bluuebunny/crossref_metadata_2025 huggingface dataset:
Flexural Behavior and Design with High-Strength Bars and Bars without a Well-Defined Yield Point
Authors: Shahrooz Bahram M. , Reis Jonathan M. , Wells Elizabeth L. (Ward) , Miller Richard , Harries Kent A. , Russell Henry G.
Published: December 2010

An ongoing project, NCHRP Project 12–77, was formed to evaluate and prepare appropriate revisions to the AASHTO load and resistance factor (LRFD) bridge design specifications and the AASHTO LRFD bridge construction specifications in reference to high-strength reinforcement as well as to other types of steel not having a well-defined yield plateau. Analytical and experimental studies are being conducted to identify and overcome deficiencies in the existing knowledge base. The focus of this study is on behavior and design of flexural members reinforced with high-strength reinforcement (ASTM A1035), as well as other types of steel without well-defined yield plateaus. Analytical formulations and experimental testing of full-scale beams are reported. For members with most commonly encountered amounts of longitudinal reinforcement ratio, flexural capacity can be established by using well-established strain compatibility analysis procedures in which the steel stress–strain behavior is idealized as being elastic–perfectly plastic, with the yield point taken as the stress at strain equal to 0.0035 or 0.005. For beams with reinforcement ratios larger than 3% and concrete strength exceeding 69 MPa (10 ksi), the use of stress corresponding to strain equal to 0.0035 is conservative and recommended. For high-strength reinforcement, the current strain limits of 0.002 and 0.005 should be changed to 0.004 and 0.008, respectively, for tension-controlled and compression-controlled members. Beams reinforced with high-strength ASTM A1035 bars exhibit adequate ductility and do not suggest any unexpected response characteristics.
Bridge Structural Health–Monitoring System Using Statistical Control Chart Analysis
Authors: Lu Ping , Phares Brent M. , Greimann Lowell , Wipf Terry J.
Published: December 2010

Technological advancements in sensing, computing, and networking have facilitated the application of long-term structural health-monitoring (SHM) and made it a more widely accepted tool to improve bridge management. A fiber-optic strain-based SHM system developed in cooperation with the Iowa Department of Transportation is described; the system continuously monitors bridge performance under ambient traffic loads to detect damage. Although this SHM system has broad potential application to numerous types of structural deterioration or damage, the system is presented here by using a case study associated with fatigue cracking in the web gap region. The described SHM system autonomously collects, reduces, and analyzes strain data and determines the damage occurrence in a near-real-time fashion. In this system, statistical control chart analysis is applied over the strategically defined damage indicator to determine the damage mathematically. Data preprocessing strategies were also studied to limit the impact of major non-structural factors causing strain variations. The effectiveness of the system was demonstrated with field-collected predamage data and synthetic postdamage data. Experimental research is being conducted to validate the system at the field-testing level.
Field Testing and Performance Evaluation of a Through-Plate Girder Railway Bridge
Authors: Chotickai Piya , Kanchanalai Torkul
Published: December 2010

The performance and behavioral characteristics of an old through-plate girder railway bridge are presented. Strain gauge instrumentation was used to monitor structural responses under current operating conditions. Loading spectra of crossing trains were measured with a train weighing system and used as applied loads in subsequent finite element models. The experimental and analytical results indicated that the stress responses of the bridge structure were controlled mainly by axle loads and axle spacings. A certain degree of continuity was observed at the stringer-to-floor-beam connections. Consequently, the typical assumption of simple shear connection could give unrealistic estimates of stress responses in the stringers. The structural responses in floor beams and plate girders were, however, less sensitive to the degree of continuity at the connections. On the basis of Miner's hypothesis, the fatigue damage accumulation and the equivalent number of stress cycles in main bridge members were evaluated. Although freight trains had greater axle loads, the fatigue damage was dominated by passenger trains because of their large number of stress cycles. The equivalent number of cycles per train crossing was found to be considerably less than the value provided in the Manual for Railway Engineering of the American Railway Engineering and Maintenance-of-Way Association. The findings provided favorable information for the performance and fatigue evaluations. The structure was shown to have an adequate capacity for current operating conditions. In addition, use of the research results would provide a more accurate estimate of the fatigue life.
In-Service Shear and Moment Girder Distribution Factors in Simple-Span Prestressed Concrete Girder Bridge
Authors: Idriss Rola L. , Liang Zhiyong
Published: December 2010

An optical fiber monitoring system was designed and built into the I-25 bridge at the Dona Ana exit in Las Cruces, New Mexico. The bridge is a simple-span, high-performance prestressed concrete girder bridge. The girders are six BT-63 high-performance-concrete girders with a span length of 112.5 ft (34.2 m). Fiber Bragg grating optical fiber deformation sensors along with thermocouples were embedded in the girders during fabrication. Sensors were installed along the top and bottom flanges and at midspan and quarter spans. Pairs of crossed sensors in a rosette configuration were embedded in the webs at the supports. The bridge was monitored for 2 years, from transfer of the prestressing force through service. The sensor data were analyzed to evaluate shear and moment girder distribution factors, in situ material properties, pre-stress losses, camber, dynamic load allowance, and bridge performance under traffic loads. This study focuses on the lateral load distribution in the bridge. Shear and moment girder distribution factors are obtained from a finite element model, sensor measurements under a live load test, as well as regular traffic loading and compared with the values specified by the AASHTO standard specifications (2002) and the AASHTO load and resistance factor design specifications (2007).
Seismic Design and Analysis of Buried Structures with CANDE-2007
Authors: Katona Michael G.
Published: December 2010

A method is presented to analyze and evaluate buried culverts and cut-and-cover tunnels for seismic loading in addition to standard static loading from dead and live loads. With CANDE-2007, a plane–strain finite element program, the soil–structure problem is characterized by a cross-sectional slice through the structure and surrounding soil envelope. First, the static design loads are applied with a series of incremental load steps. Next, the seismic loading condition is simulated by specifying quasi-static displacements at the peripheral boundaries of the soil envelope to produce a shear-racking distortion equivalent to the maximum free-field seismic shear strain from the design earthquake. The proposed method is based on two recently completed NCHRP projects and is presented here in detail. An initial linear-elastic study investigates two basic culvert shapes, circular and rectangular, wherein moment and thrust distributions from CANDE-2007 are shown to compare favorably with closed-form solutions. A second study investigates a nonlinear reinforced concrete box culvert installation under the combination of static and seismic loading. Plots of moment, thrust, and shear distributions show how and where the seismic loading alters the response of static loading, including the effect on safety factors for steel yielding, concrete crushing, and shear failure. It is concluded that the proposed seismic method is rational, easy to apply, and fulfills an engineering need heretofore unfulfilled. The procedure applies to any culvert shape, size, and material, and the safety of the culvert installation may be assessed by working either stress or load and resistance factor design.
Effect of Bedding Thickness on Behavior of Rigid Pipes as Determined by Using Numerical Crack Modeling
Authors: Motahari Ardavan , Abolmaali Ali
Published: December 2010

Numerical analyses are performed to find the loading capacity of buried reinforced concrete pipes at different performance levels. Different geometrical and material parameters play an important role in the total behavior of the pipe system. The effects of bedding thickness, middle-bedding compaction level, steel cages, and pipe thickness are studied by using dynamic nonlinear analysis capable of modeling the complex cracking behavior of the concrete pipes. Contact elements are used for modeling the actual contact behavior between the pipe's surface and its surrounding soil. The Drucker–Prager plasticity model and the isotropic hardening plasticity model were used for soil and steel materials, respectively. Two structural performance levels are defined for pipes, the first one being the instance in which the crack initiates in the pipe's surface. The second-higher performance level is defined as the time in which the crack opens. The results of the study show that increasing the bedding thickness has a significant effect on the loading capacity of the system. This increase in capacity is more dominant for smaller-diameter pipes. Providing middle beddings with lower levels of compaction can also be effective in increasing the loading capacity of the pipes.
Modeling Impedance Effects of Left Turners from Major Streets with Shared Short Lanes at Two-Way Stop-Controlled Intersections
Authors: Wu Ning , Brilon Werner
Published: December 2010

At two-way stop-controlled intersections without exclusive turning lanes on major streets, all three movements (right turn, through, and left turn) must share a lane. The Highway Capacity Manual (HCM) provides a special formula to deal with this lane configuration. However, this formula cannot consider short lanes such as left-turn pockets on major streets. This paper presents a new model that accounts for shared short lanes and thus delivers more realistic results for estimating the impedance effect of left turners. The new model can also deal with the effect of the so-called back-of-queue in reality. The presented theoretical concept can be extended to include the consequences of a short left-turn pocket on major streets and the corresponding capacities of the major streets with shared short lanes. Equations are derived for calculating the influence of the length of the left-turn pocket on the capacity of minor-street movements and on the probability of blockage to the through movement resulting from queued left-turn vehicles. Comprehensive simulation studies are conducted to confirm the derivation, and a general formula that considers both the short lane and back-of-queue is recommended for further applications. This formula will be incorporated into the upcoming edition of HCM.
Modified Critical Movement Analysis Approach for Signalized Intersections
Authors: Prassas Elena S. , Roess Roger P.
Published: December 2010

In the preparation of the fourth edition of the textbook Traffic Engineering, a modified critical movement analysis methodology for signalized intersections was developed. The methodology was developed for consistency with signal timing approaches and to allow a simplified way to do a quick, manual analysis of a signalized intersection. This paper presents this methodology and reports on a comprehensive analysis of its results as compared with those resulting from application of the 2000 Highway Capacity Manual (HCM) methodology as it is implemented in the highway capacity software package. For a wide range of situations, the critical movement analysis provides reasonable estimates of delay and level of service compared with the more complex HCM 2000 approach. This critical movement analysis methodology provides analysts with a more straightforward approach and the ability to either conduct or check an analysis manually, and it can be used as a replacement for the quick estimation method of Chapter 10 of the HCM 2000.
Urban Street Performance
Authors: Deshpande Rahul , Gartner Nathan H. , Zarrillo Marguerite L.
Published: December 2010

Effective design and evaluation procedures are essential in optimizing the performance of urban arterial streets. Current procedures rely on Highway Capacity Manual (HCM) tools for performance evaluation. Determination of level of service (LOS) on urban streets is based on urban street classification and average travel speed on the arterial. Average travel speed is computed from length of street segments and running times, which include control delay of through movements at signalized intersections. Studies have shown the inadequacies of the existing HCM procedure to take into account effects of coordination or lack of it. This paper introduces new approaches for improved quantification of the quality of progression by using the previously developed cyclic coordination function in conjunction with the HCM procedure. This enables determination of LOS on an urban street in a more systematic and accurate manner. Alternative LOS procedures for signalized urban street systems are presented. Both one-way and two-way street configurations are considered.
Estimating Sustained Service Rates at Signalized Intersections with Short Left-Turn Pockets
Authors: Reynolds William L. , Zhou Xuesong , Rouphail Nagui M. , Li Mingxin
Published: December 2010

A computational approach for incorporating the effects of short left-turn pockets on sustained service rates in a mesoscopic modeling environment is presented. Mesoscopic models, intended to handle fairly large networks while maintaining individual vehicle identity, provide a detailed yet efficient alternative to estimate sustained service rates. However, mesoscopic models typically ignore midlink perturbations and queuing, thus limiting their reliability in the presence of short left-turn pockets at signalized intersections. The model presented here relies on a gating mechanism situated at the entry point to the left-turn pocket. Through a series of logical triggers, the gating mechanism allows for the formation of a (vertical) queue of vehicles upstream of the pocket when arrivals exceed storage capacity. The method satisfies all assumed requirements for integrating the effects of short left-turn bays, which include pocket spillback, pocket starvation, and sensitivity to signal timing and phase sequence. The approach has been implemented within the mesoscopic modeling platform DYNASMART for both single and multiple left-turn pockets, with the use of varying pocket lengths and demand volumes. The resulting sustained service rates favorably compare to those generated by a representative microsimulation model (VISSIM). Further comparisons of the proposed approach against empirical observations are planned.
Estimating Performance on Two-Lane Highways
Authors: Al-Kaisy Ahmed , Freedman Zachary
Published: December 2010

This study presents an empirical investigation into the use of a new measure, percent impeded, for estimating performance on two-lane highways. Percent impeded is a point estimate of the percentage of vehicles that are impeded by slower vehicles in the traffic stream due to platooning, a common phenomenon on two-lane, two-way highways. This point measure, by definition, is closest in concept to percent-time-spent-following, a spatial measure of performance on two-lane highways that is used in the current practice yet is impractical to measure in the field. Field data were collected from two two-lane highway study sites with passing lanes in the state of Montana. Performance was examined at a single location upstream and multiple locations downstream of the passing lane at each study site. As a reference, the analyses utilized some of the currently used or suggested performance measures on two-lane highways. Overall, the percent impeded patterns and trends were consistent with the mechanism of platoon break-up and formation in the vicinity of passing lanes, a concept that is well-documented in the literature. Further, study results suggest that percent impeded has more logical and consistent sensitivity to platooning variables compared with other performance measures investigated by this study.
Consistency of Stochastic Capacity Estimations
Authors: Geistefeldt Justin
Published: December 2010

The randomness of capacity is a well-known feature of freeway traffic flow. For the estimation of capacity distribution functions based on empirical traffic data, different methodologies were developed and applied. The consistency of these estimation methods for different types of capacity distributions is analyzed. A macroscopic simulation model is used to assess to what extent a given capacity distribution function can be reproduced with the estimation methods. It is found that consistent capacity estimations are obtained only by applying methods based on statistical models for censored data.
Categorizing Freeway Flow Conditions by Using Clustering Methods
Authors: Azimi Mehdi , Zhang Yunlong
Published: December 2010

Three pattern recognition methods were applied to classify freeway traffic flow conditions on the basis of flow characteristics. The methods are K-means, fuzzy C-means, and CLARA (clustering large applications), which fall into the category of unsupervised learning and require the least amount of knowledge about the data set. The classification results from the three clustering methods were compared with the Highway Capacity Manual (HCM) level-of-service criteria. Through this process, the best clustering method consistent with the HCM classification was identified. Clustering methods were then used to further categorize oversaturated flow conditions to supplement the HCM classification. The clustering results supported the HCM's density-based level-of-service criterion for uncongested flow. In addition, the methods provide a means of reasonably categorizing oversaturated flow conditions, which the HCM is currently unable to do.
Assessing the Benefits of Incident Management Systems
Authors: Hadi Mohammed , Xiao Yan , Zhan Chengjun , Gan Albert
Published: December 2010

Most studies that evaluate the benefits of incident management have used analytical techniques such as queuing and shock wave analyses to assess the impacts of incidents with and without incident management on delays and queues. These analytical methods have been applied to basic highway segments with no consideration of the facility configurations. In addition, the analyses in most cases assumed a constant typical capacity on these segments to represent the prevailing capacities without the use of Highway Capacity Manual (HCM) procedures. These studies also assumed that input parameters such as the reduction in capacity due to incidents and incident duration are deterministic rather than stochastic variables. This paper investigates estimating the benefits of incident management by combining HCM freeway analysis procedures, detailed data archives of intelligent transportation systems, and a consideration of the stochastic variations of key inputs to the analysis rather than the use of deterministic values. The results from this analysis methodology are compared to those obtained by using the simple deterministic queuing analysis procedure, which has been used extensively in past studies. The analysis reveals that the HCM procedures produce similar results as queuing analysis for simple basic freeway facilities. The results for more complex cases indicate that queuing analysis produces lower incident delays relative to the HCM procedures because it does not model the interactions between segments of different types and geometries. Higher delay reductions resulting from incident management are estimated for one-lane blockage incidents with the use of stochastic incident attributes compared to the use of deterministic incident attributes.
Control Delay at Signalized Diamond Interchanges considering Internal Queue Spillback
Authors: Xu Hao , Liu Hongchao , Tian Zong
Published: December 2010

Control delay is the primary measure for determination of the level of service of signalized intersections. The existing analytical delay models usually work well for isolated intersections, but are not as effective when applied to diamond interchanges. The limited storage space between the two closely spaced intersections of a diamond interchange may cause queue spillback from the internal link to the outside roads. This property would give rise to unrealistic delay calculations for diamond interchanges with high traffic volumes. This paper describes the development of a new analytical delay model that takes into account the effects of internal queue spillback at diamond interchanges. Simulation studies are conducted to compare the effectiveness of the proposed approach with existing methods. The study shows that for low-overlap time conditions, the proposed model tends to agree with the Synchro and VisSim simulations and is better than Elefteriadou's method, which tends to overpredict delay. For high overlaps, the Elefteriadou method, VisSim simulation, and the proposed model tend to agree, while Synchro diverges significantly by overestimating delay. The study contributes to the literature and practice by providing an open-source analytical model that can either be used as a stand-alone delay calculation model or as a supplement to the existing methods.
Dynamic Wide-Area Congestion and Incident Monitoring Using Probe Data
Authors: Lund Andrew S. , Pack Michael L.
Published: December 2010

Traffic congestion and overall performance monitoring of roadways continues to be a major initiative of departments of transportation and planning boards nationwide. Information from traffic monitoring programs has direct relevance to both analysts and the general public. Traditional data analysis tools and methods in this area fail to connect congestion data with incident and event data and thus make the task of determining the causes of congestion difficult in many cases. As more traffic data are collected, the need for tools that can facilitate effective visualization of this data, both archived and real time, is becoming increasingly apparent. The proposed congestion and incident scanner tool is a web-based application that affords dynamic and interactive analysis of traffic congestion conditions. The tool provides an intuitive, minimalistic interface for generating congestion performance visualizations for specific date ranges and locations. These visualizations improve on existing tools by allowing users to interact with and manipulate the visualizations to better highlight specific areas of interest. The integration of incident and traffic event data with visualization allows users to easily correlate congestion abnormalities with possible causes as well as evaluate the full effects of events, such as roadwork and major incidents, on traffic conditions.
Governance of Metropolitan Planning Organizations
Authors: Bond Alexander , Kramer Jeff
Published: December 2010

Federal law requires metropolitan planning organizations (MPOs) to be governed by a board composed of local elected officials, modal authorities, and appropriate state officials. Other than this simple requirement, federal law is silent on board size, composition, voting rights of members, and advisory committees to the board. This paper summarizes results from a survey of 133 MPOs about these topics. The results show that board structures vary widely and are crafted to accommodate the intergovernmental politics of their regions. The results found that the average MPO board had 16.1 voting members and 3.1 nonvoting members. Further, 27% of MPOs had at least one seat that rotated among a group of eligible seat holders. Only 13% of MPOs had a weighted voting scheme in place. Other results discussed include nonvoting board membership types, meeting frequency, and the existence of advisory boards. Information on these topics will help MPOs compare themselves with their peers and understand the breadth of options available to them during periods of organizational change.
Development of a Microsimulation Analysis Tool for Paratransit Patron Accessibility in Small and Medium Communities
Authors: LaMondia Jeffrey J. , Bhat Chandra R.
Published: December 2010

Paratransit is a critical form of transportation for mobility-impaired, low-income, and small and medium-sized communities. Paratransit systems face many challenges that restrict how well they can serve their communities, including limited funding, aging fleets, limited to no service standard assessments, and few practical modeling and planning practices. This paper discusses a transferable paratransit microsimulation analysis tool for patron accessibility designed to address these challenges. The tool calculates paratransit patron accessibility (defined as paratransit patrons’ perceived ease of access to reach desired activities and destinations) by simulating and measuring daily paratransit patron travel patterns on the basis of service fleet and region information. The tool further allows providers to evaluate patron accessibility for any combination of population groups, travel purposes, and times of day. Transit providers can use the tool to determine how well paratransit patrons are served and the most efficient ways to improve service. The microsimulation framework, including the system of simulation models, the supporting data, and application to Brownsville, Texas, are described in detail.
Improving Shuttle Ridership Using Intelligent Transportation System Technologies
Authors: Ye Zhirui , Albert Steve , Eidswick Jaime , Law Susan
Published: December 2010

In Arizona, the Grand Canyon National Park's south rim experiences severe traffic and parking congestion during the summer. To alleviate the issues, a free pilot shuttle route was operated between the gateway community of Tusayan and the park's information plaza during the 2008 summer season. During the pilot program, a traveler information system consisting of a portable dynamic message sign and highway advisory radio was implemented along Route 64 with the intent to increase shuttle ridership. The objective of this study is to evaluate the impact of the intelligent transportation system on shuttle ridership. Data were collected during the pilot program, before and after the implementation of this system. Different analysis methods including multiple linear regression, backpropagation neural network, and support vector regression were applied for analysis. The results found that the support vector regression method performed best in modeling shuttle ridership and associated explanatory variables (traffic volume and system deployment). The results from support vector regression suggested that the traveler information system increased shuttle ridership by 30%, which was consistent with the results from visitor surveys that were completed at the same time as this study. The study showed that the system was effective in shifting visitors from passenger cars to free shuttle buses.
Incorporating Uncertainty into Transportation Decision Making
Authors: Jeon Christy Mihyeon
Published: December 2010

Incorporating uncertainty into transportation decision making has become a more important activity as evidenced by the popularity of scenario-based approaches in the regional transportation planning process. Particularly in decision making to promote sustainability, uncertainty and risk factors can be important elements because they can influence which alternative is perceived as the most desirable depending on a wide range of parameters. The objective of the study is to demonstrate how some of these uncertainties can be incorporated when a multiple-criteria decision-making method is used to choose the most desirable among competing alternatives. Using data from the Atlanta, Georgia, metropolitan region, this paper examines the sensitivity of the relative desirability of competing transportation and land use plans to changes in regional priorities and weights for sustainability parameters. Throughout the study, sensitivity analysis is used as a tool to incorporate the variability in criteria weights and concurrent variation in the sustainability evaluation results and final decision. These exercises could help decision makers determine how changing the emphasis on different regional priorities could most effectively result in desired regional outcomes.
Five Years of Experience with the ConnectOregon Multimodal Funding Program
Authors: Baker Teddie A. , Bufalino Michael E. , Ford Mark L. , Kale Steven R.
Published: December 2010

The Oregon legislature in 2005 authorized $100 million in state lottery bond revenues to be used for investments in aviation, marine, rail, and transit improvements. The revenues were to be placed in a newly established multimodal transportation fund, which was part of what became known as the ConnectOregon program. The legislature provided another $100 million for ConnectOregon in 2007 and a third round of $100 million in 2009. For the $200 million available through the first two phases of ConnectOregon, public and private sector applicants submitted 181 requests for funding. Of these, the Oregon Transportation Commission selected 73 for funding. By February 28, 2010, 36 projects had been completed, and most of the others were under construction or in design. This paper is intended to help inform other states considering a collaborative approach to multimodal transportation funding programs. The paper ( a) provides an overview of ConnectOregon legislation and administration; ( b) summarizes procedures for submitting, reviewing, evaluating, and prioritizing ConnectOregon applications and for making final funding recommendations; ( c) compares applications submitted and funded by region and mode; and ( d) discusses participant feedback and lessons learned.
Measuring Public Outreach
Authors: Terabe Shintaro , Kin Toshihiro
Published: December 2010

In the infrastructure planning process, the effective communication of information through media strategies is important in ensuring that the public is aware of and understands various infrastructure projects. To assess what media strategy is effective in involving the public, the information audience rate (IAR) was developed. This index shows the number of citizens who receive information released from government or planning authorities. Although the concept is the same as measuring the audience rate of television programs, IAR is a new and useful way to simultaneously evaluate several mass media sources. It is also applicable in planning a media strategy for different population groups. This case study, estimating the IAR of the Tokyo metropolitan area, illustrates how one group of suburban residents differs from another group–in this case, central business district (CBD) commuters and noncommuters. These groups represent two lifestyles: the CBD commuters tend to spend only nights and weekends in the suburbs. Of the 10 media considered, television and national newspaper columns had the highest IAR. The local newspaper column was effective for noncommuters, while the Internet and advertising posters in trains were effective for CBD commuters. Circulars and city bulletins were effective for both groups.
Measuring and Assessing Perceptions of Success in a Transit Agency's Stakeholder Involvement Program
Authors: Mattingly Meghan , Sriraj P. S. , Welch Eric W. , Bhojraj Barbara (Basia)
Published: December 2010

Stakeholder involvement is often a legally required activity for transit agencies. Optimally this process begins at the earliest stages of any given project and involves two-way communication and interaction that can be reflected in the resulting plans or project designs. Despite federal statutes and regulations mandating meaningful public input for federal capital funding consideration, approaches to fulfill these mandates successfully remain difficult, and stakeholder involvement practices often fail to have a deep impact on planning outcomes. A gap often exists between implementation plans and the satisfaction of stakeholders. Guided by prior research and applying cognitive mapping methods, this study uses a rail line reconstruction project of the Chicago Transit Authority in Illinois as a case study to systematically understand the gap in expectations and interpretations of success among stakeholders. Findings identify four important categories of goal nonalignment that act as barriers to optimal interaction that can lead to mistrust. Conclusions identify potential solutions for bridging the gaps.
Accessibility-Based Multicriteria Analysis for Facility Siting
Authors: Tong Daoqin , Lin Wei-Hua , Mack James , Mueller Davita
Published: December 2010

Maximizing accessibility is often an important consideration in the location of a facility. This paper describes the development of a planning procedure based on a geographic information system (GIS) to assist decision makers in site selection when various accessibility criteria are considered. The procedure is illustrated in the context of siting a new women's and children's community center in Tucson, Arizona. First, suitable sites are identified as candidates on the basis of constraints related to transportation, land use, zoning, and so forth. Then a GIS-based decision support system is designed to assess the optimality of the candidate sites on the basis of accessibility by different population groups modeled, with the use of a multiobjective mathematical programming approach. Although this analysis focuses on a single facility, the methodology discussed, including the use of visual assessment tools and the development of the optimization model, can be used for multiple site selection and easily extended to other applications in which accessibility is a key component.
Residential Property Values and the Built Environment
Authors: Diao Mi , Ferreira Joseph
Published: December 2010

By taking advantage of two recent data sets with exceptional spatial detail, this research is a comprehensive and spatially disaggregate study of the relationship between the built environment and residential property values in the Boston, Massachusetts, metropolitan area. The study computes 27 built environment variables at a 250 m × 250 m grid cell level, uses factor analysis to extract five built environment factors to mitigate multicollinearity, and integrates built environment factors into hedonic price models. Spatial regression techniques are applied to correct spatial autocorrelation. Residential property values are found to be positively associated with accessibility to transit and jobs, connectivity, and walkability and negatively related to auto dominance. Built environment effects depend on neighborhood characteristics.
Can Transit-Oriented Development Reduce Peak-Hour Congestion?
Authors: Zhang Ming
Published: December 2010

This paper presents a study of whether transit-oriented development (TOD) helps reduce peak-hour congestion, a topic of ongoing public debate. Applying conventional four-step travel demand modeling techniques, the study simulates traffic outcomes in three TOD scenarios in the Austin, Texas, area, where a commuter rail line is under construction and TOD proposals are being developed. With TOD, the portion of congested roadway in the Austin region is estimated to decrease by nearly 770 lane miles. Daily vehicle miles traveled (VMT) are reduced by 10 to 12 million in the region, or by 3.5 to 4.5 person miles traveled (PMT) per person. This magnitude of congestion relief for peak-hour commuting indicates a potentially significant amount of savings in highway investments through TOD practice. No major modal shifts from driving to transit or non-motorized modes occur in the TOD scenario. Still, PMT for transit is estimated to grow significantly. TOD's role as a congestion relief strategy largely lies in the concentrated development that shortens average trip length and hence generates less VMT and PMT than low-density sprawl. The study results also reveal challenges facing TOD practice: the non-TOD area benefits more than the TOD area, although TOD improves congestion regionwide. Traffic conditions in the TOD area may actually worsen due to the TOD-based concentration of people and jobs. Promoting walking or biking to minimize local driving is thus critical for TOD to succeed.
Random Coefficient Mixed Logit Models Based on Generalized Antithetic Halton Draws and Double Base Shuffling
Authors: Sidharthan Raghuprasad , Srinivasan Karthik K.
Published: December 2010

Mixed logit models based on quasi-random draws are increasingly being used in discrete choice analysis because of their flexibility. Currently used mixed logit models are too expensive, and their performance degrades with increasing dimensionality. To overcome those shortcomings, two new simple and practical techniques are proposed, namely, quasi Monte Carlo (QMC) with generalized antithetic draws and the double base shuffling method (QMC with generalized antithetic draws and double base shuffling). In a comparison of the performance on probability evaluation, the proposed methods are found to be statistically superior (more accurate and precise) to conventional Halton draws for various dimensions. Results show that proposed methods, unlike conventional Halton draws, are less susceptible to dimensional deterioration even at higher dimensions. Computational experiments with real and synthetic data sets also reveal that the proposed methods are significantly faster for simulated estimation of mixed logit models (at higher dimensions) than other benchmark models [standard Halton, modified Latin hypercube sampling (MLHS), and shuffled Halton draws] to achieve similar accuracy levels. For the real data, the proposed method is 2.1 times faster than conventional QMC for 15 dimensions. The speedup of the proposed methods with synthetic data sets of 15 and 30 dimensions is even greater. The speedup ratio of the proposed methods is 3.3 to 3.4 with respect to conventional Halton draws, and the factor ranges from 2 to 3.2 with respect to MLHS and shuffled Halton draws. Thus, the proposed QMC methods offer promise for the development of richer and more flexible discrete choice models in large dimensional choice contexts.
Travel Time Forecasting and Dynamic Origin-Destination Estimation for Freeways Based on Bluetooth Traffic Monitoring
Authors: Barcelö Jaume , Montero Lidin , Marqués Laura , Carmona Carlos
Published: December 2010

Traditional technologies, such as inductive loop detectors, do not usually produce measurements of the quality required by real-time applications. Therefore, one wonders what could be expected from newer information and communication technologies, such as automatic vehicle location, license plate recognition, and detection of mobile devices. The main objectives of this paper are to explore the quality of the data produced by Bluetooth detection of mobile devices that equip vehicles for travel time forecasting and its use in estimating time-dependent origin-destination matrices. Ad hoc procedures based on Kalman filtering have been designed and implemented successfully, and the numerical results of the computational experiments are presented and discussed.
Supernetwork Approach for Multimodal and Multiactivity Travel Planning
Authors: Liao Feixiong , Arentze Theo , Timmermans Harry
Published: December 2010

Multimodal and multiactivity travel planning is a practical but thorny problem in transportation research. This paper develops an improved supernetwork model to address this problem. The supernetwork is constructed mainly in three steps: a personalized network is first split into two types of networks with all links mode-specified; these are then assigned to all possible activity-vehicle states by means of state spreading from the beginning activity state. Finally, these discrete networks are connected into a supernetwork by state-labeled transition links. The proposed supernetwork is easier to construct than previous proposals and reduces the size needed to embody all combinations of choice facets explicitly. It can be proved for any activity program that any tour is a feasible solution in this representation. Consequently, every transport and transition link can be defined mode and activity-state dependent; thus standard shortest path algorithms can be used to find the most desirable tour. A case study is presented to show that the supernetwork model can be applied in a real-time manner for practical travel planning.
Comparison of Agent-Based Transit Assignment Procedure with Conventional Approaches
Authors: Wang Joshua , Wahba Mohamed , Miller Eric J.
Published: December 2010

The public transportation system, a key part of a multimodal transportation network, has been widely viewed as an efficient way to reduce road congestion and pollution. Public transportation planners use transit assignment models to forecast travel demand and service performance. As technologies evolve and smart transit systems become more prevalent, it is important that assignment models adapt to new policies, such as traveler information provision. This paper investigates three transit assignment tools that represent three approaches to modeling transit trip distribution over a network of fixed routes. These tools are the EMME/2 Transit Assignment Module (Module 5.35), commonly used by planners; Toronto, Canada, Transit Commission's transit assignment tool, MADITUC; and the newly developed Microsimulation Learning-based Approach to Transit Assignment (MILATRAS). These approaches range from aggregate, strategy-based frameworks to fully disaggregate microscopic platforms. MILATRAS presents a stochastic process approach (i.e., nonequilibrium based) for modeling within-day and day-to-day variations in the transit assignment process in which aggregate travel patterns can be extracted from individual choices. Although MILATRAS presents a different standpoint for analysis in comparison with equilibrium-based models, it still gives the steady state run loads. MILATRAS performs comparatively well with EMME/2 and MADITUC. In addition, MILATRAS presents a policy-sensitive platform for modeling the effects of smart transit system policies and technologies on passengers’ travel behavior (i.e., trip choices) and transit service performance.
Validation and Forecasts in Models Estimated from Multiday Travel Survey
Authors: Cherchi Elisabetta , Cirillo Cinzia
Published: December 2010

Multiday travel surveys (also known as panel data) have recently assumed high relevance in travel behavior analysis and activity-based modeling. Basically two types of multiday data have been collected: cross-sectional data repeated at separate points in time and data gathered over a continuous period of time. So far, the studies using panel data have focused on the estimation of demand models; little is known about the application and validation of models estimated on repeated measurements. Even the definition of the holdout sample is not obvious in panel data sets. This paper studies issues related to model validation and forecasting of continuous data sets. With both simulated and real data, empirical evidence is provided on the effects that different patterns of correlation have on model forecast and policy analysis. Results show that the way holdout samples are extracted affects the validation results and that the best results are obtained when a percentage of individuals with all of their observations are used. The logit model in the presence of taste heterogeneity could produce biased modal shifts, while failing to account for correlation across observations, did not seem to produce relevant effects on policy analysis. The real case study, estimated by using a 6-week travel diary (MobiDrive), confirms only in part the analysis on simulated data. Results also confirm that in panel data, a model with a better fit might provide a worse validation and forecast.
Calibrating Activity-Based Models with External Origin-Destination Information
Authors: Cools Mario , Moons Elke , Wets Geert
Published: December 2010

Many practitioners question the advantages of activity-based models over conventional four-step models in regard to replication of traffic counts. This paper highlights a framework that actively links travel demand models in general and activity-based models in particular with traffic counts. Two approaches are presented that calibrate activity-based models with traffic count–an indirect and a direct approach. The indirect approach tries to incorporate findings based on the analysis of traffic counts into the components of the activity-based models. The direct approach calibrates the parameters of the travel demand model in such a way that the model replicates the observed traffic counts (quasi-) perfectly. A practical example is provided to illustrate the direct approach. The study area for this practical example is Hasselt, Belgium, a city of about 70,000 residents, and its surrounding municipalities. The practical examples revealed not a single roadway to success in calibrating activity-based models, but different options exist in fine-tuning the activity-based model. It is important to recognize some open issues and avenues for further research. First, it is not always appropriate to assume that traffic counts are completely correct. Setting up some belief structure might increase the responsiveness of the activity-based model. In addition, the origin-destination matrix calibration that optimizes the correspondence between estimated and observed screen-line counts could negatively affect the correspondence to other measures, such as vehicle miles traveled. To conclude, the formulation of a multiobjective calibration method is a key challenge for further research.
Will it Work?
Authors: Giaimo Greg , Anderson Rebekah , Wargelin Laurie , Stopher Peter
Published: December 2010

The Greater Cincinnati Household Travel Survey (HTS) is a proof-of-concept study for replacing travel diaries with a large-scale multi-day Global Positioning System (GPS) survey. The objectives are to collect multiple-day data from more than 3,000 households with portable GPS devices and improve existing processing software to provide data that support modeling approaches in Ohio. No diaries are collected for household members younger than 12 years old. A subsample of follow-up prompted recall surveys allow respondents to review GPS interpreted travel information for verification. This paper, with data from the spring 2009 pilot, describes the survey process developed for this HTS. It documents that with an address-based sample frame, advance letters, and Internet and phone recruiting, a significant subsample of cell phone–only households can be recruited and surveyed with GPS; a representative sample of households can be recruited for a GPS-based survey, based on a comparison of pilot sample household characteristics with available Public Use Microdata Samples data; and response rates for difficult-to-reach households such as cell phone–only, lower income, and zero-vehicle households can be improved with a cash incentive ($25). The paper provides principles and describes the prompted recall survey developed to obtain additional data from a subset of respondents beyond the GPS recorded travel for improving imputation software.