bluuebunny/crossref_metadata_2025 huggingface dataset:
Estimating the Capacity of Freight Transportation Systems: A Model and Its Application in Transport Planning and Logistics
Authors: Morlok Edward K. , Riddle Stephanie P.
Published: April 2007

The issue of adequate capacity in the freight transportation system to accommodate growing cargo volumes is now becoming a major public policy concern. The problem of extraordinary rail line congestion and service failures in connection with the recent Union Pacific–Southern Pacific merger has galvanized attention to the problem, but the issue extends far beyond the rail system to other modes and contexts. The concept of system capacity (as opposed to link or facility capacity) is developed, and prior literature is reviewed for approaches to estimating it. A model that was developed from the most promising of these is presented. This model is multimodal in concept and is intended to be applicable to any vehicular freight mode. The model is tested through application to a portion of the rail network, and results are assessed for reasonableness and utility. Finally, the applicability of the model and approach to various capacity-related questions is described and discussed.
Estimation of Commodity Inflows to a Substate Region: An Input-Output Based Approach
Authors: Vilain Pierre , Nan Liu Louie , Aimen David
Published: April 2007

A methodology to estimate current commodity inflows to a substate region using a variant of the standard regional input-output model and commodity flow data from the 1993 Commodity Flow Survey is presented. Existing data in the Commodity Flow Survey do not go below the state level, making the estimation of commodity flows to a particular substate region difficult. By combining state-level commodity flow data with a “supply-side,” commodity-by-industry input-output model, an estimate of commodity flows to a region can be carried out based on the region’s existing industrial structure. The information on current commodity inflows is particularly useful for analyzing the total potential demand that might be captured by a new mode or service. For example, one application could be estimating the potential for air cargo shipments to an area that is not currently served by local air cargo.
Defining a Strategic Freight Network for the Greater Toronto Area
Authors: Gorys Julius , Poulos Nicholas , Gray Ross , Ruggero Alfonso
Published: April 2007

The Ontario Ministry of Transportation, in cooperation with regional municipalities, is developing a comprehensive transportation plan for the Greater Toronto Area (GTA) to enhance mobility for people and goods while supporting broader economic, environmental, and social objectives. Trucks are responsible for the transportation of an estimated 80 percent of the goods in the GTA. To provide input into the current GTA transportation planning exercise, the strategic freight network in the GTA was identified, the importance of the strategic road network for efficient and effective goods movement was assessed, and initiatives concerning operational improvements and infrastructure programs that can enhance or support goods movement were identified. It was postulated that the majority of goods-movement trips in the GTA were concentrated to, from, or in “Freight Centres” and that most truck activity took place on prominent parts of the local and regional transportation infrastructure between these Freight Centres. Four distinct and specific land uses were identified as being strong indicators of goods-movement origins and destinations. They are manufacturing and assembly facilities; warehouses; intermodal terminals; and trucking support facilities, including yards, terminals, parking, and service locations. Congestion and the absence of sufficient routing information were found to be the principal issues faced by the goods-movement industry. Several informational, capital, and operational improvements were subsequently identified and should be considered within the context of the strategic freight network that could enhance the use of the system by goods-movement operators.
Getting the Goods Delivered in Dense Urban Areas: A Snapshot of the Last Link of the Supply Chain
Authors: Morris Anne G. , Kornhauser Alain L. , Kay Mark J.
Published: April 2007

Data were analyzed from 74 “Freight Mobility Interviews”—surveys conducted with key transportation executives whose products and services are shipped into New York City’s central business district (CBD). Quantitative data collected included company profiles, defined by product category; kind of transportation service; type of distribution channel; characteristics of dispatched truck trip; and time and cost for last leg of trip. Major barriers to freight mobility identified by logistics/distribution/ transportation managers were widespread congestion, theft/vandalism, inadequate docking space, and insufficient curbside parking for commercial vehicles. Recommendations to increase productivity in the CBD included off-peak and extended delivery hours, additional truck parking zones, and incentives to upgrade docking areas. Barriers to freight mobility were consistent across industry sectors. Initiatives that have the potential to increase the efficiency of urban goods movement include improved law enforcement to deter theft/vandalism, information-based improvements such as accurate signage, the use of ITS technology and management systems to actively manage curbside commercial parking zones, and improved road maintenance. The nontraditional methodology developed for collecting urban freight mobility data provides process-oriented data that reflect changing supply chain strategies of private-sector shippers and carriers.
Infrastructure and Economic Impacts of Changes in Truck Weight Regulations in Montana
Authors: Hewitt Julie , Stephens Jerry , Smith Kristen , Menuez Nate
Published: April 2007

The overall impacts of changes in truck weight limits on the economy in Montana were determined. Four scenarios were considered with different maximum allowable gross vehicle weights (GVWs). Three scenarios, with maximum GVWs of 36,300 kg (80,000 lb), 39,300 kg (88,000 lb), and 47,900 kg (105,500 lb), represented reductions in GVWs. The fourth scenario represented an increase in allowable GVW to 58,100 kg (128,000 lb). Predictions were made of the vehicle fleets under each scenario and of the changes in demands and performance of the highway infrastructure. Only nominal changes in infrastructure demands were observed across all scenarios (maximum of $1.5 million). Case studies of the impacts expected on selected industries within the state were conducted. Changes in transportation costs of 4 to 54 percent were predicted under the 36,300 kg (80,000 lb) scenario, which were estimated to be 0.2 to 4.1 percent of the value of the goods produced. Changes in transportation costs typically were at least an order of magnitude larger than changes in infrastructure costs. Statewide economic impacts in terms of forgone gross state product amounted to -0.4 percent and, in the first year alone, were 2 to 20 times the infrastructure impacts, depending on the scenario.
Rehabilitation of Ellaville Weigh Station with Ultrathin Whitetopping
Authors: Armaghani Jamshid M. , Tu Diep
Published: April 2007

The Florida Department of Transportation constructed the first ultrathin whitetopping (UTW) project at the Ellaville truck weigh station on I-10 in northwest Florida. This rehabilitation project included the placement of UTW on the existing asphalt pavement, which had experienced severe rutting problems. Layer thicknesses for the UTW were 80 mm and 100 mm. The joint spacings for the UTW panels were 1.2 m and 1.6 m. High early strength concrete was used in this project. Polypropylene fibers were included in the concrete for the sections on the west side of the weight platform and plain concrete was used on the east sections. The joints on the east section were sealed with silicone sealant and the joints on the west section were left unsealed. Falling weight deflectometer tests and frequent condition surveys were performed on the projects. After 1 year of service and 1.1 million equivalent single-axle loads, the UTW shows good performance. Success and long-term performance of the UTW is highly dependent on the degree of bonding between the UTW and the asphalt base. During the study period, panels 1.2 m2 and 1.6 m2, concrete with and without fibers, sealed and unsealed joints, showed similar performance. It is predicted that the 1-year performance of the UTW at the weigh station is equivalent to 4.5 years of service at a medium traffic intersection.
Summary of the 1996 Portland Cement Concrete Performance-Related Specification Shadow Field Trial: Iowa State Route 23
Authors: Hoerner Todd E. , Darter Michael I. , Kopac Peter A.
Published: April 2007

The results of a “shadow” field trial (actual contractor pay was not affected) conducted to demonstrate a Level 1 prototype performance-related specification (PRS) for jointed plain concrete pavement construction are presented. The Level 1 PRS (the most practical PRS method at this time) is believed to be immediately implementable because it uses currently practiced sampling and testing procedures. The future pavement performance is represented by distress indicators that are predicted on the basis of measured acceptance quality characteristic (AQC) values. Pay factors are determined independently for each AQC from simulated pay factor versus AQC curves and corresponding equations. The overall lot pay factor is determined from a simple mathematical manipulation of the individual AQC pay factors. The specific objectives of the field trial were to verify and confirm the draft specification’s effectiveness, identify potential problem areas, and determine its reasonableness. This paper discusses all aspects of the field trial including the relevant definitions, selection of lots and sublots, sampling and testing plan, calculation of shadow PRS pay adjustments, problems encountered, and a summary of lessons learned.
Development of Florida Smoothness Specifications for Flexible Pavements
Authors: Ksaibati Khaled , Miley William , Mcnamara Ronald , Armaghani Jamshid M.
Published: April 2007

Initial pavement smoothness has been shown to improve overall pavement performance. This combined with the need to provide a comfortable ride for the driving public underscores the importance of achieving high initial pavement smoothness. The Florida Department of Transportation has developed smoothness specifications for asphalt pavements. These smoothness specifications will be used on high-speed facilities and will be based on measurements obtained with laser road profilers. The ultimate goal is to include incentive and disincentive specifications aimed at rewarding the contractor for a high-quality ride and simultaneously providing a financial deterrent to providing a poor-quality ride.
Practical Framework for Performance-Related Specifications
Authors: Weed Richard M.
Published: April 2007

As highway agencies moved away from the older prescription-type specifications and began to develop end-result and performance-related specifications, several different statistical measures of quality have been used. These include the sample mean (x); percent defective or its complement, percent within limits; and the average absolute deviation. Conformal index is yet another measure that has been proposed. What has not been undertaken during this developmental period is any sort of formal analysis to determine which, if any, of these measures accurately reflects the expected performance of the construction items to which they are applied. Specialized computer programs were developed to demonstrate potential weaknesses of current quality measures and to explore alternate approaches that may overcome these weaknesses. It was found that pay equations based on the mean and standard deviation computed from the sample can be tailored to closely match the value of the constructed product as estimated by life-cycle cost techniques. It is believed that this forms a practical starting point for the development of construction acceptance procedures more closely linked to quantified performance models.
Performance Review of a Quality Control/Quality Assurance Specification for Asphalt Concrete
Authors: Benson Paul E.
Published: April 2007

A statistical review of 50 jobs recently completed by using California’s new quality control/quality assurance (QC/QA) specification for asphalt concrete is presented. Performance is contrasted to the quality achieved under method and end-result specifications. A cost analysis is made and issues related to verification are discussed. Improvements to the current specification are proposed. The data present clear evidence that the allowable tolerance of ±0.5 percent for asphalt content is too wide for current practice. Also, an increase in compaction variability for many QC/QA jobs could be controlled by adding an upper specification limit or adopting a two-sided volumetric specification. Although bid amounts did not increase, costs for QC/QA jobs went up approximately 3 percent to pay for bonuses allowed under the specification. Analysis of the contractor’s QC test data indicate that this increase is more than compensated for by projected reductions in future rehabilitation costs. However, a significant lack of agreement between the contractor QC and agency QA testing brings this finding into question. More rigorous verification of contractor-provided test results must be incorporated into the specification and the results analyzed before the cost-effectiveness can be determined.
Evaluation of Quality Control/Quality Assurance Implementation for Asphalt Concrete Specifications in California
Authors: Douglas Kimberly D. , Coplantz John , Lehmann Ruth , Bressette Terry
Published: April 2007

The California Department of Transportation (Caltrans) has implemented a new quality control/quality assurance (QC/QA) specification for asphalt concrete. As part of this implementation, Caltrans realized the need for objective feedback on its design and implementation and selected Nichols Consulting Engineers to perform this study. The study’s objectives and the research approach used and a description of the projects included in the study are presented, along with recommendations and findings. Lessons learned from the Caltrans experience are shared to the benefit of other states implementing QC/QA specifications for asphalt concrete.
Replacement of the Suspension System of the Tancarville Bridge
Authors: Virlogeux Michel
Published: April 2007

The Tancarville bridge across the Seine was the subject of numerous design efforts during the first part of the 20th century. In 1953 the final design of a suspension structure was selected by the French authorities. Construction began in 1954 and was completed in 1959. This marked the opening of the longest suspended span in Europe for that time. Indications of rapid corrosion in the suspension cables were observed as early as 1965, and by 1970 design work was under way for possible cable replacement. This development influenced the decision to build the Normandie Bridge as a second river crossing. The matter became urgent in 1995 when a strand of one Tancarville cable broke because of advanced corrosion. Beginning with a historical review, this paper explains why the cables of the Tancarville bridge had to suffer from corrosion under tension. It shows how the owner organized the concurrent pursuit of many goals, guaranteeing structural safety, maintaining traffic, and calling for bids while developing a design to replace the entire suspension system at the earliest possible time.
Epoxy Jointing of Concrete Bridge Segments
Authors: Yazdani Nur , Issa Moussa , Wolfe Clayton
Published: April 2007

Epoxy is used between precast bridge segments to fill voids on the faces, keep water and contaminants from seeping into joints, prevent grout from bleeding into joints from posttensioning ducts, and act as a lubricant between the segments during assembly. To create a good seal at the joint faces, two experimental epoxy applications were tested: a top strip recess at the joint formed in the concrete during precasting, and a recessed annulus groove around the duct that provides a distinct guide for epoxy application. Eight beams were fabricated with various combinations of epoxy face applications, top strip, and annulus. Six segments were cast by using match casting. After curing, the beams were posttensioned with the minimum required prestress force. Tanks above the joints were used to measure the seepage of water and joint permeability comparisons. Pressurized water was used to test the cross grouting between ducts. The top strip provided slightly more resistance than did the current one face epoxy application technique and improved alignment problems, segment defects, and epoxy application procedures. The annulus created a watertight seal around the ducts and assisted in aligning the segments and coupling the ducts. The existing practice of one face application performed well in both tests, but problems occurred in epoxy thickness and clearances. The top strip and annulus features eliminated the approximation of edge and duct clearances. Both performed well together and helped the epoxy application process produce a more reliable joint without additional work in casting or erection of the segments.
Øresund Bridge
Authors: Falbe-Hansen Klaus , Larsson Örjan
Published: April 2007

The Øresund Bridge is part of the international fixed link currently under construction across the sound separating Copenhagen, the capital of Denmark, and Malmö, the third-largest city in Sweden. The link, scheduled to open in 2000, is a toll-funded motorway and railway crossing. The 15.8-km coast-to-coast part of the link consists of a 0.5-km artificial peninsula at Copenhagen Airport, a 3.5-km immersed concrete tunnel, a 4-km artificial island, and a 7.8-km bridge. The bridge includes as its central section a 1.1-km cable-stayed bridge. The 490-m main span crosses the international shipping lane Flintrännan with 57-m minimum headroom and on completion will be the longest span of any cable-stayed bridge in the world carrying both road and railway traffic. Approach spans leading up to the cable-stayed bridge are typically 140 m. The owner of the link is Øresundskonsortiet, a company jointly and equally owned by the Danish and Swedish states responsible for financing, planning, implementing, and operating the link. ASO Group is the owner’s bridge consultant responsible for the concept, the technical documentation, and for monitoring and auditing the construction of the bridge. Described are the background and strategy in procuring this major international infrastructure project and the development of the bridge design from design competition to construction.
Wearing Surfaces for Orthotropic Steel Bridge Decks
Authors: Hulsey J. Leroy , Yang Liao , Raad Lutfi
Published: April 2007

In the state of Alaska, a six-span 884.5-m orthotropic steel bridge crosses the Yukon River at a 6 percent grade. The bridge is on a gravel road, it has a roadway width of 9.2 m, and the orthotropic steel deck is supported by two steel box girders 154.9 cm wide and 414.0 cm deep. The structure is expected to support the oil pipeline, a future gas line, and a low volume of heavy loaded trucks and to respond to harsh winter temperatures. This structure was designed in the early 1970s with a 127-mm two-layer timber deck wearing surface. Since then, the wearing surface has been replaced twice with timber decks (1981, 1992) and is again scheduled for timber deck replacement in 1999. Alternative wearing surfaces for other orthotropic bridge decks are reviewed. Orthotropic steel deck flexibility is examined and design charts for selecting the thickness for a given wearing surface are presented. The design charts account for truck loads and temperature change; no provision is made for traction or abrasion. The use of these charts is illustrated. Strains caused by prepositioned truck loads were measured in the orthotropic steel deck. The deck had a two-layer 127-mm timber wearing surface. These strains were compared by analysis. The results showed that the timber-deck system was stiff. Live load tensile strains and the range of strain were low; thermal stresses are expected to be high. Cold temperature thermal cracking, abrasion, adhesion to the steel deck, and traction are important parameters for selecting a future wearing surface. Live load fatigue in the wearing surface should not be a problem for this orthotropic bridge.
Analysis of the Impacts of Freeway Reconstruction Closures in Urban Areas
Authors: Nam Doohee , Lee Jinsun , Dunston Phillip , Mannering Fred
Published: April 2007

The traffic- and business-related impact of a weekend closure of a major urban freeway is evaluated. Data were gathered from a 9-km section of 1-405 in Seattle that was closed to traffic in a single direction for two consecutive weekends, August 15-17 and August 22-24, 1997, for repaving operations. In evaluating this approach to highway reconstruction (i.e., total directional closure), the impact on vehicle travel time and total emissions including carbon monoxide, oxides of nitrogen, and volatile organic compounds was estimated. Also, a survey was conducted asking travelers how their travel patterns changed in response to the weekend closure of this section of 1-405. In addition to questions about changes in travel patterns, questions relating to the travelers’ overall impressions were asked. Limited dependent analysis techniques including ordered probit and binary logit models were used in the survey analyses. Finally, a small sample of businesses were interviewed for their impressions of the closure.
Use of Best Value Selection Process: Utah Department of Transportation I-15 Design-Build Project
Authors: Postma Stanley S. , Carlile Frank , Roberts James E.
Published: April 2007

Carter and Burgess, Inc., was selected by the Utah Department of Transportation (UDOT) to evaluate several aspects of the I-15 design-build reconstruction project under way in Salt Lake City. The evaluations are being completed in part to fulfill commitments made to FHWA, which granted a Special Experimental Project 14 status to the I-15 project, permitting design-build contracting methods. Information is presented about the selection process used by UDOT to hire a design-build team to work on the project. UDOT decided to use a “best value” selection process instead of low cost to select a contractor. Comparisons are made between the design-bid-build and design-build processes. Described is the “best value” selection process used by UDOT to evaluate and select a contractor, using the detailed selection process. A description of the organizational structure required to prepare and review the proposals is presented. Unique features of the UDOT process are discussed, including use of stipend, risk sharing, ISO 9000 certification, design life, performance specifications, best and final offer, award fees, and use of CD-ROMs to distribute the proposal information. Lessons learned in the process also are presented.
Quantifying Damage from Utility Cuts in Asphalt Pavement by Using San Francisco’s Pavement Management Data
Authors: Chow C. A. , Troyan V. B.
Published: April 2007

The City and County of San Francisco is one of the oldest cities in the United States. Over time, the roads and underground utilities have grown into a complex network of infrastructure that encompasses 1746 centerline km (1,100 centerline mi) of utilities and 18 million m2 (195 million ft2) of pavement. The estimated annual maintenance cost of a square meter of pavement is $23.03 ($2.14 per square foot). With a 20-year service life, the streets of San Francisco are worth over $8 billion today. In 1984, the Department of Public Works and pavement experts designed a Pavement Management and Mapping System (PMMS), which was intended to reduce a $78 million backlog of rehabilitation projects and allocate funds for annual street maintenance. Since that time, engineers and repair crews have observed deterioration of the pavement surrounding restored trenches. During the last decade, the city spent an average of $12 million per year for maintenance. Even with an aggressive program of resurfacing and slurry sealing, the backlog of substandard streets has grown by 60 percent. Clearly, the overall deterioration of San Francisco’s streets is not the product of traffic and weather alone. The purpose of this study is to determine if utility trenches are a notable cause of pavement deterioration. Statistical analysis of the condition data reveals that utility cuts result in a significant, immediate decrease in the condition of the pavement. This damage is roughly equivalent to several years of normal wear. City administrators and economists can use this information to quantify the pavement damage and develop policies and financial plans for pavement restoration.
Optimum Decision Policy for Management of Pavement Maintenance and Rehabilitation
Authors: Abaza KHALED A. , Ashur SULEIMAN A.
Published: April 2007

An effective practical decision policy has been developed for use in the selection of an optimum maintenance and rehabilitation program. Its main objective is the optimization of pavement condition under constrained budgets. The developed policy utilizes a discrete-time Markovian model with five condition states labeled a, b, c, d, and f. State a represents pavements in excellent condition, and State f indicates pavements in bad condition. Several decision options have been introduced based on either maximizing the proportion of “good” pavements or minimizing the proportion of “bad” pavements. State probabilities at some desired future time have been used as the main objective functions in the development of optimum maintenance and rehabilitation programs. The unknown variables in these programs are those representing improvements to pavement condition through implementation of maintenance and rehabilitation work. The resulting optimum programs are nonlinear in form, and therefore the penalty function method with functional evaluations has been successfully used to yield optimum solutions. The optimum solution to a particular program defines the type and extent of maintenance and rehabilitation work required for annual or biennial implementation. Pavement maintenance is mainly defined as routine maintenance consisting of filling cracks, patching potholes, and other applicable techniques such as chip seal coat or slurry seal. Pavement rehabilitation is defined as major rehabilitation actions to include resurfacing (overlay), resurfacing with partial reconstruction (localized reconstruction), and complete reconstruction applied to pavements in States c, d, and f, respectively.
Development of Pavement Performance Models for Riyadh Street Network
Authors: Al-Mansour Abdullah , Al-Swailmi Saleh , Al-Swailem Swailem
Published: April 2007

Pavement performance models are the main element in any Pavement Maintenance Management System (PMMS). The objectives of this paper are to investigate the factors that affect the pavement condition of the Riyadh street network, to develop pavement performance models, and to validate the developed models. The urban distress index (UDI) was used as a measure of pavement condition. The factors included in the models were pavement age, traffic level, availability of drainage system, and maintenance type. A separate model was developed for pavement sections with utility cut patching. All the developed models were found statistically significant in predicting pavement condition at the 95 percent confidence level.
Deterioration Models for Managing Flexible Pavements
Authors: Ullidtz Per
Published: April 2007

The deterioration of pavements, in terms of roughness, rutting, and cracking, is a complex process. An incremental-recursive method is needed to model this process because of the influence of time and aging and the interaction between different types of distress. A number of deterioration models are presented that may be used with the mechanistic-empirical method to model the gradual deterioration of pavements as a function of loading, climate, and aging. Comparisons of measured and calculated stresses, strains, and deflections have shown that the simple combination of Odemark’s transformation with Boussinesq’s equations (modified for nonlinearity) results in an agreement between measured and calculated values that is as good as that obtained with the finite element method. Linear elastic methods normally result in rather poor agreement. A program called Performance and Economic Rating System (PERS) is presented in which the simple mechanistic method is combined with deterioration models using the critical stresses or strains in the pavement materials to predict deterioration. With this model it is possible to consider all of the elements that are believed to be essential for pavement deterioration, including seasonal variations, aging, and interaction between different modes of distress. The program may be used on the project as well as on the network level and uses historical data for verification and modification of the models to fit the particular conditions of the network considered.
Assessment of Relative Contribution of Input Variables to Pavement Performance Prediction by Artificial Neural Networks
Authors: Shekharan A. Raja
Published: April 2007

Neural networks can be quite efficient at classification, pattern recognition, and prediction. However, the knowledge embedded in the neural network is opaque; that is, it is difficult to understand how neural networks arrive at the results. Here three explanatory mechanisms (attempts to explain the knowledge) are reviewed from the literature. Neural networks are trained to predict the present serviceability rating (PSR) of pavements with structural number, age, and cumulative equivalent single-axle loads as input variables. To determine the relative contribution of each input variable to the prediction of PSR, the method of partitioning of connection weights is employed. Neural networks are also trained with a few connection weights pruned, and the relative contribution of the input variables to the prediction of PSR is assessed. Apart from the three input variables mentioned above, another input variable, random numbers, is introduced. Its contribution to the prediction of PSR is found to be minimal.
Multiobjective Optimization in Pavement Management by Using Genetic Algorithms and Efficient Surfaces
Authors: Pilson Charles , Hudson W. RONALD , Anderson Virgil
Published: April 2007

Genetic algorithms (GAs) are becoming an increasingly popular way to search huge solution spaces to find good solutions. Pavement management problems are specialized scheduling problems for which the solution space grows exponentially with the problem size so that the solution space size becomes unmanageable by “true” optimization techniques very quickly. Pavement management is thus ideally suited for directed random search heuristics such as GAs. The formulation of a typical general project-level pavement management problem for solution by GAs is described. Both the single- and the multiobjective cases are discussed, and the results of a series of tests of the performance of the formulations are presented. A very useful insight is then presented to show how the general network problem can be solved using project-efficient surfaces. It is concluded that GAs are an extremely flexible and robust approach to solving myriad forms of pavement management problems and provide a rich area for future research. It is also concluded that using efficient surfaces to break down the network problem into project subproblems holds a great deal of promise for overcoming some of the existing problems of optimization in pavement management.
Prioritization Methods for Strategic Planning and Road Work Programming in a New Highway Development and Management Tool
Authors: Kerali H. R. , Mannisto V.
Published: April 2007

The Highway Design and Maintenance Standards Model (HDM-III), developed by the World Bank, has been used for over two decades to combine technical and economic appraisal of road investment projects, standards, and strategies. The International Study of Highway Development and Management has extended the scope of the HDM-III to provide a harmonized systems approach to road management, with adaptable and user-friendly software tools. The new Highway Development and Management Tool (HDM-4) now caters to strategic planning, work programming, and project preparation. Strategic planning involves the analysis of the road system as a whole, typically requiring the preparation of short- or long-term estimates of expenditure for road development and preservation under various budgetary and economic scenarios. Work programming involves the preparation, under budget constraints, of multiyear road work and expenditure programs in which sections of the network likely to require improvement are identified and listed by priority. Project preparation is the final stage in which the economic benefits of road schemes are analyzed before implementation. The optimization methods developed for the strategy and program applications of HDM-4, which use incremental benefit-cost ratios in the prioritization process, are described.
Automated Real-Time Pavement Distress Analysis
Authors: Cheng H. D. , Jiang X. , Li J. , Glazier C.
Published: April 2007

Pavement distress detection and analysis is an important component of pavement management systems. Conventional visual and manual pavement distress analysis techniques are very costly, time-consuming, dangerous, labor-intensive, tedious, and subjective; have a high degree of variability; are unable to provide meaningful quantitative information; and almost always lead to inconsistencies in distress detail over space and across evaluations. In this paper, a novel system for multipurpose automated real-time pavement distress analysis based on fuzzy logic and morphology is presented. The proposed system provides high data acquisition rates; effectively and accurately identifies the type, severity, and extent of surface distress; improves the safety and efficiency of data collection; offers an objective standard of analysis and classification of distress; helps identify cost-effective maintenance and repair plans; provides images and examples through the information highway to other user-researchers; and provides an image and sample bank for training or as the benchmark for testing new algorithms. The proposed system can also contribute to other research in pavement maintenance, repair, and rehabilitation.
Development of Procedure for Automated Segmentation of Pavement Rut Data
Authors: Ping W. Virgil , Yang Zenghai , Gan Liyun , Dietrich Bruce
Published: April 2007

To effectively manage pavements, it is necessary to know the current pavement condition. The Florida Department of Transportation uses an automated road profiler system to survey pavement condition. This system uses ultrasonic technology and is able to collect rut data at a high speed with tolerable accuracy. The system software processes the raw data into a density of 62 data points per kilometer. For pavement management applications, a summary of the rut data would be more useful than simply a list of them along the road. Thus, the objective of this study was to find a better way to reduce the amount of data and maintain the attributes as much as possible. To achieve the goal, an SAS (Statistical Analysis Software) segmentation program based on the cumulative difference approach (CDA) was developed to process the rut data. With this program a road may be divided into a number of segments within which the rut depth is relatively uniform. The average of the rut depths within this segment may represent the rut depth value of the whole segment. The data reduction rate and the sum of squared errors (SSE) were used in a case study as the indicators to compare the results from different user-specified constraints and to illustrate the usefulness of the CDA in rut data reduction. It may be concluded that the CDA is an effective method for rut data reduction in pavement management applications.
Profiling Flexible Highway Pavement Continuously with Rolling Dynamic Deflectometer and at Discrete Points with Falling Weight Deflectometer
Authors: Bay J. A. , Stokoe K. H. , McCullough B. F. , Alexander D. R.
Published: April 2007

Nondestructive testing of pavements plays an important role in the management of pavement infrastructure. Nondestructive testing techniques have been widely utilized in the United States during the past decade to characterize pavement systems at discrete points. Discrete-point testing is, however, not feasible for routine use as a means of continuously characterizing pavement systems. A new nondestructive testing technique for continuously profiling pavements has been developed, namely, the rolling dynamic deflectometer (RDD). The RDD is a large truck on which a servohydraulic vibrator is mounted. The vibrator is used to apply large vertical dynamic loads to the pavement with loading rollers, and the induced dynamic displacements are measured at multiple locations with rolling sensors. This arrangement permits continuous measurements at multiple locations on the pavement surface in a fraction of the time required for typical discrete-point testing at a few points along the section. In this paper, the configuration of the RDD and the procedure used to analyze RDD data are discussed. Continuous deflection profiles are presented from a test section of a flexible Interstate highway pavement, which contains several distinctly different pavement structures. The effects of the structures on measured deflections are discussed, and the capability of the RDD to delineate the extent of each feature is presented. The importance of loading frequency and resonances in the pavement structure is shown. In addition, results from the RDD are compared with results from falling weight deflectometer (FWD) tests performed at the same locations.
Estimation of Present Serviceability Index from International Roughness Index
Authors: Hall Kathleen , Muñoz Carlos
Published: April 2007

An analysis is described that was undertaken with the objective of developing realistic models for estimating present serviceability index (PSI) as a function of international roughness index (IRI) for asphalt and concrete pavements. These models were developed by first analyzing the correlation between slope variance and PSI values obtained in the serviceability correlation analyses for the Road Test conducted by the American Association of State Highway Officials (AASHO) and then analyzing the correlation between slope variance and IRI for profiles representing a broad spectrum of road roughness levels. Equations are given for the recommended PSI-IRI models for asphalt pavements and concrete pavements, respectively. The Road Test data clearly demonstrate a difference between concrete pavement serviceability and asphalt serviceability for a given level of roughness as measured at the Road Test and quantified by the slope variance as defined at the Road Test. Whether this would be true for other roughness indices is impossible to conclude from the Road Test data. For the purpose of design and evaluation of pavements according to the AASHTO methodology, serviceability will be estimated erroneously as a function of IRI if this difference by pavement type is not taken into consideration.
International Roughness Index of Asphalt Concrete Overlays: Analysis of Data from Long-Term Pavement Performance Program SPS-5 Projects
Authors: Perera Rohan W. , Kohn Starr D.
Published: April 2007

The Specific Pavement Studies 5 (SPS-5) experiment in the Long-Term Pavement Performance (LTPP) program was developed to investigate the performance of selected asphalt concrete rehabilitation treatment factors. Results of an analysis are presented that was conducted to compare the international roughness index (IRI) values of the test sections before and after overlay and to compare the IRI values that were obtained on the test sections subjected to different treatments. The data presented will be useful for highway agencies to gain an insight into the typical IRI values that can be expected when overlays are placed on asphalt concrete pavements and to obtain information on the reduction in roughness from an asphalt concrete overlay. The analysis indicated that the IRI of a pavement after overlay was not a function of the IRI before overlay. It was observed that a 50-mm-thick overlay (placed in one lift) was capable of achieving similar IRI values as a 125-mm-thick overlay (placed in two lifts). No differences in IRI values were obtained on overlays that were placed on pavement surfaces milled before the overlay when compared with surfaces not milled before the overlay. A frequency analysis of the IRI values after overlay indicated that in 85 percent of the cases, the IRI of the pavement was less than 1.2 m/km for both 50-mm- and 125-mm-thick asphalt concrete overlays.
Evaluation of In Situ Moisture Content at Long-Term Pavement Performance Seasonal Monitoring Program Sites
Authors: Jiang Y. Jane , Tayabji Shiraz D.
Published: April 2007

Time domain reflectometry (TDR) has become one of the most reliable nondestructive methods for measuring in situ soil moisture content. TDR sensors developed by the Federal Highway Administration are being used in the Long-Term Pavement Performance (LTPP) Seasonal Monitoring Program (SMP) to monitor the in situ moisture content at 64 LTPP sites. The main goal of this study is to develop procedures to produce good estimates of in situ gravimetric moisture content. All the TDR traces in the LTPP information management system database that were recorded at LTPP SMP test sections were processed using the approach described in this paper. To estimate the in situ gravimetric moisture content, methods were selected to interpret TDR traces. An algorithm and a computer program, Moister, were developed to implement these TDR interpretation methods. Then the apparent length of the TDR trace and the dielectric constant of the unbound material were computed. Models were developed to relate dielectric constant with in situ volumetric moisture content. Finally, gravimetric moisture content was computed using the volumetric moisture content value and dry density of the soil. A diagnostic study of the computed gravimetric moisture content was also conducted to evaluate the reasonableness of the computed moisture content.
Determination of Bedrock Depth from Falling Weight Deflectometer Data
Authors: Chen Dar-Hao
Published: April 2007

The accuracy of falling weight deflectometer (FWD) back-calculated moduli depends heavily on knowledge of bedrock depth. The bedrock depth can be obtained from coring, boring, and seismic refraction tests, but these operations are not practical. Determining the bedrock depth from FWD data is the easiest and least expensive way. This paper documents the effects of bedrock depth on FWD responses and makes comparisons between predicted bedrock depth and field measurements. Modified algorithms that better fit the field measurements are proposed. It was found that bedrock depth has a great influence on outer FWD sensor (r3 to r6) readings. Deeper bedrock resulted in a higher percentage of increase in r3 to r6 readings in response to increased load. When the r4 reading is less than 25.4 μm for any drop height, it is very likely that the bedrock is within 1.52 m of the surface. The time-deflection history patterns were drastically different between shallow and deep bedrock. When there is no free oscillation after the first deflection peak in a time-deflection history, shallow bedrock (within 1.52 m) is indicated. A modified equation (Equation 2) using the peak deflections provides an accuracy within 30 percent. It is recommended that these equations be used on a pavement where there is no severe surface distress. Another modified equation (Equation 6) using time-deflection history data yields an accuracy within 20 percent but cannot be used when there is no clear indication of free oscillation.
Direct Analysis Methods for Falling Weight Deflectometer Deflection Data
Authors: Wimsatt Andrew J.
Published: April 2007

Two direct methods of analyzing falling weight deflectometer deflection data are presented. One method, which involves dividing the deflection 1828.8 mm (72 in.) away from the load plate by the deflection underneath the load plate, relates directly to the ratio between the pavement modulus and subgrade modulus for a two-layer system. The other method described in the paper gives a qualitative evaluation of the stiffness of the base material as it relates to the pavement surface. Examples of using these methods are described and compared with results from the Modulus Version 5.0 computer program developed by the Texas Transportation Institute.
Influence of Tire-Pavement Contact Stress Distribution on Development of Distress Mechanisms in Pavements
Authors: Weissman Shmuel L.
Published: April 2007

It is demonstrated that accurate characterization of tire-pavement contact stress distribution is important for the correct prediction of distress evolution in flexible pavements. First, an analysis of tire imprints and measured tire-pavement contact stress distribution leads to the conclusion that the shape of the contact area depends on the load and tire pressure and that the contact stress distribution is nonuniform. Second, software for a linear-layered elastic medium contrasts the stress distribution in a pavement due to two loads: a uniformly distributed pressure on a circular area and a distribution reported earlier by de Beer and Fisher. The analysis herein demonstrates that nonuniform contact stress distribution leads to considerably larger stresses in the pavement relative to the uniform stress distribution case. Consequently, both rut and crack evolution prediction would be different if they were based on true distribution rather than on the uniform distribution assumption. It is also shown that for overloaded tires, the contact area is rectangular, where the width of the contact is a tire property independent of the applied load. Therefore, approximating the load as a uniformly distributed stress over a circular area may lead to erroneous prediction regarding the transverse or longitudinal orientation of cracks.
Measurement of Contact Stresses for Different Truck Tire Types To Evaluate Their Influence on Near-Surface Cracking and Rutting
Authors: Ann Myers Leslie , Roque Reynaldo , Ruth Byron E. , Drakos Christos
Published: April 2007

Two pavement distress mechanisms have become more prevalent in recent years: near-surface rutting and surface-initiated wheelpath cracking. Some possible factors causing these failure mechanisms include higher traffic volumes, use of lower-quality materials, and changes in tire type and structure. Although all of these factors may play a role, this study concentrated on the effects of changes in tire type and structure on surface distress. Within the last decade, trucking companies have shifted from operation on bias ply tires to an exclusive use of radial tires and the gradual introduction of wide-base (super-single) radial tires. This prevalence of radial tires causes a major change in pavement surface loading characteristics and is shown to help explain the development of surface rutting and cracking. Tire contact stresses were measured for bias ply, radial, and wide-base radial truck tires at various loads and inflation pressures to investigate the effects of tire structure, loading, and inflation pressure on surface loads applied to pavements. It was determined that contact stresses vary significantly for the different types of tires investigated. The observed variations were explained by the differences in tire construction. In fact, tire structure appeared to have a greater influence on contact stresses than variations in either load or inflation pressure for a given tire type. It was shown that the specific characteristics of the complex contact stresses under truck tires have a strong influence on asphalt pavement cracking and rutting and must be considered for proper design and evaluation of asphalt pavements.