bluuebunny/crossref_metadata_2025 huggingface dataset:
Redevelopment and Revitalization along Urban Arterials
Authors: Mejias Luis , Deakin Elizabeth
Published: May 2018

Urban arterials are both promising and problematic locations for infill development and urban revitalization. San Pablo Avenue, a multilane urban arterial traversing nine cities and two counties along the eastern shore of San Francisco Bay in California, is considered here. The road developed over a long period: first as a streetcar line, then as an intercity automobile route, and most recently as a subregional traffic and transit route. Land uses from each of these transportation eras are still present along the avenue and range from neighborhood retail to automobile-oriented strip development. Recent transit service improvements and a strong housing market are leading to new developer interest in San Pablo Avenue. Findings are reported from interviews with 11 developers who recently built infill housing and mixed-use projects on or near the arterial. Developers see San Pablo Avenue's accessibility as a major asset but view transit services as a bonus instead of a necessity; transit availability allows developers to argue for reduced transportation impact fees and reduced parking requirements. Other aspects of the arterial's design, including high speeds and unattractive streetscapes, are problematic, as are zoning ordinances that require high parking ratios, large setbacks, and lengthy, discretionary approval processes. Small land parcels, incompatible adjacent uses, and high development costs are also drawbacks but, with creative development, are manageable. Local governments could provide incentives for private development along arterials such as San Pablo Avenue by improving street designs, reducing parking requirements, and updating zoning codes and approval processes.
Transportation-Efficient Land Use Regulations and Their Application in the Puget Sound Region, Washington
Authors: Kavage Sarah E. , Moudon Anne Vernez , Mabry Jean E. , Pergakes Nicholas
Published: May 2018

This work evaluates how local land use regulations and development patterns support transportation efficiency in urban and suburban areas. An efficient transportation system includes multiple transportation modes and reduces the need to drive alone. The research sheds light on how long-term efforts to devise transportation-efficient land development regulations have shaped new development. Data include surveys of zoning and development regulations in 19 study areas of Puget Sound, Washington, and reviews of 163 projects with a building permit. Analyses focus on the frequency of use of transportation-efficient elements in land use regulations, the frequency of adherence to these elements in projects, and the connections between area regulations and development. Fifty elements classified into six categories of transportation-efficient land use serve to evaluate the characteristics of regulations and permitted projects in each study area. The research shows that local jurisdictions have adopted many transportation-efficient regulations, and many of the projects reviewed follow these regulations. Compact development stands out as a major strategy used successfully in area regulations and permitted projects. Pedestrian-oriented environment and street–sidewalk connectivity are used at the project level but less so in regulations. Parking elements are weakest at the regulatory and project levels. Washington State growth management approaches to land use appear to become integrated into local regulatory frameworks and to be followed through in the implementation and development process. Work is needed regionally to increase the use of transportation-efficient land use strategies, with particular attention to parking regulations.
Influence of Accessibility on Residential Location Choice
Authors: Zondag Barry , Pieters Marits
Published: May 2018

There has been substantial discussion among planners about the influence of transport in residential location choices. The purpose of this paper is to analyze the importance of accessibility in explaining residential location choices. The paper addresses this issue by presenting and analyzing findings from the literature and results of a housing market estimation study in the Netherlands. The research findings for the Netherlands illustrate that the transport system influences residential moves at three stages: in move–stay choice, estimation results show that households are less likely to move away from a more accessible location; travel time variables are significant for all household types, and therefore changes in the transport system will affect the size of the housing market and search area of the households; the model estimation results suggest that accessibility of a specific location for many household types is not a significant variable in their location choice. Overall, the empirical results suggest that the role of accessibility is significant but small compared with the effect of demographic factors, neighborhood amenities, and dwelling attributes in explaining residential location choices. The empirical findings are confirmed by findings in the literature; the present results are located at the lower end of findings reported in the literature. An important factor contributing to this result is that accessibility changes among regions in the Netherlands are rather small.
Spatial Econometric Models for Panel Data
Authors: Frazier Christopher , Kockelman Kara M.
Published: May 2018

Cities are constantly evolving, complex systems, and modeling them, both theoretically and empirically, is a complicated task. However, understanding the manner in which developed regions change over time and space can be important for transportation researchers and planners. In this paper, methodologies for modeling developed areas are presented, and spatial and temporal effects of the data are incorporated into the methodologies. The work emphasizes spatial relationships between various geographic, land use, and demographic variables that characterize fine zones across regions. It derives and combines land cover data for the Austin, Texas, region from a panel of satellite images and U.S. Census of Population data. Models for population, vehicle ownership, and developed, residential, and agricultural land cover are estimated; the effects of space and time on the models are shown to be statistically significant. Simulations of population and land cover for the year 2020 help to illustrate the strengths and limitations of the models.
Impacts of Comprehensive Planning and Smart Growth Initiatives on Transportation
Authors: Porter Christopher D. , ten Siethoff Brian , Smith Virginia
Published: May 2018

With the objective of achieving an array of transportation, environmental, fiscal, and social benefits, state and regional agencies are increasingly undertaking initiatives to promote local comprehensive planning as well as smart growth development patterns. Numerous metropolitan planning organizations and some state transportation agencies are looking to land use strategies to help limit the growth of vehicle travel, improve mobility and accessibility, and reduce infrastructure investment needs. Yet evidence on the transportation benefits of state and regional planning initiatives is limited. Five case studies were conducted of states and regions with a history of comprehensive planning initiatives directed toward smart growth objectives. Modeling studies, empirical research, and monitoring programs were reviewed to determine how these areas measure the performance of their policies and what findings have resulted. Models and empirical evidence suggest that land use strategies, if successfully implemented, can play a role in reducing vehicle travel and associated impacts. Implementation of state and regional policies in most areas, though, has been weak because of a limited ability to affect land use decisions at the local level. Furthermore, many areas’ initiatives are too recent to observe widespread changes to land use patterns or to measure the resulting impact on transportation conditions. Improved information systems are beginning to be deployed in some areas and should provide additional insights into the effects of state and regional planning initiatives.
Three Methods for Synthesizing Base-Year Built Form for Integrated Land Use–Transport Models
Authors: Abraham J. E. , Weidner T. , Gliebe J. , Willison C. , Hunt J. D.
Published: May 2018

Newer integrated land use–transport models require as a base-year input a representation of existing built form (building stock by type, age, density, and other variables). Available data on floor space inventory have been found to be both incomplete and inconsistent with employment and population data in three land use–transport modeling exercises in the United States: in Sacramento, California; in the state of Oregon; and in Oahu, Hawaii. This paper reports on three methods used to synthesize a built-form input at a detailed microlevel for these three models. Each method uses existing land cover data and reconciles them with population data, employment data, and data on the consumption of floor space by activity. All three approaches assign floor space quantities by type to a detailed microlevel (grid cell or parcel) inventory of land. The approaches differ in their algorithmic approach, motivations, and data requirements.
Estimation of Fleet Size for Variable Bus Schedules
Authors: Ceder Avishai (Avi)
Published: May 2018

A highly informative graphical technique addresses the problem of finding the lower bound of the number of buses required to service a given timetable of trips. The technique is based on a step function that has been applied over the past 20 years as an optimization tool for minimizing the number of vehicles in a fixed trip schedule. The step function is called deficit function (DF), for it represents the deficit number of vehicles required at a particular terminal in a multiterminal transit system. The initial lower bound on the fleet size with deadheading (DH) (empty) trip insertions was found to be the maximum of the sum of all DFs. An improved lower bound was established later; it was based on extending each trip's arrival time to the time of the first feasible departure time of a trip to which it may be linked or to the end of the finite time horizon. The present work continues the effort to calculate and improve the lower bound by considering variable departure times along with possible insertions of DH trips. Certainly, the use of shifting departure times opens up more opportunities to reduce bus fleet size than does allowing only for DH trip insertions. This work shows how to apply possible shifts in departure times, within their tolerances, to improving the lower bound. The approach presented will enable bus schedulers and transit decision makers to decide more promptly how far the fleet size can be reduced by DH trip insertions and allowing shifts in departure times.
Framework for Deployment Planning of Bus Rapid Transit Systems
Authors: Yin Yafeng , Miller Mark A. , Ceder Avishai (Avi)
Published: May 2018

Bus rapid transit (BRT) systems combine vehicles, stations, running ways, and intelligent transportation system elements into a fully integrated system with a unique identity. It has great flexibility in incremental deployment of these BRT elements. Proposed is a deployment planning framework that provides, in a sequence of steps, a general structure for optimal deployment of BRT systems. This framework and its formulation, once operationalized, would provide transit agencies a practical tool for determining the optimal deployment strategy or strategies given budgetary, institutional, and other types of constraints associated with the corridor for which they have decided to deploy BRT. A case study example is provided to illustrate how the proposed framework would be used.
Use of Automatic Vehicle Location and Passenger Count Data to Evaluate Bus Operations
Authors: Hammerle Meghan , Haynes Michael , McNeil Sue
Published: May 2018

New technologies such as automatic vehicle location (AVL) and automatic passenger counters (APC) make tremendous amounts of data available to transit planners and operators. Transit agencies would like to use these data to inform service planning and management and ultimately to provide more reliable service. This requires data processing in such a way as to provide pertinent information to transit planners. The research presented considers a sample of data collected from Chicago Transit Authority buses during the initial stage of AVL and APC implementation in Chicago, Illinois. Methods were developed for extracting information from these data that could be used to compute service reliability indicators. This research also discusses some of the challenges encountered in the data collection process. At the time of the data collection, the home garage for the bus route under consideration was not fully stocked with AVL-equipped buses. Other challenges included the misplacement of some time points and undercounting by the APC system. The data proved useful even with these challenges, and valuable information, such as bus travel patterns, schedule adherence, and headway regularity, was gained from this study. By recognizing some of the challenges faced in the data collection process, this research provided insights that can be used to inform future larger-scale studies of transit operations using AVL and APC data.
Wayfinding in Public Transportation
Authors: Woyciechowicz Anais , Shliselberg Rebecca
Published: May 2018

The Israeli Ministry of Transport initiated a project to restructure the bus network in the Metropolitan Tel Aviv, Israel, area, as part of a program to improve transit patronage. In addition to examining improvements in travel times, the project addressed ways to make the bus network easier to use. A study identified system legibility as a barrier to use. To evaluate alternative networks, a team of transportation planners developed a set of measures to evaluate the legibility of a transit network. The measures are a synthesis of common principles for city planning, transportation planning, and cognitive processes of wayfinding. These measures allow public transportation planners to evaluate the inherent legibility of various public transportation networks before the addition of navigational aids, such as maps, diagrams, signs, and others.
Moving Rural Residents to Work
Authors: Stommes Eileen S. , Brown Dennis M.
Published: May 2018

Rural areas present special challenges for meeting the transportation needs of individuals, especially people without cars. Congress established the Job Access and Reverse Commute (JARC) program in 1998 to assist states and localities in developing transportation services to connect welfare recipients and other low-income residents to jobs and other support programs. There are key results of a study examining eight rural areas receiving JARC funding in Fiscal Year 1999. Specific program elements include the implementation process, transportation services provided, and solutions developed to deal with the challenges of distance and low population densities that rural transit systems frequently face.
Successful Coordinated Transportation Services in Rural Communities
Authors: Burkhardt Jon E.
Published: May 2018

Many share the vision of improved mobility for all residents of rural communities and look forward to productive and cost-effective transportation services with much public support. But today many rural communities still face meager transportation funding, multiple funding sources and service objectives, limited services, and inadequate public interest and transportation investments. As a result, coordination initiatives are receiving even greater attention at all levels of government. A TCRP project focused on how to implement coordinated transportation services in rural communities. New data included a survey of coordination practices of all 50 states and case studies of dozens of coordinated transportation operations. Ten states and 29 local sites were found to offer significant lessons about procedures and strategies. These efforts resulted in a list of coordination strategies that rural communities could pursue toward realizing significant transportation benefits. Although the process can be challenging, coordination offers resource management strategies to improve the performance of various individual transportation services and overall mobility in a community. Greater efficiency helps to stretch scarce and precious funding and personnel resources of the agencies. Coordination can significantly reduce per trip operating costs for rural transportation providers. People with special transportation needs often benefit from the greater amount of transportation and higher-quality services when transportation providers coordinate operations. Coordinated transportation services often have access to more funds and are thus able to achieve economies of scale. They have more sources of funds and other resources. They also can offer more visible transportation services for consumers in rural communities and less confusion about how to access services.
Developing Guidelines for Median Barrier Installation
Authors: Miaou Shaw-Pin , Bligh Roger P. , Lord Dominique
Published: May 2018

Guidelines for the installation of median barriers presented in the AASHTO Roadside Design Guide have remained essentially unchanged for more than 30 years. In recent years, the need for improved guidance has prompted several states to reevaluate their guidelines and has also precipitated a nationwide research project administered by the Transportation Research Board. The objective of the study, on which this paper is based, was to develop improved guidelines for the use of median barriers on new and existing high-speed, multilane, divided highways in Texas. The purpose here is to present some modeling and benefit–cost analysis results from that study, with a focus on the results from a particular data set developed under a cross-sectional with–without study design. The highways of interest are those classified as Interstates, freeways, and expressways with four or more lanes and posted speed limits of 55 mph (88 km/h) or higher. The models employed to estimate median-related crash frequencies and severities, including the Poisson-gamma and ordered multinomial logit models as well as modeling results from a full Bayes estimation method, are presented. From the modeling results, a preliminary benefit–cost analysis is described, in conjunction with some sensitivity analyses, for developing the guidelines for concrete and high-tension-cable barriers. A discussion of the limitations of this study and potential future extensions is provided.
Evaluation of Threshold Values of Acceleration Severity Index by Using Event Data Recorder Technology
Authors: Gabauer Douglas , Gabler Hampton C.
Published: May 2018

The acceleration severity index (ASI) is used to evaluate the potential for occupant risk in full-scale crash tests involving roadside safety hardware. Despite the widespread use of the index across Europe, there is a lack of research relating this metric to occupant injury in real-world collisions. Recent installation of event data recorders (EDRs) in a number of late-model vehicles presents a different perspective on the assessment of the validity of occupant risk based on the ASI. EDRs are capable of electronically recording data such as vehicle speed, brake status, and throttle position just before and during an accident. Of particular interest is the EDR's ability to document the deceleration of a vehicle during a collision event. This research used EDR technology to investigate the correlation between the ASI threshold limits and the potential for occupant injury in crash events. The longitudinal ASI was found to be a good predictor of overall injury, and the intent of the current preferred threshold value of 1.0 appears valid. Limitations include investigation of the longitudinal direction only, lack of injuries on the abbreviated injury scale (AIS) in excess of AIS 3, and no control for occupant compartment intrusion.
Framework for Measuring State Transportation Agency Performance in Context-Sensitive Solutions
Authors: Crossett Joe , Oldham Sally
Published: May 2018

Approaches for measuring the performance of a department of transportation (DOT) in using context-sensitive solutions (CSS) are discussed. Empirical evidence indicates that state DOTs around the country are adopting CSS-based project development approaches and that they are also using performance measurement as a management tool. Such agencies, however, have almost no experience in measuring CSS performance. A proposed framework, based on dialogue with key CSS practitioners, could be used by state DOT staff and their stakeholders to develop customized performance measurement programs for CSS. The framework focuses on creating a set of measures that finds a balance between project-level and organization-level issues and between processes and outcomes. Project-level measurement focus areas discussed include use of multidisciplinary teams, public engagement, project problems and needs, project vision or goals, alternatives analysis, stakeholder satisfaction, construction and maintenance, and quality assurance review. Organization-level measurement focus areas include training, manuals, policies, staff motivation strategies, time frame and budget, and stakeholder satisfaction. It is concluded that a tailored, collaborative self-assessment approach to performance measurement that uses a balanced set of project and organizational measures that focus on both processes and outcomes can help DOTs implement CSS within their agencies more effectively.
Management of Utah Highway Culverts
Authors: Beaver Jesse L. , McGrath Timothy J.
Published: May 2018

More than 47,000 culverts have been installed under the highways of Utah. The Utah Department of Transportation (DOT) maintains these culverts but has no comprehensive system for assessing condition and planning maintenance activities. Utah DOT initiated a study to determine the condition of its culverts by field surveys. The objective was to develop a system of qualitative and quantitative performance measures to assess both the long- and short-term behavior of highway culverts and to support the Utah DOT effort to modify and populate a computerized database designed to store culvert inspection data that can be used for statewide culvert asset management. Culvert management practices currently used by Utah DOT and other agencies are described. A total of 272 culvert inspections conducted during this project showed the inventory to be aging but not generally in need of immediate maintenance. The Utah DOT database, developed to track culvert condition, is effective but could be improved. Improvements would streamline both culvert inspections and priority ranking of culvert repairs. The FHWA system for rating culvert maintenance action was adopted, with a new proposed table for rating thermoplastic pipe. Culvert ratings were adjusted with an importance modifier that focused inspection and maintenance activity on critical culverts with higher consequence of failure. Critical culverts should be placed on a regular inspection schedule, whereas other culverts can be inspected during periodic roadway repaving or rehabilitation. Culvert inspection results will be added to the database to provide more insight eventually into culvert service life than is now possible.
Energy Dissipation in Culverts by Forced Hydraulic Jump within a Barrel
Authors: Hotchkiss Rollin H. , Larson Emily A. , Admiraal David M.
Published: May 2018

Riprap and concrete stilling basins are often built at culvert outlets to keep high-energy flows from scouring the streambed. Two simple alternatives to large basins are examined: a horizontal apron with an end weir and a drop structure with an end weir. The two designs are intended to reduce the flow energy at the outlet by inducing a hydraulic jump within the culvert barrel without the aid of tailwater. This research examines the jump geometry and the effectiveness of each jump type and proposes a design procedure for practicing engineers. The design procedure is applicable to culverts with approach Froude numbers from 2.6 to 6.0. Both designs are effective in reducing outlet velocity 0.7 to 8.5 ft/s (0.21 to 2.59 m/s), momentum 10% to 48%, and energy 6% to 71%. The design layouts allow easy access for maintenance activities.
Application of Reliability Concept in Concrete Pavement Rehabilitation Decision Making
Authors: Liu Juanya , Zollinger Dan G. , Tayabji Shiraz D. , Smith Kurt D.
Published: May 2018

The application of reliability analysis during pavement design is essential to an understanding of the effects of variability on the quality of pavements so that those pavements can provide safe and comfortable service to the public. As well as being durable in service, these pavements must have minimum life-cycle costs (LCCs). Strategic analysis of pavement evaluation and repair (SAPER) software (Version 2.0) is an analysis tool developed on behalf of FHWA to assist with the evaluation and selection of appropriate strategies for the maintenance, rehabilitation, and reconstruction (MRR) of concrete pavements at the project level, where design reliability is incorporated through a decision-making process (DMP). This paper describes the current practice for including reliability concepts in the SAPER software. It addresses the reliability approach used in a DMP and for prediction of pavement life extension for various distress models and the associated LCCs that incorporate reliability analysis for candidate MRR strategies. It shows that the reliability approach used in a DMP provides a simple, practical, and precise way to take into account the various factors that control pavement performance. The results for typical examples of pavement strategy selection approaches with various reliability parameters indicate that these parameters play an important role and must be considered through MRR strategy selection.
Fast Nondestructive Field Test Method to Determine Stiffness of Subsurface Layer in Thin Surface Hot-Mix Asphalt Pavement
Authors: Mallick Rajib B. , Das Animesh , Nazarian S.
Published: May 2018

The determination of the moduli of subsurface stabilized layers in pavements with unknown and variable layers and thin asphalt layers is a challenging problem. Reliable estimation of moduli cannot be obtained from backcalculation of falling weight deflectometer data. In addition, for many stabilized layers, full-depth intact cores cannot be obtained from the field, and hence, laboratory determination of the moduli is not possible. Analysis of the seismic property of a pavement is a well-known method for estimation of the surface modulus of the pavement. This paper proposes a simple methodology on how seismic data acquired on the pavement surface can be effectively used to estimate the modulus of the surface layer as well as those of the subsequent subsurface layers of a flexible pavement. A research study was conducted on three hot-mix asphalt pavements with a foamed asphalt (FA) stabilized base in Maine. These three pavements were tested with both portable seismic and falling weight deflectometer equipment. Cores were taken from the same locations and tested in the laboratory for their resilient moduli. The modulus values obtained from different tests were compared, the effect of temperature on the modulus of the FA was evaluated, and the deflections computed from layered elastic analysis by use of the predicted modulus of the FA layer were compared with the observed deflections. It is concluded that the portable seismic equipment can be used to determine accurate moduli of subsurface stabilized layers. The practical advantages of using such equipment warrant further study for refinement of the method.
Falling Weight Deflectometer Correlation
Authors: Zaghloul Sameh , Ahmed Zubair , Swan D. J. , Jumikis Andris A. , Vitillo Nick
Published: May 2018

The falling weight deflectometer (FWD) is commonly used to perform project-and network-level structural evaluations. Some highway agencies perform network-level FWD testing as a part of their pavement management systems to assess in situ structural capacity, remaining service life, and current rehabilitation needs. Through prediction models, future condition and needs are also estimated. In contrast, project-level FWD testing is typically performed as part of the rehabilitation design process. Calibrated FWD equipment provides repeatable data for a pavement section (i.e., data obtained with the same unit, at the same location, and under similar conditions). However, different FWD devices manufactured by the same or different manufacturers do not necessarily provide similar deflection basins when they test the same section, even if they are calibrated. This paper summarizes the results of a study performed for the New Jersey Department of Transportation to assess the differences among the FWD devices available in New Jersey and to correlate the results obtained with the different devices. Two rounds of testing were performed on flexible and rigid pavement sections located in the FAA William J. Hughes Technical Center in Atlantic City. The first testing cycle was performed in November 2002, and the second was performed in May 2004. The analysis results indicate that significant differences in repeatability and reproducibility may exist between different FWD devices.
Implementation of Reliability-Based Backcalculation Analysis
Authors: Zaghloul Sameh , Helali Khaled , Ahmed Riaz , Ahmed Zubair , Jumikis Andris A.
Published: May 2018

The reliability concept provides a means of incorporating some degree of certainty into the pavement design process to ensure that the outcomes of the process will provide acceptable levels of service until the end of the intended design life. Pavement structural performance and rehabilitation design are highly dependent on the in situ layer properties. Pavement layer thickness is an essential input in backcalculation analysis performed with measured surface deflections to evaluate the in situ structural capacity of a pavement. Inaccurate thickness information may lead to significant errors in the backcalculated layer moduli and, hence, in the rehabilitation design. Because pavement layer thickness has some degree of variability (normal variability), it is important to consider this variability in the backcalculation analysis and rehabilitation design. A procedure was developed to implement the reliability concept in backcalculation analysis to account for the normal variability in layer thickness within structurally homogeneous sections. This procedure was developed on the basis of in situ layer information obtained from a ground-penetrating radar study performed for the New Jersey Department of Transportation. This paper provides an overview of the procedure, along with the results of the pilot implementation of the procedure. This reliability procedure complements the reliability factor of the 1993 AASHTO pavement design guide, as the latter reliability factor does not account for the in situ layer thickness.
Assessment of Pavement Layer Condition with Use of Multiload-Level Falling Weight Deflectometer Deflections
Authors: Park Hee Mun , Kim Y. Richard , Wan Park Seong
Published: May 2018

A condition assessment procedure for pavement layers that uses multiload-level falling weight deflectometer (FWD) deflections is presented. A dynamic finite element program that incorporates a stress-dependent soil model was used to generate the synthetic deflection database. On the basis of the data in this database, the relationships between surface deflections and critical pavement responses, such as the stresses and strains in each layer, have been established. The FWD deflection data, distress survey results, temperature, and laboratory testing results used to develop this procedure were collected from the Long-Term Pavement Performance project database. Research efforts also focused on the effect of the FWD load level on the condition assessment procedure. The results indicate that the proposed procedure can estimate the asphalt concrete (AC), base, and subgrade layer conditions. The AC layer modulus and the tensile strain at the bottom of the AC layer were found to be better indicators of the condition of the AC layer than the deflection basin parameter. It was also found that the structurally adjusted base damage index and base curvature index were good indicators for prediction of the stiffness characteristics of the aggregate base and subgrade, respectively. An FWD test with a load of 71.2 kN or less does not improve the accuracy of this procedure. The results from the study of the nonlinear behavior of a pavement structure indicate that the deflection ratio obtained from multiload-level deflections can predict the type and quality of the base and subgrade materials.
Seed Modulus Generation Algorithm for Backcalculation of Flexible Pavement Moduli
Authors: Fwa T. F. , Rani Thakur Swapna
Published: May 2018

The seed moduli chosen for backcalculation analysis of multilayer flexible pavements can have significant impacts on the performance of backcalculation software and, sometimes, the final solutions of the backcalculated moduli. Practically all backcalculation programs provide internally generated seed moduli for backcalculation analysis. However, as the internally generated seed moduli do not always produce satisfactory results, the use of user-input seed moduli is generally encouraged. With the aim of providing useful guidance in the choice of seed moduli, a seed modulus generation algorithm, 2L-BACK, for multilayer flexible pavements based on a closed-form modulus backcalculation solution for two-layer flexible pavement structures was developed. The proposed algorithm does not require any subjective judgment by the user. An evaluation analysis of the effectiveness of the proposed procedure is presented by the use of two types of backcalculation software, MICHBACK and EVERCALC, and is based on measured and computed data for flexible pavement segments from the Long-Term Pavement Performance project. A comparison was made of the backcalculation program performance and the computed moduli of solutions obtained from internally generated seed moduli and those obtained from seed moduli generated by the proposed algorithm. It was found that the proposed seed modulus generation algorithm led to enhanced program performance of MICHBACK with respect to convergence characteristics and the accuracies of the backcalculated solutions. In comparison, the corresponding improvements for the case of EVERCALC were less. The proposed seed modulus generation algorithm does not suffer from the location and pavement type transferability constraints of most regression-based seed modulus generation methods. The results of the study suggest that the algorithm can be effectively incorporated into backcalculation software for multilayer flexible pavements.
Simple Model for Pavement Damage
Authors: Ullidtz Per
Published: May 2018

A simple phenomenological damage model based on the number of load applications, the critical response, and the material modulus was used with three sets of experimental data: (a) the decrease in the modulus of an asphalt concrete (AC) under laboratory, direct tension fatigue testing; (b) the decrease in the modulus of a pozzolan–lime-stabilized sand under accelerated loading in a full-scale pavement testing facility; and (c) the increase in the permanent strain at three levels of two subgrade materials, also under full-scale accelerated loading. The model is shown to be capable of describing the damage reasonably well for all three cases, though with some limitations. For the direct tension tests with AC, the rate of damage was underpredicted for two of six samples under controlled stress testing, whereas the prediction for all 10 controlled strain tests was good. For freeze–thaw conditions, the model for permanent strain in the subgrade also tended to underpredict the damage rate. The simple damage model may be useful for incremental–recursive pavement design or for pavement management systems.
Methodology for Detection of Defect Locations in Pavement Profile
Authors: Rawool Shubham , Fernando Emmanuel G.
Published: May 2018

Pavement smoothness has become a standard measure of pavement quality. Transportation agencies strive to build and maintain smoother pavements. Road users generally perceive the quality of a pavement on the basis of how well it rides, which is severely affected by the presence of defects (bumps or dips) in the pavement profile. Defects are corrected according to the smoothness specifications prescribed by respective agencies. The effectiveness of any method used to identify defect locations depends on the decrease in roughness obtained on correction of the defects. Following this line of thought, this paper presents a method for the detection of defects based on a comparison of the original profile with a target or a desired profile. The proposed methodology is based on the international roughness index (IRI) gain function for the identification of defect locations to improve smoothness in pavements. This method uses the discrete Fourier transform to help identify defect locations on the basis of deviations of the original profile from the target or the smoothened profile. Areas with defects have a higher deviation from the smoothened profile than areas without defects. This method also estimates the contribution of each defect to roughness. Roughness statistics, such as the IRI and the present serviceability index, are used in the proposed approach to determine the severity of each defect. In addition, the use of a quarter-truck transfer function instead of the IRI gain function is demonstrated to illustrate consideration of dynamic load criteria for the detection of defects. The approach is illustrated through the use of profile data collected for in-service pavement sections.
Full-Car Roughness Index as Summary Roughness Statistic
Authors: Capuruço Renato A. C. , Hegazy Tarek , Tighe Susan L. , Zaghloul Sameh
Published: May 2018

The international roughness index (IRI) and the half-car roughness index (HRI) are the two commonly used roughness indices for pavement management, decision making, prioritization, budgeting, and planning. This work presents a new statistic, termed the full-car roughness index (FRI), for calculation of roughness from longitudinal pavement profiles. FRI is calculated from a single, equivalent profile that is a composite of four corner profiles based on both civil and mechanical engineering principles. More specifically, the full-car (four-wheel) model combines the rear and front suspension systems through an interdependent relation of motion with the longitudinal axle. To validate this model, the FRI values for different pavement sections are determined for sampling roughness measurements from several states and provinces. Then, the behavior of FRI is compared with that of IRI and HRI. The methodology of assessment uses a Monte Carlo simulation for calibration and validation of the index. Correlations derived from this sensitivity analysis on the basis of regression analysis arrive at a conversion chart to propose conversion values from these indices to FRIs. Overall, this paper suggests that the mechanical response of the proposed full-car model is more representative of the characteristics of a real vehicle than the response of a quarter- or half-car model. The results also indicate that FRI is less sensitive to the governing factors that account for the quarter-car simulation and thus provides an index that is unique, insightful, and more effective in the characterization of ride quality.
Sparking the Globalized Trade and Transportation Connection
Authors: Borrone Lillian C.
Published: May 2018

Over the past few decades, the U.S. government and private industry have actively worked to promote global trade. However, sufficient attention has not been paid to updating and improving the corresponding national transportation assets required to take full advantage of the economic opportunities in today's dynamic world market. This paper reviews the growth trends in international trade, including major shifts in the sourcing and distribution of U.S. goods from overwhelmingly domestic systems to increasingly global ones. It highlights the great stresses that these changes in freight movement place on all transport modes, especially those at international gateways, where the modes interface. The paper then examines several structural, conceptual, and funding barriers that the American private and public sectors face in framing an effective response. These transportation and trade conditions are aptly called “wicked problems,” complex problems that sow confusion and fragmentation wherever they arise. The fragmentation that wicked problems create is best faced by increased dialogue and collaboration among key stakeholders. The recommendations for dealing with the critical issues raised here stress the need for better data, the creation of common and compelling overarching goals, and an industry-wide commitment to building, educating, and motivating leadership. Three specific recommendations suggest ways that joint public and private cooperation can move the United States forward in transportation policy and practice: develop a national transportation policy framework, prepare an action plan, and set priorities to direct the needed resources and employ the best talent to move the nation's transportation systems from their lagging 20th-century position to a renewed leadership position for the 21st century.
Observed Trip Chain Behavior of Commercial Vehicles
Authors: Holguín-Veras José , Patil Gopal R.
Published: May 2018

Results are presented from a comprehensive analysis of the observed trip chain behavior of commercial vehicles in the Denver, Colorado, region on the basis of data collected by the Denver Regional Council of Governments. These analyses may provide the foundation for further research into commercial vehicle trip chain models. Trip chain behavior is characterized by number of trip chains, length of trip chains, and conditional probability of trip purpose. For this analysis, trip purposes were grouped as freight transportation; transport of people; service calls; fuel, service, and so forth; and return to base or home. Commercial vehicles were grouped as automobile, pickup van, single-unit truck, combination truck, and sports utility vehicle. The conditional probabilities were analyzed for a fixed length of trip chain and were conditioned on stop number. Although most vehicles were found to make one trip chain per day, one of four commercial vehicles made more than one trip chain per day. The analyses also indicated that the average number of stops per trip chain decreased with the number of trip chains. About 35% of the trip chains involved two stops, although some trip chains had more than 12 stops. The main trip purpose for all commercial vehicles was freight transportation, although some vehicles had mixed uses. This study apparently represents the first comprehensive attempt reported in the literature to analyze the observed patterns of commercial vehicle trip chain behavior.
Innovative Framework for Modeling Freight Transportation in Los Angeles County, California
Authors: Fischer Michael J. , Outwater Maren L. , Cheng Lihung Luke , Ahanotu Dike N. , Calix Robert
Published: May 2018

Freight transportation is a critical element of the transportation system and the economy of Los Angeles County, California. Freight transportation links the large consumer market, major manufacturing industry sector, and international trade network of Los Angeles to the rest of the United States and the world. As the agency responsible for transportation planning and programming in Los Angeles County, the Los Angeles County Metropolitan Transportation Authority needs comprehensive tools for understanding the demands of the freight transportation sector and the effects of transportation investment on this sector. A project was undertaken to design a comprehensive, innovative, multimodal modeling framework to support freight transportation decision making in Los Angeles County. The proposed modeling approach combines elements of two state-of-the-art freight modeling techniques: logistics chain modeling and tour-based truck modeling. The reasons for selecting this approach are described; background on the modeling techniques is provided; and integration of the two methods into a comprehensive modeling framework is discussed.
Measurement Tools for Assessing Motor Vehicle Division Port-of-Entry Performance
Authors: Carey Jason , Semmens John
Published: May 2018

The Arizona Department of Transportation's Motor Vehicle Enforcement Services (MVES) conducts interstate commercial vehicle operations and enforcement activities at fixed ports of entry (POEs) along Arizona's interstate and international borders. These POE facilities play an important role in commercial vehicle safety and revenue collection by screening commercial vehicle traffic for compliance with state and federal regulations. POEs provide needed services but lack a clear means of evaluating services relative to the efficiency and effectiveness of enforcement activities. This inability makes it difficult to communicate POEs achievements and identify potential improvements in service quality. Measuring efficiency and effectiveness can help to direct resources for performing MVES functions. To ensure that public funds invested in the Arizona POE program provide a return to taxpayers in the form of increased safety and reduced damage to highways, several measures of performance at MVES commercial ports are proposed. Arizona POEs are used as a case study to evaluate various ways to measure performance.
Improving Construction Communication
Authors: Done Robert S. , Semmens John
Published: May 2018

Data collected from Arizona Department of Transportation customers during the SR-51 project were examined. During the $75 million project, approximately 10 mi of SR-51 between I-10 and SR-101 was renovated to include new high-occupancy-vehicle lanes and rubberized asphalt. Communication was measured by customers’ (e.g., motorists’ as well as local residents’ and businesses’) utilization of four direct communication channels (e.g., construction signage) and four indirect communication channels (e.g., television programming). Satisfaction was measured by a composite score based on customer satisfaction with traffic, dust, noise, signage, and information during the construction process. Almost all respondents relied on at least one channel for construction communication, and almost 80% of respondents reported using between one and three channels. The most frequently used channel was construction signs (55.9%), and the least frequently used channel was e-mail alerts (1.5%). Fewer than 4% of the respondents did not use any communication channel. Direct communication channels resulted in higher customer satisfaction than did indirect communication channels. Construction bulletins contributed the most to customer satisfaction, followed by the project website. Neither television nor radio contributed to customer satisfaction. As sources of project communication, neighbors and friends had a strong but negative effect on customer satisfaction.