalization helps when comparisons are required between the data from different seasons without air temperature influence. After normalization, the noise variation over time becomes small, especially for the concrete surfaces. For the porous asphalt surfaces, all the variations are in the order of 0.1 to 0.3 db(a) within the first two periods; this result indicates a small variation of noise over time for the first months, after which there is a slight increase in noise levels. This increase may be attributable to different factors, such as the clogging of the voids. Factors other than air temperature may be affecting the SMA 9.5 surface. Macrotexture, for example, differs between the SMA and the porous materials. The measurements show that the three PFC materials lost more macrotexture than the SMA surfaces (1). However, that analysis shows the preliminary results of a longer-term study. Pavement Technology (d) FIGURE 5 Box and whisker plots for all pavement technologies over time: (a) fall 2011, (b) spring 2012, (c) fall 2012, and (d) spring 2013 (red dots 5 mean). Statistical Analysis To state the significance of the rate of change in noise over time, twosample paired t-tests were performed for each pavement surface type and for each time frame: fall 2011 to spring 2012, spring 2012 to fall 2012, and fall 2012 to spring 2013 (14). The analysis was made with and without air temperature normalization.

9 Mogrovejo, Flintsch, de León Izeppi, McGhee, and Burdisso 25 OBSI [db(a)] OBSI [db(a)] (a) Pavement Technology (b) FIGURE 6 Average overall ILs (noise) variation over time (a) without and (b) with normalization (for each pavement technology, bars from left to right show ILs for fall 2011, spring 2012, fall 2012, and spring 2013). Two-Sample Paired t-test In the two-sample paired t-test, the following assumptions were met: Data are naturally paired. The noise levels measured during the four seasons are dependent within each other and measured in the same section, the same milepost, and the same lane. The number of measurements is the same. The same number of values before (e.g., fall 2011) and after (e.g., spring 2012) are used for each season and for each surface type (e.g., PFC 9.5). t S obs D The following formulations were used: y y = SD n = where 1 2 n 1 ( di ( y1 y2) ) n 1 i= 1 2 t obs = appropriate test statistic used for analysis and defined as observed t-value that will be compared with t n 1,α/2 value chosen from t-table (14); (5) (6) n 1 = degrees of freedom of test; α = level of confidence chosen for analysis (α = 0.05 is used and represents a 95% confidence level); y1 and y 2 = means of all overall ILs of specific pavement surface types for before (e.g., fall 2011) and after (e.g., spring 2012) measurements, respectively; S D = standard deviation of individual average overall ILs with respect to difference of means ( y 1 y 2 ), shown in Equation 6; n = number of measurements (number of average overall ILs) for each section for each project (because paired data are used, n is equal for before and after periods); and d i = ith difference of average overall ILs of two seasons: before after measurements (e.g., spring 2012 average overall IL fall 2011 average overall IL). The following hypothesis was stated: the rate of change in noise levels from one season to the next is considered statistically significant if t obs > t n 1,α/2. An example of the two-paired t-test is presented in Table 5 for the NGCS, without air temperature normalization and for the period fall 2011 to spring All the statistical tests were conducted for all the sections, with and without air temperature normalization, for the

10 26 Transportation Research Record 2403 TABLE 5 Two-Sample Paired t-test for NGCS, from Fall 2011 to Spring 2012 Fall 2011 Spring 2012 t obs Section y 1i y _ 1 y 2i y _ 2 y _ 2 y _ 1 d i S D t obs t 3,0.025 SR-76 1W SR-76 1E I-64 1W I-64 1E Note: n = 4. following periods: fall 2011 to spring 2012, spring 2012 to fall 2012, and fall 2012 to spring These results are shown in Table 6. Because t obs > t n 1,α/2 for the NGCS example, the conclusion is that there is sufficient information to confirm that the rate of change in noise levels for the NGCS from fall 2011 to spring 2012 is statistically significant. The results for all the sections are presented below. The control asphalt section (SMA 9.5) shows a statistically significant change in the noise levels for both periods, with and without air temperature influence, and for all time frames. For the porous sections, the control concrete section, and the NGCS, the noise variations without air temperature influence are not statisti- TABLE 6 Statistical Analysis Before and After Air Temperature Normalization Time Frame Section Statistically Significant Rate of Change for Noise Levels Over Time With Air Temperature Influence Fall 2011 to Control spring 2012 SMA 9.5 Yes Yes Trans. tined PCCP Yes No Porous AR-PFC 9.5 Yes No PFC 9.5 Yes No PFC 12.5 Yes No Concrete NGCS Yes No CDG No No Spring 2012 to Control fall 2012 SMA 9.5 Yes Yes Trans. tined PCCP No No Porous AR-PFC 9.5 No No PFC 9.5 No No PFC 12.5 Yes Yes Concrete NGCS No No CDG No No Fall 2012 to Control spring 2013 SMA 9.5 Yes Yes Trans. tined PCCP No No Porous AR-PFC 9.5 No No PFC 9.5 No No PFC 12.5 No No Concrete NGCS No No CDG Yes No Without Air Temperature Influence (normalized) cally significant for all periods, except for PFC 12.5 during spring 2012 to fall However, this isolated case may be attributable to high variability (e.g., different contractors for different sites of this surface type). This is a short-term analysis of the data, and further testing of noise levels is recommended. Conclusions The following conclusions can be drawn from the results obtained during this short-term evaluation: The tested quiet concrete surfaces presented benefits in terms of noise reduction when compared with the control section (original transverse-tined portland cement concrete pavement). The NGCS presented noise reduction potential as high as 5 db(a), as measured under the OBSI method. The tested quiet porous asphalt surfaces (voids in total mix values from 16.1% to 17.5%, with and without rubber) also presented benefits in terms of noise reduction when compared with the SMA 9.5 control section (voids in total mix values 4%). On average, the noise reduction reached more than 3 db(a) for some of the analyzed technologies. On average, the rubber-modified mixes also showed a slightly better noise reduction potential (e.g., the AR-PFC 9.5 versus the PFC 9.5 average ILs). The normalized noise ILs over time showed a small decrease within the first months of service for the concrete and the porous asphalt surfaces [variations were in the order of 0.1 to 0.3 db(a)], followed by a small increase in noise levels during the third period. From that point it appeared that noise levels began a steady trend. The noise variations without air temperature influence were not statistically significant for the porous sections, the transverse-tined portland cement concrete pavement, or the NGCS. Air temperature normalization was important in the analysis of the noise variations because it enhanced the analysis of other factors that influenced the change in noise over time. Acknowledgments This paper was conducted as part of the Virginia Quiet Pavement Implementation Program with the support of the Virginia Center for Transportation Innovation and Research and the support and guidance of the Virginia Quiet Pavement Task Force, a cooperative entity that represents the Materials, Maintenance, and Environmental Divisions of the Virginia Department of Transportation, the Virginia Center for Transportation Innovation and Research, the Virginia Asphalt Association, the American Concrete Paving Association, the Virginia asphalt contracting industry, and the Virginia General Assembly. The authors

11 Mogrovejo, Flintsch, de León Izeppi, McGhee, and Burdisso 27 thank William Hobbs of the Virginia Tech Transportation Institute, who provided support during the field tests. References 1. McGhee, K. K., E. D. de León Izeppi, G. W. Flintsch, and D. E. Mogrovejo. Virginia Quieter Pavement Demonstration Projects: Initial Functional Assessment. In Transportation Research Record: Journal of the Transportation Research Board, No. 2362, Transportation Research Board of the National Academies, Washington, D.C., 2013, pp Rasmussen, R. Measuring and Modeling Tire Pavement Noise on Various Concrete Pavement Textures. Noise Control Engineering Journal, Vol. 57, No. 2, 2009, pp Gagarin, N. Relating Pavement Macrotexture Patterns to Tire Pavement Interaction Noise Levels. Presented at Pavement Evaluation 2010, Roanoke, Va., Wayson, R. L. NCHRP Synthesis of Highway Practice 268: Relationship Between Pavement Surface Texture and Highway Traffic Noise. TRB, National Research Council, Washington, D.C., Bernard, R., and R. L. Wayson. An Introduction to Tire/Pavement Noise of Asphalt Pavement. Asphalt Pavement Alliance, Lanham, Md., Rasmussen, R. O., R. J. Bernhard, U. Sandberg, and E. P. Mun. The Little Book of Quieter Pavements. Report FHWA-IF FHWA, U.S. Department of Transportation, Donavan, P. R. Tire Noise Generation and Propagation over Porous and Nonporous Asphalt Pavements. In Transportation Research Record: Journal of the Transportation Research Board, No. 2233, Transportation Research Board of the National Academies, Washington, D.C., 2011, pp Sandberg, U., and J. A. Ejsmont. Tyre/Road Noise Reference Book. Informex, Kisa, Sweden, Scofield, L. Development and Implementation of the Next Generation Concrete Surface. Final report. American Concrete Pavement Association, Washington, D.C., McGhee, K. Virginia Quiet Pavement Study. Presented at Seventh Symposium on Pavement Surface Characteristics, Norfolk, Va., Swanlund, M. Highway Manager Requirements for Pavement Surface Characteristics. Presented at Seventh Symposium on Pavement Surface Characteristics, Norfolk, Va., Mogrovejo, D., G. W. Flintsch, E. de Leon Izeppi, and K. McGhee. Effect of Air Temperature and Vehicle Speed on Tire/Pavement Noise Measured with On-Board Sound Intensity Methodology. Presented at 92nd Annual Meeting of the Transportation Research Board, Washington, D.C., Center for Sustainable Transportation Infrastructure, Virginia Tech Transportation Institute. Virginia Quiet Pavement Implementation Program Ott, R. L., and M. Longnecker. An Introduction to Statistical Methods and Data Analysis, 6th ed. Cengage Learning, Belmont, Calif., The Transportation-Related Noise and Vibration Committee peer-reviewed this paper.