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Columbia, United States

Tsai Y.,Georgia Institute of Technology | Wu Y.,Georgia Institute of Technology | Lai J.,Georgia Institute of Technology | Geary G.,Office of Materials and Research
Transportation Research Record

Funding shortages create pavement preservation challenges for state departments of transportation (DOTs). The Georgia DOT developed an innovative micromilling resurfacing method as a cost-effective way to preserve its pavements. The new method can save more than $5 million on an I-95 project of 84 lane miles. To ensure that the micromilled surface texture has a good bond and good runoff capability, the Georgia DOT established a stringent ridge-to-valley-depth (RVD) specification. Preliminary tests were conducted on an I-75 project with a circular track meter and an ultralight inertia profiler, but the RVD was first measured with a laser road profiler for the entire 84 lane miles of the I-95 project. The rough and smooth micromilled pavement surfaces have been studied and compared through an exploration of their statistical characteristics and patterns. Results from four 0.5-mi segments showed that both smooth and rough surface textures revealed normal distributions, although a smooth surface had a slight lognormal distribution. The smooth surface had a mean of about 2.5 mm and a standard deviation of 0.9 mm. The rough surface had a mean of about 4.6 mm and a standard deviation of about 1.1 mm. The cumulative percentage curves for both rough and smooth surface textures showed that the mean RVD value of 3.2 mm could effectively differentiate rough and smooth surfaces. The effects of different base lengths on the RVD were studied, and results showed that a 100-mm base length was adequate to differentiate between smooth and rough surfaces. Source

Johnson W.H.,State Construction Office | Johnson A.M.,Office of Materials and Research
Journal of Surveying Engineering

A 2010 survey of terrestrial laser scanner (TLS) usage among state highway agencies indicated that TLS is being increasingly used for highway construction applications among transportation agencies in the United States and Canada. To observe variations in TLS measurements for typical highway conditions, two roadway sites were studied; a 20-year-old asphalt surface and a new concrete surface. Repeated scans were conducted using a Leica ScanStation II to investigate the effects of pavement surface type and reflectance, point density, number and layout of targets, and survey method for establishing control points. Typical target arrangements were not found to greatly affect the resulting scan data for the equipment used in the study. It was observed in this case study that the collected TLS data demonstrated better relative elevation results based on the control and checkpoints established using total stations than on the control and checkpoints established using a real-time kinematic global positionin system. When using the Leica ScanStation II, reflectance of a sample of typical concrete pavement was not observed to vary greatly between 1-month-old and 1-year-old surfaces. Reflectance of asphalt pavement was observed to vary significantly between several examined surfaces ranging from new to 20 years old. © 2012 American Society of Civil Engineers. Source

Hunter M.,Georgia Institute of Technology | Boonsiripant S.,Office of Expressway System Engineering Research and Development | Guin A.,Georgia Institute of Technology | Rodgers M.O.,Georgia Institute of Technology | Jared D.,Office of Materials and Research
Transportation Research Record

Converging chevron pavement markings have recently seen rising interest in the United States as a means to reduce speeds at high-speed locations and improve safety performance. This paper reports on an investigation into the effectiveness of chevron markings in reducing vehicle speeds on two-lane freeway-to-freeway directional ramps in Atlanta, Georgia. The evaluation is based on a statistical comparison at preselected sites of speeds before and after the installation of the chevron markings. The analysis focuses on the effect of converging chevrons over the range of speed percentiles and on the mean speed. The analysis indicates that chevrons have a minimal effect on vehicle speeds, with drivers adjusting back to their previous speeds as they acclimate to the treatment. The effect of the chevrons' treatments on speed tended to be most pronounced immediately after the chevron implementation. However, by the 9th month after implementation the magnitude of the effect dropped to under 1 to 2 mph for the mean speed and most vehicle speed percentiles. Although this result does not necessarily imply that the chevron treatment is not a meaningful safety treatment, any safety benefits are not likely to result from a general decrease in speeds. Source

Lai J.,Georgia Institute of Technology | Hines S.,Office of Materials and Research | Wu P.Y.,Office of Materials and Research | Jared D.M.,Office of Materials and Research
Transportation Research Record

The micromilling technique to mill asphalt surface mix continues to be studied in the state of Georgia as part of a pavement preservation treatment in conjunction with thin asphalt overlays. Earlier research showed the results of micromilling on a deteriorated open-graded surface, which was overlaid with a new open-graded surface on I-75, south of Macon, Georgia. The micromilling produced a much finer surface texture than did conventional milling, with a ridge-to-valley depth (RVD) of less than 3 mm, and the technique could more accurately mill the deteriorated open-graded layer. A new open-graded surface was placed on top of that layer with no need for a new dense-or gap-graded layer. The result was a large cost savings compared with conventional milling and overlay. This paper summarizes research performed on a micromilling and open-graded inlay project on I-95 near Savannah, Georgia, and compares the results with those from the previous research. The new research affirms that significant cost savings can be achieved through the replacement of conventional milling with micromilling. Results obtained from the I-75 project indicated that, on the basis of 3 years of satisfactory performance of the open-graded overlay on the micromilled surface, the use of the 95th percentile RVD parameter as the threshold value for compliance with the 3.2-mm RVD acceptance requirement could be too conservative. Results from the I-95 project indicated that the mean RVD of the micromilled surface could meet the 3.2-mm RVD requirement. However, the appropriateness of this parameter's use should be determined on the basis of the long-term performance of the open-graded mix placed on the micromilled surface. Source

Zhu H.,Oregon State University | Dixon K.K.,Oregon State University | Washington S.,University of California at Berkeley | Jared D.M.,Office of Materials and Research
Transportation Research Record

The rural two-lane highway in the southeastern United States is frequently associated with a disproportionate number of serious and fatal crashes and as such remains a focus of considerable safety research. The Georgia Department of Transportation spearheaded a regional fatal crash analysis to identify various safety performances of two-lane rural highways and to offer guidance for identifying suitable countermeasures with which to mitigate fatal crashes. The fatal crash data used in this study were compiled from Alabama, Georgia, Mississippi, and South Carolina. The database, developed for an earlier study, included 557 randomly selected fatal crashes from 1997 or 1998 or both (this varied by state). Each participating state identified the candidate crashes and performed physical or video site visits to construct crash databases with enhance site-specific information. Motivated by the hypothesis that single- and multiple-vehicle crashes arise from fundamentally different circumstances, the research team applied binary logit models to predict the probability that a fatal crash is a single-vehicle run-off-road fatal crash given roadway design characteristics, roadside environment features, and traffic conditions proximal to the crash site. A wide variety of factors appears to influence or be associated with single-vehicle fatal crashes. In a model transferability assessment, the authors determined that lane width, horizontal curvature, and ambient lighting are the only three significant variables that are consistent for single-vehicle run-off-road crashes for all study locations. Source

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