Robert P Elliott

DATA ANALYSIS OF REAL-TIME SYSTEM FOR AUTOMATED DISTRESS SURVEY

Accurate data collection and interpretation of pavement data are critical for the decision-making process in pavement management. This study focused on the data analysis portion of a new automated system capable of collecting and analyzing pavement surface distress, mainly cracks, in real time through the use of a high-resolution digital camera; efficient image processing algorithms; and multicomputer, multi-CPU-based parallel computing. Features and performance of the automated system for distress survey were surveyed. Three protocols of producing distress indices incorporated into the automated system were examined: the AASHTO interim distress protocol, the World Bank’s Universal Cracking Indicator, and the Texas Department of Transportation’s method. It was found that distress results from the automated system were consistent for multiple passes of the same pavement sections.

ARKANSAS EXPERIENCE WITH CRUMB RUBBER MODIFIED MIXES USING MARSHALL AND STRATEGIC HIGHWAY RESEARCH PROGRAM LEVEL I DESIGN METHODS

Unmodified and crumb rubber modified mixes conforming to the Arkansas State Highway and Transportation Department Type II surface course specifications were designed for heavy traffic conditions and environmental conditions typical to Arkansas by using the Marshall and Superpave Level I methods. Specimens prepared at appropriate design asphalt contents were evaluated for both volumetric and performance considerations. Three mix types, an unmodified hot-mix asphalt concrete, a dry process rubber modified asphalt, and a wet process asphalt rubber, were included in the investigation. For the asphalt cement, crumb rubber, aggregate type, and aggregate gradation used, the design asphalt content and the VMA were reduced for the SHRP Level I method relative to the Marshall method. Incorporation of crumb rubber into hot-mix asphalt concrete provided increased rutting resistance; however, the rubber modified mixes did not show enhanced resilient and tensile properties when tested at 25°C. Also, the performance-rel...

Experimentation with Gray Theory for Pavement Smoothness Prediction

Riding quality is a dominant characteristic of pavement performance. In the proposed mechanistic–empirical pavement design guide (MEPDG), the functional performance indicator is pavement smoothness as indicated by the international roughness index (IRI). The MEPDG IRI prediction models were developed on the basis of a general hypothesis in which changes in smoothness are caused in part by various distresses, which can be predicted. With pavement distress data from the Long-Term Pavement Performance (LTPP) database, traditional regression analysis was used statistically to establish the MEPDG prediction equations. The gray system theory was devised in the 1980s for modeling uncertain systems with the characteristics of partially known information. A pavement performance prediction system can fit the domain of the gray system. The gray theory–based prediction method was used to develop IRI prediction equations. With the data exported from the LTPP database, it was found that certain specific distresses significantly affect the accuracy of the predictions. Combined with the results of gray relational analysis and the gray prediction methodology, gray model–based smoothness predictions are established by using influencing factors similar to those used in MEPDG. From comparisons of results from the two prediction methodologies with actual LTPP data, it is shown that the gray model–based method provides promising results and is useful for modeling pavement performance.

Feasibility Study for Gray Theory Based Pavement Smoothness Prediction Models

In the proposed Mechanistic-Empirical Design Guide (MEPDG) (NCHRP 1-37A, 2001), the functional performance indicator is pavement smoothness as measured by the International Roughness Index (IRI). The MEPDG IRI prediction models were developed based on the general hypothesis that changes in smoothness result from various distress types that can be predicted by the MEPDG program. Using pavement distress data fro the Long Term Pavement Performance (LTPP) database, traditional regression analysis was used to statistically establish the MEPDG prediction equations. This paper attempts to use a new technique for pavement smoothness prediction. The gray system theory was derived in the 1980s for modeling uncertain systems with the characteristics of partially known information. A pavement performance prediction system can fit the domain of the gray system. The gray theory based prediction method is used in this paper to develop IRI prediction equations. With the data exported from the LTPP database, it is found that certain specific types of distresses significantly affect the accuracy of the predictions. After trial and error calculations, Gray Model based smoothness predictions are established using influencing factors similar to the ones used in MEPDG. Based on the comparisons of results from the two prediction methods with LTPP field data, it is shown that the Gray Model based method provides promising results and be useful for modeling pavement performance.

Generic Multimedia Database for Highway Infrastructure Management

Images of highway right-of-way are used widely by highway agencies through their photologging services to obtain visual information for the analysis of traffic accidents, design improvement, and highway pavement management. The video data usually are in analog format, which is limited in accessibility and search, cannot automatically display site engineering data sets with video, and does not allow simultaneous access by multiple users. Recognizing the need to improve the existing photologging systems, the state highway agency of Arkansas sponsored a research project to develop a full digital, computer-based highway information system that extends the capabilities of existing photologging equipment. The software technologies developed for a distributed multimedia-based highway information system (MMHIS) are presented. MMHIS removes several limitations of the existing systems. The advanced technologies used in this system include digital video, data synchronization, high-speed networking, and video server. The developed system can dynamically link the digital video with the corresponding engineering site data based on a novel algorithm for the data synchronization. Also presented is a unique technique to construct a three-dimensional user interface for MMHIS based on the terrain map of Arkansas.

Analysis of Contractor Pay Adjustment Schedule Using Simulation

A common provision in quality control/quality assurance construction contracts is the adjustment of the contractors pay on the basis of the quality of the construction. The expected impact of the provision on the pay should be examined to ensure that the adjustments are neither unduly severe nor excessively lenient. Most pay adjustment plans have been developed around a quality index by using a percent defective approach. Analyses of these plans are complex but reasonably well defined. Other plans, however, are more complex and do not lend themselves to direct analysis. These plans can be examined by computer simulation. The use of computer simulation to examine a complex pay adjustment provision is demonstrated. The analyses show that simulation can reveal that a pay adjustment schedule behaves differently than it appears on the surface. For example, the schedule examined bases pay solely on averages and appears to ignore construction variability. The analyses, however, demonstrate that the pay adjustments are at least as sensitive to construction variability as they are to construction averages. It is also shown that the simulation process can provide a better, more detailed examination of the pay schedule than is possible by simply determining the expected pay. In particular, the simulation process can provide an indication of the variability of pay at various quality levels and can identify the factors most responsible for pay adjustments.

ACCREDITATION OF PROGRAMS IN TRANSPORTATION ENGINEERING: THE UNIVERSITY OF ARKANSAS EXPERIENCE

At its annual meeting on July 25, 1997, the Engineering Accreditation Commission (EAC) of the Accreditation Board for Engineering and Technology, Inc. (ABET), granted initial accreditation to an advanced-level program in transportation engineering at the University of Arkansas. Not only was this one of the first baccalaureate or advanced-level engineering programs accredited under EAC’s new outcomes-based Criteria 2000 process, but it also represented the first accredited program in transportation engineering at any college or university in the United States. With the passage of the Intermodal Surface Transportation Efficiency Act of 1991 and the establishment of the Mack-Blackwell Transportation Center at the University of Arkansas, the faculty of the department of civil engineering saw an opportunity to create a unique educational program. The program would address the multidisciplinary requirements of the transportation engineering profession in a more comprehensive manner than traditional programs oriented to civil engineering. Bringing together a mix of civil-engineering-oriented transportation planning, traffic engineering, and facility design courses along with requirements for exposure to private-sector transportation and logistics issues through the school of business, the University of Arkansas has created a model for an accredited program in transportation engineering. The development of this program is discussed, along with the manner in which the EAC Criteria 2000 were applied, and what should be considered the basic elements of an advanced-level program in transportation engineering.