bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Past National Bridge Inventory Ratings for Predicting Bridge System Preservation Needs
Authors: Sun Xiaoduan , Zhang Zhongjie , Wang Robert , Wang Xuyong , Chapman Jason
Published: April 2007

A bridge management system (BMS) needs an analytic tool that can predict preservation needs based on the deterioration process of bridges and answer what-if questions. Pontis software was developed to serve this purpose. Because of its intensive data requirement, Pontis has not been fully implemented by the Louisiana Department of Transportation and Development (LaDOTD). Although LaDOTD has initiated a project to collect the Pontis element data, the project will take several years to complete. An innovative approach was developed using readily available National Bridge Inventory (NBI) data in Pontis to evaluate the long-term performance of the bridge system under various BMS alternatives. The deterioration process of three NBI elements was studied, and element deterioration models were developed. Bridge preservation plans and associated cost schemes were defined according to current LaDOTD practice and available information. Findings indicate that using NBI data for BMS analysis with Pontis is not only feasible but also practical. While waiting for the completion of the Pontis database, LaDOTD can use readily available NBI data to analyze and evaluate the long-term performance of the bridge system under various budgetary and operating scenarios. Initial results indicate that LaDOTD's current annual budget of $70 million is sufficient to meet the needs of only bridge preservation, not functional improvement. If implemented successfully, the bridge preservation plan can maintain the system in good operating condition for a long time with a limited annual budget.
Bridge Life-Cycle Costing in Integrated Environment of Design, Rating, and Management
Authors: Thompson Paul D.
Published: April 2007

The discipline of bridge life-cycle costing is at a turning point: it could soon become far more useful and used than ever before for a range of decisions about bridge engineering and management and for broader asset management. Several important new research-and-development studies have provided essential tools and resources previously unavailable, and many agencies are starting to amass valuable databases of information about inventory, structures, and condition. A vision of how these diverse products of numerous researchers and sponsors can be brought together to greatly increase the practicality and value of bridge life-cycle cost analysis at the project level is presented.
Relative Effects of Sodium Chloride and Magnesium Chloride on Reinforced Concrete: State of the Art
Authors: Mussato Brent T. , Gepraegs Oliver K. , Farnden Gary
Published: April 2007

Magnesium chloride (MgCl2) use for snow and ice control is becoming a well-established practice but has been limited to the past 10 years. Impacts associated with sodium chloride (NaCl) use are well documented, but concerns have been raised regarding the potential effects of MgCl2 use on concrete and steel reinforcement. The British Columbia Ministry of Transportation intended to establish guidelines for MgCl2 use by highway maintenance contractors. Information was gathered from available literature and interviews with academia and industry. Generally, few studies directly and comprehensively address the topic, and although significant research efforts are currently under way, results are not expected for several years. Past laboratory studies suggest that MgCl2 reacts with cement paste to reduce concrete strength and degrade concrete. Studies also suggest that chloride ions associated with MgCl2 have higher diffusion coefficients than those associated with NaCl. Field studies are limited, but laboratory coefficients for chloride ion diffusion correlate with results of a field study conducted in Montana. Higher chloride diffusion coefficients can reduce the initiation time for chloride-induced corrosion of reinforcing steel. No evidence to date directly links the increased deterioration of a structure to MgCl2 use; however, the history of use is short, and caution is recommended until additional studies can establish more evidence.
Observed Dynamic Traffic Features on Freeway Section with Merges and Diverges
Authors: Bertini Robert L. , Malik Shazia
Published: April 2007

Traffic data measured on a four-lane freeway and its on-ramps (with metered flows) and off-ramps were studied for 4 days during the peak hour. Certain features were reproducible from day to day. A bottleneck arose on all 4 days because of traffic merging and diverging at a freeway location. During these times queuing arose in a freeway section with an auxiliary lane some distance downstream of the merge. Corresponding flow reductions were also measured at a downstream off-ramp. Queuing was apparently caused by drivers who had just entered the shoulder lane from the on-ramp and had slowed down to merge. The slowing of vehicles spread to both lanes and propagated upstream. The average discharge flows that accompanied the onset of queuing were 4% lower than flows measured just before the queue's formation. Upon bottleneck activation, flow reductions occurred sequentially in time and space marking the passage of the backward-moving shock. Mean shock velocities ranged from 20 to 24 mph (32 to 40 km/h). The analysis used transformed curves of cumulative vehicle counts and cumulative occupancy to obtain the measurement resolution necessary for studying important traffic features. The site is located in Minneapolis, Minnesota, and data were collected before a ramp meter shutdown experiment conducted in 2000.
Systematic Identification of Freeway Bottlenecks
Authors: Chen Chao , Skabardonis Alexander , Varaiya Pravin
Published: April 2007

The algorithm presented identifies bottleneck locations, the times for which each bottleneck is active, and the delay they cause. The bottlenecks are ranked in terms of their frequency of recurrence and the magnitude of their delay impact. The algorithm works with 5-min loop detector data. It uses speed difference as an indicator of bottleneck activation. The algorithm is applied to 3 months of data from 270 mi of seven freeways in San Diego. It identifies 160 locations whose bottlenecks cause 64% of the total delay on these freeways. The top 10 account for 61% of the delay from all bottlenecks. The method can be used in any area in which large amounts of data are available. Transportation authorities may use it to identify bottlenecks and to track their impact over time.
Comprehensive Evaluation of Feedback-Based Freeway Ramp-Metering Strategy by Using Microscopic Simulation: Taking Ramp Queues into Account
Authors: Ozbay Kaan , Yasar Ilgin , Kachroo Pushkin
Published: April 2007

One of the major criticisms of ramp metering has been delay caused on the ramps because of the queues created by ramp control strategies. Recently, several researchers proposed strategies that explicitly consider ramp queues when metering rates are determined. An isolated "feedback"-based ramp-metering strategy (mixed control) is presented. In addition to regulation of ramp input from the freeway, the strategy calls for regulation of ramp queues by explicitly incorporating them into the model. Mixed control is tested using PARAMICS, a microscopic traffic simulation package, on a calibrated test network located in Hayward, California. In addition to mixed control, ALINEA and new control are implemented. Because the focus here is on evaluation of isolated ramp control strategies, change in demand caused by ramp metering is not considered. The system is defined as the upstream, downstream, and ramp links around the metered ramp. The performance of two freeway demand patterns (congested and overcongested) is compared. From the simulation results, all the strategies tested were found to be quite effective in optimizing freeway traffic conditions [reduction in mean congestion duration on the freeway downstream link, mean downstream occupancy, and travel time (upstream and downstream links)]. However, mixed control produced the best system results (upstream, downstream, and ramp links) by achieving optimal flow on the highway while keeping the queue length on the ramp small enough to prevent spillover onto the arterial network.
Field Testing for Automated Identification of Turning Movements at Signalized Intersections
Authors: Tian Jialin , Virkler Mark R. , Sun Carlos
Published: April 2007

Obtaining turning-movement counts at signalized intersections is a routine task in traffic engineering and can be tedious and time-consuming. Previous research in automating turning-movements counts focused on estimating the turning movements from approach and departure volumes and developing detection systems for exclusive-turn lanes. The accuracy of an alternative method, called the time-and-place system (TAPS), is examined through a field study of five signalized intersections in Columbia, Missouri. TAPS uses both the locations and times of actuations from a small number of detectors to classify movements from shared approach lanes. The five intersections are representative of different geometrics and signal timings. At four intersections a standard video camera was placed at a height of about 30 ft and as close to the departure lanes as possible to provide a reasonable view. Additional cameras showed current signal indications into the departure leg. At the fifth location a single elevated camera captured both vehicle movements and signal indications. The videotape data were used to compare TAPS results with actual flows. The errors in detection were apparently due to the sensitivity of the detection system, camera angles, intersection geometrics, traffic parameters, and other factors. The ability of TAPS to identify turning movements at signalized intersections was supported by the study results. With ideal camera views the authors believe that TAPS could yield almost perfect results. The information from TAPS could enhance the capabilities of real-time traffic adaptive signal control systems, dynamic traffic assignment, and traffic demand estimation.
SCOOT and Incidents: Performance Evaluation in Simulated Environment
Authors: Chilukuri Bhargava Rama , Perrin Joseph , Martin Peter T.
Published: April 2007

SCOOT is a widely used adaptive signal control system. There have been many evaluations of SCOOT during normal traffic conditions. It is hypothesized that SCOOT's ability to adapt to varying traffic during incidents provides an added benefit over its normal congestion-relieving capability. Through an interface between CORSIM and an actual SCOOT system, this study evaluates, in a simulated environment, SCOOT's performance during incidents to quantify these additional benefits. The evaluation is made over a range of volumes and incident durations. A theoretical test network and two real-world networks are simulated. Network and intersection delay, travel time, and queue length are used as measures of effectiveness (MOEs) throughout the comparison to quantify total and marginal benefits. During a 45-min incident within the Salt Lake City downtown area network, SCOOT reduced network delay, travel time, intersection delay, and queue length by 28.3%, 22.8%, 30.7 %, and 24.2 %, respectively, relative to the optimized plan-based control. Similar results were observed on the other real-world network. Although adaptive control has benefits above plan-based signal control, the findings indicate that during incidents, SCOOT provides an additional increase in benefits. The findings indicate that average SCOOT MOEs improve by 7% for a 15-min incident, by 12% for a 30-min incident, and by 18% for a 45-min incident depending on congestion level. The additional benefits that SCOOT adaptive control provides during incidents are quantified through the system's inherent ability to respond to traffic conditions in real time.
Using Bus Travel Time Data to Estimate Travel Times on Urban Corridors
Authors: Chakroborty Partha , Kikuchi Shinya
Published: April 2007

Obtaining near real-time information of travel times is a critical element of most applications of intelligent transportation systems. The use of transit vehicles as probe vehicles for collecting travel time data for automobiles on urban corridors was examined. Because transit vehicles are increasingly equipped with an automated vehicle locator (AVL) for reporting the current location of the vehicle, it may be possible to use the AVL data for travel time purposes. In anticipation of such an application of AVL, the relationship between travel times of a transit vehicle and of an automobile is examined for stability of data and adjustment needs. Travel times of transit vehicles and automobiles were measured simultaneously along the same sections on major corridors in Delaware. The difference in travel times was relatively stable, and, hence, appropriate formulas for predicting the travel time of automobiles were developed. The model coefficients were found to be reasonable and stable for various traffic conditions. The study suggests that the AVL-equipped transit vehicle can be used as a probe vehicle to collect travel time data at regular intervals with minimum cost.
Use of Automatic Position Reporting System Data for Enhancing Transportation Planning Operations
Authors: Meaker John , Horner Mark W.
Published: April 2007

Highway speed and travel times are generally the standard for evaluating highway network performance. Yet these data are often costly or difficult to obtain. As such, recent research has focused on exploiting new technologies (e.g., cell phones) as cost-effective sources of speed and travel time information. Consistent with this work, a new source of data and an acquisition approach that provides both vehicle speed and travel time measurements from ad hoc probe vehicles at modest cost are presented. In this system, probe vehicles collect Global Positioning System speed, heading, and position data and transmit them over amateur radio frequencies. Frequencies are monitored by personal computers, which are used to receive and process the probe data. System output consists of records containing traveler location, speed, and the time at which data were transmitted. Moreover, these data are managed and maintained as layers of points in a geographic information system and lend themselves to use in several applications. Contrasted with the system described, most traditional speed measurement systems (e.g., loop sensors) are restricted to collecting data at fixed points along major highways where sensors are installed. However, probe data facilitate regional analysis since acquiring information from probe vehicles does not depend on fixed observation points. Some of these applications and advantages of the data are discussed, and a detailed comparison of speed data retrieved from the presented probe system and data collected by traffic loop sensors is provided. The analysis demonstrates that the described probe vehicle system is an effective transportation data source.
Eighty Weeks of Global Positioning System Traces: Approaches to Enriching Trip Information
Authors: Wolf J. , Schönfelder S. , Samaga U. , Oliveira M. , Axhausen K. W.
Published: April 2007

The recent Swedish Intelligent Speed Adaptation (ISA) study included a component that involved the installation of units based on the Global Positioning System (GPS) in hundreds of cars in three Swedish cities, Borlänge, Lund, and Lidköping; these vehicles were observed for up to 2 years. In Borlänge, the speed and location data of each vehicle were transmitted at regular intervals to a central server and stored for later analysis. This data set contains a wealth of travel behavior information that had not been available before. However, a data set of this magnitude introduces a major need for automated processes that can glean travel behavior details from the trip summary and collected GPS point files. A summary is presented of characteristics of and issues with the Borlänge GPS data set, which included 186 personal vehicles with at least 30 days of travel data and corresponding household sociodemographic data. (These 186 vehicles recorded 49,667 vehicle days of travel and 240,435 trips inside the study area.) Then, automated methodologies are presented for imputing trip purpose for these trips once the trip destinations are identified, as well as for correcting the GPS traces and identifying missing trip ends within these trips. Results of these automated processes for a subset of the ISA study vehicles are included.
Data Partnering Between Transportation Agencies for Mutual Benefit: The Illinois Experience
Authors: Hall James P. , Robinson Rob , Laffey Steve , Ahrens Todd
Published: April 2007

The Illinois Department of Transportation (IDOT) has taken an active approach to identifying and implementing data partnering relationships that provide mutual benefits. These partnerships involve other state agencies, local agencies, and metropolitan planning organizations. Demand has increased for comprehensive, accurate, and timely information for planning and asset management activities. Data partnering relationships can provide many benefits, including more complete data collection, data verification, and improved data accessibility. Effective data partnering requires well-defined responsibilities, cooperation, and the commitment of each agency. IDOT's data partnering relationships in three critical areas of data collection and dissemination are detailed: rail-highway crossings, traffic, and structures. Given trends in the decreasing resources for data collection, multiagency data partnering activities likely will increase. It is important to manage these activities properly to improve the enterprise data resource.
Guidelines for Calibration of Microsimulation Models: Framework and Applications
Authors: Dowling Richard , Skabardonis Alexander , Halkias John , McHale Gene , Zammit Grant
Published: April 2007

The past few years have seen a rapid evolution in the sophistication of traffic microsimulation models and a consequent major expansion of their use in transportation engineering and planning practice. Researchers and practitioners have employed an extensive array of approaches to calibrate these models and have selected a wide range of parameters to calibrate and a broad range of acceptance criteria. A methodical, top-down approach to model calibration is outlined; it focuses the initial effort on a few key parameters that have the greatest impact on model performance and then proceeds to less critical parameters to finalize the calibration. A three-step calibration/validation process is recommended. First, the model is calibrated for capacity at the key bottlenecks in the system (the capacity calibration step). Second, the model is calibrated for traffic flows at nonbottleneck locations in the system (the route choice calibration step). Finally, the overall model performance is calibrated against field-measured system performance measures such as travel time and delay (the system performance calibration step). This three-step process is illustrated in an example application for a freeway/arterial corridor.
Systematic Approach for Validating Traffic Simulation Models
Authors: Ni Daiheng , Leonard John D. , Guin Angshuman , Williams Billy M.
Published: April 2007

Modeling processes and model testing processes are discussed as parts of the model life cycle, and the tasks of these processes and their relations are highlighted. Of particular interest is the model validation process, which ensures that the model closely simulates what the real system does. A collection of validation techniques is presented to facilitate a systematic check of model performance from various perspectives. Under the qualitative category, a few graphical techniques are presented to help a visual examination of the differences between the simulation and the observation. Under the quantitative category, several statistical measures are discussed to quantify the goodness of fit; to achieve a higher level of confidence about model performance, a simultaneous statistical inference technique is proposed that tests both model accuracy and precision. As an illustrative example, these validation techniques are comprehensively applied to test an enhanced macroscopic simulation model, KWaves, in a systematic manner.
Adaptive Calibration of Dynamic Speed-Density Relations for Online Network Traffic Estimation and Prediction Applications
Authors: Qin Xiao , Mahmassani Hani S.
Published: April 2007

A dynamic speed-density relation is identified by using a transfer function model. The model recognizes the time-lagged response of speed to density as well as autocorrelated system noise. A framework for the adaptive calibration of dynamic speed-density relations in the context of real-time dynamic traffic assignment-simulation operation is presented. The model and the approach are evaluated on the basis of actual sensor data from the Irvine, California, network. The results indicate that use of the transfer function approach in the context of real-time simulation is preferable to the use of conventional static traffic flow models.
Validation of Two-Fluid Model of Urban Traffic for Arterial Streets
Authors: Jones Elizabeth G. , Farhat Wahid
Published: April 2007

A series of vehicular traffic experiments conducted in Omaha, Nebraska, shows that the two-fluid model of urban traffic is valid not only at the network scale but also at the arterial street scale. The data collected support the validity of the two assumptions of the two-fluid model for traffic on arterial streets. The two-fluid parameters are effective in assessing the quality of traffic between different arterial streets, over time on the same arterial street, and on portions of an arterial street. The scalability of the two-fluid model also permits systemwide effects of localized changes to a traffic network to be assessed.
Statistical Validation of Traffic Simulation Models
Authors: Toledo Tomer , Koutsopoulos Haris N.
Published: April 2007

Traffic simulation models support detailed analysis of the dynamics of traffic phenomena and are important tools for analysis of transportation systems. In order to evaluate correctly the impact of different traffic management schemes, simulation models must be able to replicate reality adequately. Model validation (i.e., the process of checking to what extent the model replicates reality) is discussed. The role of validation is defined within the scope of model development and calibration, and the framework for performing the validation is discussed. A hierarchy of statistical methods to validate different types of simulation outputs against observed data is examined. Also, a validation method is proposed on the basis of statistical tests on metamodels fitted to the observed and simulated data. A case study illustrates the applicability of the various methods.
Highway Maintenance Outsourcing Experience: Synopsis of Washington State Department of Transportation's Review
Authors: Ribreau Nicole
Published: April 2007

Can outsourcing of traditional categories of state-provided highway maintenance produce savings in costs or improvements in service? While marketing materials and promotional press releases tout the attractions of outsourcing, insufficient attention has been paid to a growing body of follow-up information—much of it from official audit sources—of actual outsourcing experience. Presented are after-the-fact reviews of the performance of highway maintenance outsourcing from programs in five states and British Columbia. Cases noted include ones in which costs may have gone up instead of down, services deteriorated rather than improved, administrative and supervisory arrangements proved problematic, and contractor failures left states scrambling to provide services or caught in the distraction of litigation. Despite the range of experiences, common themes emerging from these reviews can be translated into lessons learned for state officials considering programs of this type. One clear lesson is the need for proper planning and scoping. Initial exploratory phases should include asset inventories, activity-based costs, and economic analyses based on before-and-after apples-to-apples cost comparisons. Risk-management reviews should consider litigation risks and costs. Managers should develop program exit strategies in addition to well-written contracts and specifications. Contracts should include clear performance expectations, evaluation schedules, and financial performance incentives or disincentives. Finally, an experienced management team must be in place to administer and evaluate contracts. These lessons can support more effective use of public resources, leading to wiser choices about whether outsourcing should be undertaken, and, if it is, what public management strategies and resource commitments will be necessary to make it successful. This research was undertaken in part to prepare for legislation in Washington State that would open new possibilities for competitive contracting.
Model to Analyze the Effectiveness of Highway Rest Area Performance
Authors: Jha Manoj K.
Published: April 2007

The number of highway travelers in the United States has significantly increased in the past decade. In light of this increase, proper maintenance of highway rest areas is very critical. This research examined the development of a rest area evaluation model that was created for the Maryland State Highway Administration (SHA) in response to its strategic plan for gauging rest area performance and allocating maintenance funds appropriately. To measure rest area performance, a customer-evaluation card was prepared for dissemination at Maryland's 14 rest areas. The card contained 14 questions, 13 of which had 5 grading options: A through D and N/A. In the 14th question, the rest area visitors were asked to provide written comments. SHA established as a strategic planning goal that a minimum of 80% of responses show a customer-satisfaction rating of B or above on each of the first 13 questions. The evaluated cards were routinely gathered and manually entered into a Microsoft Access database, which was then imported to a Microsoft Excel spreadsheet program for further evaluation. A number of array formulas were developed in Excel to automate the analyses. The model has been in place since 2000, and the data set has grown from over 1,000 initially in 2000 to over 6,000 as of July 2003. The model has been performing satisfactorily; however, manual entry of the data has been slow and error prone. Installation of touch screen information kiosks and increased sophistication in analyses were suggested as some future enhancement measures.
Performance Evaluation of Pavement Markings Under Dry, Wet, and Rainy Conditions in the Field
Authors: Aktan Fuat , Schnell Thomas
Published: April 2007

The nighttime visibility of three types of pavement markings—a largebeaded permanent pavement marking and two types of patterned pavement marking tapes, one with high-index beads and the other with mixed high-index beads—was evaluated under dry, wet (just after rainfall), and simulated rain conditions (ongoing 1-in./h rainfall). The dependent measures were pavement-marking end-detection distance and retroreflectance. The experiment was conducted at the 3M Transportation Research Center in Cottage Grove, Minnesota. This facility features a level and straight roadway section where 1-in./h rainfall can be simulated. Eighteen subjects between the ages of 55 and 75 participated in the study. The participants drove an experimental vehicle on dry and wet test sections with the pavement-marking treatments. Participants noted the earliest point at which they were able to see the end of the right edge line pavement markings. The retroreflectance of each pavement-marking material was also measured with three handheld retroreflectometers under the three weather conditions, according to ASTM E1710 (dry), ASTM E2177 (wet recovery), and ASTM E2176 (continuous wetting) standards. In terms of end-detection distances, the patterned tape with mixed high-index beads performed best under all three weather conditions. The paint and large-bead pavement markings were comparable to the tape with high-index beads under wet and rainy conditions. Under dry conditions, paint and large-bead pavement markings performed the worst. The detection distances seemed to strongly correlate with the standard retroreflectances only if the retroreflectance data from the corresponding test method are used.
Optimal Dynamic Speed-Limit Control for Highway Work Zone Operations
Authors: Kang Kyeong-Pyo , Chang Gang-Len , Zou Nan
Published: April 2007

Despite the well-recognized fact that proper control of traffic speed can contribute to both a reduction in accidents and improved efficiency of highway operations, most existing speed-control strategies implemented in Europe and the United States tend to aim only at improving traffic safety. An on-line algorithm for variable speed-limit control at highway work zones is presented that can take full advantage of its dynamic functions and concurrently achieve the objectives of throughput maximization and accident minimization.
Injury Severity and Total Harm in Truck-Involved Work Zone Crashes
Authors: Khattak Asad J. , Targa Felipe
Published: April 2007

Society pays a high cost for work zone crashes in terms of operational disruptions, property damage, injuries, and loss of life. Given narrow lanes in work zones, large trucks are of particular concern. Truck-involved collisions in work zones, as opposed to non-truck-involved collisions in North Carolina, are empirically examined. This examination helps in understanding which work zone attributes are empirically associated with the most seriously injured occupant and total harm in a crash. Specifically, with a unique data set, effects of the following variables were explored: type of work zone, presence of warning signs and cones, type of activity in the work zone, location of the crash in the work zone, and construction impact of the work zone on the roadway. The results show that work zone crashes in North Carolina, especially those involving large trucks, were more injurious than were non—work zone crashes. Rigorous modeling results suggest that truck-involved multivehicle crashes were most injurious and harmful when ( a) they occurred on two-way undivided or two-way divided but unprotected (without a median barrier) roadways; ( b) the roadway was closed and a detour was required on the opposite side; ( c) they occurred adjacent to the work area; and ( d) the posted speed limits were higher. The results provide valuable information on high-risk factors in work zones.
Why People Cross Where They Do: The Role of Street Environment
Authors: Chu Xuehao , Guttenplan Martin , Baltes Michael R.
Published: April 2007

The role of the street environment in the way people cross roads in urban settings is modeled. Respondents were placed in real traffic conditions at the curbside of street blocks in the Tampa Bay, Florida, area for 3-min observations of the street environments. Without crossing the blocks, respondents stated their crossing preference at each of six blocks. The origin and destination of each crossing were hypothetically set and varied across the blocks. So were the options available: two options for crossing at an intersection and up to four options for crossing at midblock locations. Within the framework of discrete choice models, the stated preferences are explained with the street environment, including traffic conditions, roadway characteristics, and signal-control characteristics. All three components of the street environment are considered: midblock locations, intersections, and roadside environment. The data are described; a nested logit model of pedestrian street-crossing behavior is estimated; and its implications to researchers and practitioners are discussed.
Pedestrian Scramble Signal in Chinatown Neighborhood of Oakland, California: An Evaluation
Authors: Bechtel Allyson K. , MacLeod Kara E. , Ragland David R.
Published: April 2007

In 2002 the city of Oakland, California, implemented a scramble signal at the intersection of 8th and Webster Streets. Scrambles are traffic signals that give pedestrians exclusive access to an intersection by stopping vehicular traffic on all approaches, allowing pedestrians to cross diagonally or conventionally. The primary objective of this evaluation was to determine whether the installation of the pedestrian scramble at this location increased pedestrian safety. An analysis was conducted of pedestrian-vehicle conflicts and pedestrian violations occurring at the intersection before and after the signal was modified, and pedestrians were surveyed to ascertain public attitude toward and comprehension of the change. The modification to scramble signal phasing at the intersection resulted in a statistically significant decrease in conflicts between pedestrians and vehicles and a statistically significant increase in pedestrian violations. In general, pedestrians understood the change in the way the intersection operated and were accepting of the change. These results suggest that the scramble has been effective overall in improving safety conditions at the site. The increased number of violations occurring despite decreased conflicts is in part due to a proportion of pedestrians who cross illegally on the "safe side" crosswalk (i.e., the crosswalk parallel to moving traffic in which there are no opportunities for conflicts). It is important that the scramble signal be monitored over time to quantify the extent to which reduced vehicle-pedestrian conflicts associated with the scramble translate into measurable reductions in pedestrian injuries and fatalities.
Using Arena for Simulation of Pedestrian Crossing in Roundabout Areas
Authors: Wan Baohong , Rouphail Nagui M.
Published: April 2007

The pedestrian crossing process in roundabout areas is modeled as a two-stage crossing demarked by a splitter island. A composite queuing system is used to describe the process. The system was simulated by using Arena, a general-purpose simulator chosen for its convenient flowchart modeling capability and vast built-in statistical analysis tools. The model outputs indicate that this composite model is able to provide basic insights into the pedestrian crossing process. Sensitivity analyses revealed that often-overlooked traffic parameters, such as the pedestrian holding space in the splitter island, could have significant impacts on pedestrian crossing performance and capacity.
Applying Microscopic Pedestrian Flow Simulation to Railway Station Design Evaluation in Lisbon, Portugal
Authors: Hoogendoorn Serge P. , Hauser Miklos , Rodrigues Nuno
Published: April 2007

The assessment of station designs by applying pedestrian flow simulation models is addressed. In particular, station design issues pertain to the way access gates will affect pedestrian flow operations in regard to levels of service, congestion levels, average walking times, delays incurred at gates, and so forth. Effects of different system layouts are studied, as well as the difference between different gate systems (low- and high-capacity systems), in regard to processing passenger flows. Finally, pedestrian flow operations in case of emergency situations are of interest. To examine those issues, pedestrian traffic operations for different station design alternatives are predicted with the dynamic microscopic pedestrian flow model NOMAD. That is done for reference situations (validation) as well as for design alternatives. The NOMAD model has been extended with a new module describing pedestrian operations (i.e., user-optimal gate choice) at the gates. It is found that the simple design guidelines used to set up the design alternatives provide a satisfactory level of service to transferring pedestrians and that the gates can be installed without compromising passenger safety. Nevertheless, the need to reroute, inefficient gate use, and interactions between conflicting pedestrian flows cause small but significant delays to transferring pedestrians that cannot have been predicted without the use of an adequate microsimulation model.
Hazard-Rating Scores for Prioritization of Accident-Prone Sections on Highways
Authors: Robert R Vivian , Veeraragavan A.
Published: April 2007

Various techniques are available for monitoring, improving, and assessing safety needs on the total road network. These techniques generally include procedures that look subjectively at the standards of road safety being achieved and maintained by road-controlling authorities over their total road networks. Accident reduction studies, audits of compliance with specific standards, and highway safety management strategies have been progressively developed during the past decade; although these contribute to the overall improvement of the provision of safety elements of the road network, a quantifiable technique to undertake an audit of the result has not been available. Road safety audits are concerned with the safety of all road users—motorists, pedestrians, and bicyclists—and are to be conducted for all projects, regardless of size or type. A comprehensive road safety audit was conducted on State Highway 17 in Karnataka in India, which links Bangalore and Mysore. On the basis of the road safety audit, an attempt was made to develop hazard - rating scores for a 23-km stretch of the highway. From the hazardrating scores, a hazard ratio was also derived; it gives an indication of the safety performance of individual kilometer sections with respect to the overall average. The hazard ratio can hence be used to prioritize the sections in the stretch for improvement to enhance the overall safety of the highway.
Trade-Offs Between Time, Cost, and Uncertainty by Commuters in Hyderabad, India: Stated Preference Survey Assessment
Authors: Gorham Roger , Kanchi Seshasai , Cowart Bill , Chari Raghava , Goel Viresh , Sachdeva Yash
Published: April 2007

In developing countries, air quality assessments that include the transportation sector have tended to focus predominantly on assessing technological solutions to problems associated with vehicle pollutant emissions, energy consumption, and greenhouse gases. This focus can be justified on the basis of the favorable cost-effectiveness, political acceptance, and ease of quantifying technological measures—at least in the short term—but unfortunately it often leads to the exclusion of demand-oriented measures. Further, air quality and pollution policy analysts often use assumptions of exogenously determined travel demand patterns, implicitly excluding many opportunities to look at policies oriented toward travel demand as an air pollution control strategy. The air quality impacts of policy measures to influence vehicle kilometers traveled and mode shares, such as bus rapid transit, are investigated. The approach involves developing coefficients with a stated preference (SP) survey that could be used to test policies with a conventional four-step urban transportation model. The main purpose of the SP survey in this study was to examine traveler tradeoffs among time, cost, and reliability (measured as uncertainty in vehicle departure time). Some different methods of measuring reliability were tested during the pilot phase of the survey, as were the actual range of parameter values to be tested. Models were estimated using traveler cohorts based on levels of vehicle ownership. In comparing vehicle owners (cars and two-wheelers) with nonowners, owners were found to be substantially more sensitive to time and reliability while nonowners were more sensitive to price. All groups showed notable sensitivity to reliability. Policy implications of these results are discussed, with a notable conclusion being that demand-oriented measures appear to be a fruitful area for further investigation as air pollution control strategies, even when technological measures show strong effectiveness.
Special Factor Adjustment Model Using Fuzzy-Neural Network in Traffic Prediction
Authors: Xiao Heng , Sun Hongyu , Ran Bin
Published: April 2007

The second part of the framework of a traffic prediction model proposed in a previous paper is presented. The model first eliminates the noise caused by random travel conditions by using a wavelet denoising method, the topic of the earlier paper. The model then quantitatively calculates the influence of special factors by using a fuzzy-neural network.
Development of TrafficXML: Prototype XML for Traffic Simulation
Authors: Ni Daiheng , Leonard John D.
Published: April 2007

With the wide adoption of XML as a standard means of data representation and exchange, more XML-aware applications and open resources are added to the library. It is therefore beneficial for the transportation community to develop an industrywide common language not only to leverage the open resources but also to ease external and internal communication. A prototype of XML-based language, TrafficXML, was developed for data representation in traffic simulation, and the prototype was formally defined in an XML schema. Discussions include the role of XML in traffic simulation, procedures for developing and applying the prototype, and issues of validation with an XML schema. As an illustrative example, the prototype was applied to KWaves, an enhanced macroscopic traffic simulation software built on Java and XML technologies.
Identifying Nearest Neighbors in a Large-Scale Incident Data Archive
Authors: Qi Y. , Smith Brian L.
Published: April 2007

Large-scale data archives compiled by transportation management systems capture a wide range of experience. However, to use this experience effectively, transportation professionals must be able to search these archives efficiently to identify cases of interest. An example of this challenge is to find past events that are similar to a current event to understand traffic flow and the impact of utilized control strategies. These similar events are referred to as nearest neighbors to the current event. To identify "near" neighbors in a data archive, a distance metric is required to measure similarity between cases. However, common distance metrics, such as Euclidean distance, are not valid when used with categorical variables, which commonly make up traffic event data. To address this challenge, this research effort developed a distance metric that can be effectively used with categorical data. The metric is based on the influence of variable values on a measurable objective meaningful to the purpose of selecting nearest neighbors. The metric was developed in a case study to identify similar past incidents in an archive to a current incident, with the objective of forecasting incident duration. When this method was incorporated in a nonparametric regression forecasting model, it was demonstrated to outperform parametric forecasting models significantly.
Using Geographically Weighted Regression Models to Estimate Annual Average Daily Traffic
Authors: Zhao Fang , Park Nokil
Published: April 2007

Annual average daily traffic (AADT) is important information for many transportation planning, design, operation, and maintenance activities and for funding allocation. Many studies have attempted AADT estimation by using various methods, such as the factor approach, regression analysis, and artificial neural networks. An application of geographically weighted regression (GWR) methods for estimating AADT is presented. GWR models allow model parameters to be estimated locally instead of globally, as in the case of ordinary linear regression (OLR) analysis. The spatial variation of the parameter estimates and the local R2 from the GWR models were investigated, and the AADT estimation errors were analyzed. Compared with OLR models, the GWR models were more accurate and were useful for studying the effects of the regressors at different locations.
Developing Location-Aware Navigation Guides That Use Mobile Geographic Information Systems
Authors: Huang Bo , Li Hongga
Published: April 2007

A prototype of a location-aware travel guide for pedestrians was designed and implemented with the aid of mobile geographical information systems. Unlike traditional paper maps, the digital travel guide offers a customized user interface and a location-specific travel service. Development was done on a desktop computer, and the essential files subsequently were transferred to a personal digital assistant for field trials. By using the Global Positioning System, the prototype can accurately pinpoint a user's location to a certain tolerance. This detection is performed at specific intervals, and a list of landmarks is furnished to the user through a Visual Basic script-based interactive graphical user interface. The user can obtain comprehensive information on surrounding buildings or sights, in both textual and digital image forms. A novel indexing method built on road segmentation was implemented to increase search efficiency. Experimental results show that this indexing method has made a significant improvement in system response over the exhaustive search method and thereby helps travelers to find the right way and enjoy their trips.
Data Retention and Access Regimes for Wireless Message Logs in the United States: Exploratory Analysis
Authors: Gifford Jonathan L. , Carlisle W. Homer
Published: April 2007

The application of intelligent transportation systems (ITS) solutions for government agencies in the United States raises special concerns about how information collected by new ITS-related systems will be used and maintained. In the United States, Freedom of Information Act laws require almost all government agencies to provide the general public with access to government records, including electronic records. Government agencies are also required by state and federal courts to provide access to their records. Consequently, as government agencies apply ITS solutions, they must examine issues related to data retention and access. The development of data access and retention was examined in the case of the Capital Wireless Integrated Network (CapWIN) project, a partnership of numerous government agencies and universities of the Washington, D.C., metropolitan region that is developing the first interjurisdictional, interagency integrated and scalable wireless transportation fleet and public safety communications network in the United States. Data retention and access issues for the CapWIN system are explored in a context designed to provide guidance for the future development of ITS services.
Heavy-Duty Truck Idling Characteristics: Results from a Nationwide Truck Survey
Authors: Lutsey Nicholas , Brodrick Christie-Joy , Sperling Daniel , Oglesby Carollyn
Published: April 2007

Heavy-duty truck engine idling results in significant costs, fuel consumption, emissions, noise, and engine maintenance. Two promising alternatives to idling, grid connection ("shore power") and onboard auxiliary power units (APUs), are being pursued by industry and government. Their attractiveness is uncertain, however, because of limited information about truck operations and driver behavior. A nationwide survey of long-haul truck drivers was conducted to characterize truck operations and driver behavior better. Key variables included usage rates for accessories, duration of idling, and engine speed at idle. It was found that long-haul truck engines idled for an average of 34% of total engine run time, roughly 1,700 h per truck annually. But these averages are deceptive. Approximately 10% of drivers reported idling 10% or less of engine run time, while another 10% reported idling more than 54% of engine run time, with differences related to season, truck ownership, company idling strategies, and driver experience. The mean annual fuel used during idle was estimated to be 1,600 gal per year, but the standard deviation was 1,300. An estimated 25% of drivers consumed more than 2,300 gal of fuel during idle (worth more than $3,000 per year in U.S. dollars), and 10% of drivers consumed more than 3,400 gal per year. These findings suggest that grid connections and APUs have the potential to provide large energy, environmental, and possibly even economic benefits.