bluuebunny/crossref_metadata_2025 huggingface dataset:
SCOOT Real-Time Adaptive Control in a CORSIM Simulation Environment
Authors: Hansen Blake G. , Martin Peter T. , Joseph Perrin H.
Published: April 2007

The manner in which the adaptive signal control system SCOOT (Split, Cycle, Offset Optimization Technique) has been connected to the CORSIM traffic simulation model is described. To demonstrate the connection, CORSIM simulates the traffic activity of a six-node traffic network under SCOOT’s adaptive traffic signal control. CORSIM’s “virtual detectors” provide the necessary data for SCOOT optimization in real time. In a completed loop, the optimized signal timing is then communicated from SCOOT to CORSIM, which implements the timing and updates the traffic simulation. This means that SCOOT is now functioning in an entirely simulated environment. A comparison of delay and travel time is presented for a six-intersection street network under SCOOT control and under fixed-time area control optimized with TRANSYT-7F. The results show reductions in delay and numbers of stops of 20 to 30 percent. Previously, the measurement of the benefit of adaptive control has been limited to evaluations of systems after implementation. It is shown how SCOOT can now be evaluated under various network traffic conditions in a simulation environment and tested on a specific city network to evaluate the benefits before capital costs are committed.
Traffic Signal Coordination Across Jurisdictional Boundaries: Field Evaluation of Efficiency, Energy, Environmental, and Safety Impacts
Authors: Rakha H. , Medina A. , Sin H. , Dion F. , Van Aerde M. , Jenq J.
Published: April 2007

Some insight into the potential benefits of coordinating traffic signals across jurisdictional boundaries by using as a case study the Scottsdale Road–Rural Road corridor in the Arizona cities of Tempe and Scottsdale is provided. In particular, the feasibility of using second-by-second speed measurements from Global Positioning System-equipped vehicles for evaluation of the environmental and safety impacts of operational-level traffic improvement projects is demonstrated. The use of statistical models for the evaluation of efficiency, energy, emissions, and safety benefits of operational-level traffic improvement projects without the need to invest in expensive equipment such as emissions analyzers is also demonstrated. Furthermore, it is also shown that the use of statistical models allows evaluation of measures of effectiveness that would not otherwise be evaluated, such as accident risk. On the basis of a field evaluation of the main travel corridor of the study area, it was determined that the signal coordination project would increase the average speed on the main line by 6 percent over the a.m. peak, midday, and p.m. peak analysis periods. It was also found that the number of vehicle stops would be reduced by 3.6 percent, on average, whereas the fuel consumption would be reduced by 1.6 percent. The emissions of hydrocarbons and oxides of nitrogen remained constant, whereas the carbon monoxide emissions increased by 1.2 percent. Finally, the crash risk was reduced by 6.7 percent. The results for the three analysis periods indicated statistically significant benefits to the approaches of the retimed traffic signals. However, these benefits were found to be statistically insignificant when the 21 traffic signals of the entire main line were considered.
Comparison of VISSIM and CORSIM Traffic Simulation Models on a Congested Network
Authors: Bloomberg Loren , Dale Jim
Published: April 2007

Traffic simulation packages like CORSIM and VISSIM are frequently used as tools for the analysis of traffic since they are effective approaches for quantification of the benefits and limitations of different alternatives. The concern of those who are cautious or skeptical about the application of a complex program to making a critical design decision is often appropriate, as many models are unproven or little information about their accuracy is available. As these simulation models become easier to use, it may be practical to use more than one model in some studies. The two-model approach was applied as a means of making the analysis more reliable and the results more defensible. The results proved the consistency and reasonableness of the simulation tools and provided everyone involved with confidence about the analysis. The study also illustrated the value of using a range of performance measures and a sensitivity analysis. More generally, it proved the value of providing as much comparative information as possible before making a design decision. The results were generally consistent, and the end product was a set of clear, defensible, and well-supported conclusions. Although the experience gained through the application of CORSIM and VISSIM was in some ways unique to the study area, this experience can provide insight to other transportation professionals charged with selecting and applying these simulation models to similar networks. To that end, some of the characteristics of both models are contrasted.
Genetic Algorithms for Traffic Signal Control and Queue Management of Oversaturated Two-Way Arterials
Authors: Abu-Lebdeh Ghassan , Benekohal Rahim F.
Published: April 2007

The formulation and solution of a dynamic signal control and queue management algorithm for two-way oversaturated arterials are presented. The algorithm is structured to find optimal control and queue management in at least one direction: the primary direction. The other direction is optimized only subject to the fulfillment of the constraints on the primary direction. The main idea of the procedure is to manage queue formation and dissipation through proper design of signal control parameters such that queues are always contained within respective links and that spillbacks are prevented. The two-way control procedure presented accounts for all possible traffic flow regimes that may form as a result of queue management schemes. Genetic algorithms were used to solve the problem. The results show that although the algorithm provides optimal control and queue management in the primary direction, it was also able to manage queues in the secondary direction so that the occurrence of queue spillbacks is prevented. Progression was attainable only in the primary direction. However, the algorithm was able to effectively deal with evolving traffic queues in both directions. In all but one link, traffic was successfully contained in the respective links, thus preventing spillback.
Signal Coordination and Arterial Capacity in Oversaturated Conditions
Authors: Abu-Lebdeh Ghassan , Benekohal Rahim
Published: April 2007

Models for estimation of the capacities of oversaturated arterials were developed. The input variables in these models are capacities of individual intersections, offsets, and vehicle queue lengths. Models for quantification of capacity loss due to blockage caused by downstream queues are also presented. The proposed models show that when arterial capacity is determined in oversaturated conditions, it is not sufficient to consider only the capacities of critical intersections; instead, the capacities of critical subsystems must be considered. A critical subsystem is any two intersections plus the link that joins them where traffic processing capability is the lowest. This traffic processing capability, or critical subsystem capacity, determines the arterial capacity. It is a function of the capacities of the respective intersections, the offset between them, and the queue length on the link joining them. It is shown that a critical subsystem is not unique in that it may change location over the course of the study period. To minimize capacity loss, it is shown that offsets must be an explicit function of queue lengths. The practical use of the models was demonstrated for an oversaturated two-intersection system. The results show that improper setting of offsets can lead to significant capacity loss. In extreme cases all capacity in a given cycle may be lost if the offsets are not set properly.
Formulation of Real-Time Control Policy for Oversaturated Arterials
Authors: Lieberman Edward B. , Chang Jinil , Shenk Prassas Elena
Published: April 2007

The formulation of a real-time traffic control policy designed expressly for oversaturated arterials is presented, and the operating protocol is described. Its objectives are to ( a) maximize system throughput, ( b) fully use storage capacity, and ( c) provide equitable service. This control policy, known as RT/IMPOST (real-time/internal metering policy to optimize signal timing), is designed to control queue growth on every saturated approach by suitably metering traffic to maintain stable queues. Consistent with this approach, bounds on queue lengths and signal offsets are determined. A mixed-integer linear program (MILP) tableau is formulated to yield optimal values of signal offsets and queue length for each approach. A nonlinear (quadratic) programming formulation adjusts the arterial green-phase durations of each signal cycle so that the actual arterial queue lengths on each saturated approach will continually closely approximate the optimal queue lengths computed by the MILP formulation. The policy principles are as follows: ( a) the signal phase durations “meter” traffic at intersections servicing oversaturated approaches to control and stabilize queue lengths and to provide equitable service to competing traffic streams; and ( b) the signal coordination (i.e., offsets) controls the interaction between incoming platoons and standing queues in a way that fully uses the available storage capacity, keeps intersections clear of queue spillback, and maximizes throughput.
Calibration of Platoon Dispersion Parameters on the Basis of Link Travel Time Statistics
Authors: Yu Lei
Published: April 2007

A calibration technique for platoon dispersion parameters for the widely used TRANSYT platoon dispersion model is presented. This technique calibrates platoon dispersion factor, travel time factor, and smoothing factor directly from the average link travel time and its standard deviation and can capture practically all of the roadway and traffic conditions in the field such as road grades, curvature, parking, opposing flow interference, traffic volume, and other sources of impedance. The technique is especially suited for applications in advanced traffic management system networks in which the required link travel time data could be obtained on a real-time basis. TRANSYT’s implementation of two scenarios is examined. The first scenario inputs the calibrated platoon dispersion parameter, with the result being that the smoothing factor used by TRANSYT is different from the calibrated parameter. The second scenario inputs a revised platoon dispersion factor, which is designed to make the smoothing factor used by TRANSYT identical to the calibrated parameter. This examination induces a recommendation that the TRANSYT input card or its internal calculation procedure for platoon dispersion be revised so that the average link travel time in the geometric distributed platoon dispersion model is consistent with those from the same model. The calibration of platoon dispersion parameters with field-collected link travel time data shows that platoon dispersion parameters are different for different standard deviations of link travel times even on the same street, and, therefore, the platoon dispersion parameters must be calibrated on a site-specific basis.
Remote Simulation to Evaluate Real-Time Traffic Control Strategies
Authors: Lucas David E. , Mirchandani Pitu B. , Larry Head K.
Published: April 2007

Simulation is a valuable tool for evaluating the effects of various changes in a transportation system. This is especially true in the case of real-time traffic-adaptive control systems, which must undergo extensive testing in a laboratory setting before being implemented in a field environment. Various types of simulation environments are available, from software-only to hardware-in-the-loop simulations, each of which has a role to play in the implementation of a traffic control system. The RHODES (real-time hierarchical optimized distributed effective system) real-time traffic-adaptive control system was followed as it progressed from a laboratory project toward actual field implementation. The traditional software-only simulation environment and extensions to a hardware-in-the-loop simulation are presented in describing the migration of RHODES onto the traffic controller hardware itself. In addition, a new enhancement to the standard software-only simulation that allows remote access is described. The enhancement removes the requirement that both the simulation and the traffic control scheme reside locally. This architecture is capable of supporting any traffic simulation package that satisfies specific input-output data requirements. This remote simulation environment was tested with several different types of networks and was found to perform in the same manner as its local counterpart. Remote simulation has all of the advantages of its local counterpart, such as control and flexibility, with the added benefit of distribution. This remote environment could be used in many different ways and by different groups or individuals, including state or local transportation agencies interested in performing their own evaluations of alternative traffic control systems.
Integrated Traffic-Responsive Urban Corridor Control Strategy in Glasgow, Scotland: Application and Evaluation
Authors: Diakaki Christina , Papageorgiou Markos , McLean Tom
Published: April 2007

The new integrated traffic-responsive urban corridor control strategy IN-TUC (integrated traffic-responsive urban control) is presented. IN-TUC was developed and applied to the M8 corridor network in Glasgow, Scotland, within the European Telematics Applications in Transport project Telematics Applications in Bavaria, Scotland, and Others. The aim of the strategy, which is built on the well-known methods of the automatic control and optimization theories, is to provide, at suitably defined constant control intervals, traffic-responsive settings for the various control elements included in a corridor network area. The results of the preliminary simulation investigations as well as the results of the field implementation and evaluation of the strategy seem promising both for the particular site and for integrated corridor control systems in general.
Are Minimization of Delay and Minimization of Freeway Congestion Compatible Ramp Metering Objectives?
Authors: Banks James H.
Published: April 2007

Analysis of mechanisms by which ramp metering can reduce traffic delay, such as increasing bottleneck flow, expediting flow to exits upstream of the bottleneck, and diverting traffic around the bottleneck, suggests that minimization of delay and minimization of congestion on the freeway main line are not always compatible objectives. Simulations were performed to tentatively resolve this question. These simulations used a flow model based on Newell’s simplified kinematic wave theory and a control strategy that was a modification of that of Wattleworth and Berry. Simulation scenarios defined physical characteristics, demand patterns, and flow characteristics for hypothetical freeway sections on the basis of data from Blumentritt et al. and the San Diego area. Results of the simulations show that there are circumstances under which minimization of delay does not coincide with minimization of congestion on the main line and that relationships between delay and main-line congestion depend on the combination of the metering mechanisms in effect.
Freeway Traffic Speed Estimation with Single-Loop Outputs
Authors: Wang Yinhai , Nihan Nancy L.
Published: April 2007

Traffic speed is one of the most important indicators for traffic control and management. Unfortunately, speed cannot be measured directly from single inductance loops, the most commonly used detectors. To calculate space-mean speed, a constant, g, is often adopted to convert lane occupancy to traffic density. However, as illustrated by data from the present study, such a formula consistently underestimates speed whenever a significant number of trucks or other longer vehicles are present. This is because g is actually not a constant but, rather, a function of vehicle length. To calculate the value of g suitably, one needs to know the percentage of long vehicles or the mean vehicle length in real time. However, such information is not directly available from single-loop outputs. It is shown how the occupancy variance obtained from single-loop data can be used to estimate the percentage of long vehicles and how a log-linear regression model for mean vehicle length estimation based only on single-loop outputs can be developed. The estimated mean vehicle length is used to calculate the corresponding g-value in real-time to estimate speed more accurately. The speed estimations with corrected g-values are very close to the speeds observed by the speed trap in the present study.
Automatic Vehicle Identification Technology-Based Freeway Incident Detection
Authors: Hellinga Bruce , Knapp Geoff
Published: April 2007

The recent emergence of automatic vehicle identification technology (AVI) for use in electronic toll collection has provided an opportunity to develop automatic incident detection (AID) methods that rely on individual vehicle travel time data instead of loop detector data. The performances of three AVI-based AID algorithms are examined. Travel time data for testing of the algorithms were obtained by simulating a 12-km section of the collector facility of Highway 401 in Toronto, Ontario, Canada. The performances of the three AVI-based AID algorithms are compared with the performance of a leading loop detector–based algorithm, which was independently tested with similar simulated data. The AID performance results indicate that AVI-based AID algorithms can provide incident detection performance similar to that of existing loop detector-based AID methods.
Progressive Deployment Steps Leading Toward an Automated Highway System
Authors: Shladover Steven E.
Published: April 2007

The most serious challenge to the credibility of highway automation as a potential solution to transportation problems has been the lack of a convincing deployment strategy. Such a strategy is needed to show how to advance, step by step, from today’s transportation system to a future system that includes automated highway systems (AHSs). The existing literature on AHS deployment is reviewed, and a set of principles that can be used to govern the design of AHS deployment strategies is suggested. A deployment sequence for AHSs is proposed, beginning with adaptive cruise control and then adding elements of vehicle-vehicle cooperation and lane protection to build toward AHS capabilities within the constraints of technological and human factors and economic feasibility. Finally, some example deployment “road maps” are shown for transit buses, heavy trucks, and light-duty passenger vehicles.
Effect of Film Thickness on Rheological Behavior of Asphalt Binders
Authors: Zhai Huachun , Bahia Hussain U. , Erickson Signe
Published: April 2007

In the current Superpave® binder tests, the rheological properties of asphalt binders are determined by the dynamic shear rheometer. The asphalt binders are tested using a gap size of either 1 or 2 mm. In the asphalt mixture, the thickness of the asphalt film between aggregates can vary between a few microns and a few millimeters. Because of the interaction between the asphalt and the aggregate, rheological behavior in thin films can differ from the behavior determined at large gap sizes. In this study the rheological properties of asphalt binders were measured at different gap sizes that simulate the range in film thickness of a typical mixture. Significant changes in rheological properties were observed as the gap size changed. The results indicate that different modified binders show different trends as the gap size changes. A review of the literature was conducted for an explanation of this behavior. Four mechanisms were offered to explain similar gap effects observed for other materials. Using the data collected in this study, the disentanglement mechanism caused by adhesion to testing plates appears to fit the observations for asphalt binders. The results suggest that the current gap settings in the binder tests might not be sufficient to determine the performance of the binder in the mixture. The findings also suggest that more work is required to understand the effect on the rheological behavior of asphalt binders of physical and chemical interactions with aggregates.
Damping of Shear Vibrations in Asphalt Modified with Styrene-Butadiene-Styrene Polymer
Authors: Stastna Jiri , Zanzotto Ludo , Vacin Otaca
Published: April 2007

Shear vibrations in conventional and polymer-modified asphalt binders are examined. Using dynamic compliances instead of moduli, viscous deformation effects can be separated from total deformation and the modified dynamic loss compliance and modified loss tangent functions can be defined. These two material functions appear to be more sensitive than viscoelastic moduli to the rheological behavior of asphalt binders and to changes caused by polymer addition. The characteristic temperature of the transition from the viscoelastic to viscous behavior of asphalt binder ( Tv) can be identified by using the viscous asymptote J”. The damping of shear vibrations that likely relates to the internal structure of asphalt material can be described by the modified loss tangent. The rheological behavior of the base asphalt 200/300 penetration grade and its blends with different amounts of radial styrene-butadiene-styrene rubber is investigated. Using master curves of dynamic functions and the Williams-Landel-Ferry form of the shift factor, isochrones of the original and modified dynamic material functions are constructed. Characteristic temperatures of the viscous transition ( Tv) and the glass transition ( Tg) are determined. Damping behaviors of the base and modified asphalts are studied.
Factors Affecting Variability in Strategic Highway Research Program Binder Tests
Authors: Anderson David A. , Marasteanu Mihai O. , Mahoney James M. , Stephens Jack E.
Published: April 2007

Two binder technician workshops were held in January 1998, one at the Connecticut Advanced Pavement Laboratory at the University of Connecticut and one at the Northeast Center of Excellence for Paving Technology at Pennsylvania State University. These workshops were followed by a second set in 1999. The overall objective was to improve the repeatability of the test methods used to grade Superpave® asphalt binders. During the workshops, participants demonstrated and discussed the techniques used in their own laboratories. A document, Manual of Practice for Testing Asphalt Binders in Accordance with the Superpave PG Grading System, was developed for use by asphalt binder technicians and as a training aid for a proposed binder technician certification program. The results of the discussions that were held during the workshops and the items that are presented in the manual of practice are summarized. The results were grouped into four main categories: ( a) handling, sampling, and sample preparation; ( b) temperature measurements; ( c) equipment calibration; and ( d) testing procedures. The items discussed here and in the manual of practice supplement and clarify the current AASHTO test methods. The test methods in themselves are not sufficient to ensure uniformity in testing practice from one laboratory to the other.
New Class of Reactive Polymer Modifiers for Asphalt: Mitigation of Low-Temperature Damage
Authors: Crossley Glen A. , Hesp Simon A. M.
Published: April 2007

Results from the low-temperature performance evaluation of a new class of reactive polymer modifiers designed to improve binder-aggregate adhesion in asphalt concrete are discussed. A living free radical polymerization process was used to prepare polyisoprene (PI) with short blocks of reactive silane-functional monomer at one end of the polymer chain. Performance was evaluated with the thermal stress restrained specimen test at a cooling rate of-10°C/h. The results obtained were compared with those for unmodified and styrene-butadiene (SB)-modified mixes. When added at 3 and 6 percent by weight of the binder, SB reduced the fracture temperature of the asphalt concrete by 6°C and 9°C, respectively. Similar results were obtained with the reactive polymers. However, although all the SB-modified samples failed in a catastrophic mode, none of the samples containing the silane-functional PI did. It is hypothesized that these polymers toughened the asphalt to an extent that cracks were only able to grow in a stable mode as opposed to an unstable mode or that localized yielding occurred. The method for obtaining the desired toughening effect is flexible; lower-cost monomers, such as butadiene, and more common polymerization methods, such as emulsion or anionic polymerization techniques, could be used equally well to produce polymers with similar or better performance characteristics. An added benefit is that the tested polymers were able to improve the stripping resistance of the mix significantly.
Crack Pinning in Asphalt Mastic and Concrete: Regular Fatigue Studies
Authors: Smith Benjamin J. , Hesp Simon A. M.
Published: April 2007

The effects of finely dispersed fillers on the fatigue performance of asphalt binders and asphalt concrete mixes at relatively low temperatures are examined. A series of model binder systems containing glass spheres with narrow particle size distributions were used to study the effect of filler particle size on the fatigue performance of the asphalt mastic. Two mastic systems containing ground limestone fillers, which possessed significantly different gradations, also were tested. Fatigue performance was evaluated by applying a constant torsional strain to each specimen in a dynamic rheometer at 10°C and 40 Hz. Testing at various strain levels allowed the relationship between fatigue life and strain to be determined for the different systems. The results indicate that as the particle size of the filler decreases, the fatigue life of the asphalt mastic increases. This observation is a direct result of the mode of fatigue failure in the asphalt mastics and is in agreement with Evans’s theory on crack pinning for failure in filled brittle solids. Constant stress asphalt concrete fatigue tests on both dense- and gap-graded systems prepared with the two different ground limestone fillers show that the particle size does not significantly affect the fatigue life of the mixes. These results also confirm that crack pinning is the major mechanism responsible for improved fatigue performance.
Staffing Plan Survey of State Transportation Agencies
Authors: Hood Jacqueline N. , Alarid Tony , Albright David
Published: April 2007

A survey of state transportation agencies in the United States was conducted to identify staffing plan practices and concerns. A staffing plan involves recruiting, training, and retaining employees with skills to do the work needed for the organization to attain its objectives efficiently. Staffing plan areas studied in the survey included general information about the state transportation agency, such as the strategic plan and staffing plans, recruitment, right-sized workforce (determining the right number of employees to perform a job), flexible workforce (the ability to change the work performed and the work location), retention (keeping valuable employees), and succession planning (ensuring a qualified pool of employees for key positions). All 50 states participated in the survey. Responses indicated that most state transportation agencies have at least one primary area in human resource management that they consider innovative and that there is a broad-based interest among the states to cooperate in exploring new and better methods. The highest staffing plan priorities among state transportation agencies are employee recruitment, performance measures, and employee retention. State staffing plan priorities, current innovation in these areas, and strong interest in cooperating with other states provide a basis for broad-based improvement in staffing plans among the states and across the nation.
Asset Management: What Is the Fuss?
Authors: McNeil Sue , Tischer Mary Lynn , DeBlasio Allan J.
Published: April 2007

Interest in asset management has generated considerable activity in professional organizations, agencies, and supporting organizations. The status of several activities that have contributed to this increased level of activity is summarized. Also, the results of a survey of AASHTO member states that solicited responses to questions on the use of management tools, ranging from management systems to asset valuation and decision-making tools, are reported. The survey results support anecdotal evidence that there is a heightened awareness and activity level focused on the topic of asset management.
Measuring the Performance of State Transportation Agencies: Three Perspectives
Authors: Baird Malcolm E. , Stammer Robert E.
Published: April 2007

State transportation agencies (STAs) are under increasing pressure to implement organizational and program performance measures, and they naturally look to the theories and practices of transportation planning and engineering for guidance. However, to meet the new expectations for performance measurement, STAs also should consider the perspectives of two other disciplines: business management and public administration. The reasons for the current interest in performance measurement are reviewed, and then the perspectives of each of the three disciplines are identified and compared. Five aspects of performance measurement are considered: reasons for measuring performance, incorporating stakeholder perspectives, dimensions for measurement, comparisons as a basis for measurement, and guidelines for performance measures and measurement systems. Side-by-side comparisons are offered to promote a better understanding of each discipline’s perspective, interrelationships, and basic differences. For instance, each discipline focuses on a different reason for measuring performance. The transportation planning and engineering paradigm is that measurement leads to better understanding and therefore to better results. The public administrator’s paradigm is that measurement makes the organization more accountable and that accountability improves performance. The business paradigm is that measuring performance improves performance. The performance measurement systems used by 10 selected STAs are examined from the perspectives of the three disciplines and the five aspects of performance measurement. Suggestions are offered for additional research.
New York State’s Approach to Asset Management: A Case Study
Authors: Clash Thomas W. , Delaney John B.
Published: April 2007

The New York State Department of Transportation (NYSDOT) has undertaken an effort to design and implement an asset management system for overseeing the state’s diverse and complex transportation system. The department has built an appropriate organizational and business foundation for the effective use of sound, integrated databases and technical modeling tools. For more than a decade, well before asset management attracted interest from the transportation community, NYSDOT has advanced this concept on four fronts: developing well-defined organizational roles within a highly decentralized department; designing and implementing a formal and disciplined core business procedure (the program update process) to cover both program development and performance monitoring; developing key transportation management systems (pavement, bridge, congestion and mobility, and public transportation), even without a federal mandate; and designing and implementing a state-of-the-art automated program and project management system that serves, in part, to integrate the department’s use of the individual management systems and maintains all essential data for developing and managing the program. New York’s experience strongly suggests that despite the difficulty and time required to carry out the key processes, these four elements represent the heart of an asset management system. When identifying and developing additional technical elements, state departments of transportation should heed the importance of building and maintaining an effective organizational and business foundation.
Linking Public and Private Performance Measurement
Authors: Morash Edward A.
Published: April 2007

Transportation planning and public policy can have profound effects on private-sector performance through investment policy, financing arrangements, tax policy, infrastructure improvement, and the like. However, with increasingly competitive and global markets, transportation public policy and planning should be based on market requirements for specific transportation capabilities and performance. On one level, deregulation and global competitiveness require cooperation and collaboration among all public and private policy actors and planners so that they all “row in the same direction.” On another level, deregulation and global competitiveness require that governmental transportation policy be market-driven, stressing capabilities and performance that are deemed most important by the private sector. The relative importance and availability of performance measures and capabilities are examined in three global regions: North America, Europe, and the Pacific Basin. The three regions are in remarkable agreement as to which performance capabilities are most important to a firm’s success. Transportation dependability and customer service are ranked at the top; low logistics cost and delivery flexibility are in the middle; and surprisingly, delivery speed is at the bottom. These findings have important implications for transportation public policy and planning in terms of linking policy with private-sector performance measurement. For example, it appears that transportation public policy and plans should stress reliability over speed in terms of setting priorities. Additional findings and recommendations for transportation planning, policy formulation, and data availability are discussed.
Transportation Asset Management: The Value of Enterprise-Based Financial Reporting
Authors: Stalebrink Odd J. , Gifford Jonathan L.
Published: April 2007

The adoption of enterprise-based financial reporting practices in the public transportation infrastructure has the potential to facilitate the use of profitability analysis and, thus, the management of public transportation infrastructure assets. However, a major challenge for successful implementation is the ability to generate in a public setting what the Governmental Accounting Standards Board refers to as “satisfactory” system input values. Because market prices are not generated in these environments, they must be simulated. Two promising approaches for generating such measurements are reviewed: benefit-cost analysis and econometric studies of the productivity impacts of infrastructure investments (on productivity studies). Although the two approaches are subject to several weaknesses that inhibit them from generating satisfactory system input values, ongoing methodological advances in both indicate fair prospects for generating such values in the future. Therefore, a dismissal of enterprise financial reporting practices for public transportation infrastructure may be premature.
Advanced Educational Technologies and Intelligent Transportation Systems Training: State of the Practice
Authors: Adler Jeffrey L. , List George F. , Menyuk Brian , Cetin Mecit
Published: April 2007

During the past five years, the development of tools and materials to support intelligent transportation systems (ITS) education at university and professional levels has experienced tremendous growth. With the rapid advancement of educational technologies, there is an eagerness to develop new ways to impart ITS knowledge. A survey of state departments of transportation was performed to identify the needs for ITS education and assess the potential for delivery of this material through educational technology. A review of pertinent literature related to adult learning and its implications was conducted. Recommendations to guide the design of educational materials are presented. A taxonomy designed to aid ITS professionals in identifying available educational materials by competency area, knowledge acquisition needs, and available resources is proposed.
Multidisciplinarity in Transport Research and Education
Authors: van Zuylen Henk J.
Published: April 2007

The evolution of science has followed the path of specialization—a certain domain of knowledge within one discipline becomes a discipline in itself with its own paradigms and social structure of scientists and institutions. Multidisciplinarity is the reverse movement; progress is sought not in further specialization but in the integration of several approaches. This kind of research can take many forms. The simplest form of multidisciplinary problem solving is to split problems into subproblems and then solve each subproblem in a monodisciplinary fashion. Another way is to integrate the monodisciplinary contributions into a single, complete solution. A third way is to apply the paradigms of one discipline to enhance the problem-solving potential of another. Research in the domain of transportation is well suited to the different forms of the multidisciplinary approach. Many problems in transportation have aspects in the domains of disciplines ranging from pure engineering to psychology and ethics. Furthermore, only a few practical transportation problems can be solved satisfactorily without the cooperation of many disciplines. Finally, many examples within the domain of transportation show that completely new areas of knowledge have been developed by the integration of elements from other disciplines. Multidisciplinarity for the education of transport and traffic professionals is essential for the healthy development of the transport domain.
Analysis by High-Speed Profile of Jointed Concrete Pavement Slab Curvatures
Authors: Byrum Christopher R.
Published: April 2007

A high-speed pavement profile analysis method that detects curvature present in the wheelpaths of jointed concrete pavement slabs is presented. This technique can be used to analyze slab curvatures present in pavements and caused by curling and warping forces. The FHWA Long-Term Pavement Performance (LTPP) program has obtained high-speed elevation profiles for the jointed concrete pavements in the study. This profile analysis method reads an LTPP profile and detects imperfections in the road curvature profile, which typically are joints and cracks. It then analyzes the slab regions (intact slab segments) between these numerical imperfections for the presence of curvature. The result of a profile analysis is a road profile index—the curvature index—which represents the average slab curvature present along the wheelpaths for the profile. This profile analysis method was applied to more than 1,100 LTPP GPS3 profiles. The range of the slab curvatures encountered is described, and some key factors related to apparent locked-in curvatures (related to warping and construction) are discussed. The amount of locked-in curvature in slabs significantly affects slab behavior and long-term pavement performance. Curvature information should be available to pavement rehabilitation engineers making fix type and funding decisions for pavements. This new analysis method could be implemented rapidly in routine pavement profile analysis and pavement management systems.
Foundation Modeling for Jointed Concrete Pavements
Authors: Davids William G.
Published: April 2007

Issues related to the finite element modeling of base and subgrade materials under jointed plain concrete pavements are examined. The threedimensional finite element program EverFE, developed in conjunction with the Washington State Department of Transportation, was employed for the analyses. The relevant modeling capabilities of EverFE are detailed, including the ability to model multiple foundation layers, the incorporation of loss of contact between slab and base, and the efficient iterative solution strategies that make large three-dimensional finite element analyses possible on desktop computers. The results of parametric studies examining the effects of foundation type (layered elastic and dense liquid) and properties on the response of jointed plain concrete pavements subjected to axle and thermal loads are presented. Special attention is paid to the interactions between joint load transfer effectiveness and foundation type, and joint load transfer is shown to change significantly with different foundation models and properties. A consideration of simultaneous thermal and axle loadings indicates that the effect of foundation type and properties on critical slab stresses caused by edge loading and a positive temperature gradient is relatively small. However, the slab response is quite sensitive to foundation type for a combined negative temperature gradient and corner loading. On the basis of these results, use of an equivalent dense liquid foundation modulus in mechanistic rigid pavement analysis or design is not recommended when stiff base layers are present.
Three-Dimensional Analysis of Continuously Reinforced Concrete Pavements
Authors: Kim Seong-Min , Won Moon C. , Frank McCullough B.
Published: April 2007

Continuously reinforced concrete pavement (CRCP) performance depends primarily on early-age cracks that result from changes in temperature and drying shrinkage. Presented is the behavior of the CRCP due to the temperature change obtained by using a three-dimensional finite element model. The nonlinear effects of the bond-slip between concrete and steel and between concrete and base have been studied. Modeling for the curling effect and for the viscoelastic material characteristics also has been considered. The results from the two-dimensional and three-dimensional models have been compared to verify the possibility of using a two-dimensional model. From this study, it was found that crack width and concrete stress are dependent on the transverse steel arrangement near the edge (longitudinal joint), but they are almost independent in the interior of the slab. The tensile stress occurring at the top of the edge on the transverse steel location can be higher than that occurring at the top of the slab center. This represents the possibility of forming a transverse crack from the edge on the transverse steel location. The twodimensional model with the plane stress element gives results very close to those of the three-dimensional model, except near the edge.
Mechanistic Design of Thin Whitetopping Pavements in Colorado
Authors: Tarr Scott M. , Sheehan Matthew J. , Ardani Ahmad
Published: April 2007

A mechanistic design procedure was developed for the state of Colorado to determine the required concrete thickness of thin [12.7 cm to 17.8 cm (5 in. to 7 in.)] whitetopping overlays on asphalt pavements. Field testing was conducted to evaluate critical load locations for whitetopping with joint spacing up to 3.66 m (12 ft). The load-induced flexural strains were used to calibrate fully bonded stresses computed by applying finite element analysis techniques to partially bonded stresses measured in the field. For each test section, load testing was conducted throughout the course of a day to develop a temperature correction for the critical stresses derived for zero temperature gradient (zero slab temperature curling). Equations predicting the critical concrete flexural stresses and asphalt concrete strains for use in whitetopping were developed. A mechanistic design procedure is described that allows the evaluation of trial whitetopping thicknesses and joint spacings. The procedure computes the concrete and asphalt fatigue life for specific material properties. Iterations are required to determine the appropriate parameters that provide the required design life for both concrete and asphalt layers. In addition to the design procedure, the effect of surface preparation during construction was studied by comparing identical slabs constructed on milled and unmilled asphalt. It was concluded that existing asphalt pavement should be milled and cleaned before concrete placement for an overall reduction of 25 percent in the critical load-induced stresses. However, new asphalt, such as that placed in repair patches, should not be milled before concrete placement to avoid a 50 percent increase in critical load-induced stresses.
Analytical Predictions of Seasonal Variations in Flexible Pavements: Minnesota Road Research Project Site
Authors: Birgisson Bjorn , Ovik Jill , Newcomb David E.
Published: April 2007

The mechanistic analysis and design of flexible pavements is very dependent on knowledge of traffic loading, materials, and climatic factors. Seasonal variation of climate factors such as temperature, temperature history, and precipitation affects the subsurface conditions of the pavement layers, including the in situ temperature, moisture content, and state of moisture. In turn, these subsurface conditions have a direct relationship with the pavement strength and stiffness, causing seasonal variations in both strength and pavement layer moduli. Many agencies are now moving toward a mechanistic-empirical pavement design, in which the design inputs include, as a minimum, the seasonal variations in pavement layer moduli. The ability to analytically predict and quantify the climatic effects on pavement strength and stiffness has been investigated by numerous researchers, but few comparisons with measured field data have been completed, because of a lack of pavement sites with extensive arrays of monitoring instrumentation. Detailed is a comparison between field results and predictions obtained from an analytical tool, called the enhanced integrated climate model (ICM). The climatic factors used as inputs into the model include temperature, rainfall, wind speed, and solar radiation. The ICM is used to predict seasonal variations in temperature, moisture content, and layer moduli at two representative flexible pavement test sections at the Minnesota Road Research Project site.
Mechanistic-Empirical Rut Prediction Model for In-Service Pavements
Authors: Bae Kim Hyung , Buch Neeraj , Park Dong-Yeob
Published: April 2007

Rutting is a major mode of failure in flexible pavements. Development of accurate predictive rut performance models is an ongoing pursuit of the pavement engineering community. This has resulted in a plethora of rut prediction models ranging from purely mechanistic to empirical. Presented is the development of a mechanistic-empirical rut prediction model that uses data from 39 in-service flexible pavements from Michigan. The proposed model accounts for the rut contribution of the subgrade, subbase, base, and asphalt concrete layers. The model addresses inventory-type variables like pavement cross section, ambient temperature, and asphalt consistency properties. The applicability of the model was validated by using data from 24 Long-Term Pavement Performance–Global Positioning System (GPS) sites. For 19 of the 24 GPS sites, the predicted rut depth was within 5 mm of the measured rut depth.