bluuebunny/crossref_metadata_2025 huggingface dataset:
Data Requirements for Enhanced Digital Maps in an Advanced Curve-Speed Warning System
Authors: Aguil-Éra Vincent , Glaser Sebastien
Published: April 2007

The development of map database specifications that will enable or improve driver safety assistance systems is a topic of active research. In this context, data requirements are proposed for an advanced curvespeed warning system. Both the content of the database and the accuracy of the needed road-geometry data are addressed. First, some possible drawbacks of previous proposals in this field are sketched. Then, a model is presented to compute the highest safe speed of a road section, given three distinct submodels: vehicle dynamic, infrastructure characteristics, and driver behavior. A case study illustrates how this model may greatly improve driver suitability of curve-speed warning—control driver assistance. A sensitivity analysis formally demonstrates that the requirements concerning road-geometry data are compatible with existing low-cost measurement devices. Finally, some critiques and additions to previous works concerning map database enhancements are formulated.
Designing Automated Vehicle Location Systems for Archived Data Analysis
Authors: Furth Peter G. , Muller Theo H. J. , Strathman James G. , Hemily Brendon
Published: April 2007

Automatic vehicle location (AVL) and other automated data collection systems can provide a rich and extensive database that can be analyzed to improve transit management and performance. In the past, many such systems have failed to provide a good data archive, while others have had success. Through the use of an extensive survey and in-depth case studies of nine transit agencies, the key issues in system design that help determine whether a data collection system will provide the useful data archive that many agencies desire are examined. In issues related to design of the data collection system itself, the focus is on five different levels of spatial detail. Issues related to database design are also discussed, as are organizational issues.
Economics of Commuter Rail Alternatives: Comparative Cost Perspective
Authors: Richardson Stephen
Published: April 2007

In the North American commuter rail environment, authorities planning to commence or expand service have several rolling stock options to evaluate. In the nonelectrified mixed-traffic operating environments that are prevalent outside the northeastern United States, locomotive-hauled vehicles—diesel-electric locomotives with head-end power units used in push-pull operation with single- or multiple-level coaches—have traditionally been the equipment of choice. With the imminent reemergence of a diesel multiple unit vehicle compliant with FRA standards for mixed traffic operation, the available equipment options have expanded. Authorities must be provided with the required information to evaluate and compare the costs and benefits of this newly available option. The true direct costs (excluding track access fees and insurance; justification for the exclusion of these issues is included) associated with the life cycle of rail vehicles are evaluated to provide transit authorities with the information required to make informed procurement decisions.
Transit Capacity and Quality of Service Manual Applied to a Bus Corridor in Dublin, Ireland
Authors: Caulfield Brian , O'Mahony Margaret
Published: April 2007

The introduction of 11 quality bus corridors (QBCs) has been a success story in the provision of public transport in Dublin, Ireland, over the past few years. In a city where the bus is the main mode of public transport, the QBC initiative has resulted in decreased commute times and increased ridership. QBCs operate on dedicated traffic lanes between the hours of 7 a.m. and 7 p.m. and in certain instances on a 24-h basis. The performance of the Malahide QBC, which extends 7.5 km (4.7 mi) from the city center to the northeast of the city, is measured by examining service coverage, headway, and transit/automobile travel time (the difference in travel time between transit and private vehicles). The Transit Capacity and Quality of Service Manual (TCQSM) is used to provide quality of service measurements on the corridor to evaluate its performance. Data for the TCQSM analysis were taken from an automatic license plate recognition system that was installed on the Malahide QBC in 2003. Future plans for the QBC network are presented, along with a concluding examination of how QBCs play a role in providing a more efficient public transport system in Dublin.
Serviceability Index to Evaluate Rural Demand-Responsive Transit System Operations
Authors: Sandlin Adam B. , Anderson Michael D.
Published: April 2007

Recently, focus on the analysis of public transit systems has been increasing. The Transit Capacity and Quality of Service Manual consolidates information on current practices. By stating that no national studies support transit capacity analysis for demand-responsive operations, the manual identifies an inability to estimate capacity and level of service for agencies that provide demand-responsive transit. A procedure for calculating a serviceability index (SI) for demand-responsive transit operators based on regional socioeconomic conditions and internal operation data is presented. The methodology results from a survey of several demand-responsive transit providers in Alabama and data analysis. A case study for two counties served by the Northwest Alabama Council of Local Governments transit agency illustrates the SI calculation to identify benefits and drawbacks. Generated with input from transit providers, SI can be used to evaluate and compare demand-responsive transit operation.
Evaluating Level of Service at Airport Passenger Terminals: Review of Research Approaches
Authors: Correia Anderson , Wirasinghe S. C.
Published: April 2007

Establishing measures to evaluate the level of service (LOS) at airport passenger terminals is of interest to airlines and airport operators. Airport LOS has been evaluated at individual airports, but no standard method or reporting system exists. Airport passenger terminal LOS and capacity have been research topics over the past two decades. More recently, studies have been initiated to identify the passenger terminal problem in general and capacity and service measures in particular. In 1986, FAA responded to concerns about an inadequate understanding of passenger terminal capacity constraints by commissioning TRB to study ways to measure airport capacity. This study recognized that the capacity of any given airport facility cannot be evaluated without defining acceptable LOS values. Currently, however, little agreement exists on analysis methods. No universally accepted way exists to measure LOS for airport terminal buildings. In this regard, various approaches developed by different agencies and researchers are reviewed. This review is useful for professionals interested in applying one of the methods previously developed but not having access to all published information, especially the new approaches. The intent of this review is to motivate new research on the subject, which would facilitate the integration of various existing methods or the development of new approaches.
Auction-Based Slot Allocation for Traffic Demand Management at Hartsfield Atlanta International Airport: A Case Study
Authors: Le Loan , Donohue George , Chen Chun-Hung
Published: April 2007

Ongoing research is described for an auction model, a hybrid demand management approach for congested airports. This approach is intended to optimize the use of airport time slots by maximizing passenger throughput with safe capacity, decreasing congestion, and less delay. The two submodels mathematically formulate conflicting optimization problems of efficiency-driven airport regulators and cost-driven airlines. By ranking key factors such as monetary bidding, flight origin-destination pairs, enplanement capability, and airlines' previous investments, a framework is presented that is open to many design alternatives. Two design alternatives are analyzed in a case study of Hartsfield Atlanta International Airport, Georgia, to compare different allocation schemata and resulting airport performance. The performance analysis used a queuing model simulation. By varying weighting coefficients for bid vectors, it is proposed that the effects of administrative coordination and market force on outcomes of the auction process could be monitored to achieve airport-specific benefits. It is also suggested that the conventional auction format that uses monetary bidding alone could lead to potential distortions of the marketplace and fail to meet air transportation officials' concerns about the efficient use of national resources and policy makers' concerns about market structure and competitiveness. Future work will enlist the input from both airlines and airports.
Issues in Integrating Pavement Management and Preventive Maintenance
Authors: Zimmerman Kathryn A. , Peshkin David G.
Published: April 2007

For years, pavement-management systems (PMSs) have been used in highway agencies to improve the planning efforts associated with pavement-preservation activities, to provide the information needed to support the pavement-preservation decision process, and to compare the long-term impacts of alternative preservation strategies. As such, pavement management is an integral part of an agency's assetmanagement efforts and an important tool for cost-effectively managing the large investment in its transportation infrastructure. PMSs have been used by several agencies to demonstrate the cost-effectiveness of pavement-preservation programs that include the use of preventivemaintenance treatments. By comparing the long-term effects on pavement condition associated with an agency's current practices with a strategy that includes preventive maintenance, the benefits of a preventive-maintenance program can be demonstrated. However, agencies have had limited success expanding the use of their PMSs to support a preventive-maintenance program because most PMSs have not fully integrated preventive-maintenance treatments into the analysis. The importance of integrating preventive-maintenance treatments into a PMS to support a preventive-maintenance program is addressed, and the most common gaps between maintenance efforts and pavement management are discussed. In addition, current approaches used to integrate these programs and the advantages and disadvantages associated with each approach are presented. Finally, recommendations for improving the integration of preventive-maintenance treatments into an agency's PMS are provided.
Using Pavement-Management System Data to Evaluate Benefits from Design and Construction Improvements
Authors: Lukanen Erland O. , Holt David S.
Published: April 2007

Pavement-management data can be a valuable resource to evaluate the impact that changes in bituminous mix design, production, or placement have on pavement performance. The development of pavement distresses by type and severity can be tracked from data in pavement management systems. The rate of distress development for some distress types changes, depending on the year of construction. The change in the development of some of the distresses corresponds to changes in mix design, production, or placement that have taken place over the years. Pavement-management data can also be used to determine which distress type is causing the biggest reduction in pavement-condition ratings. Once the most dominant distress is identified, research can be conducted to find ways of reducing that distress and thereby improve pavement performance. Pavement-management data, when used in this manner, are a valuable resource that can track the performance benefits from changes in mix design, mix production, and placement; in addition, pavement-management data can be used to identify opportunities for future improvement.
Correction Curves to Modify Algebraically Aggregated Deductions for Jointed Concrete Pavements in Virginia
Authors: Habib Affan , McGhee Ken , Chowdhury Tanveer , Gilman Douglas
Published: April 2007

Developing a distress-condition index representative of the roadway has always been a challenge. The development process requires in-depth understanding of the behavior of the pavement system under load and distress, thorough familiarity with the distresses, computational and analytical skill, and, above all, a very comprehensive validation process. When the Virginia Department of Transportation (VDOT) initiated its formal pavement-management operation, VDOT tried the procedure developed and outlined by the U.S. Army Corps of Engineers. Soon VDOT pavement-management personnel felt the need to have Virginiaspecific indexes and undertook an extensive effort to develop its own indexes tailored to distresses prevalent on Virginia roads and to VDOT's business objectives. The index is obtained by algebraically aggregating deductions for all the distresses in the section and subtracting that from a perfect score of 100. In 2001, VDOT completed its first-ever comprehensive condition survey on its concrete-pavement primary routes. The initial analysis revealed that the index equations were not producing representative indexes for jointed concrete pavements. Investigation revealed that the calculated condition indexes for jointed concrete were consistently lower than the expected values. It appeared that algebraically aggregated deductions need to be lowered to offset overcounting the common effects of the various distresses present. VDOT developed a relatively simple analytical approach to address this problem and came up with a technique that reduces the algebraically aggregated deductions to reasonable values. The principles and steps behind this technique are outlined and explained.
Integration of Ramps into Pavement Management Systems
Authors: Helali Khaled , Ahmed Khan Riaz , Jumikis Andris A. , Ahmed Zubair
Published: April 2007

Ramps constitute an essential part of an agency highway network. They not only provide access to the mainline highway network, but some ramps also may be of sufficient length to be treated as a highway segment. Ramps can deteriorate faster than mainline routes, with resulting safety issues and discomfort to motorists. To be maintained in the same fashion that highway agencies maintain mainline pavements, ramps need to be included in pavement management systems (PMSs). A recent informal survey from 11 highway agencies in the United States and Canada showed that no agency had a formal maintenance and rehabilitation (M&R) program for ramps. All of them, on most occasions, include ramp M&R with adjacent mainline pavement M&R projects, and on a few occasions they fix ramps separately. A novel approach was developed to integrate ramps with the existing mainline network database that resulted from 8 years of PMS development and enhancement efforts. Included are the scope and methodology for the ramp survey and analysis, development of a ramp identification system, a condition-rating procedure for field testing of the ramp network, a ramp data-loading and data-processing procedure, and a ramp M&R and optimization analysis. Also described are the benefits of such analysis and how it can be used in other agencies to improve ramp pavements in the long term. The integration of ramps into the PMS provides the ramp's condition, needs, and budgeting summaries. The PMS modeling capabilities can be used to determine the asset value of the ramp network. Therefore, integrating ramp inventory and condition-rating data with the PMS mainline network can lead to effective ramp M&R decision making.
Effects of Airport Pavement-Profile Wavelength on Aircraft Vertical Responses
Authors: Chen Yi-hsien , Chou Chia-pei
Published: April 2007

Smooth airport pavement will help to increase pavement life, reduce structural damage to aircraft, and minimize complaints from pilots and passengers. The main objective of this study was to explore the relationship of an aircraft's vertical acceleration and gear loading to pavement-profile wavelength. The software package APRas, developed by APR Consultants, Inc., was used in this study to simulate an aircraft's vertical acceleration and pavement-loading responses. The simulation results indicated that the occurring wavelength of an aircraft's peak vertical acceleration and loading increased as the taxi speed increased and that pavement roughness had a greater influence on nose-gear loading than on main-gear loading. It was also found that airport pavement roughness was related more to flight safety than to passenger comfort. Pavement profiles of wavelengths between 3.3 and 10.0 m should be prevented in airport apron and taxiway pavements, and profiles of wavelengths between 10.0 and 50.0 m must be prevented in airport runway pavement. Regression models of peak acceleration and pavement loading wavelengths at various aircraft speeds, gross weights, and wheelbases were established. The widely used international roughness index, which is used to evaluate highway roughness, is not suitable in the assessment of airport-pavement roughness. The feasibility of adopting wavelet theory to establish a new evaluation index for airport pavement was confirmed. Further studies can be conducted to develop a new index to reflect the ride quality of passengers in the aircraft.
Assessment of Image-Based Data Collection and the AASHTO Provisional Standard for Cracking on Asphalt-Surfaced Pavements
Authors: Raman Monika , Hossain Mustaque , Miller Richard W. , Cumberledge Gaylord , Lee Hosin (David) , Kang Kihyoung (Jeff)
Published: April 2007

The network-level pavement management system of the Kansas Department of Transportation (KDOT) is known as the Network Optimization System (NOS). For input, KDOT manually collects data on cracking severity and extent on its network annually. In this study, pavement surface images were collected and analyzed to evaluate the impact of AASHTO provisional standard PP 44-01 for asphalt-surfaced pavement-cracking data collection on NOS. The study covered approximately 262 km (164 mi) of in-service bituminous and composite pavements in Kansas. Nearly 50,000 images of the pavement surface were obtained for manual and automated evaluation of pavement condition. Two different processes of image analysis were compared with existing results from the KDOT annual survey. Transverse and fatigue crack severity and extent were manually interpreted following KDOT crack-rating algorithms for all sections. In addition, the sections were analyzed with an automated crack identification procedure following PP 44-01. The images corresponding to approximately a 5% sample rated by KDOT were identified. Comparative data were available for a manual distress survey on 5% samples (by KDOT) and image-based manual and automated interpretation on the 5% and 100% samples. Statistical analysis shows good agreement between the 5% sample and 100% sample results from the manual survey and image-based manual interpretation, respectively, for both crack types. This implies that a 5% pavement sample is adequate for describing crack severity and extent in NOS. Severity of fatigue cracks from the images was more difficult to rate, probably because of the descriptive nature of severity levels in the NOS algorithm. Agreement between the results from the manual image analysis on both 5% and 100% pavement samples and the KDOT manual survey is acceptable. However, the automated image analysis technique following the provisional AASHTO standard tends to overestimate severity of cracking.
Assessment of AASHTO Provisional Standards for Profile Data Collection and Interpretation
Authors: Miller Richard W. , Vedula Kamesh , Hossain Mustaque , Cumberledge Gaylord
Published: April 2007

The Kansas Department of Transportation (KDOT) currently uses a comprehensive, network-level pavement management system (PMS) known as the network optimization system (NOS). Annual condition surveys for roughness, rutting, and faulting generate important inputs for NOS. Recently, AASHTO published provisional standards for condition surveys to harmonize data collection efforts among the states. To study the effects of these provisional standards on KDOT NOS, profile data were collected on about 320 km (201 mi) of Kansas highways according to these standards. The comparison data came from KDOT's annual condition survey with KDOT standards. The roughness values, in terms of international roughness index, were computed and aggregated for 20 test sections; rut depths were computed and compared for 16 test sections; and the fault values were computed and compared for 4 test sections. Various statistical analyses compared the results from the algorithms, according to KDOT NOS and AASHTO provisional standards. The roughness measurements and subsequent analysis using AASHTO provisional standard PP 37-00 and current KDOT methodology tend to produce statistically similar results. This may indicate that the PP 37-00 standard can be adopted for NOS without any major changes in current practice. The four-level stratification for rut-depth severity suggested by AASHTO PP 38-00 compares reasonably well with the current NOS practice. Both algorithms compared well for 3 composite pavement test sections and on 7 of 13 bituminous sections. On these sections, the effects of 0.16-km (0.1-mi) and 0.1-km (0.0625-mi) aggregation are insignificant. The dissimilarities on other sections may result from the outer sensors in the five-sensor configuration required by AASHTO PP 38-00. However, significant differences were found in calculated fault values from the two methods, even after some modification to PP 39-00.
Effects of Variation in Quarter-Car Simulation Speed on International Roughness Index Algorithm
Authors: Perera Rohan , Kohn Starr
Published: April 2007

The international roughness index (IRI) is widely used throughout the world as a measure of road roughness. A quarter-car simulation at 80 km/h is performed on the longitudinal profile to compute IRI. Questions have been raised regarding the applicability of IRI for roads that are used at speeds above or below this simulation speed. To gain more insight into the effects of simulation speed, an investigation was carried out to determine how the roughness computed from the IRI model changes for different simulation speeds of the quarter car. This investigation was performed on an asphalt concrete data set and a jointed portland cement concrete data set. For simulation speeds between 60 and 110 km/h, the response from the IRI model was within ±0.20 m/km of the IRI for 80% of the asphalt sections and 61 % of the concrete sections used in the study. Although the output from the quarter-car model for the different simulation speeds was different from the IRI (simulation speed of 80 km/h), it is unclear to what extent a user's perception of the roughness of a roadway changes with the speed of travel. If examples of roadways are found where the subjective opinion of roadway users of the roughness seems inconsistent with the IRI, it is recommended that the IRI model be used with the current speed limit of the roadway to examine whether the obtained output provides a better match with the opinion expressed by roadway users.
Development of Guidelines for Placement of Guardrail Posts in Rock
Authors: Rohde John R. , Herr Jason
Published: April 2007

Computer simulation and physical testing of posts and guardrail installations were performed to develop a W-beam guardrail system for installation where bedrock is within the normal embedment depth of the posts. Computer simulation was conducted with BARRIER VII to determine optimal post force-deflection properties and the critical impact point for a full-scale vehicle crash test. Physical testing included dynamic testing of posts in various embedment configurations and one full-scale vehicular crash test, which was performed according to the Test Level 3 criteria specified in NCHRP Report 350. Steel W152 X 13.4 (W6 X 9) posts were embedded into an elongated hole drilled into rock and backfilled with ASTM C33 coarse aggregate, size No. 57. The elongated hole was created by drilling three holes 203 mm (8 in.) in diameter on 165-mm (6.5-in.) centers. The full-scale crash test, which was performed with a 2,000-kg pickup truck, was used to verify the safety performance of the design for situations where bedrock is encountered on the surface of the ground. Guidelines based on dynamic post testing were developed for use when the bedrock is encountered at various depths below the surface.
Narrow Connecticut Impact-Attenuation System: Synopsis Including NCHRP Report 350 Crash Test Results
Authors: Smith Erika B.
Published: April 2007

The compliance of a Connecticut-designed and -developed impact-attenuation system, the Narrow Connecticut Impact-Attenuation System (NCIAS), with NCHRP Report 350 guidelines is documented. Background information about the system is given, including information on the performance of field installation locations and the availability and cost of installation. NCHRP Report 350 specifies eight full-scale crash tests for redirective/nongating devices. Three of the eight tests were not conducted on the NCIAS because they are similar to three tests conducted under the NCHRP Report 230 requirements, which the NCIAS passed. The five remaining tests were performed. One test was repeated after one of the cylinders was strengthened. All tests were conducted in accordance with the guidelines of NCHRP Report 350 for Test Level 3 devices. The NCIAS passed all requirements for four of the five test designations. It did not pass the requirements for the reverse hit test; therefore, the NCIAS must not be installed at locations where it may be struck from the reverse direction. FHWA has approved the use of the NCIAS on the National Highway System at locations where reverse-direction impacts are unlikely.
Attributes and Amenities of Highway Systems Important to Tourists
Authors: Gartner William C. , Erkkila Daniel L.
Published: April 2007

Eleven road segments in Minnesota were examined in a user survey that addressed road travelers' preferences for physical characteristics, aesthetics, and amenities of that segment. The user survey was based on earlier focus group work. Results indicated that road travelers were able to differentiate between physical and socially derived attributes and amenities associated with a particular roadway. Roads do have character, and users are able to identify and evaluate characteristics specific to each road segment. Many roadway features related to maintaining scenic and environmental qualities were highly valued. Users are not supportive of additional business development along some roadways and prefer instead that activity be clustered in communities located on the road segment. Results also indicated that even though a particular roadway may not have had official scenic designation, user evaluations were similar to those with such designation or even more focused on scenic qualities.
Characteristics of Snowmelt Runoff from Highways in the Tahoe Basin and Treatment Investigations for Improving Runoff Quality
Authors: Kayhanian Masoud , Regenmorter Louis C. , Tsay Kuen
Published: April 2007

To reduce the current trend of decreasing water clarity of Lake Tahoe, the California Regional Water Control Board's Lahontan Region imposed numeric discharge limits for five pollutants (total nitrogen, total phosphorus, total iron, turbidity, and oil and grease) for both surface water and infiltration discharges in the Tahoe basin. To assess its compliance with these discharge limits, the California Department of Transportation (Caltrans) monitored six representative sites for snowmelt and other storm water runoff from summer 2000 through spring 2003. In addition, Caltrans has investigated several existing double-barrel sand traps for their effectiveness in removing pollutants and complying with the Tahoe basin discharge limits. The results obtained to date indicate that ( a) concentrations of pollutants found in the snowmelt runoff are higher than the specified storm water discharge limits; ( b) double-barrel sand traps were capable of capturing sand and sediment, but the capture was not complete; ( c) particles that range from 100 to 2,000 μm represented the highest proportion, but no correlation was found between particles and chemical concentrations; and ( d) sand traps did provide modest improvement in runoff quality, but this improvement was insufficient to meet Tahoe basin discharge limits, and hence additional treatment was found to be needed to bring the effluent water quality into compliance.
Storm Water Pollutant Removal in Roadside Vegetated Buffer Strips
Authors: Barrett Michael , Lantin Anna , Austrheim-Smith Steve
Published: April 2007

A 2-year water quality monitoring project was conducted to evaluate the removal of storm water contaminants by existing vegetated slopes adjacent to freeways. Objectives of the study were to generate design criteria and to determine whether standard roadway design requirements result in buffer strips with treatment equivalent to those specifically engineered for water quality performance. Variables such as width, slope, vegetation density, and hydraulic loading were evaluated by studying the runoff through existing vegetated slopes at four locations in northern California and four locations in southern California. At each location, concrete channels were constructed to capture freeway runoff after it passed through existing vegetated strips of varying widths. The quantity and quality of the runoff discharged from the buffer strip were compared with freeway runoff collected at the edge of pavement. Buffer strips consistently reduced the concentration of suspended solids and total metals in storm water runoff. The strips were also effective in removing dissolved metals when the edge of pavement concentrations were sufficiently high. Little or no change in concentration was observed for nitrogen and phosphorus. Concentrations of organic carbon, dissolved solids, and hardness increased. For the constituents exhibiting a decrease in concentration, steady-state levels were generally achieved within 5 m (16 ft) of the pavement edge for slopes commonly found on highway shoulders and where the vegetation coverage exceeded 80%. Slope, vegetation type and height, highway width, and hydraulic residence time had little or no impact on the discharge concentrations.
Issues in Automating Utility Permits at Transportation Agencies
Authors: Quiroga Cesar , Pina Robert
Published: April 2007

With the proliferation of utilities within the right-of-way (ROW) of highway facilities, transportation agencies around the country are finding it increasingly difficult to allow more utilities into the ROW and, at the same time, manage their own transportation systems effectively. Outstanding issues related to the utility permitting process at transportation agencies are outlined, a prototype online utility permit data management system that supports data transfer and map-viewing capabilities is described, and recommendations for implementation are discussed and formulated. Three goals drove the development of the prototype: to automate the utility permit data entry process, to reduce utility permit processing turnaround times and paperwork substantially, and to provide a mechanism to help maintain the inventory of utilities within the transportation agency up to date by using the data collected during the utility permitting process. The current status of the prototype is described, and several actions that will assist in the prototype implementation process are outlined. Also discussed are standards and specifications and the need to implement adequate positional accuracy and utility installation documentation procedures, which are rarely addressed in utility accommodation policies or technical specifications for particular projects. Implementing those procedures would result in a number of benefits. Among them are improving the quality of utility data at transportation agencies and utility companies, bringing the installation of utilities within the highway ROW to standards comparable with those of other construction activities within the ROW, facilitating the implementation of roadside safety programs, and contributing to the effective management of the highway ROW.
Measurement of Acoustical and Mechanical Properties of Porous Road Surfaces and Tire and Road Noise
Authors: Crocker Malcolm J. , Hanson Douglas , Li Zhuang , Karjatkar Ravi , Vissamraju Krishna S.
Published: April 2007

The absorption coefficients of dense and porous road surfaces have been measured in the laboratory with core samples with 4- and 6-in.-diameter impedance tubes and with an impedance tube mounted vertically in situ on the pavement surfaces. The 6-in. tube allows the absorption of a large core sample surface to be determined, but only up to a frequency of about 1,250 Hz. The 4-in. tube allows the absorption coefficient to be determined up to a frequency of about 1,950 Hz. The two different-diameter impedance tubes also were mounted vertically on some of the same pavement types, and the absorption coefficients of these pavement types were measured in this way too. The measured peak sound absorption coefficients of the fine- and coarse-mix aggregate porous surfaces suggest that the first peak frequency and peak absorption coefficient magnitude are only slightly different for the two types of porous surfaces. Because the fine-mix aggregate porous surface is smoother, it is preferred because it should result in less tire-tread impact noise and thus lower overall tire noise than the coarse aggregate surface. A porous surface between 1.5 and 2.0 in. thick is recommended for the type of porous surface examined, if a peak absorption frequency of about 1,000 Hz is desired, so as to be most effective at reducing the Interstate highway noise of automobiles.
Performance-Based Fracture Criterion for Evaluation of Moisture Susceptibility in Hot-Mix Asphalt
Authors: Birgisson Bjorn , Roque Reynaldo , Page Gale C.
Published: April 2007

The laboratory testing procedures currently available for testing hot-mix asphalt moisture susceptibility all evaluate the effects of moisture damage in the laboratory by measuring the relative change of a single parameter before and after conditioning (i.e., tensile strength ratio, resilient modulus ratio). The use of a single parameter to evaluate moisture damage must be questioned. Instead, a single unified framework that accounts for changes in key mixture properties is needed to evaluate the effects of moisture damage in mixtures effectively. The use of a new performance-based fracture parameter, the energy ratio (ER), for quantifying the effects of moisture damage on the fracture resistance of mixtures is evaluated here. ER is used to determine the effects of moisture damage on changes in the fracture resistance of six granite mixtures prepared with and without the use of an antistripping additive. The granite aggregate used is a known stripping aggregate. In addition, one limestone mixture with a known high resistance to stripping was used. The results indicate that not only is the ER capable of detecting the effects of moisture damage on the fracture resistance of mixtures, it is also shown to detect the presence of antistripping agents in mixtures. Results indicate that the ER may form the basis of a promising combined performance-based fracture criterion for evaluating the effects of moisture damage in mixtures as well as the overall resistance to fracture.
Analysis of Temperature Data for the National Center for Asphalt Technology Test Track
Authors: Watson Donald E. , Zhang Jingna , Powell R. Buzz
Published: April 2007

Several combinations of mix type, aggregate type, asphalt binder type, and layer thickness are in place at the National Center for Asphalt Technology (NCAT) test track. It was desirable to examine the effects these various combinations may have on temperatures within the pavement. The purpose of this study was to evaluate measured versus predicted temperatures, evaluate the effect of mix type on pavement temperature, and compare the effect of surface layer thickness on pavement temperatures. On the basis of temperature data from the NCAT test track, some of the general conclusions are that ( a) both the Strategic Highway Research Program (SHRP) and Long-Term Pavement Performance (LTPP) temperature models slightly underpredicted high pavement temperatures at 50% reliability and slightly overpredicted temperatures at 98% reliability and ( b) the low-temperature models for SHRP overpredicteded low pavement temperatures for both 50% and 98% reliability. The LTPP models were also overly conservative at 98% reliability. These results indicate that asphalt binders may not need to be as soft as specified in the Superpaver; performance grading system for low-temperature performance.
Field and Laboratory Performance of Superpave Mixtures in Nevada
Authors: Sebaaly Peter E. , Hand Adam J. T. , McNamara W. Marty , Weitzel Dean , Epps Jon A.
Published: April 2007

The Nevada Department of Transportation (NDOT) has strongly supported Superpaver-related research and implementation efforts since the completion of the Strategic Highway Research Program. However, it is one of the state highway agencies that has not implemented use of the Superpave mix design system. Instead of rapidly implementing Super-pave in the mid-1990s, NDOT chose to build field test sections composed of Superpave and the mixtures conventionally used at the time (Hveem) and placed side-by-side to evaluate the Superpave system relative to the system in use. Extensive laboratory evaluations were conducted on the materials and mixtures placed on each section, and field performance was monitored over time. This study presents a synopsis of the field and laboratory performance information gathered over the past 6 years. Planned NDOT evaluations of Superpave mixtures based on the findings of this effort to date are outlined.
Variability of Air Voids and Mechanistic Properties of Plant-Produced Asphalt Mixtures
Authors: Mohammad Louay N. , Wu Zhong , Zhang Chenggang , Khattak Mohammad J. , Abadie Chris
Published: April 2007

The results of a laboratory and field evaluation of the variability of physical and mechanistic properties of plant-produced asphalt mixtures are presented. Three asphalt mixtures from two overlay rehabilitation projects were selected. Comparison analyses were conducted on density measurements between two laboratory (AASHTO T166 and ASTM D6752-02, or CoreLok) and one in situ (pavement quality indicator) test methods. In addition, two laboratory mechanistic tests—indirect tensile (IDT)-strength and frequency-sweep-at-constant-height tests—and two field nondestructive tests with falling weight deflectometer (FWD) and light falling weight deflectometer (LFWD) were performed to characterize the variability of the plant-produced mixtures evaluated in this study. Superpaver gyratory compactor (SGC) samples and field cores were used in the laboratory testing program. A strong correlation was observed between the two laboratory bulk specific gravity test methods: AASHTO T166 and CoreLok. The IDT strengths of SGC samples were higher than those of field cores. A good correlation was found between the complex shear moduli of SGC samples and field cores. Field test results indicated that the LFWD test may be used as an alternative to the FWD test in pavement structure evaluation.
Effect of Superpave Defined Restricted Zone on Hot-Mix Asphalt Performance
Authors: Zhang Jingna , Cooley L. Allen , Hurley Graham , Parker Frazier
Published: April 2007

The effect of the Superpaver defined restricted zone on hot-mix asphalt rutting performance was evaluated. One gradation that violated the restricted zone (TRZ) and two gradations that did not violate the restricted zone (BRZ and ARZ) were evaluated. Evaluated mixes represented a range of maximum aggregate sizes (MASs), design traffic levels, and aggregate types. Three laboratory tests—asphalt pavement analyzer, rotary-loaded wheel tester, and Marshall test—were used to evaluate the rutting performance. From the analysis, it was found that mixes with gradations violating the restricted zone performed similarly to or better than the mixes with gradations passing outside the restricted zone with respect to laboratory rutting tests. This conclusion was drawn from the results of experiments with 12.5-, 19.0-, and 25.0-mm MAS gradations at Ndesign (design number of gyrations) values of 100, 75, and 50 gyrations. This conclusion is confirmed and supported by the recently completed NCHRP Project 9-14: The Restricted Zone in the Superpave Aggregate Gradation Specification. The results also showed that rutting performance of mixes having gradations below the restricted zone, which was commonly recognized to be rut resistant, appeared to be more sensitive to aggregate properties than mixes having gradations above or through the restricted zone.
Reduced Confined Dynamic Modulus Testing Protocol for Asphalt Mixtures
Authors: Sotil Andres , Kaloush Kamil E. , Witczak Matthew W.
Published: April 2007

The dynamic modulus ( E*) of asphalt mixtures correlates well with field performance. Studies have shown that in comparisons of dense-, gap-, and open-graded mixtures, confined E* ( C-E*) tests are recommended to rank and compare the expected field performance of the different mixtures. Unfortunately, C-E* tests are harder to perform than unconfined E* ( U-E*) tests. Factors such as time, availability of equipment, technical complexity, and financial needs must be carefully considered when a confined laboratory-testing program is being proposed. The objective of this study was to develop a simple method by which C-E* values could be predicted from U- E* results with a reduced number of C- E* tests. The methods analyzed were developed by using E* test results conducted on nine asphalt rubber mixtures at different confinement levels and were validated by using three conventional densegraded mixes previously tested at Arizona State University. The U- E* and C- E* test results generally showed a linear relationship with the applied bulk stress and were almost parallel regardless of the confinement level. An approach to predict a C- E* relationship from U- E* test data was developed by using one (or two) confined test(s) instead of the five required by current test protocols. The methods investigated potentially would provide a decrease in laboratory testing time of at least 50%. Because some level of laboratory confinement is recognized for gap- and open-graded mixes, the methods investigated in this study also may prove helpful in the development of more accurate pavement distress prediction models.
Dynamic Modulus Testing of Asphalt Concrete in Indirect Tension Mode
Authors: Kim Y. Richard , Seo Youngguk , King Mark , Momen Mostafa
Published: April 2007

This study presents the results from an analytical and experimental study on the dynamic modulus testing of hot-mix asphalt using the indirect tension (IDT) mode. An analytical solution for the dynamic modulus in the IDT mode was developed with the use of linear viscoelasticity. To verify the analytical solution, temperature and frequency sweep tests were conducted on 12 asphalt mixtures commonly used in North Carolina; both axial compression and IDT test methods were used. A modified dynamic modulus test protocol is introduced to reduce the required testing time by using more frequencies and fewer temperatures on the basis of the time-temperature superposition principle. A comparison of results from the axial compression and IDT test methods shows that the dynamic modulus master curves and shift factors derived from the two methods are in good agreement. It also was found that Poisson's ratio was a weak function of the loading frequency; its effect on the phase angle master curve is discussed.
Evaluation of Simple Performance Tests on Hot-Mix Asphalt Mixtures from South Central United States
Authors: Bhasin Amit , Button Joe W. , Chowdhury Arif
Published: April 2007

Since development of the Superpaver mix design procedure under the Strategic Highway Research Program about a decade ago, there has been a need to develop some type of a simple physical test to complement the Level 1 volumetric mixture design procedure. NCHRP Project 9-19 recognized the dynamic modulus test along with the flow time and flow number tests as the top three candidates for a simple performance test that could identify mixtures susceptible to permanent deformation. A critical evaluation of these three tests is presented along with the Super-pave shear test-frequency sweep at constant height with the asphalt pavement analyzer (APA) as the torture test to identify mixes susceptible to permanent deformation. The Hamburg wheel-tracking device (HWTD) also was used on selected mixtures. Special laboratory hot-mix asphalt mixes designed to exhibit low dynamic modulus but high recovery of strains were included in this evaluation. Results indicated that flow number value and flow time slope correlated better with laboratory rutting (APA and HWTD) than dynamic modulus. Flow number value, flow time slope, E*/sin Φ at 1 Hz, flow number slope, and flow time value were among the best five correlations with both the APA and the HWTD rut depths.
Evaluation of the Dynamic Angle Validator
Authors: Moseley Howard L. , Page Gale C. , Musselman James A. , Sholar Gregory A. , Upshaw Patrick B.
Published: April 2007

Current test methods specify that the angle of gyration of a Superpaver gyratory compactor (SGC) be measured externally or outside of the mold. The external angle of gyration may not accurately portray the actual angle inside the mold during compaction. Significant differences in compacted density have been observed in specimens compacted with different SGCs. Measuring the angle of gyration inside the mold would reveal the cause for varied levels of compaction in different SGCs. The dynamic angle validator (DAV) was developed to measure the internal angle of gyration. The Florida Department of Transportation evaluated the DAV with several mixtures and compactors. Mixture stiffness had an effect on the internal angle measurement in some SGCs. Measuring and setting SGC angles of gyration internally statewide should reduce the variability in compacted density among different SGCs. Other factors not related to angle of gyration can contribute to density variability. The compactor needs to be clean and in good working order, and the molds and plates need to be checked for wear. These factors should also be addressed on a statewide basis.
Benefits of Warranties to Indiana
Authors: Gallivan Victor L. , Huber Gerald R. , Flora William F.
Published: April 2007

Several states have experimented with performance warranties on hotmix asphalt (HMA) pavements. Generally, the quality of warranted HMA is perceived to be better. Also, it is believed that HMA extends pavement life. Various methods can be used to define the benefits of warranties. Benefits have to be related to the performance life of the pavement and the cost. This study documents the effectiveness of the Indiana 5-year performance warranties and demonstrates that projected lifetimes of the warranted HMA pavements are being extended an additional 9 years in evaluations of international roughness index (IRI) and rutting criteria over the typical design life of the pavements. The cost-effectiveness of the warranted pavements, even though the initial costs are 5% to 10% higher, is significant when one considers the extended life of the warranted pavements. Overall cost to maintain the network Interstate smoothness at a constant 2002 value is $ 1.08 billion with warranties and $ 1.47 billion for nonwarranty projects, or a savings for warranty projects of 27%. Warranty projects require fewer demands on budgets and provide for lower network IRI at the same effective age of the pavements. Indiana HMA warranties have accomplished the initial goals of both the Indiana Department of Transportation and the HMA industry by providing smoother and safer pavements with fewer defects over a longer period of time, which reduces delays and congestion. At the same time, the economic benefits of warranted pavements are significant.