Transportation Systems and Materials

Research Project Abstracts: 2001 - 2002

Evaluation of Safety, Design, and Operation of Shared Use Paths
J. E. Hummer, N. M. Rouphail, and J. S. Milazzo II
Federal Highway Administration
10/00 to 9/03
Off-street paths used by pedestrians, bicyclists, and other non-motorized users are becoming common in the U.S. The purpose of the project is to develop and validate a quantitative procedure for estimating the quality of service offered by paths of different widths and configurations handling different volumes of users. A major work element in this research is the collection of operational data on paths across the U.S. The research team will also collect an extensive database of path user perceptions. Another important part of the research is the development of a plan to communicate the quality of service procedure to designers and operators across the U.S.

Guidance on the Safe Implementation of Unconventional Arterial Designs
J. E. Hummer
Southeastern Transportation Center
8/00 to 7/01
Unconventional arterial designs like median u-turns, superstreets, and continuous flow intersections have the potential to significantly reduce delay compared to conventional arterial designs of similar size. However, designers avoid these new designs because they are concerned that drivers will not understand how to negotiate them when first introduced. The research team has 1) examined case studies from the southeast and elsewhere where agencies opened new designs; 2) looked at traffic control devices, enforcement levels, and public relations tools used by those agencies; and 3) gathered detailed reactions to those devices and tools from a focus group of typical drivers.

Phase IV Planning Assistance and Support Services to the NCDOT Rail Division
J. E. Hummer
NC Department of Transportation (NCDOT)
8/00 to 12/01
To overcome some of the problems with traditional active warning devices at railroad grade crossings, the EVA Signal Corporation has developed a new, relatively low-cost system. As part of a team assembled by the Institute of Transportation Research and Education, we will evaluate the new system at an installation in Rich Square, NC. We will test the reliability of the system and assess driver responses to the new types of signals using motorist surveys, field observations, and video recordings.

State Farm Insurance Program-Intersection Safety Study
J. E. Hummer
City of Charlotte, NC
9/00 to 8/01
State Farm Mutual Automobile Insurance Company recently began an effort to stem the tide of collisions at some of the most hazardous intersections in the U.S. and make the public aware of the frequency of crashes at these locations. In one component of the program, State Farm has offered the responsible highway agencies up to $20,000 per intersection to study these sites and produce countermeasure recommendations. Four of the five most hazardous intersections in North Carolina as identified by State Farm are in Charlotte, and three of these will be the subjects of this study. Our particular focus will be on examining potential unconventional design solutions at those intersections.

Communicating Changes in Horizontal Alignment
J. E. Hummer
Michigan State University
08/01 to 08/03
Working as a subcontractor on National Cooperative Highway Research Program Project 3-61, we are investigating ways to more effectively and consistently warn drivers about upcoming horizontal curves. We are gathering information about current curve warning devices and methods through a literature review and a series of surveys. We will then be developing new methods and devices. Our primary role at NC State is to test existing and new methods and devices at sites on North Carolina highways.

Evaluation of the Effects of Mixture Properties and Compaction Methods on the Predicted Performance of Superpave Mixtures
N. P. Khosla
NC Department of Transportation/Federal Highway Administration
7/00 to 6/02
Objectives are evaluate the effects of compaction type on a mixture's performance as measured by the APA, Wheel Tracking Device, and Repeated Shear Constant Height Test; evaluate how changes in aggregate and asphalt source affect compaction and performance in these test systems using SUPERPAVETM mixtures from NC sites; compare the predicted performance of test samples compacted in the field to the same mixtures compacted in the lab; evaluate and compare the field densification of mixtures with varying degrees of compaction in the SUPERPAVETM gyratory compactor; and evaluate mixtures' frictional resistance with new load cell plate technology for SGC and compare to results of other performance prediction equipment.

Development of Visco-Elasto-Plastic Continuum Damage Model for Asphalt-Aggregate Mixtures
Y. R. Kim
Arizona State University
3/00 to 12/01
This project is a subcontract from Arizona State University as a part of the NCHRP 9-19 project "Superpave Support and Performance Models Management." The objective of this project is to develop test protocols and models for characterization of asphalt concrete that are needed for structural design and mix design. The NC State University research team will perform experimental/analytical research to evaluate elastic, viscoelastic, and viscoplastic responses of asphalt concrete under varying conditions and to develop a constitutive model that can be implemented in finite element analysis for performance prediction of asphalt pavements.

Impact of Price Reductions on the Long-Term Pavement Performance of HMA
Mixes in North Carolina
Y. R. Kim
NC Department of Transportation (NCDOT)
7/01 to 6/03
Article 105-3 of the NCDOT Standard Specifications for Road and Structures provides guidance on price adjustments for hot mix asphalt pavements that are not within reasonably close conformity with the specifications but for which the work is to be accepted and remain in place. The primary objective is to determine whether price reduction under the provisions of Article 105-3 is adequate by conducting both field and laboratory analyses of deficient pavements and specification pavements with similar structures and traffic history. The types of deficiency to be addressed include asphalt content and in-situ density. Both fatigue and rutting performance will be evaluated.

Laboratory Evaluation of Lime-Modified Asphalt Mixtures for City of
Charlotte
Y. R. Kim
Chemical Lime Company
11/00 to 10/01
The primary objective of this project is to evaluate the effect of lime modification in asphalt mixtures. Unmodified and lime-modified asphalt mixtures are acquired from the overlay job of a test road in City of Charlotte. These mixes will be characterized for fatigue cracking and rutting using the following three types of specimens: (1) laboratory-compacted specimens by Superpave Gyratory Compactor (SGC); (2) 150-mm-diameter cores obtained from the pavement immediately after the construction; and (3) scaled-down laboratory pavements.

A Unified Approach to Predicting Long Term Performance of Asphalt-Aggregate Mixtures
Y. R. Kim, R. H. Borden, and Y. Horie
National Science Foundation
9/98 to 8/01
The research objective is to develop test methods and models for predicting long term performance of asphalt concrete that can account for viscoelasticity, damage, volumetric/deviatoric coupling, temperature, and aging. The objective will be accomplished by applying the elastic-viscoelastic correspondence principle and the continuum damage theory. The constitutive model will be incorporated into the ABAQUS finite element code and used to predict the response and performance of laboratory pavements loaded by the Model Mobile Load Simulator. Nondestructive surface wave tests will be performed to determine the change in material properties due to fatigue damage growth.

Development of Specification Testing to Promote Fracture Fatigue Resistance and to Optimize Microdamage Healing
Y. R. Kim and M. N. Guddati
Texas A&M Research Foundation/Western Research Institute/Federal Highway Administration
7/99 to 6/03
The ultimate goal of this project is "to be able to classify/specify/improve asphalts by their healing rates and efficiencies using chemical data that can be acquired more rapidly than by mechanical methods." To accomplish this goal, the viscoelastic, continuum damage model developed by the PI will be tied to the micromechanical properties of component materials using microscopic lattice modeling. Various test methods will be explored for binder specification testing using the viscoelastic, continuum damage formulation and micromechanical simulation with an objective to promote fatigue resistance and to optimize the microdamage healing potential.

The Effects of Roundabouts on Pedestrian Safety
J. R. Stone
University of Tennessee Southeastern Transportation Center (USDOT University Transportation Center)
8/00 to 8/01
Roundabouts have proven their effectiveness at improving vehicle safety at intersections. However, U.S. professionals debate their effectiveness for pedestrians. This research will examine available pedestrian safety data with appropriate statistical and case study methods to provide additional information on pedestrian safety at roundabouts.

Transit Customer Satisfaction with Real-Time Information
J. R. Stone
Winston-Salem Transit Authority
7/00 to 12/01
New technology including automated scheduling and vehicle location, digital communications, interactive telephone service, and dynamic variable message signs permit real-time bus locations and estimated arrival times to be communicated to passengers. This research will examine the effects of selected technologies on transit customer satisfaction and transit system performance.

Traditional Neighborhood Development Trip Generation Study
A. Khattak (UNC-CH) and J. R. Stone
NC Department of Transportation
07/02 to 06/03
This project focuses on Southern Village, a Chapel Hill high-density development that combines residential, business, and office land uses. In concept having potential trip origins and destinations close to one another will enhance walking, biking, and transit transportation, and, thereby, reduce the need for automobile travel to the usual suburban destinations. Evaluation of behavioral travel surveys and traffic data for Southern Village versus a conventional suburban development will test this concept.

Development of North Carolina Traffic Forecasting Tools
J. R. Stone
NC Department of Transportation
7/01 to 6/02
Highway projects depend on accurate estimates of truck and automobile traffic to determine designs for lanes, intersections, interchanges, and pavements. Such traffic estimates originate from course daily traffic forecasts taken from regional planning models. For design traffic estimates must include hourly estimates of through and turning movements. This research will provide appropriate techniques to improve project traffic estimates.

Materials Characterization and Performance Properties of Superpave Mixtures
A. A. Tayebali
NC Department of Transportation (NCDOT)
1/01 to 12/02
A critical step in the implementation of mechanistic/empirical design procedure is the development of strain-fatigue life relationship. In this investigation, materials characteristics and fatigue performance of few asphalt mixes currently used in North Carolina will be evaluated. The study of these mixes will initiate the development of a better understanding of the capacity of Superpave mixes to resist fatigue distress by providing information that can be used to identify deficiencies and make necessary improvements in the current NCDOT design procedures.

Effect of Percentage Baghouse Fines on the Amount and Type of Antistripping Agent Required to Control Moisture Sensitivity
A. A. Tayebali
NC Department of Transportation
07/01 to 12/02
This research study proposes to use a Prompt Gamma Neutron Activation Analysis (PGNAA) device developed by IntroTek, Inc. of Raleigh, NC to detect the concentration and map the distribution of polyester fiber additives within a sample of SMA mixture. The objective of this research study is to a) determine the ability of PGNAA technique to detect the presence of polyester fibers and its concentration in SMA mixtures; and b) map the distribution (dispersion) of the polyester fiber content within a compacted sample of SMA mixture.

Shear and Axial Repeated Load Behavior of Asphalt Concrete Mix Designed Using Marshall and Superpave Mix Design Procedure.
A. A. Tayebali
Nichols Consulting Engineers
07/01 to 12/01
The objective of this study was to evaluate three mixes using Keystone, Wells, and Zolezzi aggregates from Nevada designed using the Superpave and Marshall mix design procedures. Repeated axial and shear tests were conducted using the Simple Shear Test machine (SST). Axial and shear test results indicate that, in general, there was no difference in the behavior of the mixes designed using the Superpave or the Marshall procedure. In some cases, the behavior of the Marshall-designed mix was found to be better than the Superpave mixes.

A Mechanistic Approach to Evaluate Contribution of Prime and Tack Coats in Composite Asphalt Concrete Pavements
A. A. Tayebali and S. Rahman
NC Department of Transportation (NCDOT)
7/00 to 6/02
The importance of proper AC layer interface bonding cannot be overemphasized for good performance of AC pavements. A strong bonding between layers is critical to dissipate shear stresses into the entire pavement structure, but lack of bonding may cause slippage phenomenon and activate distress mechanisms that will rapidly lead to total pavement failure. The objective of this study is to evaluate the effects of different prime and tack coats on the bond strength in relation to the thickness of the asphalt concrete layer. Based on the results of the study, correlation will be developed between delamination parameters and stress-strain-displacement field.