David A. Kuemmel

Noise characteristics of pavement surface texture in Wisconsin

Twelve portland cement concrete pavement (PCCP) test sections were constructed to compare with standard PCCP and asphaltic concrete pavement (ACP) to quantify the effects of the pavement surface texture on noise, safety, and winter maintenance. Asphalt pavements studied included a Strategic Highway Research Program asphalt, stone matrix asphalt (SMA), and Wisconsin standard asphalt. A dependency between the pavement textures and their noise characteristics was observed. Noise measurements indicated that uniformly transverse tined PCCP created dominant noise frequencies that were audible adjacent to the road and inside the test vehicles. Careful design and construction of transversely tined PCCP can reduce tire-road noise. No significant acoustical advantages of open-graded asphalts over the standard dense asphalt were found. The results of this research are preliminary and have not yet been approved by the Wisconsin Department of Transportation Council on Research.

NOISE ISSUES OF CONCRETE-PAVEMENT TEXTURING

The second phase of a project researching the texture and noise characteristics of portland cement concrete (PCC) pavements was sponsored by the Wisconsin Department of Transportation and FHWA. The team of Marquette University and HNTB Corporation measured and analyzed the noise and texture parameters of 57 test sites in Colorado, Iowa, Michigan, Minnesota, North Dakota, and Wisconsin. Conclusions pertaining to tire-and-pavement noise were drawn using data from several types of acoustical tests, including objective noise measurements (exterior and interior), subjective noise evaluations, and a prominent frequency analysis. Texture parameters of all test sites were measured with the road surface analyzer (ROSAN). ROSAN texture measurements proved invaluable in analyzing why different textures exhibited different noise characteristics. Both uniform and random transverse tining provide higher interior and exterior noise levels than skewed or longitudinal tining. Transverse tining, even in some random-spaced textures, can cause a discrete frequency or whine. As the depth and width of tining increased, so did the noise levels. Randomly spaced patterns are sensitive to spacing. Ground PCC pavement exhibited no discrete frequencies. Recommendations include the need for better quality control over tining and a wet-pavement-accident study of longitudinal tining. If noise considerations are paramount, longitudinal tining is recommended. If texture is paramount, skewed tining is recommended. If a skew is not possible, then carefully constructed random transverse is recommended.

Public Perceptions of the Midwest's Pavements: Explaining the Relationship Between Pavement Quality and Driver Satisfaction

A three-phase study involving focus groups and sample surveys was conducted in three Midwestern states to assess the amount of satisfaction that motorists who drive on rural, two-lane state highways have with the pavement characteristics of those highways and to explain the relationship between the actual physical condition of the pavements and motorists’ satisfaction. Consistently in each state, the direct relationship between pavement quality and driver satisfaction was mediated by cognitive structure—a set of five specific beliefs motorists have about the pavement. The part of the study that (a) applies a powerful psychological model to the task of understanding motorists’ satisfaction with pavements; (b) offers reliable measures of driver satisfaction with pavement quality and of belief-based cognitive structure related to pavements; (c) has accomplished the important task of identifying the most salient pavement features considered by members of the public when they evaluate pavement quality; and (d) illustrates very clearly the importance of considering motorists’ beliefs about the pavement, issues of trust, and aspects of the Fishbein’s attitude model and Ajzen’s theory of planned behavior when trying to predict or understand driver satisfaction are covered. Although the pavement management indices used by the state departments of transportation will continue to be used to establish thresholds for improvement triggers, these indices alone do not explain such broad concepts as satisfaction with a particular pavement.

Public Perceptions of the Midwest's Pavements: Policies and Thresholds for Pavement Improvement on Rural Two-Lane Highways

A 5-year, pooled fund study with the Iowa, Minnesota, and Wisconsin departments of transportation assessed the public’s perceptions of pavement improvement strategies and developed thresholds of satisfaction using the departments’ physical indices, such as pavement ride and condition on rural, two-lane highways in the states. Approximately 3,600 drivers in the three states were involved in the three phases of the project, which included 18 focus groups, 400 statewide surveys in each state, and 2,300 targeted surveys across the three states. A multidisciplinary team from Marquette University and a mass media survey lab conducted the studies. A summary of focus group methods and purposes and a three-state summary of policy and improvement issues are provided. More than 450 highway segments were surveyed in Phase III, with input from 2,300 drivers through a two-step recruitment and postdrive interview. Thresholds of International Roughness Index and condition indices are summarized for the three states. The study found a high degree of trust in the three departments of transportation and public support for building longer-lasting pavements and minimizing delay. A three-step methodology is recommended for other state studies. Physical data thresholds using both public satisfaction and the agreement to improve are presented for each state’s physical pavement indices (ride and condition).

USING A ROAD SURFACE ANALYZER TO EXPLAIN NOISE CHARACTERISTICS OF PORTLAND CEMENT CONCRETE PAVEMENT SURFACE TEXTURE

Uniformly spaced, transverse-tined portland cement concrete (PCC) pavements have been in extensive use in the United States since the early 1970s. Recent research by the Wisconsin Department of Transportation (WisDOT) and FHWA has led to an interim guideline for randomization of the tining pattern, with spacings varying from 10 to 40 mm and 50 percent of the spacings at or below 25 mm. At least five states have experimented with this random pattern. A six-state research study, funded by WisDOT and FHWA, was completed in 2000 by Marquette University and the HNTB Corporation. This study investigated 57 different PCC pavement textures, including a wide range of transverse and longitudinal tining patterns. One goal was to explain noise differences within and between various textures as well as to document noise and texture differences. The laser-based road surface analyzer (ROSAN), developed cooperatively by the Turner Fairbanks Research Center and private industry, was utilized for surface textural measurements. Before the advent of laser-based texture measurement devices, large studies of this type would have relied on manual volumetric (sand patch) measurements to quantify surface textural differences, making virtually impossible the determination of reasons for differences in noise characteristics of various textures. The use of ROSAN is described, tools developed to analyze textural variations and noise characteristics of tined pavement surfaces are presented, and correlations between ROSAN outputs and other variables, including noise level and sand patch measurements, are provided. Examples of simple and more subtle causes of noise discrepancies on random transverse tined PCC pavements are presented by use of ROSAN outputs. A great variation in surface texture, including tine spacing, width, and depth, was found among different PCC pavement sections constructed to identical tining specifications. Significant variations were also noted within any given test section in all states. A low correlation between ROSAN estimated texture depth and noise was observed. A more significant correlation between depth and width of tining was observed with use of ROSAN outputs. Recommendations include the need for quality control of tine depth, the need for a wet pavement accident study to determine tining depth requirements, and the development of an improved measurement device for measuring longitudinally tined PCC pavements.

Public Perceptions of Wisconsin Pavements and Trade-Offs in Pavement Improvement

Findings are reported from Phase II of a three-phase pooled-fund project in Wisconsin, Iowa, and Minnesota to determine perceptions of drivers regarding pavement of rural two-lane highways. Among the survey topics were drivers’ trust in the state department of transportation (DOT), pavement improvement trade-offs, and pavement evaluation. Results of the Wisconsin portion of the survey data are the focus of this study. The survey questionnaire was based in part on Phase I focus groups conducted to gauge beliefs about pavements as well as the language describing ruts, tining, and other pavement characteristics. Phase II entailed a statewide telephone survey of at least 400 randomly selected drivers in each of the three states. Although the focus here is on Wisconsin results, survey responses across the three states were very consistent. Included in the findings discussed are perceptions of pavement and the state DOT and pavement improvement options relating to construction, travel time, and delays. Results disclose key public perceptions of priorities with regard to spending limited funds. Also discussed are statistically significant relationships providing additional insights into public perceptions and pavement improvement on rural two-lane highways.

DESIGN OF A RANDOMIZED TINING RAKE FOR PORTLAND CEMENT CONCRETE PAVEMENTS USING SPECTRAL ANALYSIS

Uniformly spaced, transverse-tined portland cement concrete (PCC) pavements have been in extensive use in the United States since the early 1970s. However, driving on tined pavements generates an uncomfortable acoustic “whine”that has a discrete frequency. Recent research by the Wisconsin Department of Transportation (WisDOT) and FHWA led to an interim guideline for randomization of the tining pattern. The guideline called for tine spacing varying from 10 to 40 mm, with 50 percent of the spacing below 25 mm. At least five states have experimented with this random pattern, with limited success in eliminating the whine. A study was completed recently as part of a WisDOT contract with Marquette University and the HNTB Corporation, and funded by FHWA, to analyze all of the pavements. The tonal properties of acoustical noise were related to the serial arrangement of the tining, showing that the frequencies can be predicted from the power spectrum of the series of tines. A method of designing the series of tines that minimizes and possibly eliminates the presence of these whines is proposed and explained. By predicting the tonal properties of acoustical noise at the rake-design stage, the construction effort in building and researching noise and texture characteristics is substantially reduced. A random rake, designed using the proposed methodology, has been used in tining a road section, and preliminary spectral analysis of the acoustic noise revealed no tining-related discrete tones.

PUBLIC PERCEPTIONS OF THE MIDWEST'S PAVEMENTS: POLICIES AND TRADEOFFS IN PAVEMENT IMPROVEMENT

With the budget crisis plaguing so many states, pavement management will compete more vigorously for limited funds. Findings reported from a tri-state pooledfund research project provide insights and guidelines for pavement improvement derived from the perceptions of the driving public. The Phase II responses from statewide surveys in Iowa, Minnesota, andWisconsin address the topics of perceptions of the State Departments of Transportation (DOTs), pavement repair tradeoffs, and pavement evaluation. The results disclose specific public perceptions of priorities for spending limited highway funds. Implications for pavement management, policy, planning, as well as for marketing to garner additional funds are explored.