bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectiveness of Open-Graded Base Layer on Subgrade Moisture Regime and Overall Pavement Performance
Authors: Salem Hassan , Bayomy Fouad , Smith Robert , Abdelrahman Magdy
Published: May 2018

Rockcap (open-graded crushed aggregate with a nominal maximum size of 2.5 in.) base layer is commonly used in the construction of asphalt pavements in Idaho. The effectiveness of the rockcap layer on the subgrade moisture regime and the overall pavement performance were evaluated. Two pavement sites were selected in northern and southern regions of the state. At each site, two pavement sections that are identical and adjacent to each other were instrumented by temperature, frost, and moisture sensors using time domain reflectometry (TDR) probes. One was constructed by a well-graded 3/4-in. aggregate base, whereas the other was constructed by the rockcap base. Data collected over approximately 4 years included moisture, temperature, frost condition, climatic information, groundwater level, and deflections using a falling weight deflectometer for structural support evaluation. These data were analyzed to assess effects of the rockcap layer on the variation of moisture in the subgrade and on the overall structural capacity of the pavement system. Results showed that the rockcap layer helped reduce the subgrade moisture content in pavements with daylight ditch drains, and it showed an increase in subgrade moisture for sections where the rockcap was confined by native soil and did not continue to side drains. However, performance analysis showed that sections with rockcap layer were always stronger than sections with aggregate base, even when the subgrade moisture content under rockcap was greater. The predicted rutting life for pavement sections with rockcap base layers was approximately five times greater than for sections with aggregate base.
Safety Effectiveness of Stop Control at Ultralow-Volume Unpaved Intersections
Authors: Souleyrette Reginald R. , Tenges Ryan J. , McDonald Thomas , Maze T. H. , Carriquiry Alicia
Published: May 2018

Establishment of the proper level of traffic control on low-volume rural roads can be problematic for local agencies. Ten years of crash data for more than 6,000 rural, unpaved intersections in Iowa were analyzed, with stop-controlled intersections compared with uncontrolled intersections. Crash models were developed with logistic regression and hierarchical Poisson estimation. For ultralow-volume intersections, those used by fewer than 150 vehicles per day, results indicated no statistical difference in the safety performance of each level of control. The effect of excessive use of control on safety performance also was tested for rural and urban applications, with no detrimental effect generally being indicated.
Two-Dimensional Moisture Flow–Soil Deformation Model for Application to Pavement Design
Authors: Long Xiaoyan , Aubeny Charles P. , Bulut Rifat , Lytton Robert L.
Published: May 2018

Seasonal cycles of wetting and drying in highway subgrade soils induce corresponding cycles of soil swelling and shrinkage that contribute to roughness and loss of serviceability of pavements. The design of defensive measures to mitigate the effects of this process requires a realistic model of moisture diffusion and associated swelling and shrinkage of soil. A Windows-based two-dimensional finite element program, FLODEF, is presented; it performs a sequentially coupled flow-displacement analysis for the prediction of vertical movement in highway subgrade soils. The theoretical formulations of moisture flow and stress–deformation components of the model are introduced first. Parametric studies illustrate capabilities of the model to evaluate the effectiveness of vertical moisture barriers, horizontal barriers, soil replacement or improvement, and paved medians in reducing swell–shrink deformations beneath highway pavements.
Improving the Prediction of Annual Average Daily Traffic for Nonfreeway Facilities by Applying a Spatial Statistical Method
Authors: Eom Jin Ki , Park Man Sik , Heo Tae-Young , Huntsinger Leta F.
Published: May 2018

Annual average daily traffic (AADT) data are important for various transportation research areas, including travel model calibration and validation, pavement design, roadway design, and air quality compliance. Specifically for model calibration and validation in long-range transportation planning, a base-year model requires numerous count locations across the study region. Sometimes count data for the lower classified roadways are not readily available. Detailed models require traffic counts for not only higher classifications of roadways such as freeways and arterials but also collector and, in some instances, local roadways. To predict AADT better for desired count locations on nonfreeway facilities, spatial dependency is considered. The theory behind the use of spatial dependency is that the traffic volume at one monitoring station is correlated with the volumes at neighboring stations. The spatial regression model takes into account both spatial trend (mean) and spatial correlation, which is modeled by a geostatistical approach called kriging. The spatial regression model is applied to AADT in Wake County, North Carolina. Results indicate that the overall predictive capability of the spatial regression model is much better than that of the ordinary regression model. In addition, the urban area has more reliable prediction than the rural area. Finally, the spatial regression model is expected to provide better predictions for desired count locations where no observed data currently exists due to budget limitations.
Incorporating Wavelet Decomposition Technique to Compress TransGuide Intelligent Transportation System Data
Authors: Qiao Fengxiang , Liu Hao , Yu Lei
Published: May 2018

With the improvement and application of various data collection techniques, intelligent transportation system (ITS) data have created obstacles for the effective storage, transmission, and retrieval of data. Some traffic management centers (TMCs) collect ITS information and maintain the “recent” data until it can be transferred to users for ultimate long-term storage, management, or both. Others archive data in convenient storage formats (usually compressed text) without action on data usage and analyses. In currently compressed ITS data (e.g., TransGuide zipped data), many redundant and empty spaces can be eliminated and compressed. Sophisticated approaches must be developed to compress ITS data in TMCs effectively. The wavelet-incorporated ITS data compression method not only makes use of conventional data-compression techniques but also incorporates the advanced one-dimensional discrete wavelet-compression approach. Three compression indices are constructed, and one threshold selection algorithm is proposed. The identified threshold can balance both compression ratio and signal distortion. Results of a case study in San Antonio, Texas, indicate that the proposed method and algorithm can achieve a compression ratio that is about 8.12% of what TransGuide currently provides. The entire compression ratio is <1% for a typical day's data. Results of impact analyses indicate that the selection of wavelet forms does not significantly affect the final compression ratio, whereas higher decomposition levels yield smaller decomposition ratios.
Real-Time Detection of Crash-Prone Conditions at Freeway High-Crash Locations
Authors: Hourdos John N. , Garg Vishnu , Michalopoulos Panos G. , Davis Gary A.
Published: May 2018

Because of growing concern over traffic safety and rising congestion costs, recent research efforts have been redirected from the traditional reactive traffic management (crash detection and clearance) toward on-line proactive solutions for crash prevention. Such a solution for high-crash areas is explored by the identification of the most relevant real-time traffic metrics and the incorporation of them in a model to estimate crash likelihood. Unlike earlier attempts, this model is based on a unique detection and surveillance infrastructure deployed on the freeway section that has the highest crash rate in Minnesota. State-of-the-art infrastructure allowed the video capture of 110 live crashes, crash-related traffic events, and contributing factors while measuring traffic variables (e.g., individual vehicle speeds and headways) over each lane in several places in the study area. This crash-rich database was combined with visual observations and analyzed extensively to identify the most relevant real-time traffic measurements for detecting and developing an on-line model of crash-prone conditions. This model successfully establishes a relationship between quickly evolving real-time traffic conditions and crash likelihood. Testing was performed in real time during 10 days not previously used in model development, under varied weather and traffic conditions. The crash likelihood model—and, in turn, the detection algorithm—succeeded in detecting 58% of the crashes, with a 6.8 false decision rate.
Predicting Urban Arterial Travel Time with State-Space Neural Networks and Kalman Filters
Authors: Liu Hao , Van Zuylen Henk , Van Lint Hans , Salomons Maria
Published: May 2018

A hybrid model for predicting urban arterial travel time on the basis of so-called state-space neural networks (SSNNs) and the extended Kalman filter (EKF) is presented. Previous research demonstrated that SSNNs can address complex nonlinear spatiotemporal problems. However, SSNN models require off-line training with large sets of input–output data, presenting three main drawbacks: ( a) great amounts of time and effort are involved in collecting, preparing, and executing these training sessions; ( b) as the input–output mapping changes over time, the model requires complete retraining; and ( c) if a different input set becomes available (e.g., from inductive loops) and the input–output mapping has to be changed, then retraining the model is impossible until enough time has passed to compose a representative training data set. To improve SSNN effectiveness, the EKF is proposed to train the SSNN instead of conventional approaches. Moreover, this network topology is derived from the urban travel time prediction problem. Instead of treating the neural network as a “black-box” model, the design explicitly reflects the relationships that exist in physical traffic systems. It allows the interpretation of neuron weights and structure in terms of the inherent mechanism of the network process with clear physical meaning. Model performance was tested on a densely used urban arterial in the Netherlands. Performance of this proposed model is compared with that of two existing models. Results of the comparisons indicate that the proposed model predicts complex nonlinear urban arterial travel times with satisfying effectiveness, robustness, and reliability.
Risk Perception Training for Novice Drivers
Authors: Pradhan Anuj K. , Fisher Donald L. , Pollatsek Alexander
Published: May 2018

Younger novice drivers are overrepresented in fatal and nonfatal crashes. A major cause appears to be their failure to scan for information where potential threats may appear. Recent studies have assessed whether personal computer (PC) based training in risk perception helps novice drivers to identify high-risk locations while driving in a simulator. In particular, the Risk Awareness and Perception Training (RAPT) program was designed to teach novice drivers about categories of risky situations normally encountered in driving. RAPT, a PC-based interactive presentation with plan views of roadways demonstrating risky scenarios, provides information about inherent risks in each scenario and indicates areas where attention should go, to detect risks. A previous study showed that RAPT improved scanning behavior by novice drivers in a driving simulator immediately after training. The present study evaluated effects of such a training program an average of 4 days after training. One group of novice drivers was trained with RAPT and subsequently tested on a driving simulator; a matched control group was evaluated without previous training. The test contained 16 scenarios, each with information vital to safe navigation. An eye-tracker recorded drivers’ point of gaze during drives. Trained drivers fixated significantly more often on predetermined regions where hidden risks could materialize; they were almost twice as likely to scan risky regions as were untrained drivers. Because the size of this training effect was the same as that when the test immediately followed training, it indicates that results of this training are reasonably long lasting. This training also raised performance of novice drivers close to the level of more experienced drivers, as tested in a previous related study.
Synthesis of Commercial Motor Vehicle Safety Technology Surveys
Authors: Dick Virginia , Murray Daniel , Houser Amy
Published: May 2018

This paper documents and synthesizes the major qualitative survey efforts within the United States relating to stakeholder design, use, and perspectives of onboard truck safety technologies. The Federal Motor Carrier Safety Administration (FMCSA) and American Transportation Research Institute (ATRI) have conducted a survey synthesis and meta-analysis to consolidate, analyze, and identify gaps in existing survey research on safety technologies. Over the past several years, there has been an increasing interest in onboard truck safety technologies. At different times, entities such as FMCSA, FHWA, American Trucking Associations (ATA), and ATRI have undertaken different survey projects to document and understand onboard safety technology applications. While a wide variety of data has been collected by these projects, there has been little effort to aggregate data across projects. The current synthesis includes analysis of more than 11 survey, interview, and focus group instruments, representing 558 respondents and 56 unique questions. Preliminary results indicate that while existing research addresses many issues related to carrier purchase and use of technologies, there is a considerable gap in research addressing driver attitudes, experiences, and preferences. Satellite or cellular communication between terminal and vehicle and Global Positioning System are the technologies most commonly used by carriers. Most carriers that have a safety technology installed on their fleets have already realized the desired safety benefits, often intangible from a quantitative perspective. Cost and lack of clear data about benefits are the two biggest factors preventing wider installation of safety technologies.
Development and Implementation of Driver Safety History Indicator into Roadside Inspection Selection System
Authors: Lantz Brenda , Loftus Jeff
Published: May 2018

The majority of previous research and analysis has indicated driverrelated factors as the main cause of most commercial vehicle-related crashes. The main goal of the current project is to provide greater concentration on the commercial driver, so as to have the most significant impact on the number of crashes. The ultimate outcome of this study is to save lives, prevent injuries, and prevent property damage associated with commercial vehicle-related crashes. To accomplish this crash reduction goal, the current study combines and expands on two previous research efforts: development of the Inspection Selection System (ISS) and a project analyzing the use of driver traffic conviction data to identify high-safety-risk motor carriers better. To accomplish greater focus on the commercial driver, the first objective of the current project was to analyze further the data and weightings associated with the carrier driver conviction measure created through the conviction data study. With use of results from this first objective, the second objective of the present project was to then integrate the carrier driver conviction measure into the current ISS and conduct a pilot test of this new ISS algorithm, termed ISS-D. Results from the pilot test indicate an approximate 10% increase in driver out-of-service rates after the ISS-D algorithm implementation. In addition, there was an almost doubling of the driver out-of-service rate when the ISS-D recommended the inspection.
Limits on Adhesive Bond Energy for Improved Resistance of Hot-Mix Asphalt to Moisture Damage
Authors: Bhasin Amit , Masad Eyad , Little Dallas , Lytton Robert
Published: May 2018

The loss of physical adhesion between the aggregate and the asphalt binder is one of the important mechanisms that accelerate moisture damage in hot-mix asphalt pavements. In this study, two parameters related to bond energy—adhesive bond energy between the aggregate and the asphalt and reduction of free energy when asphalt debonds from the aggregate surface in the presence of moisture—were quantified with surface energies of both materials. Threshold values of these parameters to identify asphalt–aggregate combinations susceptible to premature moisture damage were derived by comparison of the values of these parameters with observed field performance for several mixes. Results show significant differences in bond energies developed between various aggregates and a given binder. This finding illustrates the importance of binder–aggregate compatibility and the sensitivity of calculated bond strength to surface energy measurements. Asphalt binders from different sources with the same performance grade were also found to develop different bond energies with any given aggregate. The results show that binders differ in their sensitivity to changes in aggregate source in terms of the developed bond energy. The methodology of using surface energy and concomitant bond energy calculations to assess the moisture sensitivity of asphalt concrete mixes is discussed as well as the advantages of using this technique compared with conventional mechanical tests.
Investigating Pavement Cracking
Authors: Loizos Andreas , Karlaftis Aristides
Published: May 2018

Because of the combined practical and theoretical interest in pavement performance modeling, much research has concentrated on this area during the past few years. The objectives of this study are, first, to cluster pavement distress data into homogeneous groups depending on the extent of distress and, second, to identify and assess the influence of a variety of exogenous variables on the extent of pavement distress. To achieve these objectives, a two-step clustering and classification evolutionary modular neural network is developed with a large (more than 1,000 observations) and recent (1998) data set collected from in-service pavements in 15 European countries. The results indicate that the extent of the cracking distress (magnitude of cracking) can be separated into five homogeneous clusters (with Cluster 1 suggesting very low cracking and Cluster 5 very extensive cracking), with different explanatory variables affecting the extent of cracking in each of these clusters.
Near Side, Far Side, Uphill, Downhill
Authors: Furth Peter G. , SanClemente Joseph L.
Published: May 2018

One of the factors affecting where bus stops should be located is the expected delay associated with the stop location. On hills, the effect of gravity on already weak diesel engines can lead to considerable additional delay if a bus has to accelerate from a stop. An empirical bus acceleration profile, modified to account for gravity, was applied to constant grade, sag curve, and crest curve profiles. The marginal impact of grade on stopping delay ranged from –4 to 11 s, depending on grade. At signalized intersections, a deterministic model was created that accounted for deceleration, acceleration, and queue interference. Relative to a stop placed away from an intersection, far-side stop placement either causes a very small reduction in delay or has no effect. Near-side placement can reduce delay in a few cases such as reserved bus lanes, but more often it increases delay, sometimes considerably depending on factors such as red ratio, volume:capacity ratio, cycle length, and stop setback. Measures that reduce interference with the queue tend to reduce the net delay from a near-side location; these measures include increasing stop setback, shortening cycle length, and giving the bus a (near) exclusive lane. Results are presented with default adjustments for hills and signalized intersections that can be used in the context of a stop spacing study.
Organizational Structures for Brokerage of Paratransit Services
Authors: Pagano Anthony M. , Metaxatos Paul
Published: May 2018

The benefits of interagency coordination of public and human service transportation have been recognized and promoted by federal, state, and local governments. This paper contributes to successful interagency coordination of paratransit services by developing a conceptual model of alternative organizational structures for implementing a paratransit brokerage, then applying the model to three Illinois paratransit implementations: Peoria, South Central Transit, and Macomb. The selection of the sites and the development of model brokerages were based on extensive case analyses of paratransit brokers and interviews with transportation service providers within Illinois. The design of the appropriate brokerage organization for each site is based on the management literature, in which an organizational structure is developed from individual functions and the strategy to be implemented. These functions then serve as the building blocks of the organization.
Benefits of Campus Transit Pass
Authors: Myers Gene , Hagen Daniel A. , Russo Tony , McMullin Cari , Lembrick Andrew , Silbaugh Brianne , Parker Kyle
Published: May 2018

The problem of estimating the expected net benefits of an unlimited-access campus transit pass, which would also fund an increase in critically needed services, is an example of the problem of estimating the value of a public good. Students at Western Washington University in Bellingham, Washington, used a referendum-format contingent valuation survey to measure students’ willingness to pay (WTP) for a mandatory transit pass. Responses by 935 students (a 44.7% response rate) were analyzed with censored logistic regression and revealed a mean WTP of $32.08 per academic quarter (corrected for estimated self-selection bias) for the proposed program. The program could actually be provided by contract with the local transit agency for $20.00 per student per quarter. Thus the estimated net benefit per student per quarter is $12.59, or $428,624 across the campus population. On-campus residents and those who commute via bus or bicycle showed higher WTP. WTP was substantially lower for those who live more than 10 mi from campus. Frequencies of “yes” votes showed majorities supporting the pass up to the $35.00 per quarter fee level, and strong majorities up to the $20.00 level, suggesting the proposal would pass easily by a student vote. Content analysis of reasons given for support, lack of it, or indecision showed that students were persuaded by nighttime bus service, safety, monetary savings, and environmental benefits. Doubts were raised by the mandatory nature of the proposed fee, services not meeting needs, and opposition to more student fees.
Video-Based Automated Identification of Freeway Shoulder Events
Authors: Qi Yi (Grace) , Tang Yin , Smith Brian L.
Published: May 2018

Transportation agencies have increasingly turned to information technology to help address the growing challenges of managing congested urban freeways. Although off-the-shelf information technology products, such as closed-circuit television (CCTV) systems and video image vehicle-detection systems (VIVDS), have proved very useful, their full potential cannot be achieved without integrating the products. The purpose of this research effort was to build on an existing prototype of an integrated CCTV–VIVDS system to provide automatic shoulder event identification functionality. This paper presents the design of the integrated system, provides details on the tools and effort required to support integration of the information technology elements, and describes the results of field testing of the system.
Method for Creating a Real-Time Distributed Travel History Database
Authors: Marca James E. , Rindt Craig R. , Jayakrishnan R.
Published: May 2018

A novel distributed method for estimating a trip table in real time is described. The system is called “persistent traffic cookies” by analogy with the use of cookies by web servers to keep track of the current state of web browsers navigating a web site. The method uses traffic cookies placed on in-vehicle computers to maintain the state (current trip) of vehicles moving through the system. These cookies are persistent from day to day; taken together, they form a complete travel history for a traveler or vehicle. The method leverages the vehicles to store their own travel data and then physically do carry those data around the network. Advantages include scalability in both storage and computational effort as well as the unique ability to incorporate the travel behavior of individuals into real-time traffic predictions. A small-scale simulation is presented to illustrate the concept and its potential applications.
Enhanced Roadway Geometry Data Collection Using an Effective Video Log Image-Processing Algorithm
Authors: Wu Jianping , Tsai Yichang (James)
Published: May 2018

With the advancement of information technology, video logging has become a feasible and common practice for state-level departments of transportation (DOTs) to visualize roadway conditions to support various transportation activities. A new and innovative image-processing algorithm and method using video log images to enhance the highway roadway geometry data collection is presented. The algorithm is based on Canny edge detection, slope-adaptive edge reduction, a novel recursive approximation of the vanishing point, localized color thresholding, and knowledge-based Hough transform. Experiments on real digital images indicate that the algorithm is feasible for automated road geometric data collection, especially in recognizing lane marks and shoulder edges. The algorithm was implemented with Visual C++ language and tested on a Pentium IV 3.06-GHz computer. It indicates that the average processing speed is about 280 ms for an image size of 1,300 × 1,050. The developed method can be used by state DOTs to save money and cost by flagging the video images with a variation index. Thus, the video images with a high variation index (e.g., changing lane location) can be identified for a focused visual measurement Future studies for evaluating the algorithm under various weather, lighting, and roadway conditions are also discussed.
Potential Application of Flashing Yellow Arrow Permissive Indication in Separated Left-Turn Lanes
Authors: Knodler Michael A. , Noyce David A. , Kacir Kent C. , Brehmer Christopher L.
Published: May 2018

The consideration being given to the adoption of the flashing yellow arrow (FYA) permissive indication has led to a number of additional studies evaluating potential scenarios in which FYA may be effectively used. One potential scenario is in intersections with wide medians where the left-turn lane and the corresponding signals are separated from the adjacent through and right-turn lanes. Left-turn maneuvers at locations with wide medians typically operate with protected-only left-turn phasing and separate signal displays, as drivers cannot see the adjacent through movement signals; however, some transportation professionals have implemented a flashing red arrow (FRA) that requires drivers to first stop before accepting a gap in the opposing traffic stream. This research quantified driver comprehension of the FYA permissive indications compared with that of the FRA indication for use at locations with wide medians. The research used both driving simulator and static experiments with 264 drivers responding to 1,260 experimental scenarios. The results found that drivers understood the meaning of the FYA indication. Nevertheless, FYA was associated with fail–critical response errors in the driver's first exposure to the FYA indication. The large number of drivers who interpreted the FRA as a yield condition was consistent with that from previous evaluations and indicated an incorrect comprehension of the indication. At locations with wide medians where the use of protected-only left-turn phasing may not be desirable, the use of the FYA or FRA permissive indications should be used only after consideration of the safety and operational issues common to the initial implementation.
Navigation Signing for Roundabouts
Authors: Inman Vaughan W. , Katz Bryan J. , Hanscom Fred R.
Published: May 2018

The focus of this study was on navigational signage that is intended to assist motorists with anticipating the correct roundabout exit and selecting an appropriate approach lane for that exit. The objective was to support recommendations on double-lane roundabout signage for FHWA's Manual on Uniform Traffic Control Devices Team and the National Committee on Uniform Traffic Control Devices (NCUTCD). The Traffic Control Devices Pooled Fund Study identified the need for this research. Four navigation signing methods that are currently in use were evaluated. Volunteer participants were shown guide signs and markings in a roundabout context and were asked to identify which lane they should be in and which exit they should use for a given destination. Response correctness, speed, and confidence for lane choices and leg identifications were assessed. Overall, the conventional and diagrammatic signs yielded the best performance, particularly for the participants’ reaction times and decision confidence. The current NCUTCD markings subcommittee's recommendations for lane control markings were used in the contextual stimuli presented to the participants. For all navigation sign types, lane selection performance was less than 70% correct and not far from the results obtained by chance, given the assumption that in the absence of other information drivers would use the left lane for left turns, the right lane for right turns, and either lane to continue straight through. Further research is recommended to determine whether the current recommended markings are sufficient for driver comprehension.
Probabilistic Approach to Controlling Dilemma Occurrence at Signalized Intersections
Authors: Tarko Andrew , Li Wei , Laracuente Luis
Published: May 2018

This paper proposes a new probabilistic method of protecting drivers against Type I dilemmas that may occur on the display of a yellow traffic signal. At the onset of yellow, an approaching vehicle may be too close to stop but also too far away to pass the stop line before the end of yellow. The occurrence of this dilemma is affected by factors such as driver preference and perception–reaction time, which cannot be fully determined in real time. In this study, the dilemma likelihood function is derived and a method for the identification of the optimal green extension that minimizes this likelihood is proposed. A property of the likelihood function is noted and is used to devise an efficient search algorithm for the optimal green extension. In selecting an optimal extension time, the positions of all vehicles on the approaches, the vehicle types, the speeds, and even the pavement conditions can be considered. To evaluate the effectiveness of this method, numerical simulations are performed on the basis of data collected in the field. The method was found to reduce the frequency of Type I dilemma occurrence significantly while the average green extension was quite short.
Determining Return on Long-Life Pavement Investments
Authors: Haas Ralph , Tighe Susan L. , Falls Lynne Cowe
Published: May 2018

It is becoming increasingly necessary in life-cycle analysis (LCA) of infrastructure assets, including pavements, to take a longer-term approach than has been used, mainly to ensure sustainability and assess the impacts of today's decisions accurately. LCA can include primarily life-cycle cost analysis (LCCA), but it also can include considerations of resource conservation, environmental impacts, energy balance, and so forth, and it can involve short-, medium-, and long-term periods. It is thus possible to develop a context for LCA of likely and uncertain societal activities, including transportation, over these periods. Conventional LCCA is directed toward comparing competing alternative investment strategies and can involve a range of stakeholders. Of the methods available, present worth of costs is almost exclusively used in the pavement field. However, when medium- to longer-term life-cycle periods are involved, rate-of-return and cost-effectiveness formulations can be applicable. A numerical example shows how an agency can determine the internal rate of return for two investment alternatives involving different pavement designs and a life-cycle period of 50 years. In addition, a cost-effectiveness example is provided for a sidewalk network, again with a life-cycle period of 50 years. Conventional LCCA for calculating present worth of costs will undoubtedly continue to be used in the pavement field as a primary tool. However, using a rate-of-return or cost-effectiveness formulation, especially for medium- to longer-term life-cycle periods, should be given more consideration.
Accelerated Stiffness Profiling of Aggregate Bases and Subgrades for Quality Assessment of Field Compaction
Authors: Joh Sung-Ho , Kang Tae-Ho , Kwon Soo Ahn , Won Moon C.
Published: May 2018

As a compaction control parameter, stiffness has been investigated as an alternative to dry unit weight, because the design of pavement is based on the elastic modulus of pavement layers. A reliable and practical quality assurance system was proposed to accelerate the quality assessment of field compaction. The proposed system, which has evolved from the spectral analysis of surface waves (SASW) method, profiles the shear wave velocity of the unbound aggregate base and subgrade. The system consists of dedicated hardware for surface wave measurements and an analysis algorithm to automate the interpretation and analysis procedures. The measurement hardware consists of two sensor units and one source unit and can be operated by one person. The automation in interpretation and analysis was implemented with the peak–trough method and the frequency wave number technique. Consequently, the surface wave measurement for stiffness profiling is reduced to a 10- to 15-min task. The validity of the proposed hardware and algorithm was verified by a comparison of the results acquired by the conventional SASW measurements with the results acquired by the accelerated SASW system. Twenty-one subgrade and 11 base sections were selected at three pavement construction sites and tested with the accelerated SASW system, the dynamic cone penetrometer (DCP), the plate-bearing test, and the falling weight deflectometer (FWD). Results indicated that the shear wave velocity predicted by the accelerated SASW system showed a favorable agreement with DCP index at both subgrades and bases. Young's modulus evaluated from the shear wave velocity also agreed roughly with the FWD modulus and subgrade reaction coefficients.
Sustainable Earthworks Specifications for Transport Infrastructure
Authors: Fleming Paul R. , Frost Matthew W. , Lambert John P.
Published: May 2018

The specification of the materials and methods used in earthworks and foundations for highways, railways, and airfield runways can be approached in several ways. There is a need for a more sustainable use of resources, and specifications that make best possible use of material properties are required. A performance-based approach is considered the best way to achieve this. The functional requirements of a performance-based specification for UK highway foundations were considered. The recently researched performance-based specification, demonstrating the steps to its development, determination of the engineering requirements, suitable target values, and potential construction-related implications, is explained. Performance-based specifications offer the advantage of better incorporation of the principles that underpin sustainable construction and require a fuller understanding of material behavior for their development and implementation. However, contractual issues and implications for construction need to be considered carefully to allow a full performance-based approach to be adopted successfully. In the United Kingdom, a staged implementation of a performance specification is needed to gain experience in both the process and the field measurement methods, some of which are relatively novel, and to reduce the risk of contractual disputes or potential failures and thus a negative reaction from the industry.
Deformation–Resistance Model for Geogrid-Reinforced Unpaved Road
Authors: Leng Jianjun , Gabr Mohammed A.
Published: May 2018

Unpaved road sections experience degradation and accumulation of plastic deformation under repeated loading. Geogrid placed between subgrade and aggregate base course (ABC) can improve section performance through several mechanisms and lead to reduction in stresses and plastic deformation. An unpaved road design model that includes provisions for mobilization of subgrade bearing capacity under axisymmetric condition is proposed. The model incorporates base course property, mobilization of subgrade bearing capacity with rutting, degradation of base course stress attenuation with cyclic load, and the effect of reinforcement inclusion. An elastic layer method has been used to back-analyze the vertical stresses on subgrade with data from previous cyclic plate load tests performed in the laboratory. The degradation of unpaved sections was expressed as a reduction in base course–subgrade elastic modulus ratio ( E1/ E2) with an increasing number of cycles or a decrease in stress distribution angle of base course. The proposed model has been validated by data from a field study. Computed base course thickness matched well with the test results, but further verification of the method based on field testing is needed before it is accepted as a viable design tool.
Analysis and Instrumentation of a Steel Bridge for Investigation of Superload Effects
Authors: Wood Scott M. , Akinci Necip Onder , Liu Judy , Bowman Mark D.
Published: May 2018

The number of superload trucks, which often carry loads three to 15 times those of common design vehicles, has increased in recent years. The increased frequency of occurrence has prompted concerns about the ability of highway bridges to accommodate such loads and remain in serviceable condition. To address these concerns, an analysis of effects of superloads has been conducted for a case study bridge. A detailed finite element (FE) model of the bridge, including all primary and secondary members, was created to evaluate the behavior. The FE analysis results were compared with results from a controlled load test of the bridge. The girder distribution factors determined experimentally and analytically were found to be significantly lower than comparable design values. Furthermore, from the load tests, the rotational restraint at the girder ends due to the abutments was determined to be as high as a fixed support. The FE model was then used to predict the effects of various superload trucks. The analysis results and field data suggest that some of the stiffener plates and cross-frame members of the analyzed bridge would be overstressed by certain superload truck configurations.
Nondestructive Evaluation of Installed Soil Nails
Authors: Gong Jie , Jayawickrama Priyantha W. , Tinkey Yajai
Published: May 2018

This paper presents the findings from a research study that evaluated nondestructive test (NDT) methods that may be useful for quality assurance purposes during construction of soil nail retaining walls. More specifically, the new NDT procedure will be used to evaluate the integrity of the grout column surrounding the steel tendon and to measure the grouted length of the installed soil nail. A preliminary evaluation of the existing NDT methodologies was undertaken to identify candidate NDT methods. The selected NDT methods, sonic echo and impact echo, were subjected to a detailed evaluation through three series of full-scale field NDT testing. The findings from the sonic echo tests are presented in this paper. The field studies demonstrated that the sonic echo method can be used successfully to detect major defects in installed soil nails. The nail condition predictions from sonic echo tests were confirmed by actual nail conditions observed after all the soil nails were exhumed.
Comparison of Measured and Computed Stiffness of High-Density Polyethylene Pipe
Authors: Burgon Rex P. , Folkman Steven L. , Moser A. P.
Published: May 2018

This paper examines the ability of traditional analytical methods and linear finite element models to predict the stiffness of high-density polyethylene (HDPE) profile-wall pipe in a parallel-plate test. The stiffness of typical pipe 36 in. and larger in diameter can be predicted quite accurately with a traditional analytical method. However, hand stiffness calculations for smaller-diameter pipes can have significant error. The most commonly used formula for calculating pipe stiffness is based on the assumption that deflections are a result of ring-bending stresses alone, an accurate assumption when a solid-wall pipe is being considered. However, for profile-wall pipe, shearing stresses, thrust stresses, and stability can have significant influences on pipe deflections and in turn on the pipe stiffness. Small-diameter pipes typically have larger profile height-to-diameter ratios. These “taller” profiles are more susceptible to the influence of thrust and shearing stresses. A more accurate formula for calculating pipe stiffness, one that accounts for shear and thrust stress, was developed. Stiffness values determined from these traditional analytical methods were compared with results from finite element models as well as from the physical test data. In addition, in parallel-plate testing, significant deflections occur in the pipe rib just under where the pipe comes in contact with the flat plate. These localized deflections reduce the computed pipe stiffness if the pipe deflection is based on the displacement of the plates. If the deflections of the inside diameter of the pipe were used to compute pipe stiffness, higher pipe stiffness values would be obtained.
Development of Transport Mode Choice Model by Using Adaptive Neuro-Fuzzy Inference System
Authors: Andrade Katia , Uchida Kenetsu , Kagaya Seiichi
Published: May 2018

Developing precise travel behavior models is important for estimating traffic demand and, consequently, for planning transportation systems. A study is presented that suggests a hybrid model that combines a stochastic model with a neuro-fuzzy inference system. The model is applied for estimating traveler behavior in the context of the problem of transport mode choice. Particularly, the multinomial logit model with neuro-fuzzy utility functions is developed to investigate shopping traveler preferences regarding the modes of bus, subway, and automobile. The model is evaluated by comparing its results with the results of a multinomial logit model. Moreover, the probabilities of selecting a transport mode obtained by applying the two models are compared with the actual transport mode choices, which show better performance of the proposed model. In addition, the model demonstrates good performance by estimating a large number of right choices during the validation process. A sensitivity analysis demonstrates the influence of time variations of mode subway on the probabilities of selecting a transport mode. The analysis highlights different behaviors of the models caused by the different utility functions. The results confirm that the proposed model can describe uncertainties regarding traveler decisions on the time of transport mode choice.
Use of Walk Opportunities Index to Quantify Local Accessibility
Authors: Kuzmyak J. Richard , Baber Charles , Savory David
Published: May 2018

A research effort was undertaken by the Baltimore Metropolitan Council, Maryland, to explore further the relationship between land use and transportation to support regional planning analysis. Particular attention was given to quantifying the role of key land use factors such as density, diversity, and design (3Ds) and regional accessibility in determining rates of vehicle ownership and vehicle miles traveled (VMT). The research was facilitated by a recent regional household travel survey and significant untapped geographic information system (GIS) resources. What began as an effort simply to replicate the approach of an earlier published study that incorporated the 3Ds took an unexpected turn. The result was an entirely new measure, a walk opportunities index, which combines information on the number, character, and desirability of key activities located within walking distance of a household. GIS procedures were used to trace walk paths to each destination by using the street grid and to compute travel times while adjusting for topography and difficult street crossings. By using the gravity model paradigm, each opportunity was then discounted by its travel time and the results summed into a single measure of walk opportunities. When used in combination with measures of entropy, regional accessibility, and socioeconomic characteristics, this new index had important statistical value in regression models of household auto ownership and VMT. The ability of these models to address the travel effects of alternative transportation and land use development plans or policies makes them a potentially powerful tool in regional planning activities.
Conceptual Model of Location of Small Office Firms
Authors: Elgar Ilan , Miller Eric J.
Published: May 2018

A conceptual model of location decisions of small office firms is presented. Most firm location models consider all firms in a region; this process usually enables market segmentation only according to the industry classification of a firm. This approach introduces a high level of heterogeneity into the modeling system, since firms’ attributes vary greatly in multiple dimensions. Moreover, most firm location models assume utility maximization behavior and use random utility models. In this conceptual model, an effort is made to reduce heterogeneity through focusing on the relatively homogeneous population of small office firms. Small office firms are also theorized to be satisficers rather than maximizers or optimizers; consequently, more adequate models for the phenomenon may incorporate rule-based approaches rather than random utility techniques. The conceptual model depicted constitutes a first step toward the validation of the proposition that firm location models should be more sensitive to market segmentations and that different methods of decision-making models need to be applied to firms from different parts of the economy.