bluuebunny/crossref_metadata_2025 huggingface dataset:
Speed Factors on Two-Lane Rural Highways in Free-Flow Conditions
Authors: Medina Alberto M. Figueroa , Tarko Andrew P.
Published: May 2018

The mean free-flow speed and its variability across drivers are considered important safety factors. Despite a large body of research on operating speeds, there is still much to learn about the factors of free-flow speeds, especially on tangent segments of two-lane rural highways. The roadway factors of speed dispersion across drivers are largely unknown. Also, the use of the entire free-flow speed distribution suggested by other authors has not yet been addressed. Consequently, the existing models are not aimed to evaluate the speed variability at a site. This paper presents free-flow speed models that identify factors of mean speed and speed dispersion on tangent segments and horizontal curves of two-lane rural highways. Ten highway variables, six of them functioning as both mean speed and speed dispersion factors, were identified as speed factors on tangent segments. Four highway and curve variables, two of them functioning as both mean speed and speed dispersion factors, were identified as speed factors on horizontal curves. The developed free-flow speed models have the same prediction capabilities as traditional ordinary-least-squares models developed for specific percentile speeds. The advantages of the developed models include predicting any user-specified percentile, involving more highway characteristics as speed factors than traditional regression models, and separating the impacts on mean speed from the impacts on speed dispersion.
New Concepts for Context-Based Design of Streets and Highways
Authors: Garrick Norman W. , Wang Jianhong (Jane)
Published: May 2018

Street and highway designers are increasingly being challenged to develop context-based design solutions that support the development of places that are more livable or that are compatible with meeting goals for sustainable development. However, conventional design standards have not yet caught up to this new design paradigm and so do not fully support the needs of designers working in this new environment. The evaluation of the AASHTO-based approach to design in this paper shows the two main areas of concern that must be addressed in developing a more coherent and context-based approach to design. Specifically, the issues of ( a) how to define context better and ( b) how to design for appropriate operations (including speed) need to be addressed. In addition, there is a clear need for a comprehensive and coherent design framework that ties together the urban (or place) function and the mobility function of streets and highways and that takes into account the full context for the design, including multimodal accommodation and full integration into the context.
Preliminary Assessment of Lower Landing Minima Capabilities in the Small Aircraft Transportation System Program
Authors: Xu Yue , Trani Antonio A. , Baik Hojong
Published: May 2018

A preliminary assessment is presented of the required lower landing minima (LLM) capabilities needed to support the Small Aircraft Transportation System (SATS) Program. The goal of this analysis is to understand the number of potentially challenged SATS airports and to identify methods to remove obstacles by using technology solutions. Four obstacle removal methods are considered to assess the challenges faced by the SATS Program in providing LLM capabilities to 3,416 U.S. airports. Two views of runway obstacle analysis are presented: a critical object analysis and a detailed multiobject analysis that includes terrain information. A comparison is made between decision altitudes (DAs) derived by approach lighting infrastructure and glide path angle thresholds and DA values considering other airport characteristics such as terrain. A detailed case study is presented to compare the single critical object analysis with the more detailed multiobject analysis, which was performed for Blacksburg Airport, in Virginia.
Modeling Service Trade-Offs in Air Itinerary Choices
Authors: Adler Thomas , Falzarano C. Stacey , Spitz Gregory
Published: May 2018

The application of a mixed logit approach using stated-preference survey data to the development of itinerary choice models is described. The models include the effects on itinerary choices of airline, airport, aircraft type, fare, access time, flight time, scheduled arrival time, and on-time performance. The empirical results demonstrate the importance of explicitly accounting for traveler preference heterogeneities by using segmentation by trip purpose, interaction effects involving frequent flier status, and random parameter specifications. Explicitly including preference heterogeneity by using the mixed logit specification results in significant statistical improvements and important coefficient differences as compared with using a standard fixed-parameter logit model. The calculated marginal rates of substitution show the relative importance that travelers assign to key service variations among itineraries. All service features that were included in the model had significant values to travelers, and the values were affected, as would be expected, by the traveler's frequent flier status. Although current reservation and ticketing services provide information to prospective travelers on most of these itinerary features, most services do not report on-time performance, which, however, can be an important selection criterion for travelers.
Enterprisewide Spatial Data Integration of Legacy Systems for Asset Management
Authors: Hall James P. , Robinson Rob , Paulis Mary Ann
Published: May 2018

This paper describes the spatial information system infrastructure implemented by the Illinois Department of Transportation (IDOT) to enable delivery of information to management decision makers in asset management applications. This spatial data warehouse infrastructure makes extensive use of geographic information system (GIS) technologies to integrate information from a variety of database structures and formats. GIS products and tools have been developed to portray and analyze these data in useful combinations focused on practitioner needs. In June 1999 the Governmental Accounting Standards Board issued Statement 34 requiring governments to have a systematic approach to managing their assets. As a result, transportation agencies have placed an increased emphasis on developing mechanisms to integrate information from disparate management information systems and legacy databases. IDOT has used GIS to develop a spatial data warehouse to enable integration. A valuable characteristic of the department's information systems infrastructure is the embedding of the underlying link–node structure into roadway inventory databases to enable the direct linkage of data through various system identifiers, including differing milepost referencing and project numbering schemes. This direct linkage enables the complex integration of asset management–related data files across the enterprise and provides access to historical asset information. Changes to route referencing systems are readily accommodated, without loss of integrative capabilities. Outputs include a variety of user-developed analyses and output products with accessibility through networks, intranets, and the Internet.
Assessing Issues, Technologies, and Data Needs to Meet Traffic Input Requirements by Mechanistic–Empirical Pavement Design Guide
Authors: Li Shuo , Nantung Tommy , Jiang Yi
Published: May 2018

As part of the implementation initiatives undertaken by the Indiana Department of Transportation Research Division, this paper presents the effort made to identify potential issues arising from traffic data processing and to assess technologies and data needs to meet the requirements of traffic design inputs in the Mechanistic–Empirical Pavement Design Guide. Global Positioning Systems (GPSs) and geographical information system (GIS) technologies were proposed to manage weigh-in-motion (WIM) and automatic vehicle classification site information and manipulate the traffic design input database. Computer programs were developed to process the raw data ASCII files generated from a WIM vendor's software. A platform was developed to combine GPS coordinates, GIS base maps, data processing programs, and the traffic database into an integral unit. Three WIM sites were selected for trial study. It was demonstrated that, with this platform, the WIM sites and database can be accessed visually and more efficiently. In addition, the computer programs can save significant data processing time. Other issues, such as the possible effect of unclassified vehicle count, were identified. On the basis of findings from the implementation initiatives, necessary efforts and future implementation activities are outlined.
Evaluating Factors Affecting Safety at Highway–Railway Grade Crossings
Authors: Park Young-Jin , Saccomanno Frank F.
Published: May 2018

Various countermeasures can be introduced to reduce collisions at highway–railway grade crossings. Existing improvements to crossings include the installation of flashing lights or gates, the addition of extra warning devices such as four-quadrant barriers or wayside horns, and the enforcement of speed limits on the approaching highway. Statistical models are needed to ensure that countermeasures introduced at a given crossing are both cost-effective and practicable. However, in large part because of issues of colinearity, poor statistical significance, and parametric bias, many existing statistical models are simple in structure and feature few statistically significant explanatory variables. Accordingly, they fail to reflect the full gamut of factor inputs that explain variation in collision frequency at individual crossings over a given period of time. Before statistical models can be used to investigate the cost-effectiveness of specific countermeasures, models must be developed that more fully reflect the complex relationships that link a specific countermeasure to collision occurrence. This study presents a sequential modeling approach based on data mining and statistical methods to estimate the main and interactive effects of introducing countermeasures at individual grade crossings. This paper makes use of Canadian inventory and collision data to illustrate the potential merits of the model in decision support.
Legibility Distances of Smaller Letters in Changeable Message Signs with Light-Emitting Diodes
Authors: Ullman Brooke R. , Ullman Gerald L. , Dudek Conrad L. , Ramirez Elizabeth A.
Published: May 2018

This paper presents the results of a legibility study of 9-in. and 10.6-in. letters on changeable message signs (CMSs) with light-emitting diodes. The study, conducted in Dallas, Texas, consisted of 60 subjects, demo-graphically balanced with respect to age, gender, and education. The subjects drove a test vehicle as they approached CMSs with one of the above letter heights. Study administrators recorded the distance from the sign at which the participant could correctly read a three-letter word. Data were recorded for three trials on each of the letter heights for each participant. Data were collected during daylight (sun overhead) and nighttime conditions. The 85th percentile legibility distance for the 9-in. letter height was 228 ft for daytime conditions and 114 ft for nighttime conditions. For the 10.6-in. letter height, the 85th percentile legibility distances were 324 ft for daytime conditions and 203 ft for nighttime conditions, respectively. The 85th percentile legibility distances for each letter height were used to estimate available viewing times under various approach speeds. These available viewing times dictate the units of information that can be presented on a CMS of a particular letter size.
Spacing Chevrons on Horizontal Curves
Authors: Rose Elisabeth R. , Carlson Paul J.
Published: May 2018

The chevron alignment sign is an important traffic control device used to warn drivers of the severity of a curve by delineating the alignment of the road around that curve. FHWA's Manual on Uniform Traffic Control Devices for Streets and Highways provides the following guidance on the spacing of chevrons around a curve: “The Chevron Alignment sign should be spaced such that the road user always has at least two in view, until the change in alignment eliminates the need for the signs” and “the Chevrons should be visible for a sufficient distance to provide the road user with adequate time to react to the change in alignment.” This guidance is broad to account for geometric design features and site obstructions such as steep vertical curvature or heavy vegetation. It also allows flexibility based on site characteristics and available funds, and the use of this verbiage creates a lower liability risk than there would be if a spacing chart were used. However, the broad wording allows for inconsistencies in the roadway system and provides little guidance for maintenance personnel. A field study was conducted to investigate the impacts of varying the number of chevrons in view around a curve. A spacing chart was then developed to simplify maintenance personnel's responsibility for choosing appropriate chevron spacing. The results of the field study indicated that having more than two chevrons in view around the curve provided a benefit in the form of a reduction in speed of about 3 mph at night. Smaller speed reductions were observed during daylight.
Measurement and Significance of the Coefficient of Thermal Expansion of Concrete in Rigid Pavement Design
Authors: Mallela Jagannath , Abbas Ala , Harman Tom , Rao Chetana , Liu Rongfang , Darter Michael I.
Published: May 2018

The coefficient of thermal expansion (CTE) is a fundamental property of concrete. It has long been known to have an effect on joint opening and closing in jointed plain concrete pavement, crack formation and opening and closing in continuously reinforced concrete pavement, and curling stresses and thermal deformations in both types of pavements. However, it has not been included as a variable either in materials specifications or in the structural design of concrete pavements. Hundreds of cores were taken from Long-Term Pavement Performance sections throughout the United States and were tested by FHWA's Turner–Fairbank Highway Research Center laboratory, using the AASHTO TP 60 test procedure. The CTE values were then assimilated into groups on the basis of aggregate types, and the mean and range of CTE were calculated. These results were then used in the new mechanistic–empirical pavement design guide to determine the significance of the measured range of CTE on concrete pavement performance. The CTE of the concrete was found to vary widely, depending on the predominant aggregate type used in the concrete. Sensitivity analysis showed CTE to have a significant effect on slab cracking and, to a lesser degree, on joint faulting. Its overall effect on smoothness was also significant. Given that CTE has not been used before in routine pavement structural design, the conclusion is that this design input is too sensitive to be ignored and must be fully considered in specifications and in the design process to reduce the risk of excessive cracking, faulting, and loss of smoothness.
Predicting Asphalt Pavement Temperature with a Three-Dimensional Finite Element Method
Authors: Minhoto Manuel J. C. , Pais Jorge C. , Pereira Paulo A. A. , Picado-Santos Luis G.
Published: May 2018

A three-dimensional (3D) finite element (FE) model was developed to calculate the temperature of a pavement located in northeast Portugal. A case study was developed to validate the model. Input data to the model were the hourly values for solar radiation and temperature and mean daily values of wind speed obtained from a meteorological station. The thermal response of a multilayered pavement structure was modeled with a transient thermal analysis for 4 months (December 2003 to April 2004), and the analysis was initiated with the full-depth constant initial temperature obtained from field measurements. During these 4 months, the pavement temperature was measured at a new pavement section, located in IP4 main road, near Bragança, in northern Portugal. At this location, seven thermocouples were installed in the asphalt concrete layers at seven different depths. These pavement data were used to validate this simulation model by a comparison of model calculated data with measured pavement temperatures. The 3D FE analysis proved to be an interesting tool to simulate the transient behavior of asphalt concrete pavements. The suggested simulation model can predict the pavement temperature at different levels of bituminous layers with good accuracy.
Quantification of the Joint Effect of Wheel Load and Tire Inflation Pressure on Pavement Response
Authors: Prozzi Jorge A. , Luo Rong
Published: May 2018

Most pavement design and analysis procedures predict performance on the basis of expected pavement damage under traffic loads expected during design life. Some failure criteria are primarily dependent on wheel loads and almost independent of contact stresses. Others are primarily dependent on normal and shear stresses, not on load magnitude. Wheel load is used as a proxy for tire pressure to account for the effect of contact stresses indirectly. In most pavement design methods, tire–pavement contact stress is assumed to be equal to tire inflation pressure and to be uniformly distributed over a circular area. A methodology that explicitly accounts for the effect of tire inflation pressures and the corresponding contact stresses on pavement response is not available. In this research, pavement responses of typical pavement structures under the combined actions of variable wheel loads and tire pressures were evaluated. A multilayer, linear–elastic computer program was used to estimate three critical pavement responses: longitudinal and transverse tensile strains in asphalt and compressive strains in the subgrade. The differences of the strains estimated by the two models were statistically analyzed to quantify the effect of the assumption of uniform stress over a circular shape. The traditional model proved to be reliable to estimate compressive strains in the subgrade layer. The tensile strains in the asphalt layer under actual contact stress, however, were quite different from those under uniform constant stress. Contrary to initial expectation, for the general case, the assumption of uniform stresses is a conservative approach.
Travel Demand Modeling for Regional Visioning and Scenario Analysis
Authors: Marshall Norm , Grady Brian
Published: May 2018

Regional visioning and scenario analysis projects are becoming an increasingly important focus in the modeling of regional travel demand. This report summarizes model enhancements that have proved useful in these types of projects from experience in the regions of Baltimore, Maryland; Chicago, Illinois; and Austin, Texas. The enhancements focus on key goals in regional visioning and scenario analysis projects, including increasing sensitivity to microscale effects on land use, that affect a response by choice riders to high-quality transit service and that account for induced travel from increased roadway capacity.
Investigating the Sensitivity of Optimal Network Safety Needs to Key Safety Management Inputs
Authors: Lamptey Godfrey , Labi Samuel , Sinha Kumares C.
Published: May 2018

This paper uses optimization methodologies and project-level cost and effectiveness data to assess long-term safety needs for a network. The optimal solution specifies values of decision variables (locations, years, and safety improvement types) such that overall cost-effectiveness at the network level is maximized under budgetary constraints. The paper evaluates the impact of alternative levels of safety funding on systemwide crash reduction and investigates the sensitivity of optimal funding levels to key safety management inputs. To demonstrate the methodology, data from Indiana's state highway system are used. It is shown that increases in overall safety funding have an increasing effect on crash reduction, but such increasing benefit tapers off after a certain point. It was determined that over a 10–year period (2005 to 2015) the optimal annual average safety need for the network is approximately $450 per mile. Furthermore, it is shown that the overall network safety funding need is sensitive to the method for identifying hazardous locations and the criterion for economic evaluation. The results show that with currently available data it is possible for highway agencies to incorporate road safety proactively into their transportation planning processes in a comprehensive and systemwide context. Also, agencies can use the methodology to determine optimal safety funding levels on their networks for possible comparison with current levels.
Developing Operational and Safety Guidelines for School Sites in Texas
Authors: Cooner Scott A.
Published: May 2018

The objective of a two-year study was to recommend school site planning guidelines for transportation-related elements such as site selection, general site requirements and design, bus operations, parent drop-off and pickup zones, driveways, turn lanes, signing and marking, parking, and pedestrian and bicycle access. The research team based these guidelines on a comprehensive review of existing guidelines and the results of field studies at school sites in Texas. Examples are provided of good practices and of practices to avoid for three of the more prominent guidelines. The guidelines are focused on transportation design, operations, and safety within school sites—with a particular focus on the parent drop-off and pickup zones. A site plan review checklist based on the 21 consensus guidelines approved by the project advisory panel is provided. Texas Department of Transportation engineers, field crews, architects, and school district personnel can use this checklist to coordinate efforts and improve the safety and efficiency of school site access and traffic flow.
Bus or Car?
Authors: Rhoulac Tori D.
Published: May 2018

School-related traffic congestion causes increased commuter travel times in many communities because of high volumes of passenger cars on school campuses that often queue onto adjacent streets. To change modal choices and behaviors ultimately to prompt a decrease in this recurring congestion, research was done to gain a better understanding of the student, household, and trip attributes and behaviors that influence school transportation mode choice for students living beyond walking distance of school. When home-to-school distances make nonmotorized modes infeasible, families typically must choose between the automobile and the school bus for travel to and from school. School transportation mode choice models were developed to estimate morning and afternoon modal split between these two modes for a North Carolina school district. The factors that exhibited statistical significance in estimating mode choice for kindergarten to eighth-grade students included the total number of students in those grades living in a household, student grade, household income, and subjective variables that attempted to quantity the convenience of each modal alternative and parents’ perceptions of modal safety. Two models were developed because the variables related differently to morning and afternoon school trip mode choice. In comparison with traditional mode choice models, the school transportation mode choice models developed as part of this research exhibit several similarities as well as distinct differences. Household income, for example, was found to be inversely proportional to the probability that a student will travel by automobile for morning or afternoon school trips.
Evaluation of Emergency Evacuation Strategies for Downtown Event Traffic Using a Dynamic Network Model
Authors: Kwon Eil , Pitt Sonia
Published: May 2018

This research studied the feasibility of applying a dynamic traffic assignment model, Dynasmart-P, to evaluate the effectiveness of alternative strategies for evacuating the traffic in downtown Minneapolis, Minnesota, under a hypothetical emergency situation that included the evacuation of a sellout crowd in the Metrodome. For this study, the southwest portion of the Twin Cities metro area was selected as the study network, and a set of different network configurations was evaluated for effectiveness in coping with a given emergency situation. The simulation results indicate that managing traffic conditions at the outbound freeway links in the given network during the evacuation period and the access capacity from the downtown area to those outbound freeway links are the critical factors affecting the effectiveness of evacuation operations. For example, the evacuation time under the contraflow operations with the freeways surrounding the downtown area was substantially reduced when the capacities of the key entrance ramps were also increased.
Safety Implications of Multiday Driving Schedules for Truck Drivers
Authors: Park Sang-Woo , Mukherjee Aviroop , Gross Frank , Jovanis Paul P.
Published: May 2018

The detailed analysis of preexisting crash and noncrash data representing an estimated 16 million vehicle miles of travel has revealed strong consistency between crash analysis using data from the 1980s and field experiments conducted in the 1990s. Time of day of driving is associated with crash risk: night and early morning driving has elevated risk in the range of 20% to 70% compared with daytime driving. Overall, 16 of 27 night and early morning driving schedules had elevated risk. Irregular schedules with primarily night and early morning driving had relative risk increases of 30% to 80%. In addition, there remains a persistent finding of increased crash risk associated with hours driving, with risk increases of 30% to more than 80% compared with the first hour of driving. These increases are less than previously reported and are of similar magnitude to the risk increases caused by multiday schedules. Finally, there is some evidence, although it is far from persuasive, that risk increases may be associated with significant off-duty time, in some cases in the range of 24 to 48 h. The implication is that “restart” programs should be approached with caution. Areas for additional research include further studies of crash risk associated with extended off-duty time, closer examination of irregular schedules that better reflect truckload operations, and analysis of irregular schedules with primarily daytime driving (largely nonexistent in this data set) to further explore the effect of variability.
Pilot Test of Fatigue Management Technologies
Authors: Dinges David F. , Maislin Greg , Brewster Rebecca M. , Krueger Gerald P. , Carroll Robert J.
Published: May 2018

This study involved over-the-road testing of four fatigue management technologies (FMTs) in trucking operations in Canada and the United States. Technologies bundled into a single intervention came from four fatigue management domains: one providing objective information on driver sleep need, one providing objective information on driver drowsiness, one providing objective information on lane tracking performance, and one reducing the work involved in controlling vehicle stability while driving. The objective was to determine driver reactions to such technologies and whether FMT feedback would improve alertness, especially during night driving, or increase sleep time on workdays or nonworkdays. A within-subjects crossover design was used to compare the effects of FMT feedback to no feedback. Each driver underwent the conditions in the same order: 2 weeks of no feedback (control) followed by 2 weeks of FMT feedback (intervention). Data from the devices and other driving performance variables were recorded every second of truck operation for 28 days for each driver, with a resulting 8.7 million data records among the 38 drivers. Support was found for FMT effects. During night driving, FMT feedback significantly reduced driver drowsiness (p = 0.004) and lane tracking variability (p = 0.007). However, there was evidence from probed psychomotor vigilance task testing that these improvements may have had cost because of the effort (in attention and compensatory behaviors) required to respond to information from the devices. In general, participants agreed that commercial drivers would benefit from FMT and were more positive about those involving vehicle monitoring than those involving driver monitoring.
Toll Pricing and Heterogeneous Users
Authors: Mahmassani Hani S. , Zhou Xuesong , Lu Chung-Cheng
Published: May 2018

This paper presents both exact and approximation algorithms for finding extreme efficient time-dependent shortest paths for use with dynamic traffic assignment applications to networks with variable toll pricing and heterogeneous users (with different value of time preferences). A parametric least-generalized cost path algorithm is presented to determine a complete set of extreme efficient time-dependent paths that simultaneously consider travel time and cost criteria. However, exact procedures may not be practical for large networks. For this reason, approximation schemes are devised and tested. Based on the concept of ε-efficiency in multiobjective shortest path problems, a binary search framework is developed to find a set of extreme efficient paths that minimize expected approximation error, with the use of the underlying value of time distribution. Both exact and approximation schemes (along with variants) are tested on three actual traffic networks. The experimental results indicate that the computation time and the size of the solution set are jointly determined by several key parameters such as the number of time intervals and the number of nodes in the network. The results also suggest that the proposed approximation scheme is computationally efficient for large-scale bi-objective time-dependent shortest path applications while maintaining satisfactory solution quality.
Analysis of Route Choice Decisions by Long-Haul Truck Drivers
Authors: Knorring John H. , He Rong , Kornhauser Alain L.
Published: May 2018

This study has done an empirical analysis of long-haul truck drivers’ route choice decision making as they navigate the U.S. highway network. The most important factor that has been analyzed is how long-haul truck drivers trade off between distance and time when faced with multiple routes. From information gathered from a revealed preference data set consisting of about 250,000 trucks over a 13-day period, a logistic model was constructed to describe route choice behavior when truck drivers are faced with alternate routes. The logistic model predicted the percentage of trucks that used the bypass route as a function of the perceived speed on the downtown route. The results of this study show that time is a significant factor in the decision-making process.
Real-Time Estimation of Origin–Destination Matrices with Partial Trajectories from Electronic Toll Collection Tag Data
Authors: Kwon Jaimyoung , Varaiya Pravin
Published: May 2018

The origin–destination (O-D) matrix of a traffic network is usually estimated from link traffic counts combined with a sample survey. Partially observed vehicle trajectories obtained with vehicle reidentification or automatic vehicle identification techniques such as electronic tags provide a new data source for real-time O-D matrix estimation. However, because of incomplete sampling, accurate estimation of O-D matrices from these data is not trivial. A statistical model was developed for such data, and an unbiased estimator of the O-D matrix was derived based on the method of moments. With further exploitation of the sound statistical model, the bootstrap standard error estimate of the O-D matrix estimator was also developed. The algorithm can be computed quickly and performs well under simulation compared with simpler estimators. Applied to data from vehicles with electronic toll collection tags in the San Francisco Bay Area, the algorithm produces a realistic time series of the hourly O-D matrix. The relationship of the proposed estimator with similar methods in the literature was also studied and extension of the methods to general, more complex networks is discussed.
Adjustable Preference Path Strategies for Use in Multicriteria, Stochastic, and Time-Varying Transportation Networks
Authors: Opasanon Sathaporn , Miller-Hooks Elise
Published: May 2018

In this paper, an exact algorithm is proposed for determining adjustable preference path strategies in multicriteria, stochastic, and time-varying (MSTV) networks. In MSTV networks, multiple arc attributes are associated with each arc, each being a time-varying random variable. Solution paths that seek to minimize the expected value of each of multiple criteria are sought from all origins to a specified destination for all departure times in a period of interest. These solution strategies allow a traveler to update a preference for which criterion of multiple criteria is of greatest importance and then adaptively select the best path for the selected criterion at each node in response to knowledge of experienced travel times on the arcs. Such adjustable preference path strategies are particularly useful for providing real-time path-finding assistance.
Strategies for Online Inventory Routing Problem under Real-Time Information
Authors: Giesen Ricardo , Mahmassani Hani S. , Jaillet Patrick
Published: May 2018

The inventory routing problem (IRP) under real-time information studied in this paper involves repeated delivery of products from a depot to a set of retailers that face stochastic demands over a long period. This system is controlled by a central decision maker who operates with real-time information about the complete state of the system. To address this online IRP under real-time information, rolling horizon approaches are proposed: plans are updated and solve a mixed integer programming formulation for the off-line version of the problem. In this mixed integer programming formulation, an incremental inventory cost (IIC) function is introduced to combine inventory and transportation costs in the same objective function. This IIC function takes into account additional inventory costs associated with serving a customer at a different time and refilling an amount different from that prescribed by the best inventory policy with fixed transportation costs. Three rolling horizon strategies for the real-time version are compared. These policies are based on repeated reoptimization of different instances of the offline IRP and differ in the number of steps that are implemented for current solutions and the events that trigger plan updates. These policies are compared with a benchmark policy of operating the system in a decentralized manner. The comparison is conducted with a general simulation framework. New replanning policies are shown to outperform systematically the benchmark policy under all scenarios considered.
Transit Network Optimization
Authors: Zhao Fang , Ubaka Ike , Gan Albert
Published: May 2018

This paper presents a mathematical methodology for transit route network optimization. The goal is to provide an effective computational tool for optimization of a large-scale transit route network. The objectives are to minimize transfers and maximize service coverage. Formulation of the method consists of three parts: representation of transit route network solution search spaces, representation of transit route and network constraints, and a stochastic search scheme capable of finding the expected global optimal result on the basis of an integrated simulated annealing, tabu, and greedy search algorithm. The methodology has been tested with published solutions to benchmark problems and applied to a large-scale realistic network optimization problem in Miami–Dade County, Florida.
Regional Transportation's Consensus Building between Local and Tribal Governments in New Mexico
Authors: Espinosa Judith M. , Valencia DeAnza , Jensen Michael , White Mary E.
Published: May 2018

Despite the area's notable heterogeneity, the North Central Regional Transit District (NCRTD) is the first regional transit district (RTD) certified in New Mexico. The NCRTD contains the state's largest and smallest pueblos, the poorest and richest counties, and rural communities steeped in 500-year-old Spanish traditions near the New Age cosmopolitanism of Santa Fe. The diverse geographical, political, and economic landscape of the NCRTD can make it difficult to pursue new or ambitious projects across the disparate jurisdictions. Organizational and jurisdictional barriers can create roadblocks to effective collaboration. The New Mexico Department of Transportation Research Bureau provided funds to develop a case study and model that could be followed by other potential RTDs in the state. As the organizing and research entity, the Alliance for Transportation Research Institute of the University of New Mexico was charged with developing the RTD model and staffing the effort. An organizing committee, representing public and private interests, was tasked with producing the certification documents and supporting materials, presenting them clearly and effectively to governing bodies and the public, and providing an example of crossjurisdictional transit collaboration. Creation of the NCRTD required public hearings in every jurisdiction. One-on-one “study sessions” raised public awareness in every jurisdiction and fueled the process for obtaining the needed affirmative votes to join the NCRTD. The NCRTD, composed of 10 initial members, has completed the necessary steps for creating an RTD and was certified by the New Mexico Transportation Commission in autumn 2004 as the first RTD in New Mexico.
Commuting Stress
Authors: Wener Richard , Evans Gary W. , Boately Pier
Published: May 2018

This study took advantage of a major improvement to the infrastructure of a commuter rail line to conduct a field study examining the effects of that change on commuter stress. The study used a multimethod approach, employing self- and significant other–report data, behavioral measures, and physiological measures of stress. Cross-sectional and longitudinal data were collected with a pretest–posttest design including both within- and between-group comparisons. The results on psychophysiological, self-report, and job strain measures revealed that those commuters using improved transit service showed reduced stress in the postchange period and those staying with the previous service remained constant. Commuters who switched to the new train service also experienced a reduced level of job strain after the implementation of the line. A subgroup of rail passengers with elevated sensitivity to commuting conditions were also uncovered. On both a behavioral index of motivation and perceived job strain, women who had children at home especially benefited from the intervention. Multimethodological evidence from a natural experiment indicates that transit infrastructure improvements not only increase efficiency but also enhance passenger well-being by reducing commuting stress.
Optimal Land Use–Transport Strategies
Authors: May Anthony D. , Shepherd Simon P. , Emberger Guenter , Ash Andrew , Zhang Xiaoyan , Paulley Neil
Published: May 2018

There has been growing interest in Europe in the development of integrated transport strategies, in which individual policy instruments are combined to complement one another and to achieve improved performance against a given set of policy objectives. This paper applies an optimization procedure to identify optimal strategies for packages of transport policy instruments without, and then with, constraints on finance and targets for global warming and safety. Some exploratory tests have also been carried out on land use strategies, and they are reported here in brief. Results demonstrate that the methodology is robust and can be applied with different transport models and with constraints applied both to policy instruments and to objectives. All optimal strategies found involved substantial reductions in fare levels throughout the study area. Where it was not possible to change fares, the strategies were substantially less effective when measured against the objectives. Most optimal strategies involved increases in public transport frequencies, although their scale varied between cities. All optimal strategies included peak-period cordon charges to enter the city center, though the optimal level varied between cities. Financially constrained strategies were found to involve smaller fare reductions and higher cordon charges; in some cases frequency increases were smaller. These constrained optima still performed well; the greatest reduction in benefit was only 15%. The net present value of the benefit generated was about €2,000M (€1 = $1.20 US, 2005) in Edinburgh and more than €4,000M in Leeds, United Kingdom. The impact of transport strategies on land use was small, and development constraints had to be used to reverse urban sprawl.
Approach of Environmental Justice to Evaluate the Equitable Distribution of a Transit Capital Improvement Program
Authors: Fruin Geoffrey , Sriraj P. S.
Published: May 2018

Environmental justice is a concept that is progressively gaining attention in the public policy arena. In its simplest form environmental justice is the notion that all populations should benefit equitably from investments financially supported by the public sector. Traditionally, public transit systems serve a diverse set of populations, and therefore equity is an important issue that transit agencies encounter. A methodology developed to evaluate equitable distribution of a transit capital improvement program is presented. Environmental justice neighborhoods are identified by demographic and economic data aggregated at the census-tract level. The neighborhoods are defined on the basis of previous equity studies and guidance materials produced by the federal government. With geographic information systems, perceived benefits of each capital project are mapped onto a layer of census tracts. Finally, the capital budget is allocated to various census tracts on the basis of spatial locations of perceived benefits each project will produce. Numerous tabular and spatial results can be generated from the methodology, such as funding ratios between environmental justice neighborhoods and non–environmental justice neighborhoods. Because of the long-term nature of capital investments, time series data should be collected and analyzed. This will allow for measuring the significance of funding ratio fluctuations in current-year programs. Ultimately, the methodology can become a decision-making aid to help transit agencies prioritize capital projects. Application of the methodology to the Chicago Transit Authority, in Chicago, Illinois, provides a context for the reader to understand the potential applications (planning- and service-related) in a better manner.
Use of Performance Measures for Surface Transportation in Different Institutional and Cultural Contexts
Authors: Meyer Michael D.
Published: May 2018

This paper examines the use of performance measures in three countries: Australia, Japan, and New Zealand. The organizational context for the use of performance measures, the identification of key performance measures, and observations on interesting aspects of the performance-based planning approach used are discussed for each case. Attention is given in particular to performance measures relating to safety, congestion, and freight movement. The paper concludes by noting common characteristics of each case, including the use of a common framework for performance measurement, the importance of collaboration among different agencies for performance categories that transcend one policy area, the use of performance measures at different levels of planning and decision making, the vertical integration of information flow in agencies, the distinction between outcomes and outputs, the importance of data collection capability and the use of information technologies, the importance of performance measurement as a means of providing greater accountability and visibility to the public, and the need for top management leadership and commitment in the development and use of a performance measurement scheme.
Optimal Control of Freeway Networks with Bottlenecks and Static Demand
Authors: Hegyi A. , De Schutter B. , Hellendoorn J.
Published: May 2018

Optimally coordinated freeway traffic control for networks containing bottlenecks with capacity drop and hysteresis behavior is considered. Because of the multitude of traffic jams and the spatial and temporal relationships between control actions and traffic behavior, this problem is not as straightforward as that for local control. The order in which the measures are applied may be relevant, or it may be possible that not all jams can be resolved. In that case the best possible locations of jams should be determined. An approach to address these problems is developed in which a generalized representation of flow-limiting control measures and bottlenecks is used. Whether a certain set of control measures is sufficient to improve network performance is determined. The approach also supplies the necessary sequence of control actions and the necessary relocation of traffic jams to achieve the network state corresponding to the best achievable performance.
Optimizing Traffic Signal Timing through Network Decomposition
Authors: Lieberman Edward , Chang Jinil
Published: May 2018

A signal control system named Real-Time/Internal Metering Policy to Optimize Signal Timing (RT/IMPOST) has been under development for several years. It is designed to compute signal timing plans for the entire range of operating conditions from under- to oversaturation for control systems ranging from first generation (GEN 1) to highly responsive advanced traffic management systems. The different flow regimes of urban traffic control are reviewed. Then the focus is on the treatment to develop cycle-based signal timing plans for inclusion in the data libraries referenced by GEN 1 real-time traffic control systems for the undersaturated-flow regime. This approach decomposes a grid network into its constituent arterial subsystems in a way that is responsive to user-specified priorities. The user may define and rank the arterial systems subsumed within a grid network so as to satisfy strategic objectives responsive to traffic demand patterns and local needs. The procedure computes optimal signal timing plans for all these arterial subsystems in a priority-ranked sequence and integrates these arterial-based timing plans to form a networkwide signal timing plan. Field and simulation test results are presented. The field tests confirm that the IMPOST timing plans improved the operational performance of traffic along an arterial system in New York State relative to a fine-tuned existing control. The simulation studies compared the performance of traffic responding to IMPOST signal timing plans with that responding to Synchro 6.0 signal timing plans. The benefits of network decomposition and of arterial priority ranking are also documented.
Using Hardware-in-the-Loop Simulation to Evaluate Signal Control Strategies for Transit Signal Priority
Authors: Byrne Neil , Koonce Peter , Bertini Robert L. , Pangilinan Chris , Lasky Matt
Published: May 2018

The City of Portland, in collaboration with TriMet (Portland's regional transit service provider) and the Oregon Department of Transportation, has implemented transit signal priority (TSP) at more than 240 intersections on seven transit routes as a part of the Streamline program. This study focuses on the simulation of one intersection in Portland by using hardware-in-the-loop simulation to examine the effects of TSP signal control strategies on transit performance. More specifically, near- and farside bus stops are studied with hardware-in-the-loop traffic simulation to determine the effect of stop location on the effectiveness of the Portland TSP system. This analysis is verified by using a deterministic spreadsheet model to determine the effectiveness of the system and to address whether a green time extension plan should be used if there is passenger activity at a nearside stop.