bluuebunny/crossref_metadata_2025 huggingface dataset:
Probabilistic Advancing Cross-Diagnosis for Bridge Structures by Using Coherent Laser Radar
Authors: Fu Gongkang , Moosa Adil G. , Peng Juan , Chase Steven B.
Published: April 2007

Global diagnosis for bridges involves identifying the existence of deterioration or damage, as well as its location or vicinity. This research project develops a new technique for global diagnosis—the probabilistic advancing cross-diagnosis (PAC) method—by using a recently developed coherent laser radar system (CLRS). The PAC method takes advantage of CLRS’s efficient deformation-data acquisition by scanning a large area and then processing the data to perform probability-based cross-diagnosis. This method was applied in the structures lab at Wayne State University to a model structure, with the cooperation of FHWA’s Turner-Fairbank Highway Research Center. Several damage scenarios were simulated by increasing and reducing stiffness of the test beam in the model structure. Results show that the proposed PAC method is promising and should be tested in the field.
Fatigue Design of Modular Bridge Expansion Joints
Authors: Connor Robert J. , Dexter Robert J.
Published: April 2007

Experimental and analytical research was recently performed to develop performance-based specifications and commentary for the fatigue design of modular bridge expansion joints (MBEJ). The resulting proposed fatigue-design and test specifications resulting from this research are discussed. These specifications are intended for integration into the present AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications. For consistency with the bridge design specifications, the proposed MBEJ fatigue-design specifications used the same fatigue-design truck as was used by the present AASHTO bridge specifications. However, one important modification of the AASHTO truck loading for MBEJ is the explicit recognition that the rear axles of the HS series trucks actually represent tandem axles. A simplified method to estimate the distribution factor (i.e., the fraction of the range of the design-wheel load assigned to a single “centerbeam”) is recommended. Dynamic impact on both the vertical and horizontal direction is discussed. Also, guidance on structural analysis of MBEJ, good detailing practice, and fatigue resistance and testing are presented. MBEJ designed under the proposed specifications should be resistant to fatigue cracking. The additional material and the improved details, which will be required to comply with the proposed specifications, are not expected to increase the initial first cost of MBEJ substantially.
Simplified Nonlinear Modeling for Seismic Assessment of Complex Bridges
Authors: Thorkildsen Eric , Barsoum Emad
Published: April 2007

A common procedure used for the seismic assessment of complex bridges is a three-dimensional linear-response spectrum analysis. The linear nature of such an analysis can lead to erroneous results and misdiagnosis of vulnerable components. Analysis that accounts for the nonlinear behavior of components is desirable, but the human resource effort required to properly model an entire bridge is usually more than what most owners would like to invest. The use of simplified nonlinear modeling as a complement to larger linear models is discussed, providing the engineer with a true sense of structure response during the seismic event. The result is a proper diagnosis of vulnerabilities without a large analytical design effort. Three bridge case studies illustrate examples of nonlinear assessment of retaining walls, reinforced concrete connections, steel members, and viscous damping devices.
Modeling Motorway Driving Behavior
Authors: Hogema Jeroen H.
Published: April 2007

Microscopic traffic simulation constitutes a useful method for predicting the effects of new transport telematic systems on road traffic. In such a simulation, the driver model is a key element describing the dynamic individual driving behavior in relation to the vehicle, the road environment, and other traffic participants. The driver model presented in this paper was developed partly on the basis of literature and partly on the author’s own experimental research with a driving simulator and an instrumented vehicle. The driver model includes free driving (speed control), car following (distance control), and lane-change behavior. It interacts with a vehicle model at a detailed level (pedals and gear status). The driver model uses the vehicle controls with the aim to reach or maintain the individual, situation-dependent desired speed or following distance. The model includes aspects such as reaction time, perception thresholds for speed differences, and comfort levels for accelerating and decelerating. Since the traffic simulation model was designed to study the effects of systems such as adaptive cruise control (ACC), the driver model also includes a component that describes the driver’s interaction with ACC. In addition to a description of the model and its background, an illustration of the model’s application is given in a case study on ACC, where the ACC’s reference speed was influenced externally by a modeled beacon system. In conditions with high traffic volumes, the beacon system influenced the traffic upstream to try to create a homogeneous, steady traffic flow.
Preliminary Validation of Driving Simulator Based on Forward Speed
Authors: Klee Harold , Bauer Chris , Radwan Essam , Al-Deek Haitham
Published: April 2007

This research was a preliminary step in the process of determining whether the driving simulator at the University of Central Florida (UCF) provides a realistic driving experience. Thirty volunteers from the driving population were asked to drive an instrumented car along a section of road on the UCF campus. A distance measurement instrument provided a log of instantaneous speed, cumulative distance, and elapsed time at designated points along the route for subsequent analysis. The second phase of the research entailed driving in the UCF driving simulator, which consists of a complete vehicle cab with a wraparound screen for displaying computer-generated images of a synthetic road and surroundings. Computer-generated imagery of the identical campus road and environment was viewable to the subjects in the simulator. Drivers were asked to perform the same task in the simulator as they did in the real driving environment. Identical information was acquired during field testing and the simulation runs. Speed data from the field and simulator were analyzed using conventional statistical tests to determine whether drivers responded differently in the simulator compared with their response during the real driving experience. Preliminary results of the statistical analysis indicated that the drivers behaved similarly at 10 of 16 designated locations along the road. Confidence intervals for the difference between the simulator and the field mean speeds indicated a tendency of drivers to travel at slower speeds in the simulator. These results, along with qualitative feedback from the subjects concerning the handling characteristics of the simulator, are being studied to determine the necessary simulator refinements and upgrades required before additional validation testing.
Developing Highway Driving Simulations Using Virtual Reality Modeling Language
Authors: Burnette Charles , Moon Sook
Published: April 2007

Implementation of interactive highway driving scenes that have most of the functional capacities provided by sophisticated simulation software packages by using virtual reality modeling language (VRML) is described. VRML is a relatively simple, cross-platform, file-interchange format for publishing three-dimensional web pages that can be interactively experienced in a browser over an intranet or the Internet. The use of OpenWorlds VRML script nodes to quickly encapsulate preexisting simulation system software code to drive a VRML model in real time is also presented to demonstrate that existing simulation hardware systems can be readily integrated into VRML simulations. A related software package, HumanOpenWorlds, also enables the integration of anthropometrically correct human figure models into the VRML simulations for dynamic ergonomic analysis. Together these software tools deliver a comprehensive, cross-platform system capable of supporting human factors assessment of advanced driver interfaces over local or wide-area networks. These recent developments indicate that with adequate network bandwidth connections, real-time simulation scenes may be “driven” from remote locations controlled by signal input from mouselike devices or an instrumented driving buck. The proof-of-concept demonstration by the Advanced Driver Interface Design/Assessment Project described in this paper establishes the feasibility of producing cost-effective, flexible, and convincing simulations through which to assess human factors in complex operating environments using VRML. The applications should now be further developed and more thoroughly benchmarked against competing technologies.
Development of a Flared Energy-Absorbing Terminal for W-Beam Guardrails
Authors: Sicking Dean L. , Reid John D. , Rohde John R.
Published: April 2007

A new flared W-beam guardrail terminal that incorporates energy-absorbing technology has been developed and successfully crash tested to meet the criteria presented in NCHRP Report 350. The terminal, designated FLEAT-350, incorporates an impact head designed to dissipate impact energy by producing a series of plastic hinges in the W-beam as the impact head is pushed down the guardrail. The energy-absorption mechanism allows the flared terminal to absorb large amounts of kinetic energy before the vehicle is allowed to gate through the system. Most components of the new terminal are similar to those incorporated in the SKT-350 terminal. The terminal system is 11.4 m (37.5 ft) long and incorporates a straight flare with a final end offset of between 0.76 m (2.5 ft) and 1.2 m (4 ft). The terminal uses two breakaway posts in foundation tubes and five rough-cut controlled-release terminal posts of 150 by 200 mm (6 by 8 in.). The energy-absorbing design minimizes problems associated with vehicles that penetrate the terminal and strike slopes, ditches, or other hazards behind the guardrail while still traveling at a high rate of speed. Furthermore the new design has fewer components and is less sensitive to post location and installation details than some other flared systems.
Roadside Safety Analysis Program as a Tool for Economic Evaluation of Roadside Safety Projects
Authors: Khasnabis Snehamay , Naseer Mubashir , Baig Mirza F. , Opiela Kenneth S.
Published: April 2007

Highway agencies are continually called upon to make decisions about roadside safety projects by considering their relative benefits and costs. ROADSIDE software is a tool developed in the late 1980s for costeffectiveness analysis of safety features and has been used by different highway agencies. As a part of the continuing effort to improve such costeffectiveness procedures, the Roadside Safety Analysis Program (RSAP) has recently been developed at the Texas Transportation Institute. RSAP uses a simulation technique to replicate single-vehicle accidents on a highway facility and can test the effectiveness of the various countermeasures that are used to reduce the severities of these accidents. The application of RSAP to actual case study sites and the outcome of a study recently conducted at Wayne State University are described. Various median treatments on freeways were tested, and their respective benefit-cost ratios, as estimated by RSAP output, were examined. A set of sensitivity analyses of the RSAP output to various input parameters was also conducted. It is found that RSAP is user-friendly software and is fully operational on a personal computer with a Pentium processor in the Windows 95 environment. RSAP provides a summary of the accidents predicted for each scenario tested, and those are segregated by each feature coded along with its respective severity and cost. The economic analysis procedure is based on strong analytic principles, and the results are sensitive to accident cost, cost of construction, and interest rate. The software output is generally sensitive to the input parameters, and the trends appear to be logical. Additional research to calibrate the accident prediction model with historic accident data at the project site will be highly desirable.
Videolog Assessment of Vehicle Collision Frequency with Concrete Median Barriers on an Urban Highway in Connecticut
Authors: Fitzpatrick Michael S. , Hancock Kathleen L. , Ray Malcolm H.
Published: April 2007

In-service performance evaluation is the process of assessing the performance of roadside safety hardware under real-world service conditions. The purpose of in-service evaluation is to determine and document the manner in which a safety feature performs during a broad range of collision, environmental, operational, and maintenance situations for typical real-world site and traffic conditions. An in-service performance evaluation of the concrete median barrier (CMB) in Connecticut was undertaken to determine how often CMBs are struck and how often such collisions are reported to the police. The method used to perform the inservice performance evaluation of the CMB is described, and the results are presented. Data were collected for a section of CMB located on I-84 in Hartford, Connecticut. Accurate information about impacts with CMBs is difficult to obtain because so many collisions are unreported. Even for severe collisions, damage to the barrier is rare, and little maintenance is required. In many cases, police reports are the only means of monitoring when, where, and how severe the CMB collision was. Videologging was used to accomplish the in-service performance evaluations of CMBs to document the extent of unreported collisions.
Heavy-Goods Vehicle Collisions with Steel Road Safety Barriers: Combined Influences of Position of Center of Mass and Tire-Pavement Friction
Authors: Montella Alfonso , Pernetti Mariano
Published: April 2007

Vehicles that collide with highway safety features do not always produce the same effects. The outcome for each vehicle that collides with a feature will be different, depending greatly not only on its mass, velocity, and impact angle but also on the position of its center of mass and on the tire-pavement friction. The ways in which barrier and striking vehicle behaviors are affected by changes in the position of the center of mass and in the tire-pavement side friction were analyzed to identify the most dangerous loading systems. Toward this aim numerous simulations of a collision of a truck against a steel road safety barrier were carried out through nonlinear, dynamic finite-element analysis. The results obtained demonstrate that the position of the center of mass is of greater consequence in collisions in which the impact energy is close to the maximum barrier containment capacity and under conditions that favor friction. The longitudinal position of the center of mass has a large impact on the risk that the vehicle will pass over the barrier or roll over. If it is in the back, the most common loading system, the risk of passing over the barrier is rather limited compared with the risk of rolling over. As the position of the center of mass is pushed forward, the risk of rolling over is reduced but the risk of passing over the barrier increases. If the height of the center of mass increases, the rollover risk is higher, but a higher center of mass does not significantly influence displacement and the risk of passing over the barrier.
Variation in Characteristics of Abraded Roadway Particles as a Function of Particle Size: Implications for Water Quality and Drainage
Authors: Sansalone John J. , Tribouillard Thierry
Published: April 2007

Storm-water runoff from highway pavement is capable of mobilizing and transporting a wide gradation of particulates and solids. A significant fraction of this particulate matter is generated from traffic activities, including the abrasion between tires and pavement. Particulate accumulation and characteristics from an urban Interstate pavement site are investigated. The southbound asphalt pavement section studied consisted of four traveled lanes and two paved shoulders with a measured average daily traffic of 110,000. The pavement section has a transverse slope of 0.020 m/m and a longitudinal slope of 0.004 m/m. Recovery of deposited particulate matter indicates that accumulation of particulate matter along the east paved shoulder (the downslope shoulder) is significantly greater than that along the the west paved shoulder (the upslope shoulder) or the pavement. Particles larger than 25 μm were separated mechanically to generate particle size distributions (PSDs) and also to separate particles for further analysis. The east shoulder PSDs were consistently coarser across the entire size gradation than the west shoulder and pavement PSDs. Particle specific gravity ranged from 2.70 to 3.01 g/cm3 across all gradations. Particle specific surface area increased with decreasing particle size for all gradations. In contrast, total particle surface area decreased with decreasing particle size. Integration of metal element concentration (in micrograms per gram) of zinc, copper, cadmium, and lead with the mass fraction of each particle size demonstrates that most of the metal mass is associated with the coarse to mid-range-size particles. Study results are useful for design of roadway drainage appurtenances and water quality control devices that clarify storm water mainly through the separation of particles.
Intercity Rail Fixed-Interval, Timed-Transfer, Multihub System: Applicability of the Integraler Taktfahrplan Strategy to North America
Authors: Maxwell Ross R.
Published: April 2007

The Integraler Taktfahrplan (ITF) strategy for coordinating intercity rail and other modes at multiple timed-transfer hubs is described. The ongoing Swiss experience in establishing a countrywide ITF system is presented, and the ITF strategy is applied to North America, using a region within the United States. The Swiss Rail + Bus 2000 Plan will bring all intercity public transportation modes into a comprehensive fixed-interval, timed-transfer, multihub system, including high-speed intercity trains, regular intercity and regional trains, buses, ferries, and funiculars. Timed connections with urban transit systems will be provided. The repeating schedule, associated with the ITF strategy, allows for two powerful analysis and communication tools: ( a) a schedule map and ( b) symmetrical train graphs. The schedule map helps planning, marketing, scheduling, engineering, and operations work together as they iteratively design the system. The map, which graphically combines routes and schedules, is easy to understand and sell to policy makers and the public. Symmetrical train graphs help with the detailed engineering and cost-benefit analyses. The ITF strategy first develops the schedule on the basis of the potential market and then selects the most appropriate mode and infrastructure improvements to make any required travel-time savings needed for the timed transfers. Because a view of the system as a whole is provided, the benefits of a large capital investment or an ongoing operating subsidy can be properly weighed. For intercity passenger rail, this strategy provides a way to capitalize on the existing rail resources in a cost-effective manner: to build and fund only what is needed, but also to build and fund what is truly needed.
Estimating Patronage for a Feasibility Study of High-Speed Rail in Thailand
Authors: Stopher Peter R. , Metcalf Helen M.A. , Wilmot Chester G. , Catalina Anthony J. , Schimpeler Charles C.
Published: April 2007

A feasibility study of a system of high-speed rail lines for the kingdom of Thailand is described. Absent comprehensive local data and any intercity forecasting models for the nation, an incremental demand model and an incremental mode-choice model were chosen as the modeling techniques to use for the study. The incremental demand model used variables of population, gross provincial product, and the log sum term of level of service from the mode-choice model. The mode-choice model itself was synthesized using parameter values from similar efforts in other countries, adjusted to local currency values and income per capita. The steps taken to estimate base-year demand and market shares are described, and the application of the models to forecasting demand for four alternative technologies is discussed. Within the context of the input forecasts of population and gross domestic product, the models were found to produce reasonable results, with intuitively appropriate sensitivities. The results were also found to be adequate to guide initial assessments of feasibility.
Comparisons of Biofuels in High-Speed Turbine Locomotives: Emissions, Energy Use, and Cost
Authors: Pier Jerome R.
Published: April 2007

The performances of a 2984-kW (4,000-hp) gas turbine–powered passenger locomotive fueled with different biofuels are compared with the performance of the same locomotive fueled with Diesel #2. The process of selecting a small number of biofuels from a detailed evaluation of 13 readily available biofuels is explored. A simulation of operation in an actual high-speed corridor is used to develop exhaust emission values in terms of tonnes (tons)/year for a complete service, and then in terms of g (lb)/trip of primary smog-producing pollutants. Energy use and cost per trip are developed from the same simulation. All of these values are compared with Diesel #2 values developed in previous research. Bio-fuel use in respect to turbine maintenance costs is discussed. Explored are the implications of carrying and delivering the biofuels on a locomotive in terms of ( a) projected range with a given fuel tank size and ( b) the minimum fuel tank size required to serve a typical corridor.
Evaluation of Unassigned Sign Colors for Incident Management Trailblazing
Authors: Neale Vicki L. , Barker Julie A. , Dingus Thomas A. , Brich Stephen C.
Published: April 2007

Efforts to design and evaluate a new sign design for incident route trailblazing are reported here. Phase 1 was an off-road field experiment conducted to determine the best sign color combination, letter stroke width, and letter size for emergency signs. Based on the results of Phase 1, three color combinations were chosen for testing (black on coral, black on light blue, and yellow on purple) against a baseline color combination of black on orange. Phase 2 was conducted with an instrumented vehicle through a construction zone-related detour. Questionnaire data were also obtained. The independent variables of interest were sign color combination, age, and visibility condition. The findings of Phase 2 indicated that use of a color combination other than the traditional black-on-orange sign would improve driver performance and safety when used for trailblazing during critical incidents. The following conclusions were reached: ( a) yellow on purple or black on light blue will likely result in fewer late-braking maneuvers if the road geometry includes many tight curves; ( b) black on light blue will result in the fewest number of turn errors; ( c) black on orange will result in more turn errors, especially during the day and particularly when it is overlapped with existing detour and construction zone signs; ( d) black on coral is least preferred by older and younger drivers; and ( e) younger drivers tend to prefer yellow on purple and older drivers tend to prefer black on light blue.
Study of Effectiveness of Selected School Zone Traffic Control Devices
Authors: Schrader Michael H.
Published: April 2007

The effectiveness of five different school zone traffic control devices was tested. Each was tested at a unique site. Speed data were obtained at each site before the devices were added and again 1 month and 6 months after the devices were installed. The five devices tested in the study were fiberoptic signs, spanwire-mounted flashing yellow beacons, post-mounted flashing yellow beacons, transverse lavender stripes, and large painted legends. Of the five sites tested, only the site with the fiber-optic signs experienced a speed reduction significant at the 95 percent level. Several of the other sites also experienced decreases in speeds; however, these decreases were not statistically significant.
Visual Target Detection Models for Civil Twilight and Night Driving Conditions
Authors: Zwahlen Helmut T. , Schnell Thomas
Published: April 2007

A luminance contrast-based computer visibility model is discussed and compared with the civil twilight method, which has recently been introduced. The civil twilight method attempts to predict the visibility of ordinary objects (reflectance 3 to 79 percent, average size) by using only the headlamp illuminance at the target. It is suggested that the one-factor approach used by the civil twilight method is insufficient to satisfactorily address target visibility in the field. Developers of more advanced visibility models generally attempt to design models based on the current state of the visibility research and with enough capability to obtain a reasonable degree of realism. The level of the benchmark illuminance (3.2 lx) used in the civil twilight method is considered by the authors to be too high, leading to very short detection distances for pedestrians under automobile headlamp illumination at night. The developers of the civil twilight method claim that the 3.2-lx visibility benchmark is based on systematic visual observations made by astronomers over a century ago. The use of the civil twilight method for pedestrian detection under automobile headlamp illumination at night is strongly discouraged by the authors of this paper, because the method may be misused by forensic experts if there is a need to produce arbitrarily short pedestrian detection distances, regardless of factors such as clothing reflectance, contrast, pedestrian size, windshield transmittance, and atmospheric transmissivity.
Violations at Gated Highway–Railroad Grade Crossings
Authors: Carlson Paul J. , Fitzpatrick Kay
Published: April 2007

In 1995, legislation was passed by the 74th State Legislature of Texas requiring the Texas Department of Transportation to install and operate automated enforcement systems at up to 10 highway–railroad grade crossings as a demonstration project. An issue that arose early was determination of which gated crossings were best suited for automated enforcement systems in terms of maximizing potential safety benefits. To resolve this issue, research was conducted to identify operational and geometric variables that may influence violations at gated highway–railroad grade crossings. Because crashes at gated crossings are such infrequent events, which can limit the effectiveness of statistical analyses, drivers’ actions at gated crossings were recorded and used as the measure of effectiveness. They were classified into two categories: those who violated and those who complied with the traffic laws. Vehicle and train operations at 19 gated highway–railroad grade crossings in Texas were recorded for a minimum of 24 continuous hours per site. A total of 868 opportunities to violate the traffic laws associated with gated crossings were recorded. Motorists committed violations during 460 of these opportunities. Models were developed that can be used to identify gated crossings that are expected to have high violation rates compared with other gated crossings. Because these models focus on violations instead of crashes, they are more sensitive to the level of hazardous behavior that occurs at gated crossings. Use of the proposed models should lead to better selection of gated crossings where automated enforcement systems or additional conventional enforcement will be most effective.
Supervised Interconnection Circuits at Highway–Rail Grade Crossings
Authors: Mansel Douglas M. , Waight Vernon H. , Sharkey John T.
Published: April 2007

After the tragic 1995 collision between a school bus and a commuter train outside of Chicago, Illinois, much attention has been given to the subject of highway-rail grade crossing safety. The 1988 edition of the Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD) addresses traffic signal preemption for intersections near grade crossings as well as the electrical circuit or “interconnection” that makes traffic signal preemption possible. The objective of this study is to examine the basic interconnection circuit, as defined in the MUTCD, and explore some of its limitations. Possible improvements to the basic interconnection circuit are presented and evaluated.
Evaluation of Two New Crossbuck Designs for Passive Highway–Railroad Grade Crossings
Authors: Zwahlen Helmut T. , Schnell Thomas
Published: April 2007

Two new crossbuck designs for use at passive highway–railroad grade crossings were evaluated. The standard improved and the Buckeye cross-buck were evaluated in Ohio with respect to their potential to alter driver risk-taking behavior (Part I), their accident reduction potential (Part II), user acceptance (Part III), and with respect to their photometric performance at night (Part IV). It was found that the percentage of noncompliant drivers was about the same for both crossbuck designs, with slightly more conservative risk-acceptance times obtained for the Buckeye cross-buck. Based on the past 10 years of Ohio railroad crossing (RRX) accident history, the overall number of accidents at passive RRX has continued to drop. Since the statewide installation of the two new cross-buck designs, no accident reduction pattern could be attributed to one of the two crossbuck designs. A user acceptance survey indicated an overwhelming preference for the Buckeye crossbuck among the user groups surveyed. Photometric crossbuck luminance measurements conducted under automobile low-beam illumination at night indicate that thanks to their increased reflectorization, both new designs provide superior visual stimuli to an approaching driver at night. The Buckeye crossbuck provides by far the strongest visual signal among the measured crossbucks at night. Amendments to the national standard for crossbucks at passive RRX in the Manual on Uniform Traffic Control Devices are recommended. Postreflectorization (four-sided) is recommended and the additional use of a striped, angled shield is recommended in situations that require a maximum visual stimulus, ensuring the shortest possible perception reaction times, and in situations that involve visual obstructions, frequent fog, or blinding snow.
Visibility of Road Markings as a Function of Age, Retroreflectivity Under Low-Beam and High-Beam Illumination at Night
Authors: Zwahlen Helmut T. , Schnell Thomas
Published: April 2007

A study was conducted to obtain visibility data for old and young subjects performing a pavement marking end detection task on a fully marked road under headlamp illumination conditions. A total of 20 healthy subjects (10 old and 10 young) were used. It was found that observer age had a highly significant effect on pavement marking visibility. The effect of headlamp illumination (high-beam versus lowbeam) was found to be rather weak, probably because of the low-beam headlamp pattern, which favors the right-edge line. Pavement marking retroreflectivity was found to be significant at the levels investigated in the experiment. The new yellow dashed centerlines (tape) with a gapto-stripe ratio of 9.1/3 had a retroreflectivity of RL = 222 mcd/m2/lx and RL = 399 mcd/m2/lx under the medium and high conditions, respectively. The new white edge lines (tape) had a retroreflectivity of RL = 268 mcd/m2/lx and RL = 706 mcd/m2/lx under the medium and high conditions, respectively. The average end detection distances ranging from 124.8 m (average preview time 5.1 s for 88.5 km/h) for the old group under low-beam illumination on the medium retroreflectivity road to 237.3 m (average preview time 9.7 s for 88.5 km/h) for the young group under high-beam illumination on the high retroreflectivity road may appear to be rather long. However, the reader should be aware that markings as bright as the ones used in this research are the exception instead of the rule in real-world driving situations. The aim of this study was to determine the end detection distances obtainable under fairly favorable pavement marking material conditions.
Benefit Sensitivities of Adaptive Traffic Control Strategies at Isolated Traffic Signals
Authors: Stewart J.A. , Lepik K. , Van Aerde M.
Published: April 2007

A study of the possible benefits of using traffic adaptive and actuated signal control strategies at traffic signals is described here. The study indicated that delay estimates produced by INTEGRATION closely matched the delay estimates of the 1997 revision to the U.S. Highway Capacity Manual. Second, benefits of time-of-day control and adaptive control became more pronounced as the level of demand peaking increased. Third, well-designed time-of-day plans easily outperform fixed-time and adaptive strategies when the prevailing traffic demands match the controller’s expectations. Adaptive strategies performed better than simple fixed-time control strategies, which were optimized only for the average demand level. It was also observed that all types of control strategies, especially adaptive control strategies, could be improved by introducing signal actuation. Finally, it was found that actuation improved the performance of the intersection for both uniform and random departure headways. Improvements were greatest when an adaptive control strategy was being implemented and the departure headway was random.
Use of Multicriteria Decision Making To Identify the Critical Highway Safety Needs of Special Population Groups
Authors: Dissanayake Sunanda , John Lu J. , Chu Xuehao , Turner Patricia
Published: April 2007

With the recognition of the importance of addressing special-population groups’ safety needs, with the aim of increasing highway safety in the United States, the requirement arises to identify the critical issues. A multicriteria decision-making approach was used to identify the most critical highway safety needs of six special population groups: older drivers, young drivers, school-age children, international tourists, new immigrants, and people with disabilities. Two surveys were conducted in which the opinions of highway safety professionals were sought for identifying the most critical groups, and an index was developed on corresponding critical highway safety issues and concerns. The index corresponds to a score representing a multidimensional situation and estimates the weighted sum of all the six criteria considered. The six criteria considered were the impact on crash rates, the effectiveness of applying roadway design changes to address the issue, the effectiveness of applying policy changes to address the issue, the cost of implementing the change, the ease of implementing the change, and the priority to address the issue. Three different methods were used in assigning the weights for the six criteria, and ranking orders were compared for the reliability of the outcome. It was found that the ranking orders were almost consistent irrespective of the method used to determine the weights.
Study of the Impact of Police Enforcement on Motorists’ Speeds
Authors: Sisiopiku Virginia P. , Patel Hitesh
Published: April 2007

One method to enforce speed limits on U.S. highways is through the use of police enforcement. One major problem with this approach is the high cost associated with the employment of police officers for patrolling purposes. Thus, the effectiveness of police presence in controlling highway speeds should be carefully assessed prior to making a decision on increasing police patrolling operations on the transportation network. A study was undertaken to evaluate the effects of police presence on the speed of vehicles in a recently increased speed-limit zone and to determine the “halo” effects of police presence (lasting effects when police are gone) on vehicular speeds. Data were collected on Interstate 96 in Ionia County, Michigan. Marked police cars circulated in both directions on the study segment, which was approximately 45 km (29 mi) long. Net speed reductions at a distance of 1.6, 3.2, and 4.8 km (1, 2, and 3 mi) upstream and downstream of each counter were used in the data analysis. Two methods were applied to study the effects of police presence. First, the average speed in the area without the police presence was compared to the average speed after the police presence. Second, the difference between the speed at the place where the police vehicle was positioned and the speed downstream was calculated. It was found that the average speed just upstream of the police car’s location was reduced, but as soon as vehicles passed the patrol car, drivers accelerated to their normal speeds or more. Moreover, no “halo” effects on the vehicles at the increased speed zone under study were observed.
Can We Make Red-Light Runners Stop?: Red-Light Photo Enforcement in San Francisco, California
Authors: Lucero Fleck Jack , Smith Bridget B.
Published: April 2007

Violating red lights is a serious safety issue. In recent years, awareness of this problem has become especially acute in the United States. In San Francisco, California, with its compact driving environment and dense network of signalized intersections, red-light running reached a political crisis in 1994. The city and county of San Francisco recently completed a pilot red-light photo-enforcement program. The number of vehicles photographed violating red lights at the photo-enforced locations dropped by more than 40 percent just 6 months into the pilot. Recent statistics indicate that San Francisco’s combined efforts to combat red-light running have resulted in a significant decrease in the number of annual collisions caused by red-light violators citywide. Based on the success of the pilot and supportive state legislation, San Francisco is moving forward to expand the red-light photo-enforcement program. This collaborative effort involving several agencies soon will be one of the largest programs in the United States, with 26 cameras rotated through 36 intersections. San Francisco’s experience with red-light photo enforcement is valuable for all jurisdictions considering the use of automated enforcement. Discussion includes the level of preparation required to initiate a program, the legal framework, the cost-effectiveness of automated enforcement, the criteria for site selection, and suggestions for increasing citation issuance rates. Recommendations from San Francisco’s experience stress the importance of creating partnerships within your agency and without, combining engineering and enforcement efforts with an educational campaign, and influencing local legislation.
Human Factors Issues Related to Use of Vision Enhancement Systems
Authors: Gish Kenneth W. , Saplin Loren , Perel Michael
Published: April 2007

Vision enhancement systems (VESs) are being developed to improve nighttime driving safety by providing enhanced contrast to drivers. To determine how to evaluate the potential benefits or limitations of such systems, a small-scale investigation of driver performance and behavior with a mockup VES was conducted. To maximize external validity and minimize safety risks, a field experiment was designed and conducted on a closed test track. Four younger observers (ages 26 to 36 years) and four older observers (ages 56 to 70 years) drove an instrumented vehicle and verbally reported the detection and recognition of targets while performing speed monitoring and navigation tasks. Targets near the edges of the lane of travel were detected with and without a mock-up VES and with and without headlight glare. Video recordings of the VES, road scene, driver, and data acquisition screen were obtained. Time code, distance traveled, verbal reports, and gas pedal, brake pedal, and steering wheel measurements were recorded. Results suggested that although the mockup VES provided target contrast at longer preview distances than low-beam headlights alone, the VES enhancements were not always detected by drivers because of the visual, scanning, and cognitive demands of the driving tasks. Also, older drivers were less willing to use the mock-up VES. On the basis of verbal reports, the consensus among all observers was that the VES increased curve detection distances relative to those achieved with low-beam headlights alone. The implications of the study findings for VES use, design, and evaluation are discussed.
Overview of Some Human Factors Design Issues for In-Vehicle Navigation and Route Guidance Systems
Authors: Srinivasan Raghavan
Published: April 2007

In-vehicle navigation and route guidance systems have been proposed as solutions to the congestion problem. For these systems to be effective, drivers should be able to understand the information and respond in a safe manner. Some of the human factors issues associated with the design of these systems are discussed. The focus is on the safety and human factors issues while the person is driving on the road. The following issues are addressed in detail: mode of information presentation, information content and format, message timing, display location, and driver interaction with devices. Conclusions and areas for future research are also provided.
Recent Pedestrian Planning Issues and Initiatives in Japan and South Korea
Authors: Sriver Jeffrey J. , Kwon Young-In
Published: April 2007

Pedestrians in Japan and South Korea have faced many simiar challenges in the years since their countries have become motorized. The history of pedestrian transport issues in the to countries is discussed, along with several strategies of the Japanese and South Korean goverments to meet motorized transport challenges. The most recent comprehensive, neighborhood-wood traffic schemes in each country—Japan’s “community zones” and South Korea’s Site Traffic Mangement program—are also introduced.
Assessment of a Gap-Actuated Pushbutton Signal Using a Traffic Simulation Model
Authors: Mohsin M. , Sarker J. , Koike Hirotaka , Morimoto Akinori
Published: April 2007

A main concern with pedestrian crossings is the time that pedestrians are expected to wait before a traffic light changes. Pushbutton signal systems are mainly set to accommodate vehicular flow efficiency, and the interval for pedestrians to cross the street remains the same even if no vehicles are on the road or if there is a long gap between oncoming vehicles. Pedestrians often cross the road against the go-ahead pedestrian signal when they perceive an acceptable vehicular gap, sometimes even after pressing the pushbutton. Vehicles must stop even if no pedestrian is waiting to cross the street. This study examined a gap-actuated pushbutton signal via a traffic simulation model. The results show a substantial decrease in pedestrian waiting time with negligible effects on vehicular flow.
Model for Road Safety Planning: Theory and Policy Example
Authors: Navin Francis P.D.
Published: April 2007

A fundamental relationship has been developed that should allow authorities to forecast the results of various road safety interventions. Risk is defined to include attributes of the road, vehicle, driver, and speed enforcement. The model may be linked to the traditional Forgiving Highway design and to vehicle crashworthiness. The probability of a crash, or the Caring Highway variables, may also be studied for policy decisions. Also, by manipulating the exposure element, the model may be used by transportation planners to include road safety in their analysis of transportation impacts. The new model will help authorities—in developed and developing countries—to select the most effective road safety programs and to understand some of the interactions between programs.
Quantitative Approach to Bridge Aesthetics for the 21st Century
Authors: Figg Eugene C.
Published: April 2007

Many important qualities must be considered for the proper aesthetic design of bridges to develop harmony with their environment. Methodologies for segmental bridge design that create bridges that preserve the existing landscapes and complement, and even enhance, their settings are examined. Bridges considered have received 123 design awards in the past 21 years, including 3 Presidential Awards through the National Endowment for the Arts. Proper scale and proportions of various bridge members to create balanced and slender appearances are quantified, including proper span-to-depth and pier width-to-height ratios for graceful structures. The design methodology for aesthetics includes a quantitative and qualitative sorting of natural site features to determine appropriate shapes for the superstructure and substructure. Criteria for selecting and evaluating the visual effects of shape, shadows, vistas, color, textures, and the use of native materials are addressed. Quantification of the cost of aesthetic decisions and determination of aesthetic value are addressed for different elements of these bridges. Case studies are used to quantify aesthetic features for such bridges as the Natchez Trace Parkway Arches [first precast concrete arches with 177-m (582-ft) main arch span], Tennessee; Sunshine Skyway Bridge, Florida; Linn Cove Viaduct, North Carolina; Hanging Lake Viaduct, Colorado; and Wabasha Street Bridge, Minnesota.
Contextual and Urban Design Considerations in Design of Major Bridges
Authors: Rosales Miguel , Gottemoeller Frederick
Published: April 2007

Bridges are prominent features of many landscapes. They are often justifiably called on to meet public objectives beyond their transportation function. It becomes the responsibility of the designer to determine what these requirements are and whether the proposed design is really addressing all of the dimensions of the problem, including objectives that may not express themselves in the form of number of lanes, minimum clearances, and other physical criteria. Public requests for structures that emulate historical bridges or architecture are especially difficult to meet given modern transportation demands on the structure and given modern materials and techniques. The process must include recognition of the needs and effects of adjacent interchanges. The techniques used to incorporate contextual and urban design concerns into the design of contemporary bridges so that the public’s desire for landmark bridges can be met without resorting to the use of imitations of historical precedents are described. Three case studies are used to illustrate the ideas: the new Charles River Bridge in Boston, Massachusetts, Florida’s Clearwater Memorial Causeway Bridge, and the designs for two major crossings of the Raccoon River in Des Moines, Iowa. The aesthetic urban design and community considerations that guided the design for the bridges will be described by the projects’ architects and urban designers.