bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrating Public Transportation Facilities and Equipment Management Systems into Capital Improvement Planning Process
Authors: Chang James , Collura John
Published: April 2007

A Public Transportation Facilities and Equipment Management System (PTMS), as proposed in the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA), is a tool to assist in the management and utilization of transit facilities and equipment so as to ensure the efficient and effective use of resources. A framework for the application of PTMS elements in the public transit capital improvement planning process is proposed. By using a PTMS as a part of the capital planning process, broad concepts such as needs fulfillment and performance improvement may be embodied in a systematic process to program transit bus capital investments. With data from the Federal Transit Administration’s National Transit Database (NTD), the practical applicability of this framework is investigated in the context of the capital planning process employed by the regional transit authorities and the state transportation agency in Massachusetts. Vehicle replacement needs for a Massachusetts regional transit authority are estimated for a 5-year planning window using the NTD data in conjunction with predictive condition models. These models, developed by Purdue University and the University of Massachusetts at Amherst, use easily quantifiable and objective measures such as age and mileage to predict the future condition of a vehicle. NTD data are also used to identify opportunities for performance-based capital incentives among the Massachusetts regional transit authorities.
Evaluating Interface Standards for the Public Transit Industry
Authors: Hickman Mark , Tabibnia Sam , Day Theodore
Published: April 2007

The rationale behind the current research and development of interface standards for the public transit industry is explored. Recent efforts to define an information systems architecture for public transit have not sufficiently discussed the underlying need for information system standards and what impacts these standards might have on the transit industry as well as on vendors. Both advantages and disadvantages to the development of these standards are identified. For public transit agencies, there appears to be a well-reasoned yet unsupported belief that interface standards will be beneficial for systems integration. To explore the impacts for vendors, a survey was developed and fielded to learn about the characteristics of products and vendor attitudes toward interface standards. The results, though not conclusive, suggest that vendors are willing to consider standards; however, needed product customization and more comprehensive systems are important factors weighing against open interface standards. Also reported are three case studies of recent technology applications in the San Francisco Bay Area in which experiences with technical system design and systems integration are described. These case studies strongly suggest that key factors such as market timing, vendor-agency communication, and “learning by doing” affect the development of interface requirements and standards for the transit industry.
Bus Lane Capacity Revisited
Authors: Levinson Herbert S. , St. Jacques Kevin R.
Published: April 2007

Bus use of urban roadways and past bus-capacity experience are reviewed. Field studies and bus simulation analyses were used to validate, update, and extend existing bus stop and berth capacity procedures. A 60-percent coefficient of dwell time variation was used to obtain new estimates of likely failure, and the maximum achievable capacity was based on a 25-percent failure rate. Capacity adjustment factors for skip-stop operation and right turns are derived. Service planning implications are identified. Bus lane capacities depend on how frequently the stops are placed, how long the buses dwell at each stop, traffic conditions and control systems along the bus lane or route, and whether buses can pass and overtake each other. Keeping dwell times and dwell-time variations to a minimum, providing multiple berth stops, and establishing skip-stop patterns will increase the bus and passenger capacity of bus lanes.
Benefit Evaluation of Crash Avoidance Systems
Authors: Godbole Datta N. , Sengupta Raja , Misener James , Kourjanskaia Natasha , Michael James B.
Published: April 2007

A five-layer hierarchy to integrate models, data, and tools is proposed for benefits assessment and requirements development for crash avoidance systems. The framework is known as HARTCAS: Hierarchical Assessment and Requirements Tools for Crash Avoidance Systems. The analysis problem is multifaceted and large-scale. The driving environment is diverse and uncertain, driver behavior and performance are not uniform, and the range of applicable collision avoidance technologies is wide. Considerable real-world data are becoming available on certain aspects of this environment, although the collection of experimental data on other aspects is constrained by technological and institutional issues. Therefore, analyses of collision avoidance systems are to be conducted by collecting data on nominal operating conditions to the greatest extent possible and by using such data to build models for analysis of the rare, abnormal conditions. HARTCAS provides a framework within which to structure the collection and use of such knowledge. It is described in general terms, and its use is illustrated by analysis of a forward collision warning system. How to quantify the relationships between the effectiveness of a warning and the probability that the warning is a nuisance is shown. System benefits are also quantified.
Commuter Response to Traffic Information on an Incident
Authors: Koo Ronald , Yim Youngbin
Published: April 2007

How traffic information is obtained and how it affects travel behavior when a major freeway is congested are presented and discussed. Immediately following a major highway incident south of San Francisco that caused congestion, a telephone survey was conducted of commuters who use the affected corridor of the highway. The behavior of commuters before and during their commute at the time of the incident was determined, including obtaining traffic information and how the information influenced changes in route, mode of travel, and departure time. The results of the survey suggest that traveler behavior is largely unaffected by individual incidents of congestion. Furthermore, although a fair proportion of commuters do obtain traffic information, they do not often modify their travel behavior in response. This study is one of several that collectively will provide insight into how travel behavior changes over time and allow the authors to assess the impact of TravInfo Traveler Advisory Telephone System in the San Francisco Bay Area.
Sizing the Airport Passenger Departure Lounge for New Large Aircraft
Authors: Barros Alexandre G. , Wirasinghe S. C.
Published: April 2007

The introduction of new large aircraft (NLA) is expected to cause a significant impact on planning and design of airports. Besides the problems caused by its large dimensions on airport airside design, the increased passenger capacity featured by the NLA will require larger passenger-processing facilities. Given the high costs implied both by changes in existing facilities and by the construction of new areas, anticipating the changes with a reasonable precision might help airports save a considerable amount of money. One of the most affected passenger terminal facilities will be the departure lounge. Current studies carried on by major manufacturers indicate that the NLA might be able to carry as many as 800 passengers. This is double the capacity of the largest existing passenger aircraft, the Boeing 747. To accommodate all these passengers in the same lounge, many solutions have been proposed. Examples of such solutions are the construction of a second level to allow an increase in passenger storage capacity without the need for horizontal expansion, and the use of the satellite section of a pier-satellite terminal as a single NLA gate. The implications of high-capacity aircraft on the passenger departure lounge are discussed. Using deterministic queuing theory, some analytical methods are presented to evaluate possible solutions and to assess both the lounge area and the number of seats that minimize the overall cost of the lounge. The use of a spreadsheet to implement the methods is also explained.
Planning and Design Model for Transit Route Networks with Coordinated Operations
Authors: Shih Mao-Chang , Mahmassani Hani S. , Baaj M. Hadi
Published: April 2007

A heuristic model is presented for the design of bus transit networks with coordinated operations. Different from past solution methodologies focusing on conventional uncoordinated transit systems, this model addresses the design of transit networks with coordinated operations, using a transit center concept and incorporating a trip assignment model explicitly developed for coordinated (timed-transfer) systems. In addition, this model determines the appropriate vehicle size for each bus route and incorporates demand-responsive capabilities to meet demand that cannot be served effectely by fixed-route, fixed-schedule services. This model is composed of four major procedures: ( a) a route generation procedure (RGP), which constructs the transit network around the transit center concept; ( b) a network analysis procedure, which incorporates a trip assignment model (for both coordinated and uncoordinated operations) and a frequency-setting and vehicle-sizing procedure; ( c) a transit center selection procedure, which identifies the suitable transit centers for route coordination; and ( d) a network improvement procedure, which improves on the set of routes generated by the RGP. The model is demonstrated via a case-study application to data generated from the existing transit system in Austin, Texas.
Demand Forecasting Model for Park-and-Ride Lots in King County, Washington
Authors: Hendricks Susan , Outwater Maren
Published: April 2007

As the demand for using park-and-ride lots grows, the need to accurately forecast these trips also grows. Initially, demand for park-and-ride lots was forecast using a technique that identified the draw area for each lot and estimated demand without regard to capacity. These were simplifying assumptions that are no longer appropriate with respect to current demand for park-and-ride lots. In King County, Washington, the 12 largest park-and-ride lots are currently operating at 95 percent utilization. According to a recent park-and-ride lot survey in King County, there is significant latent demand for using lots that are full. The analysis of demand for parking in park-and-ride lots in King County was developed as part of the Washington State Department of Transportation Public/Private Partnership Program for the Park-and-Ride Capacity Enhancement Project. There were 17 park-and-ride lots considered for capacity enhancement. The approach to evaluate park-and-ride lot demand uses a technique to identify intermediate stop choices, such as park-and-ride lots, as part of the overall modal choice. User and nonuser surveys were evaluated to identify the importance of specific variables, such as security or amenities. A combination of the survey results and an application of the demand forecasting model were used to estimate shifts in demand for parking from increased capacity and user fees. Several different user fees were tested and compared with stated preference results from the user and nonuser surveys. The project resulted in significantly different demand for park and ride than previous modeling efforts because of the impact of lot capacity and effects of user fees.
Rail Transit Safety Analysis: 1993, 1994, and 1995
Authors: Tennyson E. L.
Published: April 2007

Safety must come first, but absolute safety may not be fully attainable. Urban public transit suffers almost 60,000 accidents per year at an estimated cost of $360 million. Each major accident is thoroughly investigated by the National Transportation Safety Board, but its recommendations are not always implementable. This analysis has been made to review the relative safety of alternative modes of urban travel, particularly rail. It may be useful in determining where effort and priority should be focused for improvement. Fatalities are the most certain measure of accidents, as most other measures, such as collisions and injuries or damages, are limited by differing state rules on reporting. Costs are a reliable measure of accident severity, as they are audited and reported annually with respect to their magnitude. This analysis compares the fatality rates, the personal injury rates, the cost, and the types of accidents among the alternative modes of urban travel. The four major modes of rail travel are analyzed separately to assess their relative safety. Rail rapid transit (heavy rail) has very few grade-crossing accidents by definition. Commuter rail has low on-board accident rates because most passengers are seated for longer trips. Light rail suffers the most collision accidents per passenger kilometer because of street operation but experiences the fewest other types of accident. Automated guideways experience no grade-crossing accidents but have a high rate of station accidents. Automobiles experience the most fatalities, but the injury rate is indeterminate because of state cutoff rules on reporting at differing levels of accident cost. Almost all transit accidents are reported. Fatalities will be measured by the number per 100 million passenger km (100 million passenger mi). This is the standard measure for air and highway travel. Injuries will be measured per 1 million passenger km (1 million passenger mi) because there are so many more of them. It is a simple matter to multiply by 100 to obtain a comparison with the fatality rate. It would appear, based on the casualty rates and cost of accidents, that rail transit is the safest way to go, but improvements are still necessary.
Considering Build-Later as an Alternative in Major Transit Investment Analyses
Authors: Chu Xuehao , Polzin Steven
Published: April 2007

How the stream of benefits, discount rate, and other parameters of a major transit project affect its optimal timing are examined. A theoretical model of the timing of public infrastructure projects is used. The model takes into account the net benefits of a project, the variation of benefits with project age and timing of investment, construction cost and its growth, and discount rate. The model is used to examine three questions: Under what conditions is build-later optimal? How do changes in the discount rate and other parameters of an investment affect its optimal timing? How significantly do differences in the stream of net benefits from an investment affect its optimal timing? The first two questions are examined analytically, and the last question is examined numerically. When the stream of net benefits stays constant, declines, or shifts parallel with the timing of investment, build-later is not optimal. When the stream of net benefits grows over time, however, build-later can be optimal. A necessary condition for build-later to be optimal is that initial net benefits be relatively small. When build-later is optimal, how much later to build varies significantly.
Longitudinal Restraint Response of Existing Bridge Bearings
Authors: Barker Michael G. , Hartnagel Bryan A.
Published: April 2007

Fifteen rocker bridge bearings were cyclically tested to determine their bearing response to simulated seismic longitudinal loads. The objective of the tests was to examine the load-deformation characteristics and energy dissipation capabilities of bearings that have been in service for many years. The results are to be used to determine if existing in-place bearings may be utilized in seismic retrofitting of earthquake-susceptible bridges. The bearings were cycled within working ranges in each direction in the as-received state. The desired friction force hysteretic loops were determined from the net horizontal force-deformation test results. The cycles were applied in a sinusoidal manner in deflection control with a 4-s period to simulate dynamic demand on the bearing. An equivalent friction coefficient was calculated for each bearing. Four of the bearings were tested statically to failure to examine the limit state response. The ultimate limit tests produced horizontal load-deformation data. The horizontal force was applied slowly in deflection control while data were acquired until failure. The ultimate bearing tests showed that all four bearings had large deflection capacities before instability.
Japanese Manual for the Aesthetic Design of Bridges
Authors: Sugiyama Kazuo , Tajima Jiro
Published: April 2007

The Japan Society of Civil Engineers first published Manual for the Aesthetic Design of Bridges in 1982, and Volume 2 was published some 11 years later, in 1993. The primary intention of this paper is to introduce this second volume. More specifically, the background and events leading to its publication (and that of the preceding Volume 1) are discussed, as well as the manual’s approach to introducing the aesthetic aspects of bridge design to those involved in their construction. A range of keywords was sought in an attempt to establish conventions in bridge form. Further, the concept of continuity, the main theme of the manual, is introduced, together with a discussion of the advantages and limitations of this single-theme approach. It is shown how this one theme captures the essential elements of “good form,” “organized form,” and “unified form” and how it can be applied to both physical continuity and conceptual continuity. Continuity is also presented as embodying three aspects: connection, continuity, and recurrence. In conclusion, it is proposed that the achievement of continuity is a fundamental concept in aesthetic bridge design.
Seismic Retrofit of 1958 Carquinez Bridge
Authors: Hinman John , Toan Vong , Thoman Steve
Published: April 2007

The 1021-m (3,350-ft) long steel through truss bridge carrying the east-bound lanes of Interstate 80 across the western end of the Carquinez Strait about 40 km (25 mi) north of San Francisco opened to traffic in 1958. It was the first major highway bridge in the United States to use high-strength (T1) steel, the first to use welded built-up members, and the first to use high-strength bolted connections. These “firsts,” combined with the size of the bridge and the traffic demands, presented a formidable challenge to the retrofit design team. The retrofit objective was to prevent collapse of the bridge during an earthquake with an expected mean return period in the range of 1,000 to 2,000 years. Under this noncollapse criterion, significant damage to the bridge, such as yielding and buckling of members, was considered acceptable. It was important, then, that a measure of acceptable damage be defined and that the postyield behavior of the structure be both very predictable and very ductile. A preliminary design was prepared based on an elastic analysis with geometric non-linearities. The retrofit design was then examined by incorporating material nonlinearities into the model; adjustments to the retrofit design were required in some isolated areas. Design issues that the team addressed included connections for loads as high as 60 to 50 kN (13,500 kips); local buckling of thin-walled, high-strength members; postyield behavior of major load-carrying steel members; rocking of rigid A-frame tower assemblies; and an expansion joint for an 8-ft movement rating.
Accounting for Effects of Corrosion Section Loss in Steel Bridges
Authors: Prucz Zolan , Kulicki John M.
Published: April 2007

A systematic, multiphase approach for evaluation of the effects of corrosion section loss on bridge capacity is presented. The first phase of the evaluation process is to identify the corrosion mechanisms, determine the extent of corrosion, and estimate the possible consequences. In addition to material loss, corrosion can cause unintended fixities, movements, and distortions and contribute to fatigue and fracture failures. The second phase of the evaluation process is a quantitative evaluation of corrosion effects. A two-level office evaluation approach is recommended. The Level I evaluation is based on simplified methods suitable for routine office applications. If needed, a Level II office evaluation that can demonstrate additional reserves in strength not taken into account in the original design may be used. To obtain a direct measure of the effects of corrosion section loss, a residual capacity factor concept is proposed. Using residual capacity factors, which are ratios between deteriorated and original member capacities, reduces the effects of other factors, such as the analysis method and the factors of safety used to determine capacities. Since the capacity of members affected by corrosion could be governed by modes of failure that did not control their original design, all likely failure modes must be addressed. The evaluation criteria need to include strength and stability, serviceability, and fatigue and fracture. Provisions for assessing the effects of uniform and localized corrosion with respect to strength and stability criteria are presented as an illustration of the proposed approach.
Optimization of Structural Design for High-Performance Concrete Bridges
Authors: Ralls Mary Lou , Carrasquillo Ramon L. , Burns Ned H.
Published: April 2007

High-performance concrete (HPC) bridges can be cost-effective both initially and in the long term, provided the design and construction optimize the improved performance characteristics of HPC. Using the high-strength characteristic of HPC can reduce the required number and size of beams. Using the improved durability characteristics of HPC can reduce maintenance requirements and extend the service life. Practical guidelines help design and construction engineers implement HPC in bridges.
Data Reconciliation–Based Traffic Count Analysis System
Authors: Zhao Ming , Garrick Norman W. , Achenie Luke E. K.
Published: April 2007

Traffic volume data, especially average annual daily traffic (AADT), are important in transportation engineering. They are required in managing and maintaining existing facilities and in planning and designing new facilities. Many state highway agencies use the ramp counting procedure described in FHWA’s Traffic Monitoring Guide to estimate AADTs for freeways. The procedure involves counting all entrance and exit ramps between two established mainline counters (anchor points) and then reconciling the count data to estimate mainline AADT. The reconciling of count data includes three steps. First, AADTs for the ramps and the anchor points are estimated from the count data. Then AADT for each uncounted mainline link is calculated by addition or subtraction of ramp AADT to or from mainline AADT, starting from one anchor point. Finally, adjustments of the AADT are performed to achieve a match at the second anchor point if necessary. The process can be time-consuming and labor-intensive if it is done manually. A computer program to automate the process is required. The traffic count analysis system (TCAS) developed to automate the reconciling of count data in the ramp counting process is described. The TCAS was developed on the basis of data coaptation and data reconciliation techniques frequently used in the processing of network flow rate data. Data coaptation is used to calculate flow rates for uncounted links, and data reconciliation is used to adjust and balance the flow rates. The TCAS has been tested for the two longest freeways in Connecticut. The results are close to those from the ramp counting procedure. However, the TCAS significantly reduces the time and labor required for processing traffic volume data for freeways.
Reliability of Traffic Data
Authors: Cunagin Wiley D. , Kent Perry M.
Published: April 2007

The results of an investigation into reliability of traffic data are presented. Accurate and reliable traffic data are essential to a wide variety of transportation applications, including pavement and bridge design and performance evaluation, programming, planning, and budgeting activities, as well as legislative and administrative policy development. Millions of dollars are spent each year to collect, process, and disseminate these data to users. The development of the AASHTO reliability concept for pavement design was investigated and expressions for traffic data variability were developed. Extensive actual traffic data files were analyzed. The resulting statistics were used to determine the importance of traffic data variability on the reliability of traffic projections for pavement design.
Geographic Information System Use for Hydrologic Data Development for Design of Highway Drainage Facilities
Authors: Olivera Francisco , Maidment David
Published: April 2007

A significant part of the cost of most highway projects is attributable to drainage facilities such as storm drains, highway culverts, bridges, and water quality and quantity control structures. A geographic information system (GIS) for hydrologic data development for design of drainage facilities is presented. The system was developed to reduce the analysis time and improve accuracy by integrating spatial data describing the watershed with hydrologic theory. A grid-based GIS to estimate potential extreme peak discharges, watershed parameters, peak discharges for different frequencies, isochrone lines, and runoff curve numbers is presented. Data from the State of Texas were used in an example application.
Research Needs for Determining Spatially Resolved Subfleet Characteristics
Authors: Bachman William , Granell Jessica , Guensler Randall , Leonard John
Published: April 2007

Future emission models will need spatially resolved subfleet characteristics to determine mobile emission inventories. The use of geographic information systems and regional registration data for developing location-specific vehicle characteristics that can feed future models is addressed. Issues regarding data availability and quality are explored to define gaps in the research that may prevent development of comprehensive and accurate estimates. As a component of a larger research project studying vehicle emission modeling, a six-step process was developed and implemented for a 100 km2 area in Atlanta. Vehicles were geocoded by using registration addresses, and vehicle characteristics were determined through a series of computer programs, commercial software, and related datasets. During the process, many research issues were identified that prevent a comprehensive assessment of spatially resolved fleet characteristics. The data and research needed to further improve the capability to generate spatially resolved subfleet characteristics were identified.
Environmental Consequences of Reducing the Federal Role in Transportation: Legal Framework
Authors: Downing Donna , Noland Robert B.
Published: April 2007

The Intermodal Surface Transportation Efficiency Act (ISTEA) currently provides transportation grants to states financed by the Highway and Mass Transit Trust Funds and establishes a variety of requirements that seek to make environment a key factor in transportation planning and implementation. Devolution of the federal role would make states responsible for financing highway and transit improvements and for making related policy and program decisions. Although ISTEA is not primarily an environmental law, it contains numerous provisions that take into account the environmental implications of authorized activities. In addition, federal funding can trigger requirements for “major investment study” and National Environmental Policy Act (NEPA) processes that consider environmental impacts of proposed projects and allow for public comment. Devolution could affect the number of transportation projects subject to such scrutiny, where federal funding is the sole element that “federalizes” a project enough to make major investment study or NEPA requirements apply. And, although many other federal and state laws provide environmental protection, they typically do not focus on achieving an environmentally friendly transportation system. The impacts that devolution could have on environmental protection are explored here. The environmental provisions currently in ISTEA are reviewed and the potential role of NEPA and the Unfunded Mandates Reform Act in a devolution environment is identified. Other federal or state laws that may be available to “stand in” for environmental provisions eliminated or weakened by devolution are explored, and the potential environmental impacts of a reduced federal role in transportation oversight are discussed.
Post-National Environmental Policy Act Monitoring of Environmental Impacts and Mitigation Commitments
Authors: Wallace Daniel P. , Shalkowski Joseph S.
Published: April 2007

Post-National Environmental Policy Act (NEPA) phase tracking tools have been developed and applied successfully to monitor changes in environmental impacts and mitigation commitments identified during the NEPA process as transportation projects advance and are refined through the highway final design process. The tools have been used effectively on two Pennsylvania Turnpike Commission (PTC) expansion projects currently under development in the Monongahela River Valley region of southwestern Pennsylvania. The tools include a set of computerized spreadsheet/database tracking tables that identify the environmental impacts and mitigation commitments contained in the final environmental impact statement (FEIS), the memorandum of agreement for cultural resources, the FHWA record of decision, and the Pennsylvania Agricultural Land Condemnation Approval Board adjudication. As refinements were made to the project and its right-of-way requirements during final design, any associated changes to environmental impacts were recorded. The tables provided the PTC, state, and federal agencies with a means to efficiently evaluate the resulting environmental impacts for the projects and assess the applicability of the mitigation commitments as defined in the FEIS. Any refinements needed in the mitigation commitment were incorporated into the final design plans. The rationale behind the development of these tools in conjunction with their functional value to the NEPA process is presented.
Comparison of Environmental Implications of Asphalt and Steel-Reinforced Concrete Pavements
Authors: Horvath Arpad , Hendrickson Chris
Published: April 2007

The public, industry, and governments have become increasingly interested in green design and sustainable development. Construction activities affect the environment significantly, so environmental issues should be considered seriously. Thousands of miles of roads are paved every year with asphalt and steel-reinforced concrete. What are the environmental effects of the two materials? If asphalt has been used overwhelmingly over concrete, is it a better choice for sustainable development? We present results of a life cycle inventory analysis of the two materials based on publicly available data. We find that for the initial construction of equivalent pavement designs, asphalt appears to have higher energy input, lower ore and fertilizer input requirements, and lower toxic emissions, but it has higher associated hazardous waste generation and management than steel-reinforced concrete. When accounting for the uncertainty in the data and when annualizing environmental effects based on assumed average service lives of the two pavement types, the resource input requirements and the environmental outputs are roughly comparable for the two materials. However, asphalt pavements have been recycled in larger quantities than concrete pavements, with consequent resource savings and avoided pollution, which suggests that asphalt may be a better choice from a sustainable development viewpoint. Of course, special functional requirements or economics may dictate the use of one material over the other in particular applications regardless of the overall environmental effects.
EverFE: Rigid Pavement Three-Dimensional Finite Element Analysis Tool
Authors: Davids William G. , Turkiyyah George M. , Mahoney Joe P.
Published: April 2007

The interactive and computational features of EverFE, a new rigid pavement three-dimensional (3D) finite element (FE) analysis tool, are presented. To date, the use of 3D FE analysis has been hampered by (a) the difficulty of model generation and result interpretation, (b) the inability of many programs to adequately model joint shear transfer due to aggregate interlock and dowel action, and (c) the large computational requirements of conventional solution techniques employed by available programs. The development of EverFE is motivated by the desire to make 3D FE analysis feasible for routine analysis of rigid pavements. The intuitive graphical user interface employed by EverFE, which greatly simplifies model generation and result interpretation, is demonstrated using a sample problem. A novel technique for modeling aggregate interlock joint shear transfer that rationally incorporates nonlinearities is developed and presented, as is a new method for modeling dowel joint shear transfer. The solution strategy employed by EverFE that allows realistic 3D models to be simulated on desktop computers is briefly described, and its performance is presented.
Applicability of Superpave to Modified Asphalts: A Mixture Study
Authors: Jones Stephen D. , Mahboub Kamyar C. , Michael Anderson R. , Bahia Hussain U.
Published: April 2007

Superpave binder and mixture specifications are currently being reviewed for their applicability to modified asphalts. This study was designed to evaluate a series of modified binders with the same Superpave performance grade (PG 76-22). The experiment was based on the following hypothesis: The performance characteristics for a given asphalt mixture will be the same for all PG 76-22 binders. The performance indicators analyzed in this study were obtained from a suite of laboratory mixture performance tests. The study, which also included a PG 64-22 asphalt to serve as the control, revealed that the hypothesis may be rejected. That is, mixture performance potential would be significantly different for various modified asphalts of the same performance grade. Loading frequency and strain dependency were noted as the most significant behaviors to address. Finally, recommendations were made for possible modifications of Superpave specifications to address these issues.
Low-Temperature Cracking and Aging Performance of Modified Asphalt Concrete Specimens
Authors: Fortier Richard , Vinson Ted S.
Published: April 2007

The thermal stress restrained specimen test (TSRST) was used to evaluate the low-temperature cracking resistance and aging performance of modified asphalt concrete (AC) specimens. One aggregate, two asphalt cements (AAA-1 and AAB-1), five modifiers (latex polymer, ethylene acrylate copolymer, rubber powder, elastomer, and a blend of polypropylene and Kevlar fibers), and four 85°C oven aging levels (0, 5, 25, and 50 days) were considered. The results of the bending beam rheometer test (BBRT) on binders at −20°C showed that AAA-1 displayed a smaller creep stiffness than AAB-1. Only two modifiers increased the deflection and softness of AAB-1. The additives in AAA-1 did not improve its lowtemperature rheological behavior. These results served as the basis for comparison with those from the TSRST. The fracture strength and temperature of AC specimens are sensitive to asphalt type (4.11 MPa and −32.2°C for AAA-1, 3.28 MPa and −25.4°C for AAB-1) and degree of aging (from 4.11 to 2.04 MPa and from −32.2 to −21.2°C for AAA-1 for aging levels from 0 to 50 days at 85°C). Only one modifier in AAB-1 (among the two candidates identified with the BBRT) improved the low-temperature performance of the AC specimens. After 50 days of aging, no improvement was observed. The modified AAA-1 AC specimens displayed an optimum improvement in performance for aging levels of 25 and 50 days. Several modified AC specimens displayed a low-temperature failure without apparent fracture. This behavior would appear to be advantageous for the performance of pavements in cold regions.
A Rational Method for Relating As-Built Quality to Pavement Performance and Value
Authors: Weed Richard M.
Published: April 2007

Highway construction specifications routinely use adjusted-payment provisions to award payment in proportion to the level of quality received. Work that meets the level of quality defined as acceptable is eligible for 100 percent payment, whereas work that fails to meet the desired quality level but that is not sufficiently deficient to warrant removal and replacement typically receives some degree of pay reduction. More recently, many agencies have begun to offer monetary incentives in the form of bonus provisions for work that substantially exceeds the desired level of quality. Although the pay-adjustment approach to highway quality assurance is now widely used, there is not yet a consistency of practice regarding the magnitude of pay adjustment judged appropriate for varying levels of as-built quality. To achieve consistency and make this approach more effective and defensible, there is need for a method to relate as-built quality to expected performance, which can then be related to value by engineering-economics procedures. The extension and refinement of earlier work are described here and an example structured around one of the performance relationships in the AASHTO Guide for Design of Pavement Structures is provided. This methodology suggests that many pay schedules currently in use may not fully recoup the real costs incurred by highway agencies as a result of defective work.
Consideration and Characterization of Pavement Construction Variability
Authors: Patel Arti , Thompson Marshall
Published: April 2007

Recently, many state highway agencies have adopted quality control/ quality assurance (QC/QA) techniques with the desire to improve the quality of construction and provide an incentive or environment for contractors to try new or innovative construction methods or materials. Reduced construction and material variability is one measure of improved “quality” of construction. Although decreased variability may be desirable, there is considerable debate and confusion about the cost-effectiveness of the QC/QA programs. The data collection effort and three variability analysis techniques that may be used to evaluate the effectiveness of the QC/QA programs are discussed here. Characterization of variability and application of the techniques for Illinois’ QC/QA program are also presented.
Accelerating Major Freeway Reconstruction Projects: The Houston Experience
Authors: Benz Robert J. , Fenno David W. , Voigt Anthony P.
Published: April 2007

Several steps in the planning, execution, and evaluation of the I-45 Pierce Elevated reconstruction in Houston provide a strong framework for preparing for projects that affect critical links in the nation’s transportation system. These elements include preconstruction traffic modeling, public information, and data collection before and during each phase of construction. Traffic modeling helped to prepare for construction by first developing delay numbers for the estimated user cost used in the A + B bidding. Second, preconstruction modeling identified bottlenecks that were temporarily remediated at strategic locations. Finally, modeling provided speed and travel time data used in mounting a public information campaign. Data collection and monitoring of traffic conditions immediately before, immediately after, and a few weeks after construction began provided an immediate picture of traffic conditions and identified problem locations that could be corrected during construction. A critical public information campaign was undertaken using television, radio, newspaper articles, billboards, fliers, and variable message signs. Each of these provided advance warning to motorists in the weeks before construction began and variable message signs, radio, and the Internet were used to provide real-time information during construction. Preparations for the Pierce Elevated reconstruction went beyond standard procedures and planning typically used for major construction projects. Although engineers have traditionally been designers as well as project managers, they will be called on more to become brokers of information that will allow the public to use the transportation network in the most time- and cost-effective manner under adverse construction conditions.
Estimating the Probability of Freeway Congestion Recurrence
Authors: Cottrell Wayne D.
Published: April 2007

The 1991 Intermodal Surface Transportation Efficiency Act, along with the National Highway System Designation Act of 1995, mandated that congestion management systems be established in urbanized areas with population of 200,000 or more. The mandate created a need for congestion monitoring. A 1995 informal national survey of transportation agencies by FHWA indicated a need for tools to evaluate the impacts of remedial strategies. Further, some agencies have sponsored research on topics such as congestion thresholds and measurement methods. This paper proposes a model that estimates the probability of congestion recurrence at existing and potential freeway bottlenecks. The objectives were that the model accept data that are commonly collected, evaluate existing conditions, predict future conditions, and assess the impacts of mitigating actions. A logistic regression equation is developed from 163 observations. The equation is bivariate, with the annual average daily traffic volume to hourly capacity ratio ( AADT/C) and the K-factor as explanatory variables, and RECON, a binary congestion indicator, as the response variable. The model correctly classifies 83 percent of the data sites used in its development, but it needs to be tested on other data. An AADT/C value of 8.5 may be a critical threshold separating the noncongested and congested regimes. Future research might experiment with other explanatory variables. A larger database might yield an improved classification rate. The extra data might also enable the development of a nested logit model that estimates the probabilities of no congestion, congestion once a day, and congestion twice a day at a bottleneck.
Freeway Service Patrols: A State of the Practice
Authors: Feno David W. , Ogden Michael A.
Published: April 2007

Freeway service patrols have been cited as one of the most effective elements of an incident management program for reducing incident detection time and incident duration. Service patrol programs utilize roving vehicles to patrol congested and high incident sections of urban freeways. The state of the practice of freeway service patrol programs in the United States is documented in this paper. A telephone survey was conducted with managers of 53 freeway service patrols in 22 states. Approximately 74 percent of the surveyed service patrols are sponsored exclusively by public agencies. Approximately 47 percent of the surveyed patrols are sponsored exclusively by Department of Transportations; 6 percent are sponsored exclusively by police agencies; and 21 percent are sponsored by multiple public agencies. Approximately 34 percent of the patrols receive federal support funding. Finally, 27 percent of the patrols operate with private funding sources. Service patrol hours of operation vary from program to program, with the most common being coverage of the weekday a.m. and p.m. peak periods. Approximately 70 percent of the surveyed agencies own and operate their own vehicles, whereas 26 percent contract with private tow companies to provide drivers and vehicles. Benefits associated with service patrols are typically quantified by multiplying a value of time by the estimated delay reduction provided by the service patrol in vehicle-hours. Available benefit to cost analyses for 15 of the service patrols studied ranged from 2:1 to 36.2:1. A contact list and recommendations for agencies interested in starting a new service patrol program are also included in this paper.
Motorist Behavior and Opinions Toward High-Occupancy Vehicle Lanes at Ramp Meters
Authors: Newman Bruce R. , Washburn Scott S. , Nihan Nancy L.
Published: April 2007

High-occupancy vehicle (HOV) lanes at metered on-ramps are intended to provide incentives for people to carpool or use transit. However, violations of the minimum passenger occupancy requirements penalize metered vehicles with extra delay and undermine the effectiveness and integrity of bypass lanes. Additionally, the perception of high violation rates can erode public support for HOV facilities. The purpose of this study was to gain a better understanding of the design factors and behavioral characteristics that influence violation rates at HOV bypass lanes at metered on-ramps. An on-ramp in Seattle, Washington was selected for data collection. This on-ramp consists of one metered lane and one HOV bypass lane. The site has a number of characteristics believed to influence violation behavior, including a minimum three-person vehicle occupancy requirement (most local facilities have only a two-person requirement), frequent extensive queuing, and little area for police enforcement. During data collection, all users of the HOV bypass lane were observed, and vehicle passenger occupancies and vehicle license plates were recorded. A high-speed video camera was utilized to assist with data verification. Subsampling of vehicle license plates from the metered lane was also performed. A mail-back survey with questions on travel habits, demographic and socioeconomic characteristics, and opinions toward and understanding of HOV and ramp metering policies was sent to the registered owner of each sampled vehicle. Ordered probit and binomial logit modeling, as well as general descriptive statistic methods, were utilized for survey analysis. Additionally, comparisons were made of subjects’ observed behavior and their reported behavior. Findings from this study can help guide future policy on the implementation of HOV bypass lanes (and possibly other HOV facilities), identify appropriate methods to preserve the integrity of these facilities, and, in turn, maintain a positive public image.
Real-Time Traffic Signal Optimization with Transit Priority: Recent Advances in the Signal Priority Procedure for Optimization in Real-Time Model
Authors: Conrad Mark , Dion Françlois , Yagar Sam
Published: April 2007

Real-time traffic signal optimization software was developed using object-oriented techniques based upon the SPPORT (Signal Priority Procedure for Optimization in Real Time) model. SPPORT is a rule-based model that provides specialized mechanisms for transit priority. Based upon a flexible discrete-event traffic simulator that realistically models the effects of transit operations on the general flow of traffic, and equipped with rules designed to provide effective transit priority while still giving appropriate consideration to other traffic, SPPORT generates signal timings to minimize an objective function in which transit vehicles may be weighted as deemed appropriate in relation to other traffic. In developing this software, the SPPORT model was extended to support user-defined intersection configurations, multiphase traffic signal operation, and a more advanced form of transit priority that considers both nearside and mid-block transit stop locations. The fundamental concepts of the SPPORT model and their relationships to the key components of the SPPORT software are the foci of this paper. An illustrative example and a set of simulation test results are also presented.