bluuebunny/crossref_metadata_2025 huggingface dataset:
Orthotropic Deck Fatigue Investigation at Triborough Bridge, New York
Authors: Abdou Samia , Zhang Wuzhen , Fisher John W.
Published: April 2007

The Triborough Bridge connects the boroughs of Manhattan, Queens, and the Bronx in New York City. The bridge has suspended spans with a total length of 2,700 ft (823 m). The existing concrete deck is being replaced with an orthotropic steel deck to reduce the overall dead load. Before deck replacement, a prototype steel orthotropic deck was installed on the main span for a length of 120 ft (36.6 m). About 300 strain gauges were installed at critical locations to investigate the fatigue strength under static and dynamic loads of the AASHTO fatigue truck and under normal traffic. The strain gauge testing was done in three phases, and structural refinements were made to the deck system between phases. Traffic monitoring was conducted for the most critical locations over a 30-day period during Phase III. The results from three phases of the strain gauge testing, including influence lines and traffic monitoring data, were used to calculate fatigue stress ranges and the fatigue life for each detail. In addition to strain gauge testing, a finite element analysis of the orthotropic deck was performed with loading criteria set by AASHTO load and resistance factor design. The results from the finite element analysis were compared with the results obtained from the strain gauge testing. It was concluded that the heavy trucks on the bridge cause fatigue stresses higher than what had been anticipated by AASHTO. The investigation assisted in modifying the design to obtain a longer service life for the deck system under heavy-truck traffic.
Field Tests and In-Service Monitoring of Newburgh-Beacon Bridge, New York
Authors: Shenton Harry W. , Chajes Michael J. , Sivakumar Bala , Finch William W.
Published: April 2007

Field tests previously conducted on the Newburgh–Beacon Bridge in New York captured anomalous stress spikes in the critical hangers of the truss bridge. The very high magnitude spikes occurred sporadically, without warning and under various conditions. The cause and nature of the spikes were of great concern to the bridge owner, the New York State Bridge Authority. Originally, the spikes were thought to be due to some combination of wind, thermal effects, and an unlocking of stresses due to fabrication errors in the pin-and-hangers systems. A series of short- and long-term field tests were recently conducted on the bridge to help identify the cause of the spikes. Sections of the bridge were instrumented with strain gauges around two different pin-and-hanger members. One site was continuously monitored for over 3 months to obtain statistical data on the spikes. Through a series of different test setups, designed to debug the problem, the anomalous spikes were found to be caused by radio interference in the environment, which was being picked up by the strain gauge wires. The test setup, test program, and test results are described. The tests resolved a long-standing concern of the bridge authority and avoided costly and unnecessary retrofits.
Structural Performance of Storm Water Detention System with Bundled High-Density Polyethylene Pipes
Authors: Folkman Steven L. , Moser A. P.
Published: April 2007

Buried parallel pipes are used for storm retention systems. Traditional retention-detention systems have spaced parallel pipes that permit soil columns between pipes. A new design allows for the parallel pipes to be placed side by side in contact with each other. The performance of such a system of bundled high-density polyethylene (HDPE) pipes that is subjected to vertical earth loads is reported. This bundled system consists of parallel HDPE pipes wrapped with a geogrid and a geofabric. The actual loads ranged from shallow cover to vertical loads equivalent to 55 ft (16.8 m) of cover. The embedment soil selected for the research was a silty sand. This soil was selected because its structural qualities are generally considered to be the least acceptable for these types of applications. The soil that typically would be specified is a crushed stone. Therefore, the results from the tests are conservative. Structural performance is reported, and photographs present the pipes in the bundled system during installation and after subjection to earth loads. Load-deflection curves for the pipes in the system are also given.
Global Environment Facility Support for Sustainable Transport: Early Lessons from World Bank–Assisted Projects in Mexico City, Mexico; Santiago, Chile; and Lima, Peru
Authors: Graftieaux Pierre , Vergara Walter , Johnson Todd
Published: April 2007

Global Environment Facility (GEF) support for World Bank sustainable transport activities is described. An overview is presented of current GEF strategy for sustainable transport, which reflects a shift beyond individual technology interventions toward broader objectives, including modal shift, demand management, and land use planning. Ongoing GEF projects that exemplify this shift are reviewed by examining projects in Latin America and Asia whose aim is improving public transport, nonmotorized programs, and institutional capacity related to sustainable transport. The major lessons that can be drawn from these projects, most of which are still at an early stage, is that local authorities are often enthusiastic about getting involved in programs that simultaneously address key transportation concerns in their cities (such as access, safety, congestion, local air quality) and result in less overall energy use and greenhouse gas emissions. Much can be achieved as long as project communications and promotion are addressed and carefully targeted at decision makers and potential beneficiaries.
Strategies to Promote the Safety of Vulnerable Road Users in Developing and Emerging Countries: South African Experience
Authors: Ribbens Hubrecht
Published: April 2007

Road casualties are discussed from a worldwide perspective. More than 80% of annual traffic casualties occur in developing and emerging countries in Asia, Latin America, the Caribbean, sub-Saharan Africa, and the Middle East. Vulnerable road users such as pedestrians and bicyclists are a major road safety problem in these countries. In Asia, Africa, the Caribbean, and the Middle East, more than 40% of annual road fatalities involve pedestrians compared with less than 20% in Europe and the United States. The focus of this study is South Africa’s strategy to promote the safety of vulnerable road users. The extent of casualties among vulnerable road users and contributing factors are highlighted. Over the last decade, pedestrian fatalities have gradually and steadily declined in South Africa. This study describes the various policies, strategies, and action plans developed and implemented by different government levels in South Africa to promote road traffic safety, particularly the safety of vulnerable road users such as pedestrians and bicyclists. Barriers to successful implementation are also pointed out. Apart from applying a holistic approach by involving all relevant disciplines, a coordinated and sustained effort of all government levels was encouraged. Joint-venture funding projects among different government levels was emphasized to improve hazardous pedestrian locations. The role of the private sector in South Africa to promote pedestrian safety is also discussed. Practical guidelines are presented for developing and emerging countries to promote the safety of vulnerable road users.
Streamlining Chinese Highway Accident Data Acquisition, Communications, and Analysis
Authors: Yi Ping , Ran Bin
Published: April 2007

This research examines a streamlined accident data acquisition, communications, and analysis system to improve the Chinese highway safety program. A data logger compatible with the Global Positioning System and geographic information system is proposed to identify highway accident locations and organize the data into a database format. A data encoding concept is used to transform Chinese characters into numbers, so that the encoded data are easy to integrate into a large data system. A three-tier client–server networking system is set up as the backbone framework for data communications between the central database and distributed local offices. Using local database functions, traffic police at the client level can view crash data through data mapping and attribute listing and analyze the data through nested query and sorting operations. A data graphing and analysis module was tested for automatically constructing a collision diagram on selected data. The proposed approach to crash data acquisition and analysis was found to be feasible and effective and will help to enhance China’s highway safety program after full implementation.
Traffic Safety Diagnostics and Application of Countermeasures for Rural Roads in Burkina Faso
Authors: Lord Dominique , Abdou Hamidou Mamadou , N’Zué Antoine , Dionne Georges , Laberge-Nadeau Claire
Published: April 2007

The government of Burkina Faso has recently been making important macroeconomic changes to encourage the economic growth of the country. To maintain this growth, the government has implemented a transportation program to improve road network efficiency and safety. A 2000 study to improve the safety of rural roads in Burkina Faso is described. The primary objectives were to assess traffic safety problems and propose countermeasures to reduce the number and severity of collisions on rural roads. Many rural roads were evaluated on site; all accident data and important socioeconomic variables were collected; and key staff members from various governmental and private agencies were interviewed. The study has shown that traffic safety problems in Burkina Faso are multidimensional, involving inefficient traffic safety management and policy, inadequate road networks, untrained drivers, and defective vehicles. Several traffic safety countermeasures have been proposed for immediate, short-, and long-term application. The most important countermeasures are to create a new institutional framework for improving traffic safety management and train the key personnel responsible for implementing these countermeasures. For the short term, the counter-measures mainly relate to roadway infrastructure improvements and better enforcement tools. For the long term, the countermeasures include a review of current highway traffic laws and their application, evaluation of existing countermeasures, and driver training improvement.
Comparison of the New W-lnterchange with Conventional Interchanges
Authors: Thompson Cipriana D. , Hummer Joseph E. , Kluckman Roger C.
Published: April 2007

Congestion is a problem at many urban interchanges, particularly at diamond interchanges. A new interchange design, called the W-interchange, seeks to reduce congestion at a reasonable cost. Similar to the Michigan urban diamond interchange (MUDI), which uses U-turn structures, the W-interchange attempts to reduce delay by eliminating the left-turn movements onto and off of the cross street. The new W-interchange was compared with other, more commonly used designs for freeway-to-arterial interchanges, specifically the diamond interchange, the single point urban interchange (SPUI), and the MUDI. A major portion of the effort was a comparison of the travel times and stops across a range of traffic demands using a microscopic traffic simulation package. The results from the simulations indicated that the W-interchange minimized the number of stops and produced an overall travel time that was lower than the diamond interchange and comparable with the MUDI. The W-interchange had lower travel times than the SPUI for a few of the cases simulated, but generally the SPUI had lower travel times. A design of the W-interchange was created to estimate its construction and right-of-way cost. At about $14 million, the W-interchange costs about $4 million more than the SPUI and about $6 million more than the diamond interchange. Overall, the W-interchange performed well enough in the simulations and has enough other advantages to justify further research in the areas of cost, signing and marking, continuous frontage road operation, and a possible freeway-to-freeway design.
Methodological Framework for Strategic Assessment of Transportation Policies: Application for Athens 2004 Olympic Games
Authors: Tsamboulas D. , Kopsacheili A. G.
Published: April 2007

Consistent decision making requires a structured, systematic evaluation of the advantages and disadvantages of different choice possibilities. For the evaluation of transportation policy measures, various multicriteria analysis (MCA) methods have been developed to complement conventional cost–benefit analysis. These methods investigate and evaluate all relevant effects of an alternative by introducing some key policy criteria that are particularly relevant in assessing strategic-level impacts, such as environmental impacts and equity issues. Design of the appropriate assessment approach has to take into account the different problem settings in which decision making takes place. That is particularly important in the context of evaluating policies as opposed to plans and programs, such as evaluating transportation policies at the strategic level in contrast to evaluating transportation projects. Hence, there is a clear need for a systematic approach to the strategic assessment of transportation policies. That need is addressed: an evaluation and assessment framework based on three widely used MCA methods is presented, and a comprehensive framework for the strategic assessment of spatial–economic and environmental–economic transportation policy instruments is provided. This framework is applied in the specific case of the Athens 2004 Olympic Games to test its robustness and assist in the formulation of policy actions.
Addressing Educational Needs in Spatial Data, Information Science, and Geomatics in the Civil Engineering Undergraduate Curriculum
Authors: Sarasua Wayne A. , Davis William J.
Published: April 2007

The technology-driven, rapidly advancing field of spatial data and information science (SDIS) is an integral part of numerous engineering professions. Many college civil engineering programs are struggling to find ways to accommodate this subject in an already crowded undergraduate curriculum. There are several reasons that taking a course in SDIS is desirable for civil engineers entering today’s demanding job market. First, technologies related to surveying, spatial data, and information science are among the fastest developing in the industry, and there is significant demand for skills in the latest technology. Second, spatial data collection and analysis are essential to all civil engineering disciplines; thus, a fundamental understanding of data collection and analysis techniques is desirable. The transportation discipline of civil engineering may face the greatest need for professionals specializing in SDIS. Transportation planning, system design, facilities management, and transportation logistics rely heavily on SDIS technologies, including conventional surveying, geographic information systems, Global Positioning System, remote sensing, and digital terrain modeling. A description is given of a widely transferable and technically up-to-date course in geomatics that expands on traditional surveying by incorporating modern methods of spatial data collection, management, and analysis. Including a course on geomatics early in students’ undergraduate civil engineering curriculum may plant the seed for the development of future SDIS and SDIS for transportation professionals. Lessons learned in developing geomatics courses at Clemson University, Georgia Tech, and The Citadel are presented. Findings and recommendations are summarized with respect to broader application issues affecting the civil engineering curriculum.
Building on Common Desire for Better Tribal–State Governmental Relationships: 2002 Four Corners Institute for Tribal-State Relations
Authors: Kozak Jim , White Mary E.
Published: April 2007

Overcoming 500 years of fractious relations between tribal and nontribal cultures and governments is an endeavor not easily achieved in America, nor is it one that has always been marked by steady progress. Interpretations of tribal sovereignty have been long disputed. In the past 30 years, this often-debated concept has become an issue of great importance to state and federal governments. Differences of opinion still exist over the impact of tribal sovereignty on policies, procedures, or protocol. However, state and federal policy makers have begun to view the tribes as independent entities entitled to due consideration and an appropriate cultural sensitivity. All branches and levels of governments—including tribal ones—struggle to define mutual areas of responsibility, communication, and cooperation. Decision makers from state, federal, and tribal governments have had some opportunities to share experiences and information in the past. But this practice is still a work in progress despite the most sincere wishes for a better outcome by those participating on a policy level. The common desire of these parties is that intergovernmental relations become more symbiotic and less adversarial, as cooperation can facilitate the mutual interests of all. Accomplishing this task in ways that do not threaten tribal sovereignty is difficult. The 2002 Four Corners Institute for Tribal–State Relations concept is covered along with its participants, methodology, results, limitations, and recommendations for further research. New methodology will be discussed including the remote venue, Native Americans as facilitators, participants as fellows, and the method for choosing format and discussion topics.
Sustainable Development Planning Tools: Suite of Models Useful in Large Metropolitan Regions
Authors: Johnston Robert A. , Garry Gordon
Published: April 2007

Planning for sustainable development requires models that can represent the effects of land use and transportation policies on economic welfare, social equity, and the natural environment. Various urban models and geographic information system impact models have been in development for use in the Sacramento, California, region for several years. A comprehensive set of models is proposed. With the improvement of the urban economic model and the addition of a model for real-time scenario generation and evaluation, it is thought that a full suite of models exists for comprehensive regional planning. All the models are free, public license models, appropriate for application in large metropolitan planning organizations and other regional agencies.
Field Performance of Embankments Stabilized with Recycled Plastic Reinforcement
Authors: Parra Jorge R. , Loehr J. Erik , Hagemeyer David J. , Bowders John J.
Published: April 2007

The performance of earth slopes reinforced with arrays of slender reinforcing members is currently being investigated. The reinforcing members used are fabricated from recycled plastics and other waste materials to form sections 90 mm (3.5 in.) × 90 mm (3.5 in.) × 2.4 m (8 ft) long. A design methodology was adopted to estimate the limit resistance provided by each member, which is then incorporated into conventional limit equilibrium slope stability analyses to calculate the improvement in the factor of safety under various reinforcement scenarios. Four field test sites were stabilized using recycled plastic reinforcement to demonstrate the effectiveness of the stabilization scheme and to evaluate the load transfer mechanisms between the soil and the reinforcement. One additional site was stabilized with similarly sized steel pipe members for comparison with the recycled plastic members. The stabilized slopes are performing well, whereas several control sections have experienced failures. The performance of each site is being monitored with field instrumentation to monitor lateral movements, pore pressures, strains within the reinforcing members, and the lateral loads applied to the members. Observations to date indicate that the slopes are performing well and that the reinforcing members have significant remaining capacity to maintain the stability of the slopes.
Evaluation and Quality Control of Dry-Jet-Mixed Clay Soil-Cement Columns by Standard Penetration Test
Authors: Liu Songyu , Hryciw Roman D.
Published: April 2007

Dry jet mixing has been widely used since the 1980s for stabilization of soft soil. The quality and strength of the dry-jet-mixed columns must be evaluated to confirm the success of the stabilization. The standard penetration test (SPT) is shown to be a simple and effective method for this task. The strength characteristics along the length of the column were determined, and correlations between the SPT blow count and the unconfined compressive strength were developed.
Effect of Bridge-Soil Interaction on Behavior of Piles Supporting Integral Bridges
Authors: Duncan J. M. , Arsoy Sami
Published: April 2007

As the temperature of an integral bridge changes, the length of the bridge increases and decreases, so that the abutments are pushed against the approach fill and then pulled away, causing lateral deflections at the tops of the piles that support the bridge. As a result, complex interactions take place among the abutment, the approach fill, the foundation soil, and the piles supporting integral bridges. Finite element analyses were performed to investigate these complex interactions. The results of this study indicate that these interactions have a beneficial effect on the stresses in the piles supporting the bridges. Because of these interactions, the foundation soil acts as if it were softer, resulting in reduced shear and moment in the piles at a given amount of deflection at the tops of the piles and therefore reduced stresses in the piles.
Analysis of Deeply Buried Flexible Pipes
Authors: Suleiman M. T. , Lohnes R. A. , Wipf T. J. , Klaiber F. W.
Published: April 2007

CANDE is one of the most commonly used programs for analysis of buried pipe; however, CANDE is limited to applications with small deflections. This limitation is typically not problematic, but there are some instances in which analysts may be interested in large-deflection behavior. This limitation led to the consideration of other analysis tools. In this study ANSYS, a general finite element program, was used to model the soil-pipe system. Small- and large-deflection theories of ANSYS were used in the analysis of several case studies, and the results were compared with those of CANDE. Also, a code was written to run within ANSYS to include the following soil constitutive models: the hyperbolic tangent modulus with both power and hyperbolic bulk modulus. Results obtained using ANSYS with the modified soil models were in good agreement, with less than 10% difference, except in one case: CANDE results for 6.1 m of soil cover above the springline for 610-mm pipe diameter with SM and ML soils. Use of large-deflection theory resulted in an insignificant effect, less than 5%, when compared with ANSYS small-deflection theory results for soil heights up to 6.1 m above the springline, which proves that small-deflection theory is adequate for these cases. Comparing CANDE and ANSYS for 1,200-mm-diameter polythylene (PE) pipes with experimental results showed that ANSYS more accurately describes the PE pipe behavior for cases of 9 m of soil cover or more and that large-deflection theory describes the PE pipe behavior better than small-deflection theory for a vertical deflection of 4% or more. The pipe material effect was investigated by comparing the results of ANSYS small- and large-deflection theories for both PE and polyvinyl chloride pipes. The difference between the small- and large-deflection theories for both pipe materials becomes significant, more than 10%, at a vertical deflection of 4%.
Simulation of Fracture Initiation in Hot-Mix Asphalt Mixtures
Authors: Birgisson Bjorn , Soranakom Chote , Napier John A. L. , Roque Reynaldo
Published: April 2007

A displacement discontinuity boundary element method is presented to explicitly model the microstructure of asphalt mixtures and to predict their tensile strength and fracture energy density. The loading response of three mixtures was simulated to assess the mechanics of fracture in the Superpave indirect tension test. The predicted tensile strength and fracture energy density of three samples were comparable with the test results for the samples. The predicted crack initiation and crack propagation patterns are consistent with observed cracking behavior. The results also imply that fracture in mixtures can be modeled effectively using a micromechanical approach that allows for crack growth both along aggregate surfaces and through the aggregates. Finally, the nonlinear Mohr–Coulomb type of failure envelope used to model the mastic appears to result in reasonable predictions. It can be concluded that the explicit fracture modeling with the displacement discontinuity boundary element method has the potential to evaluate the mechanics of fracture in asphalt mixtures.
Using Pseudostrain Damage Theory to Characterize Reinforcing Benefits of Geosynthetic Materials in Asphalt Concrete Overlays
Authors: Cleveland Gregory S. , Lytton Robert L. , Button Joe W.
Published: April 2007

Reflective cracking is one of the more serious distresses associated with existing hot-mix asphalt (HMA) or portland concrete cement pavements overlaid with a thin bituminous layer. Preventive maintenance techniques have included incorporating geosynthetic materials (defined here as grids, fabrics, or composites) into the pavement structure. These materials have exhibited varying degrees of success, and their use within a particular agency has been based primarily on local experience or a willingness to try a product that appears to have merit. A methodology is described that was used to compare the relative effectiveness of six commercially available geosynthetic materials in reducing the severity or delaying the appearance of reflective cracking in HMA overlay. Each geosynthetic material was incorporated into compacted HMA specimens and tested to failure. Engineering fracture mechanics and pseudostrain energy concepts based on the elastic-viscoelastic correspondence principle were used and demonstrated to be appropriate and efficient in characterizing the fatigue damage process. By considering the effects of the geosynthetic products on the loading and unloading paths of the HMA specimens, a new concept was developed and termed the reinforcing factor, R. The use of this value allows the industry to characterize the relative reinforcing benefits of geosynthetic materials in reducing reflective cracking in HMA overlays. A crack speed index was then derived to summarize the complex interactions of the material properties. In general, grids and composites performed better than fabrics, which in turn performed better than a thin tacked surface as compared with unreinforced specimens. Design equations were developed between the fracture properties of the geosyntheticmixture system and the relaxation modulus properties of the HMA, which can be used in forward-calculating design methods to predict the rate of crack growth and support the design of an HMA overlay to resist reflective cracking. To calibrate the design equations, comparative field test pavements were constructed in three regions of Texas (Amarillo, Waco, and McAllen) using each geosynthetic material. These pavements will be monitored over the next 4 years.
Integrated Model for Studying Small Aircraft Transportation System
Authors: Trani Antonio A. , Baik Hojong , Swingle Howard , Ashiabor Senanu
Published: April 2007

A systems engineering methodology was used to study the National Aeronautics and Space Administration’s (NASA’s) Small Aircraft Transportation System (SATS) concept as a feasible mode of transportation. The proposed approach employs a multistep intercity transportation planning process executed inside a Systems Dynamics model. Doing so permits a better understanding of SATS impacts to society over time. The approach is viewed as an extension to traditional intercity transport models through the introduction of explicit demand–supply causal links of the proposed SATS over the complete life cycle of the program. The modeling framework discussed is currently being used by the Virginia SATS Alliance to quantify possible impacts of the SATS program for NASA’s Langley Research Center. There is discussion of some of the modeling efforts carried out so far and of some of the transportation modeling challenges facing the SATS program ahead.
Part Privatization of United Kingdom’s Airspace: National Air Traffic Services’ Experience One Year On
Authors: Majumdar Arnab , Ochieng Washington
Published: April 2007

Air traffic in the United Kingdom has increased rapidly in the past two decades and is forecast to grow at a rate of 4.3% per year between 1998 and 2020. The failure to develop the air traffic system to cope with this growth has had undesirable consequences, for example, a rise in flight delays and near misses. Given the investment required in air traffic control systems to cater for this growth, the U.K. government in 2000 part-privatized the National Air Traffic Services (NATS), the body in charge of the United Kingdom’s airspace in a public–private partnership (PPP). The U.K. Airline Group acquired 46% of NATS and effective operational control, although the government retains a share in NATS and safety regulation is in the public sector. However, serious doubts about safety were raised during the debate on the PPP. Main issues surrounding the part-privatization of NATS were analyzed. First highlighted was the U.K. government’s provisions for the PPP and their implementation in the post-PPP NATS in six different categories: funding, new technology and project management, safety, pricing regime, international opportunities, and customer responsiveness. The September 11, 2001, terrorist attacks have had major impacts on air travel, and their consequences for NATS in the six categories are highlighted. Finally, attention was given to concerns that must be addressed to ensure the success of the partnership for NATS.
Preliminary Analysis of Taxiway Deviation Data and Estimates of Airplane Wingtip Collision Probability
Authors: Cohen-Nir D. , Marchi R.
Published: April 2007

The introduction of new large airplanes (NLAs), initially the Airbus A380, into existing older airports poses a wide range of dimensional clearance issues, primarily related to wingspan and tail height. Many existing airports cannot meet FAA’s Airplane Design Group VI (ADG VI) design standards appropriate to NLA. FAA is conducting ongoing data collection of measured deviations from taxiway centerlines experienced by Boeing-747 airplanes under various weather and visibility conditions, to allow the estimation of the collision risk while taxiing. A preliminary analysis was conducted on the risk of collisions involving airplanes in common taxiing situations, based on FAA data collected at Anchorage International Airport in Alaska from September 2000 to April 2002, and at New York’s John F. Kennedy Airport (JFK) from June 1999 to February 2000. Investigated were 29,544 deviations at Anchorage and 20,702 deviations at JFK. Analyses were performed to assess probabilities of large deviations. The probabilities were finally used to assess the risk of NLA wingtip contact with fixed or movable objects and the joint probability of collision between two airplanes that are taxiing simultaneously. The probability of wingtip collision between two taxiing A380 airplanes is calculated as 1.74 × 10-2 for ADG Code V taxiways, 4.91 × 10-15 for a JFK taxiway separation of 300 ft, and 4.42 × 10-23 for ADG Code VI taxi-ways. The probability of collision between a taxiing B-747-400 and an A380 is 1.5 × 10-11 for ADG Code V taxiways, 4.91 × 10-15 for a JFK taxiway separation of 300 ft, and 2.12 × 10-23 for ADG Code VI taxiways.
Intersection Diagnostic Review Module: Expert System for Geometric Design Review of Intersections on Rural Two-Lane Highways
Authors: Kindler Carrie , Wood Richard M. , Harwood Douglas W. , Neuman Timothy R. , Potts Ingrid B. , Antonucci Nicholas
Published: April 2007

FHWA has sponsored the development of an expert system for diagnostic review of at-grade intersections on rural two-lane highways as a component of the Interactive Highway Safety Design Model (IHSDM). This system, the Intersection Diagnostic Review Module (IDRM), has been developed because conventional design practices and design review procedures often fail to explicitly address the safety consequences of geometric design decisions. In particular, combinations of geometric features may pose safety problems that current design policies do not address (e.g., an intersection in combination with a sharp horizontal curve and a steep grade). The expert system allows such problems to be identified and evaluated in an automated and organized fashion. The structure and knowledge base of this expert system are presented. The system identifies potential safety problems in an intersection design by applying decision rules based on models that quantify the extent to which particular problems may or may not be present. Established geometric design models (such as the sight distance models used in current design policies) as well as new models that have been developed from literature synthesis and judgments by geometric design and safety experts are included. The models that IDRM uses to identify potential safety problems and the threshold values used to determine whether particular problems exist are described. IDRM provides a series of advisory messages indicating design features that should be reviewed for potential safety-related concerns. The advisory messages are based on the nature and extent of concerns identified by comparison with established threshold values.
Cable and Wire Rope Barrier Design Considerations: Review
Authors: Alberson Dean C. , Bligh Roger P. , Buth C. E. , Bullard D. Lance
Published: April 2007

Cable or wire rope barrier was being used in the 1940s and maybe earlier for vehicle containment. Through the years the designs have changed, but engineers continue to see cable barrier as an inexpensive barrier for use in some roadside applications. Recently, cable or wire rope has gained popularity as a median barrier for the prevention of cross-median accidents. Cross-median accidents are typically violent collisions with a high probability of multiple serious injuries and deaths. Thus, the design trend is gravitating toward providing positive vehicle containment in wider medians for which barriers have not historically been warranted. Wire rope often provides a cost-effective solution for this design scenario. Field experience with cable or wire rope barriers has identified areas for design improvement. It is desirable that cables remain taut to improve interaction with the vehicle, reduce dynamic deflections, and minimize maintenance. Additionally, reduced design deflections result in more potential application sites. Recent research demonstrates that such improvements are practical and cost-effective. Besides the initial tension in the wire ropes, other factors that can have a significant influence on dynamic deflections include post spacing and horizontal curvature. Computer simulations with cable barriers with various post spacings and horizontal curvatures were used to develop guidelines for expected design deflections. Finally, full-scale crash tests were completed with a new, cost-effective cable terminal system, and a brief review of the design and crash test results is included.
Freeway Weaving: Comparison of Highway Capacity Manual 2000 and Dutch Guidelines
Authors: Minderhoud M. M. , Elefteriadou L. Elefteriadou
Published: April 2007

Weaving sections are a commonly adopted freeway facility both in the United States and in Europe. Knowledge about the capacity and level of service achievable on different types of weaving segments is necessary for the design and management of freeways. Guidelines such as those of the U.S. Highway Capacity Manual (HCM) provide capacity values for different weaving configuration types. The Dutch guidelines for the design of weaving segments are compared with those of the U.S. HCM. Differences between their respective approaches are identified, and a comparison of capacity values is conducted. It was found that there are large differences in capacity estimates for certain weaving configuration types. The results of a sensitivity analysis explain these differences in capacity values to a large extent. This analysis showed that it is important to consider the weaving proportions per leg. Currently, neither the HCM nor the Dutch approach considers different weaving flows per incoming leg. The introduction of an additional variable into the calculation procedure that takes into account the presence of asymmetrical weaving flows is recommended.
Example Analysis and Handling of Uncertainty in the Highway Capacity Manual with Consideration of Traffic Diversion
Authors: Tarko Andrzej P. , Tian Zong
Published: April 2007

Dealing with uncertainty is inevitable when the performance of transportation systems is estimated and predicted. Various sources of uncertainty and how uncertainty can be handled are demonstrated. An example single stream at an unsignalized intersection is considered as an illustration. The data collected in the field were used to present sources of uncertainty and their contribution to prediction error. Interval values are proposed to represent the prediction uncertainty. This approach is advantageous over rigorous statistical estimation when distributions of the variables and interactions between them are not well specified. Also addressed is drivers’ adjusting behavior to changing traffic performance. A simple volume elasticity approach is used to address traffic diversion and to provide realistic estimation of interval values of future delay. This study should be a useful introduction to the uncertainty issue in traffic analysis based on the Highway Capacity Manual.
Freeway Planning Methodology
Authors: Prassas Elena Shenk , McLeod Douglas , Bonyani Gina
Published: April 2007

A major new chapter of the Highway Capacity Manual (HCM) 2000 is on freeway facilities. It is a detailed operational methodology that combines analyses of basic freeway segments, weaving areas, off-ramp areas, and on-ramp areas. However, the new chapter does not contain guidance or examples for planning or preliminary engineering applications. To meet its numerous needs, Florida Department of Transportation engineers wanted to develop a freeway facility application that extends the HCM for generalized planning and preliminary engineering purposes but is not inconsistent with HCM 2000. Such a methodology was developed, documented, made into an executable software program called FREEPLAN, and is now being implemented throughout the state. The methodology is firmly based on HCM detailed analysis procedures but has assumptions and defaults that allow planners and engineers to use it effectively. At a generalized planning level, the basic construct was to provide tables of design volumes, v, and annual average daily traffic that could be achieved for various levels of service and freeway configurations for the default parameter values. At a preliminary engineering level, specific freeway facility inputs are used to determine v/c ratio, average travel speed, average density, and level-of-service grades. The initial results of applying the Florida freeway planning methodology to actual Florida data were outstanding in both urbanized and rural areas.
Signalized Intersection Level of Service Incorporating Safety Risk
Authors: Zhang Lin , Prevedouros Panos D.
Published: April 2007

A methodology that quantifies potential conflicts between left-turning vehicles and opposing through vehicles and pedestrians is presented. The methodology was based on and designed to be compatible with the Highway Capacity Manual 2000. A model was developed to combine delay and safety to get a comprehensive level-of-service indicator, the delay and safety index (DS). A case study of two intersections shows that if potential conflict is not considered, the signal timing plan with permitted left turns delivers a better level of service than that with protected left turns. However, if potential conflict is considered, the level of service under protected left-turn phasing is better than that under permitted left-turn phasing, according to the DS, when the safety weight factors exceed a certain value. The proposed method models the trade-off between safety and efficiency explicitly and considers both vehicle-to-vehicle and vehicle-to-pedestrian conflicts associated with left turns.
Uncertainty Analysis for Two Freeway Sites
Authors: Higgins Nathan , List George , Eisenman Stacy
Published: April 2007

Uncertainty is a major issue in many phenomena. The operation of highways is no exception. Yet one of the most common methodologies for assessing the performance of facilities such as intersections and freeways lacks the ability to reflect uncertainty in the inputs or the outputs. Methods that allow explicit examination of the variations that arise in the performance of given facilities or systems are necessary. The issue of uncertainty is examined for two freeways. Ideas are presented about how uncertainty might be treated for such facilities. One focuses on uncertainty during the peak hour. The other considers the entire year and asks whether such an approach gives a more complete picture of performance.
Optimal Coordination of Variable Speed Limits to Suppress Shock Waves
Authors: Hegyi A. , De Schutter B. , Hellendoorn J.
Published: April 2007

A model predictive control (MPC) approach is presented to optimally coordinate variable speed limits for highway traffic. A safety constraint incorporated in the controller is formulated that prevents drivers from encountering speed limit drops larger than, say, 10 km/h. The control objective is to minimize the total time that vehicles spend in the network. This approach results in dynamic speed limits that reduce or even eliminate shock waves. To predict the evolution of the traffic flows in the network, which is required by MPC, an adapted version of the METANET model is used that takes the variable speed limits into account. The performance of the discrete-valued and safety-constrained controllers is compared with the performance of the continuous-valued unconstrained controller. It is found that both types of controllers result in a network with less congestion, a higher outflow, and hence a lower total time spent for drivers. For the benchmark problem, the performance of the discrete controller with safety constraints is comparable with the continuous controller without constraints.
Mixing Microscopic and Macroscopic Representations of Traffic Flow: Hybrid Model Based on Lighthill–Whitham–Richards Theory
Authors: Bourrel Emmanuel , Lesort Jean-Baptiste
Published: April 2007

The hybrid traffic flow model, coupling a microscopic (vehicle-based) and a macroscopic (flow-based) representation of traffic flow, may be a useful tool to better understand the relationships between the various types of representation. It can also be a basis for implementing various model extensions, which may be easier with using one type of representation or the other. The hybrid model presented here combines a flow and a vehicular representation of the same model, which is the classical Lighthill–Whitham–Richards model. The use of a simple and unique model makes it possible to focus on the specific problems raised by translating boundary conditions from vehicular to flow formulation and conversely. This translation is made in order to ensure the conservation of flow and proper transmission of information both downstream and upstream and to minimize the perturbations induced by transitions between a continuous and a discrete representation of flow. The resulting model is shown to have good properties, particularly concerning congestion propagation and flow smoothing at the interfaces between the two models.
Framework for Investigation of Level-of-Service Criteria and Thresholds on Rural Freeways
Authors: Kim Jin-Tae , Courage Kenneth G. , Washburn Scott S. , Bonyani Gina
Published: April 2007

The Highway Capacity Manual prescribes level-of-service (LOS) criteria as a function of traffic density to categorize the operational conditions of both rural and urban freeway sections. This density-based level of service is ideally suited to the assessment of urban freeways when the performance must be optimized to meet high traffic demand. There is, however, some question as to whether density is the appropriate indicator of the quality of service on rural freeways, since drivers may think more in terms of psychological or emotional comfort for freeways, which generally serve long, high-speed trips and rarely experience more than moderate congestion levels. Three specific measures are examined that have at least an intuitive relationship to the concept of driver comfort: ( a) acceleration noise, which is a measure of the physical turbulence in the traffic stream; ( b) number and duration of cruise control applications, which could serve as a general indication of driver convenience or inconvenience; and ( c) percent time spent following, which is already accepted as the basis for determining the level of service on rural two-lane highways. The three candidate measures were estimated for a hypothetical section of rural freeway by simulation, using the CORSIM model. The kinematic relationships of individual vehicles within the traffic stream were estimated by postprocessing the simulation data for each second of operation. All of the measures considered in this study have conceptual appeal. All have produced interesting and potentially usable results with respect to their relationships to traffic volume. Although the simulation results are interesting, further studies focusing on driver opinions, behavior, or field measurements, or all three, would likely be necessary to support the development and recommendation of a specific set of LOS criteria that recognizes the differences between the urban and rural freeway driving environments.
Capacity of Unsignalized Intersections with Mixed Vehicle Flows
Authors: Li Wenquan , Wang Wei , Jiang Dazhi
Published: April 2007

On the basis of gap-acceptance theory, mixed traffic flow composed of two representative vehicle types—heavy and light vehicles—is analyzed with probability theory. A capacity model is set up for an unsignalized intersection in which the minor-stream mixed traffic flows cross m major lanes and the traffic flow headways fit the M3 distribution; it is an extension of minor-lane capacity theory for one vehicle type and one major-stream traffic flow. A more complicated case with minor-stream flow composed of discretionary vehicle types is also considered, and the corresponding formula is given. After field testing in China, the conclusion is drawn that this model is better for analyzing Chinese traffic conditions than are other existing models.