bluuebunny/crossref_metadata_2025 huggingface dataset:
Runway Instrumentation and Response Measurements
Authors: Al-Qadi Imad L. , Portas Silvia , Coni Mauro , Lahouar Samer
Published: December 2010

This paper presents ongoing research to measure the in situ response to airplane traffic of flexible pavement on a runway at Cagliari-Elmas Airport in Italy. Understanding how pavement materials respond to traffic and environmental loading is fundamental to designing pavements and assessing their performance. The pavement material behavior is affected by many factors (i.e., load magnitude, material properties, and environmental conditions). The influence of these factors can be simultaneously taken into account by measuring in situ stresses and strains using embedded instruments. The pavement layers of the Cagliari-Elmas runway were equipped with 149 instruments: 36 linear variable differential transformers, 36 pressure cells, four time domain reflectometers, 28 T-thermocouples, and 45 hot-mix asphalt strain gauges. The instrumented area, 55 m2, allows measuring the responses during three main loading maneuvers: taking off, landing, and taxiing. The preliminary data acquired during and after the runway's construction and before its opening to airplane traffic and its analysis show that the instrumentation process was a success. The instrument response testing includes falling weight deflectometer, truck, and airplane loading of various types, magnitudes, and speeds. The collected data were successfully compared with preliminary numerical simulations. Further data collection and research will be performed, particularly involving airplane traffic data. Data analysis will include the effect of the environmental data (i.e., moisture and temperature) and airplane configuration and speed. The collected data will be used to validate advanced pavement modeling and predict pavement runway performance. In addition, data resulting from this research have the potential to support and improve runway pavement design and to improve the evaluation process for new and existing runway pavement performance and damage prediction.
Interaction between System Design and Operations of Variable Speed Limit Systems in Work Zones
Authors: Fudala Nicholas J. , Fontaine Michael D.
Published: December 2010

Variable speed limits (VSLs) have been shown to improve safety and operations on European freeways, but work zone applications of VSLs have been limited. In July 2008, a VSL system was installed on a congested portion of the Washington, D.C., Beltway (I-95–I-495) in a major work zone. A limited field evaluation of that system revealed some deficiencies related to the system's configuration, resulting in inconclusive operational effects. Those results raised questions about the relative importance of different VSL system parameters on the ultimate effectiveness of work zone VSLs. This paper describes an evaluation that used a calibrated simulation model to evaluate the influence of several parameters. The results showed that VSLs can delay the onset of congestion and help produce more rapid recovery from congestion, provided that demand volumes are not too far above the work zone capacity. When demand volumes are extremely high, VSLs offer no appreciable benefit over static speed limits. The simulation also showed that VSL sign location is extremely important, and signs must be positioned so that drivers will accelerate back to a reasonable speed once they pass through a bottleneck. Algorithm design also proved to play an important role in system effectiveness.
Closed-Course Test and Analysis of Vibration and Sound Generated by Temporary Rumble Strips for Short-Term Work Zones
Authors: Schrock Steven D. , Heaslip Kevin P. , Wang Ming-Heng , Jasrotia Romika , Rescot Robert
Published: December 2010

Driver distraction and speeding are two contributors to crashes in construction and maintenance work zones. Rumble strips can be effective and have been used in some states to alert drivers to reduce speed in advance of some change in the driving situation, such as at intersections. Previous research has examined the potential of using temporary rumble strips in advance of work zones. The purpose of this research was to compare the attention-getting characteristics of several temporary rumble strips with permanent rumble strips. Two types of devices were tested and compared with permanent rumble strips: portable plastic rumble strips and adhesive rubberized polymer rumble strips. These devices were tested for their ability to generate steering wheel vibrations and in-vehicle and roadside sound. Analysis revealed that the portable plastic rumble strips were more effective on cars than on trucks for generating in-vehicle vibration and increasing the in-vehicle sound level. Further, they were generally better than the adhesive rumble strips in matching the characteristics of the tested permanent rumble strip. This was also true for the configurations that contained fewer than six portable plastic rumble strips. If the vibration and sound generated by the permanent rumble strips is considered the standard performance, various configurations of the portable plastic rumble strips can be implemented in short-term work zones and provide results similar to those of permanent rumble strips.
Joint Merge and Its Impact on Merging Speeds in Lane Reduction Areas of Construction Zone
Authors: Idewu Wakeel I. A. , Wolshon Brian
Published: December 2010

To increase the efficiency and safety of traffic flow in the vicinity of lane reduction transition areas, engineers have begun to use innovative techniques to facilitate traffic flow through these bottleneck areas. One technique, alternating merging, encourages drivers to take turns when merging in freeway lanes and ramps. This paper discusses the development of the joint merge, a new traffic control design that facilitates alternating merge patterns, along with the results of a field experiment to examine its effects on traffic flow. The key feature of the joint merge design is its two-sided taper in which both approach lanes are reduced simultaneously into a single lane, thereby eliminating an assigned lane priority. To evaluate its effect on traffic, a field study was conducted in which a joint merge configuration was erected in a live, work intensity–controlled work zone in Louisiana. Lane-specific volume and vehicle speeds in the joint merge were compared with those observed in a conventional merge design at the same site. Overall, merging speeds were found to be relatively similar at volumes ranging from 600 to 1,200 vehicles per hour and did not affect the discharge rate at the merge outflow point. However, the experimental results did suggest that drivers were more cautious in their merging maneuvers. This was thought to be attributable to the joint merge, which produced a more evenly balanced lane volume at the transition zone entrance.
Real-Time Measurement of Travel Time Delay in Work Zones and Evaluation Metrics Using Bluetooth Probe Tracking
Authors: Haseman Ross J. , Wasson Jason S. , Bullock Darcy M.
Published: December 2010

This paper describes the collection and use of 1.4 million travel time records that were collected over a 12-week period in 2009 to evaluate and communicate quantifiable travel mobility metrics for a rural interstate highway work zone along I-65 in northwestern Indiana. The effort involved the automated collection and processing of Bluetooth probe data from multiple field collection sites, communicating travel delay times to the motoring public, assessing driver diversion rates, and developing proposed metrics for a state transportation agency to evaluate work zone mobility performance. Collected travel time profiles were compared with traditionally measured hourly flows in both incident and nonincident conditions. Through the 12-week period over which work zone performance was measured, the work zone had 422 h of congested conditions in which travel time delay was greater than 10 min. Despite the display of real-time delay measurements to the motoring public through portable dynamic message signs, a negligible percentage of the travel probes were observed to divert in advance of the congested work zone through self-guidance. Implementation of a targeted alternate route starting the weekend of July 24 resulted in an increase of observed probes diverting along the trail-blazed route from none to more than 30%. The paper concludes by suggesting that acquisition of work zone travel time data provides a mechanism for assessing the relationship between crashes and work zone queuing. Real-time monitoring of these travel time data may also enable future contracts to include innovative travel time reliability clauses.
Variation of Impact of Cold Temperature and Snowfall and Their Interaction on Traffic Volume
Authors: Datla Sandeep , Sharma Satish
Published: December 2010

This paper presents a detailed investigation of highway traffic variations with severity of cold, the amount of snow, and various combinations of cold and snow intensities. Separate analyses for starting, middle, and ending months of winter seasons are conducted to study the variations in traffic-weather relationships within the winter season. The study is based on hourly traffic flow data from 350 permanent traffic counter sites located on the provincial highway system of Alberta, Canada, and weather data obtained from nearby Environment Canada weather stations, from 1995 to 2005. Multiple regression analysis is used in the modeling process. The model parameters include three sets of variables: the amount of snowfall as a quantitative variable, categorized cold as a dummy variable, and an interaction variable formed by the product of these two variables. The study results indicate that the association of highway traffic flow with cold and snow varies with day of week, hour of day, and severity of weather conditions. A reduction of 1% to 2% in traffic volume for each centimeter of snowfall is observed when the mean temperature is above 0°C. For the days with zero precipitation, reductions in traffic volume due to mild and severe cold are 1% and 31%, respectively. An additional reduction of 0.5% to 3% per centimeter of snowfall results when snowfall occurs during severe cold conditions. Study results show lesser impact of adverse weather conditions on traffic during severe winter months (mid-November to mid-March) and the months thereafter compared with early (starting) winter months.
Improving Road Weather Hazard Products with Vehicle Probe Data
Authors: Drobot Sheldon , Chapman Michael , Schuler Elena , Wiener Gerry , Mahoney William , Pisano Paul , McKeever Benjamin
Published: December 2010

One of the goals of RITA's IntelliDrive initiative is utilization by the public and private organizations that collect, process, and generate weather products of vehicle sensor data to improve weather and road condition hazard products. Some users may not be able to, or not want to, contend with the complexities associated with vehicle data, such as data quality, representativeness, and format. With funding and support from the U.S. Department of Transportation's RITA IntelliDrive initiative and direction from FHWA's Road Weather Management Program, the National Center for Atmospheric Research is conducting research to develop a vehicle data translator (VDT) to address these vehicle-based data challenges. This paper first describes the VDT quality check (QCh) concept and then examines QCh pass rates for temperature and pressure data collected from 11 specially equipped vehicles operating in the Detroit test bed in April 2009. Results show that temperature pass rates are higher than pressure pass rates. Additionally, pass rates are somewhat affected by vehicle type, vehicle speed, ambient temperature, and precipitation occurrence for both temperature and pressure.
Integrating the Impact of Rain into Traffic Management
Authors: Billot Romain , Faouzi Nour-Eddin El , Sau Jacques , De Vuyst Florian
Published: December 2010

A new approach to the integration of the effects of inclement weather into traffic management strategies is presented. Adverse weather conditions are a critical factor affecting traffic operations and safety. Previously, a methodology for the analysis of the impact of rain has been addressed, and this impact on key traffic indicators (e.g., free-flow speed, capacity) has been quantified. As a result of these quantification studies, a first parameterization of the fundamental diagram according to rain intensity has been proposed. Since the fundamental diagram represents the basis of many simulation tools, the goal is to develop weather-responsive traffic state estimation tools that can be useful for control applications and traffic management. More precisely, the online traffic state estimation takes place within a Bayesian framework with particle-filtering techniques (i.e., sequential Monte Carlo simulations) in combination with a parameterized first-order macroscopic model. This approach has already been validated for sensor diagnosis and accident detection. In this paper the goal is to show how the integration of the weather effects can improve this efficient tool. The approach is validated with real-world data from the ring road section in Lyon, France (eight sensors from a homogeneous section). The results from different scenarios show the benefits of integrating the impact of rain into traffic state estimation. Strategies to detect a rain event in time and space are also suggested.
Implementation of Structural Control Measures to Mitigate Avalanche Hazard along Transportation Corridors
Authors: Hewes Joshua T. , Decker Rand , Merry Scott , Yount Jamie
Published: December 2010

Avalanche hazards along transportation corridors in the United States have traditionally been addressed by forecasting their potential and actively controlling them through explosive release while the roadway is closed. This approach reduces the threat of avalanches cascading onto the roadway and thus reduces danger to the traveling public. However, active control methods cannot always be implemented in a timely fashion, can be ineffective, and can have large associated economic impacts. An alternative to active control is passive, structural avalanche defenses. They are passive in that they do not require maintenance during winter storm periods. Structural defense measures include snow sails, snow-supporting structures, and snow sheds. Despite their extensive use in Europe and their potential for effectively reducing avalanche hazards, few examples are found in the United States. The potential for negative impacts to the visual attributes of the landscape has been a significant reason for their lack of domestic use. This paper discusses several types of structural defense measures, criteria for their selection at a given site, and their relative effectiveness. Passive structural defense measures designed for implementation at the Milepost 151 avalanche on US Route 89/191 near Jackson, Wyoming, are described. Details are given on important collaborations between landscape architects and engineers that led to successfully addressing National Environmental Policy Act requirements for retention of visual attributes at the Milepost 151 avalanche site in the presence of snow support structures deployed for the purpose of avalanche hazard reduction.
Modeling Operating Speed and Deceleration on Two-Lane Rural Roads with Global Positioning System Data
Authors: Zuriaga Ana Maria Pérez , García Alfredo García , Torregrosa Francisco Javier Camacho , D'Attoma Pierangelo
Published: December 2010

In the road design process, speed variation along the road segment is an important issue to consider in adapting road geometry to drivers' expectations. To achieve this objective, speed criteria are used to evaluate road consistency. Being able to estimate the operating speed in the design phase can lead to safer road alignment. With this objective, several researchers have developed operating speed models. Most of these models are based on collected spot speed data. They assume constant speed on curves and, therefore, deceleration that occurs entirely on the approach tangent. According to these assumptions, spot speed data are collected at the center of the horizontal curve and at the midpoint of the preceding tangent to obtain operating speed models. This paper presents a new methodology based on the use of Global Positioning System devices that allow continuous collecting and processing of speed data. With this new methodology, not only can new and more accurate operating speed models be developed, but cited hypotheses can also be checked. Observed speed continuous profiles allow studies that previously could not be done, especially as related to deceleration and speed variations. This study calibrated new speed models, including three for horizontal curves with a radius curve and the curvature change rate of a single curve as explanatory variables, and one for tangents that incorporates the curve speed model. Tangent-curve speed variations are evaluated, with comparison of Δ85V and ΔV85, analysis of the deceleration length occurring on a curve, and development of two deceleration models.
Proposal for Incorporating Public Transit Provisions into a State Highway Access Management Code
Authors: Lutin Jerome M.
Published: December 2010

This paper describes how New Jersey Transit, a statewide public transit operator, participated in a project sponsored by the New Jersey Department of Transportation (DOT) to revise New Jersey's State Highway Access Management Code (access code). The transit operator advocated including public transit requirements in a revised access code as a means of mitigating traffic impacts created by new developments and of improving mobility for transit riders. The paper discusses the problems that led to the transit agency's involvement in the process, conditions under which transit access should be considered, the transit operator's role in the review process, criteria, and suggested transit provisions. The following premises were posited as a rationale for incorporating public transportation requirements into a revised access code: public transportation can effectively be used to improve the efficiency of the state highway system by providing an alternative to single-occupant vehicles and a way to mitigate traffic congestion created by development; developers can take specific actions and incorporate specific features in their projects to facilitate the efficient use of public transportation; the degree to which actions to facilitate the use of public transportation must be incorporated into projects seeking access permits should increase in proportion to the size of the development and the traffic generated. Revisions are still undergoing review by the New Jersey DOT and have not yet been finalized.
Dynamic Amplification of Pier Column Internal Forces Due to Barge–Bridge Collision
Authors: Davidson Michael T. , Consolazio Gary R. , Getter Daniel J.
Published: December 2010

In the United States, bridge design provisions for waterway vessel collision typically involve static application of code-prescribed impact loads. However, results from full-scale experimental impact tests have revealed that significant mass-related inertial forces can develop in affected piers because of the overlying superstructure. In part on the basis of these findings, a dynamic (time history) analysis technique was previously developed; it predicts both impact load and structural response. In the current research, the dynamic analysis technique is combined with recently developed barge force–deformation relationships and a simplified bridge modeling technique to conduct a detailed investigation of collision-induced dynamic amplification phenomena. Design forces are quantified for a wide range of bridge types by using dynamic and static analyses. For each bridge considered, dynamic amplifications are numerically quantified by comparing dynamic to static predictions of pier column demand. Significant amplification effects are consistently found among the barge–bridge collision simulations conducted, indicating that dynamic phenomena should be accounted for in bridge design.
Review and Assessment of Fire Hazard in Bridges
Authors: Kodur Venkatesh , Gu Li , Garlock Maria E. Moreyra
Published: December 2010

Bridge fires are low-probability but high-consequence incidents. Generally, bridge design codes and standards, in contrast to building codes, do not take into account the concept of fire safety. However, recent high-profile fire incidents on bridges and in other infrastructure have opened a debate on the need for fire resistance requirements on bridges. An overview of fire hazard in bridges is presented. A state-of-the-art review related to the bridge fire hazard was carried out. Different conditions and complexities associated with characterizing fire hazards in bridges are discussed, and a design strategy to integrate performance-based fire safety into bridge design is suggested. Further, a strategy to assess and repair fire-damaged bridges is proposed. A case study is presented to evaluate the fire performance of a composite steel bridge girder. Finally, needed research that can lead to improved performance of bridges during fire incidents is highlighted.
Design Fatigue Load of Sign Support Structures Due to Truck-Induced Wind Gust
Authors: Hosch Ian E. , Fouad Fouad H.
Published: December 2010

This research presents a universal approach for determining the design fatigue load due to truck-induced wind gust for highway overhead sign support structures. The fatigue load is determined on the basis of the dynamic properties of the structure. It is applicable to structures in which the dynamic response can be approximated by a single-degree-of-freedom system. Typical examples include cantilever- and bridge-type overhead sign support structures. The developed approach incorporates these parameters in a simplified systematic procedure that can be readily used by engineers. Principles relating to mechanical vibration and utilization of the shock response spectrum were used to determine the load. The fatigue load is selected from the shock response spectrum in terms of the natural frequency of the structure and the speed of the truck. Comparisons were made with the current truck-induced gust fatigue design provisions given in the 2009 AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals. Additional comparisons were made with dynamic finite element analysis of a modeled support structure.
Structural Analyses, Design, and Testing of Retrofit Bridge Rail
Authors: Williams William
Published: December 2010

The Roy B. Inks steel truss bridge (listed in the National Register of Historic Places) over the Llano River in Llano, Texas, is approximately 794 ft in length with a posted speed limit of 40 mph. This bridge design is common to many of the historic bridges in the state. The bridge railing does not meet the current safety requirements of NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features (NCHRP Report 350) for Test Level 2 (TL-2). The railing used is attached directly to steel truss members. On the basis of structural analyses, many of these members are not adequate to resist TL-2 crash forces. The purpose of this research was to develop a retrofit bridge railing design that is crashworthy with respect to NCHRP Report 350 requirements and a design that can be used on similar historic steel bridges within Texas. Crushable pipe blockouts located between the new retrofit rail and the truss members were developed as part of this research and were used to minimize the crash forces transmitted to the steel truss members. The new rail design retains the historic appearance of the bridge. The retrofit rail design, along with a rail expansion joint developed for this project, was successfully crash tested with respect to NCHRP Report 350 TL-3 requirements. The results of this research, the new bridge rail design, and the crash test results for the new design are presented.
Simplified Erection Guidelines for Double I-Girder Systems during Bridge Construction
Authors: Yu Baolin , Zhao Qiuhong , Burdette Edwin G.
Published: December 2010

In current design specifications, only the individual girder inside the double-girder system is checked for lateral torsional buckling between the intermediate cross frames. However, the overall lateral torsional buckling of double-girder systems may be critical during bridge erection because of the limited lateral bracing present at this stage. Therefore, close attention should be paid to the overall stability of double I-girders during construction, and research was conducted for the simply supported case and the cantilever case under self-weight only. Through extensive finite element analyses, the formulas developed by Yura and colleagues on the overall lateral torsional buckling capacity of double-girder systems were first verified for the simply supported case and modified for the cantilever case. A stability index L/S was developed for estimating the stability of double-girder systems during erection, which equals the ratio between the girder span L and the girder spacing S. Formulas were then derived for the maximum span Lmax and the maximum stability index (L/S)max, beyond which the double-girder system would lose stability under its self-weight. Parametric studies were conducted to determine the dominant parameters for Lmax and (L/S)max for various girder sections with different spacing. A quick and reliable method was also established to check the stability of double-girder systems during erection by using the L/S ratio.
Rationally Designed Staged Posttensioning to Abate Reflective Cracking on Side-by-Side Box-Beam Bridge Decks
Authors: Ulku Evren , Attanayake Upul , Aktan Haluk M.
Published: December 2010

Side-by-side box-beam bridges are often used at sites with tight under-clearance requirements and specified for accelerated construction. However, longitudinal reflective deck cracking is a recurring problem for these bridges and it raises concern for their durability and long-term safety. North American practices of the transverse connection design of this particular bridge are discussed in NCHRP Synthesis 393, and the Michigan design is presented as the preferred procedure. The most recent design in Michigan is an empirical procedure that incorporates the majority of the Synthesis 393 recommended best practices. Yet reflective deck cracking persists. A rational design procedure for which an analysis model was developed is presented here. In the rational design procedure, the analysis model is utilized to calculate the moment demand along the transverse joints. A two-stage transverse posttensioning procedure is recommended following AASHTO load and resistance factor design stipulations based on the moment demand calculated from the analysis model. The second stage of posttensioning precompresses the cast-in-place concrete deck, ensuring crack control. The objective of this study is to demonstrate the effectiveness of the two-stage posttensioning design and implementation procedure to mitigate reflective deck cracking. The effectiveness of the recommended design is demonstrated by utilizing a multistep finite element simulation of the construction process under construction and service loads. The cracking potential of the deck is evaluated under both current Michigan Department of Transportation and the proposed two-stage transverse posttensioning schemes. It is demonstrated that the two-stage posttensioning process can eliminate tensile stresses developed under gravity loading and reduce the temperature load effects to abate reflective deck cracking.
Bond and Anchorage of High-Strength Reinforcing Steel
Authors: Harries Kent A. , Shahrooz Bahram M. , Soltani Amir , Reis Jonathan M. , Wells Elizabeth L. (Ward) , Miller Richard , Russell Henry G.
Published: December 2010

Recent revisions to the AASHTO load and resistance factor design (LRFD) construction specifications permit the specification of ASTM A1035 reinforcing steel. ASTM A1035 reinforcing bars are low-carbon, chromium steel bars characterized by a high tensile strength and a stress–strain relationship having no yield plateau. The AASHTO LRFD bridge design specifications limit the yield strength of reinforcing steel that may be used in design to 75 ksi (520 MPa) for most applications. Therefore, although ASTM A1035 may be specified, the higher yield strength cannot be used in design. The objective of this work is to evaluate existing AASHTO LRFD bridge design specifications in reference to the use of high-strength reinforcement represented by ASTM A1035. Issues of bar splice development and hooked-bar anchorages of ASTM A1035 reinforcing steel are discussed. Four spliced-beam straight-bar development tests and 18 hooked-anchorage pullout tests were performed as proof tests of the current AASHTO requirements. The study clearly demonstrates that the current AASHTO and American Concrete Institute requirements for both straight-bar tension development and hooked-anchorage tension development may be extended to develop bar stresses of at least 125 ksi in up to 10-ksi concrete. The results of this study and previous work clearly indicate that confining reinforcement should always be used when ASTM A1035 reinforcing steel is developed, spliced, or anchored.
Inspection of Voids in External Tendons of Posttensioned Bridges
Authors: Im Seok Been , Hurlebaus Stefan , Trejo David
Published: December 2010

Segmental posttensioned bridges are major structures that carry significant traffic. Recent investigations of these bridges identified voids in their ducts. The exposed strands at these void locations can undergo corrosion. The corrosion of strands may lead to the failure of tendons. As such, an effective inspection process for identifying these voids is needed. From a literature review, several nondestructive testing methods are compared for applicability to void inspection in external tendons. The impact echo, ultrasonic pulse velocity, and sounding inspection methods are then selected and assessed for further preliminary testing. The sounding inspection method is further assessed for its effectiveness in identifying voids in a full-scale, external tendon system. The results indicate that sounding inspection slightly underestimates the size of the voids. However, the inspected size and locations of voids have a close correlation with actual voids in ducts. Thus, sounding inspection can be an effective tool for identifying voids because of its easy application in the field.
Crack Detectability and Durability of Coaxial Cable Sensors in Reinforced Concrete Bridge Applications
Authors: Chen Genda , McDaniel Ryan , Brower Michael , Pommerenke David
Published: December 2010

The working mechanism and the measurement principle of topology-based crack sensors made of coaxial cables are briefly reviewed. The sensitivity, spatial resolution, and ruggedness of two coaxial cable sensors, respectively made of rubber and Teflon dielectric materials, were compared and validated with laboratory testing of a 4/5-scale, T-shaped, reinforced concrete beam-column specimen. Two Teflon sensors were installed on one of the solid decks of a three-span continuous highway bridge to investigate their durability and measurement repeatability. Laboratory tests indicated that both types of sensors have high sensitivity, but the Teflon sensor has a higher spatial resolution and a negligible spillover effect of any significant cracks. At a 90-degree bend, however, the Teflon sensor is more susceptible than the rubber sensor to the rubbing action of the outer conductor of a coaxial cable against its dielectric layer. No cracks were observed during the field load tests of the instrumented bridge. Both sensors indicated high durability in real-world application but a certain variation of waveforms was measured over a period of 5 years because of the use of different instruments. Future research is directed to develop an online calibration of crack sensors with a small portion of built-in standard cable at the end of the cable sensor.
Condition Assessment of Bill Emerson Memorial Cable-Stayed Bridge under Postulated Design Earthquake
Authors: Yan Dongming , Wang Wenjian , Chen Genda , Hartnagel Bryan A.
Published: December 2010

In this study, a three-dimensional finite element model of the Bill Emerson Memorial cable-stayed bridge was developed and validated with the acceleration data recorded during the M4.1 earthquake of May 1, 2005, in Manila, Arkansas. The model took into account the geometric nonlinear properties associated with cable sagging and soil–foundation–structure interaction. The validated model was used to evaluate the performance of a seismic protective system, the behavior of cable-stayed spans, and the accuracy of two simplified bridge models that have been extensively used by the structural control community. The calculated natural frequencies and mode shapes correlated well with the measured data. Except that the hollow columns of two H-shaped towers were near yielding immediately above their capbeams, the cable-stayed spans behaved elastically as expected under the design earthquake that was scaled up from the recorded rock motions at the bridge site. The minimum factor of safety of all cables is 2.78, which is slightly greater than the design target.
Effect of Fiber-Reinforced Polymer Configuration on Reliability of Flexurally Strengthened Concrete Beams
Authors: Okeil Ayman M. , Andrepont Scott
Published: December 2010

External bonding of composite materials in the form of strips, plates, and laminates to add tensile capacity in deficient zones has proved to be an efficient strengthening technique. The performance of composite materials in strengthening ailing infrastructure components has made them a mainstream alternative in some applications such as strengthening concrete structures. The technique is mature enough that design standards have been published. Few researchers have investigated the reliability of concrete structures strengthened with fiber-reinforced polymer (FRP). The results of these reliability investigations were incorporated in some of the recently published design guidelines. It is a well-known fact that FRP debonding is the dominant mode of failure. Nevertheless, the impact of different FRP configurations on the reliability of strengthened concrete beams in flexure has not yet been investigated. An analytical study is presented of the reliability of FRP-strengthened concrete beams in two of the most popular configurations: U-wrap and soffit-only. Material, fabrication, and model uncertainties are accounted for in a strength limit state function to analyze the reliability of strengthened reinforced concrete beams by using the first-order reliability method. Results from this study show that the reliability of U-wrap configurations is higher than that of soffit-only configurations. This finding can be used in establishing different resistance factors for each case such that the use of more materials in the U-wrap configuration is rewarded by the ability to predict its performance better.
Empirical Analysis of Effects of Wait Time and Rain Intensity on Driver Left-Turn Gap Acceptance Behavior
Authors: Zohdy Ismail , Sadek Shereef , Rakha Hesham A.
Published: December 2010

An empirical study was conducted to quantify the impact of several variables on driver left-turn gap acceptance behavior. These variables included gap duration, the driver's wait time in search of an appropriate acceptable gap, the time traveled by a driver to clear a conflict point, and the rain intensity. Gap acceptance data for a permissive left-turn maneuver at a signalized intersection were collected over a 2-month period. Logistic regression models calibrated to the data reveal that the acceptable gap duration decreases as a function of the driver's wait time and increases as the rain intensity increases. The study then demonstrates how the critical gap is influenced by a number of parameters, including the wait time and rain intensity, and also demonstrates how rain intensity affects the permissive left-turn saturation flow rate. It is anticipated that these findings can be used to develop weather-specific traffic signal timings that account for changes in traffic stream saturation flow rates due to changes in critical gap values as a function of weather conditions.
Level of Service
Authors: Roess Roger P. , Vandehey Mark A. , Kittelson Wayne
Published: December 2010

The concept of level of service (LOS) was introduced in the 1965 edition of the Highway Capacity Manual (HCM). It provided for the familiar letter-grade system for characterizing the quality of operations on a variety of traffic facilities from intersections to freeways. The LOS concept will remain primarily unchanged in the next edition of the HCM, expected in 2010. It will, however, introduce material directly related to user perceptions for the first time, and discussions surrounding LOS have raised interesting issues that may result in more extensive changes in the future. This paper attempts to address some of these issues in the context of the history of the LOS concept and its use in the planning, design, and analysis of traffic facilities. Among the major issues that should be thoroughly examined in the future is whether the concept is needed with the rapidly advancing state-of-the-art, which produces many quantifiable measures of service quality. The application of LOS to corridors, networks, and multimodal systems needs to be addressed, as it will differ from previous applications to points and uniform segments. Incorporating the results of research concerning user perceptions into the LOS framework has also raised interesting issues as the 2010 HCM has been developed. With the forthcoming 2010 HCM as a starting point, this paper explores current issues and makes suggestions as to how to address them while moving toward the as yet undefined edition that will follow the 2010 HCM.
Predicting Arrival Flow Profiles and Platoon Dispersion for Urban Street Segments
Authors: Bonneson James A. , Pratt Michael P. , Vandehey Mark A.
Published: December 2010

This paper describes the development of a procedure for predicting the arrival flow profile for an intersection approach. This profile describes the variation in flow rate during the average signal cycle as it would be measured at a specified point downstream of a signalized intersection. Research indicates that platoon decay (due to midsegment driveway access and egress) tends to have a more significant impact on the arrival flow profile than platoon dispersion. Platoon dispersion reflects drivers' desire to increase their headway, while platoon decay reflects vehicles departing the platoon at midsegment access points. The procedure is recommended for inclusion in the Urban Street Segments chapter of the forthcoming 2010 Highway Capacity Manual.
Differentiated Analysis of Level of Service F within the German Highway Capacity Manual
Authors: Brilon Werner , Estel Anja
Published: December 2010

In the American as well as the German Highway Capacity Manual, the quality of service that is determined by different measures of effectiveness can be described by six levels of service. While there are five levels (A to E) to distinguish undersaturated flow conditions, only one level of service (LOS) describes congestion. A differentiation of oversaturated traffic flow conditions (LOS F) is not possible so far. As traffic networks have become more and more congested this is insufficient, and instruments are needed to identify the worst bottlenecks. The paper presents approaches for a division of LOS F into differentiated sublevels of saturated flow (F1 to F4) and proposes corresponding calculation methods. Different traffic flow models and queuing equations are considered for the estimation of travel times as a function of traffic demand. Four potential methods for standardization are discussed that differ in the performance measures used. They are described by using freeway sections as an example, but they can be applied for all types of road facilities. The methods are analyzed and compared in terms of their significance, their sensitivity, and the availability of input data. On that basis, a 24-h analysis of traffic performance is recommended for implementation within the guidelines because it is able to evaluate congestion in a multidimensional way. The evaluation methods developed within this research can be used to assess the quality of service on existing congested facilities depending on traffic demand. They can help decision making and ensure that funds are spent efficiently.
Impact of Left-Turn Spillover on through Movement Discharge at Signalized Intersections
Authors: Osei-Asamoah Abigail , Kulshrestha Ashish , Washburn Scott S. , Yin Yafeng
Published: December 2010

While the Highway Capacity Manual (HCM) 2000 does provide a separate procedure to estimate the back of queue for a lane group, its signalized intersection analysis procedure does not explicitly account for the impact to through movement traffic as a result of left-turn bay spillover. If the HCM methodology is used for an analysis of an intersection approach where left-turn spillover interferes with the discharge of through vehicles, the estimated delay results, and corresponding level of service, will be overly optimistic. Thus, the objective of this study was to determine the factors that significantly affect left-turn lane spillover and develop a model, or models, to predict the expected through movement capacity and discharge rate as a function of this spillover. Two approaches were used in this study: an analytical approach that developed a probability of left-turn spillover equation to incorporate into a capacity estimation equation, and an empirical approach incorporating the use of microsimulation to develop equations to estimate through movement discharge as a function of left-turn spillover. The developed probabilistic model was an enhancement to one from the literature. However, its accuracy of estimation was still limited due to the issue of intercycle queue-formation dependencies not being taken into account. The two models developed from regression analysis of simulation data—one for intersection approaches with only a single through lane and one for intersection approaches with multiple through lanes—replicate the simulation results quite reasonably.
Analysis of Left-Turn Saturation Flow Rates and Capacity at Signalized Intersections
Authors: Wang Ming-Heng , Benekohal Rahim (Ray) F.
Published: December 2010

This study investigated and developed left-turn saturation flow rate models by considering the operation characteristics of left-turn traffic and the arrival and departure types of the opposing traffic. Methodologies for measuring left-turn saturation flow rates and capacity were proposed for the protected-then-permitted phasing with an exclusive left-turn lane at signalized intersections. The permitted left-turn saturation flow rate was developed on the basis of the opposing nonplatoon flow rate during the unblocked (unsaturated) time instead of using average opposing flow rates during the entire green time. The results of simulation show that the protected left-turn saturation flow rate is about 0.97, 0.96, or 0.95 of the saturated through traffic flow rate when opposed by one, two, or three lanes, respectively. The permitted left-turn saturation flow rate depends not only on the opposing flow rate but also on the number of opposing lanes. For facing multiple opposing lanes, the left-turn saturation flow rate decreased by 8% to 57% compared to facing only a single opposing lane. Even for multiple opposing lanes, additional reductions in the left-turn saturation flow rate, when facing three versus two opposing lanes, ranged from 8% to 18%. The estimation of the left-turn capacity using the proposed models was validated by comparing the capacity from the simulation.
Pedestrian Delay at Signalized Intersections with a Two-Stage Crossing Design
Authors: Wang Xuan , Tian Zong
Published: December 2010

An improved pedestrian delay model was developed for signalized intersections with a two-stage crossing design. This model provides a timely enhancement tool for the Highway Capacity Manual for conducting multimodal-oriented level of service assessments at signalized intersections with unconventional pedestrian crossings. The proposed model is presented in a general form that provides estimation of three portions of pedestrian delay involved in a two-stage crossing: the first-stage delay; the second-stage delay for pedestrians who crossed during the Walk phase of the first stage; and the second-stage delay for pedestrians who crossed during the flashing Don't Walk and Stop phases of the first stage. The model was validated through microscopic simulation under a wide range of traffic scenarios. Statistical analysis suggests that the proposed model is able to give satisfying results (R2 = 99.9%, p-value = .000). The model can be applied in various cases knowing some basic input parameters and variables.
Best Practices and Common Approaches for considering Sustainability at U.S. State Transportation Agencies
Authors: Barrella Elise , Amekudzi Adjo A. , Meyer Michael D. , Ross Catherine L. , Turchetta Diane
Published: December 2010

Recent federal, state, and international initiatives suggest growing interest in the sustainability of transportation systems, environmentally, economically, socially, and otherwise. This paper explores commonalities and variations in sustainability activities and describes best practices in sustainable transportation planning and evaluation at state departments of transportation (DOTs) in the United States. A survey of the 50 state DOTs identified current policies, programs, and evaluation methods. With a 94% response rate, the survey results reflect well the range of practices at state DOTs. The survey shows that some state DOTs appreciate the importance of sustainability in their external and internal activities and can point to specific initiatives that demonstrate their interest in sustainability. However, agencies clearly are focused on a range of activities and address sustainability at different levels of engagement. The survey results also reveal several general trends driven largely by federal requirements and state or regional priorities. Each DOT has a unique package of policies or programs, but all state DOTs point to their environmental planning activities as evidence of sustainable practices. Overall, DOTs in the Pacific division are most active in sustainable transportation practices, while those in the Northeast are particularly active in climate change planning and land use planning. Based on the survey responses and supporting literature, a national policy on sustainable transportation may provide guidance for state DOTs and other transportation agencies on specific elements of sustainable transportation, but it will need to be flexible to allow DOTs to address local issues and priorities.