bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimizing Policies of Railway Ballast Tamping and Renewal
Authors: Zhao Jianmin , Chan A. H. C. , Stirling A. B. , Madelin K. B.
Published: May 2018

This paper discusses optimizing ballast tamping and renewal (T&R) jointly to reduce the life-cycle cost of ballast. A life-cycle cost model is developed to incorporate a track deterioration model and a tamping model. Based on the models, three optimal policies of ballast T&R are investigated, which include fixed intervention level, constant interval of tamping, and optimal nonconstant intervals of tamping. Three algorithms are presented to obtain the optimal solutions for the three policies. An example is presented to illustrate model performance. From a whole life point of view, eight options based on the three policies are compared for a better understanding of the effectiveness of the policies. The results show that considerable benefit could be achieved by considering ballast tamping and renewal together and implementing the optimal policy.
Laser–Air-Coupled Hybrid Noncontact System for Defect Detection in Rail Tracks
Authors: di Scalea Francesco Lanza , Rizzo Piervincenzo , Coccia Stefano , Bartoli Ivan , Fateh Mahmood
Published: May 2018

Recent train accidents, with associated direct and indirect costs as well as safety concerns, have reaffirmed the need for developing rail defect detection systems that are more effective than those used today. One of the recent developments in rail inspection is the use of ultrasonic guided waves and noncontact probing techniques to target transverse-type defects. Besides the obvious advantages of noncontact probing, which include robustness and potential for large inspection speed, such a system can detect transverse defects under horizontal shelling or head checks. A rail inspection prototype based on these concepts and funded by the FRA is under development at the University of California–San Diego. This work reports on the status of the prototype development, including hardware and software development. Key features of the software are the feature extraction and the automatic pattern recognition algorithms. The laboratory results demonstrate the detection and sizing of transverse, surface-breaking cracks that extend for less than 20% of the rail head cross-sectional area.
Toolbox with Nondestructive Testing Methods for Condition Assessment of Railway Bridges
Authors: Helmerich Rosemarie , Niederleithinger Ernst , Wiggenhauser Herbert
Published: May 2018

The unified economic structure of the European market requires a unified transport infrastructure to ensure seamless and barrier-free transportation of passengers and goods. The European Commission has been funding the European Integrated Project, Sustainable Bridges, to comply with future traffic demands. The main objective of the project is to assess reliably and upgrade the bridge infrastructure for the required increase of axle loads and transport volume. Thirty-two institutes from 12 countries have developed unified procedures for the assessment and improvement of the existing railway bridge stock under the guidance and review of six major European railway companies. Nondestructive testing (NDT) has been given a high priority. One of the work packages concentrates on the potential of advanced NDT methods and creates a toolbox with advisable methods for the condition assessment of all types of railway bridges. Although NDT methods are implemented in the quality assurance process in many industries, their application in the railway infrastructure is not common. Only a few countries have included selected NDT methods in their advanced condition assessment procedures for the management of their bridge stock. This paper describes current activities to enhance pulse-phase thermography, impulse radar, and acoustic methods. The advanced methods enable infrastructure owners to verify construction plans; assess structures, repair, and strengthening quality; or identify in-service damages. An automated scanning system for combined acoustic and electromagnetic measurements has been developed recently. The results can be combined through data fusion techniques to increase their value for the bridge owners.
Evaluation of Collision Warning–Collision Avoidance Systems Using Empirical Driving Data
Authors: Zheng Pengjun , McDonald Mike , Wu Jianping
Published: May 2018

Collision warning–collision avoidance (CWCA) systems are showing increasing promise in preventing rear-end collisions. The effectiveness of many prototype systems has been evaluated on driving simulators or through numerical simulation, and several field tests are under way. Most investigations have focused on the safety benefits to host vehicles. Possible effects of CWCA-equipped vehicles on other traffic, especially the direct follower, have received little attention. Results of an evaluation study of this issue are presented. It is found that CWCA vehicles may have higher risk of rear-end collision with following vehicles. Thus, it may be necessary to design a CWCA system that is able to offer a balanced protection to host vehicles and to other traffic by considering possible effects of CWCA systems on other traffic.
Providing Intersection Decision Support under Challenging Conditions
Authors: Shladover Steven E. , VanderWerf Joel , Ragland David R.
Published: May 2018

Results of simulation studies are described: the studies were designed to determine how effectively left-turning drivers can be alerted to imminent conflicts with opposing traffic under difficult operating conditions and with limited detector capabilities. These conditions include approaching vehicles changing speed in locations not covered by detectors and detectors that may be able to detect only vehicle presence, but not speed. In cases without direct speed detection, one may try to rely on historical speed statistics to estimate the speed of approaching traffic, but unless the approach speeds are confined to a narrow range, the system is vulnerable to both false positive and false negative alerts in the respective cases of the real vehicle speeds being less than and greater than the assumed historical value.
Rural Expressway Intersection Surveillance for Intersection Decision Support System
Authors: Alexander Lee , Cheng Pi-Ming , Donath Max , Gorjestani Alec , Menon Arvind , Newstrom Bryan , Shankwitz Craig , Ward Nic , Starr Ray
Published: May 2018

More than 30% of all vehicle crashes in the United States occur at intersections; these crashes result in nearly 9,000 annual fatalities, or approximately 25% of all traffic fatalities. Moreover, these crashes lead to approximately 1.5 million injuries per year, accounting for approximately 50% of all traffic injuries. In rural Minnesota, approximately one-third of all crashes occur at intersections. AASHTO recognized the significance of rural intersection crashes in its 1998 Strategic Highway Safety Plan and identified the development and use of new technologies as a key initiative to address the problem of intersection crashes. A study of 3,700 rural Minnesota intersections showed that right-angle crashes account for 36% of all rural intersection crashes. Approximately 50% of crashes at intersections that have higher than expected crash rates are right-angle crashes. Further investigation also found that poor gap selection is the predominant causal factor in these crashes. To address the problem of poor gap selection, the University of Minnesota and the Minnesota Department of Transportation have a rural intersection decision support (IDS) system under development. When deployed, it will provide a driver with the additional information needed to make correct decisions concerning the available gap. The surveillance component of a rural IDS system is described. The surveillance system uses sensors, processors, and a communication system to determine the intersection “state,” including location, speed, acceleration, lane of travel, and vehicle classification (where necessary) of each vehicle in the surveillance zone. This state information will determine when to activate alerts and warnings.
Advanced Traveler Information System for Metropolitan Expressways in Shanghai, China
Authors: Gan HongCheng , Sun LiJun , Chen JianYang , Yuan WenPing
Published: May 2018

Many metropolitan cities experience severe congestion on their expressways. Advanced traveler information systems (ATISs) have been proposed as possible solutions for reducing congestion. A novel type of ATIS is presented; it is designed for network control of expressways and consists of three new kinds of variable message signs (VMSs). These VMSs are network-level guidance signs, road section signs, and entrance condition signs. Network-level guidance signs and road section signs provide traffic information in a graphical form, and entrance condition signs provide information about on-ramp conditions in a textual style. The ATIS composition and the functions of different VMSs are first presented. Then the information provision method for VMSs is addressed, followed by site placement of VMSs. ATIS evaluation results are presented and, finally, recommendations for future research are described.
Tools for Supporting Implementation Decisions of Intelligent Transportation Systems
Authors: Khattak Asad J. , Dahlgren Joy W. , McDonough Patrick
Published: May 2018

Planners and engineers may consider both conventional capacity improvements and intelligent transportation systems (ITS) to address transportation problems. Examples of ITS include freeway service patrols, advanced vehicle location systems, and certain elements of employee transit pass programs, each with various advantages. Details of a system to help planners and engineers make informed decisions about ITS deployment are provided. ITS Decision is designed to provide comprehensive information about state-of-the-art ITS technologies in a relevant form—the user can access desired information without sifting through irrelevant material. In addition, ITS Decision offers innovative tools to help users identify ITS appropriate for particular transportation problems. An expert system queries the user about specific conditions, diagnoses the problem, and suggests ITS remedies. The case-based reasoning tool lets users match historical cases that are most similar and see the effects. Given the still limited penetration of ITS into appropriate settings, the expert system and case-based reasoning tools are meant to stimulate greater deployment of promising technologies in localities that have not adopted such systems.
Risk-Averse Time-Dependent Route Guidance by Constrained Dynamic A* Search in Decentralized System Architecture
Authors: Chen Yanyan , Bell Michael G. H. , Wang Dongzhu , Bogenberger Klaus
Published: May 2018

Both the risk of concentration phenomenon for the navigation system and the risk of encountering unacceptable delay are reduced by guiding risk-averse drivers along reliable paths while avoiding high-risk links as far as possible. A constrained dynamic A* algorithm is proposed to search for a reliable path subject to a trip duration constraint in a time-dependent road network. The efficiency of the dynamic A* search is increased by taking advantage of information computed off-line. The algorithms proposed are implemented, and their computational performance is analyzed in simulation.
EZ M-Parking System
Authors: Jin Mingzhou , Guo Weiwen
Published: May 2018

M-commerce has been applied in parking payment systems since 2001. However, its complicated user interface increases time for motorists to complete transactions and, therefore, hurts the popularity of mobile phone–based parking systems. A new m-commerce parking system called the EZ M-parking system is proposed for both on-street and off-street parking. A unique number including a check digit is assigned to and painted on each parking space. Motorists need dial only a single number to start or end their parking service. Short message service (SMS) messages are used to send confirmations or reminders to motorists. Parking enforcement officers can check the occupancy of a parking space online or based on the SMS messages received from the management center. Officers can also send SMS messages to motorists if necessary. This system allows flexible pricing and accurate charging and includes several methods to reduce operation errors. The real-time parking occupancy data can help develop parking guidance systems and facilitate traffic and parking analysis. Motorists can buy prepaid parking cards similar to phone cards to deposit money into the account connected to their mobile phones. The EZ M-parking system is more cost-effective, user-friendly, and error-proof than conventional parking payment methods and other mobile phone–based parking systems.
Travel Time Estimation Techniques for Traffic Information Systems Based on Intervehicle Communications
Authors: Xu Huaying , Barth Matthew
Published: May 2018

As traffic congestion continues to grow on our roadway systems, trip travel times are becoming less consistent and less predictable. To help travelers plan trips better, traffic information systems are becoming increasingly valuable. These traffic information systems can be used off board (e.g., on the Internet before trip departure) or on board; several navigation systems exist that can provide real-time traffic information. Most traffic information systems are based on a centralized architecture focused on a traffic management center (TMC) that collects, processes, and disseminates traffic data. As an alternative approach, there has been recent interest in decentralized traffic information systems, that is, those that are based on intervehicle communications (IVC). As IVC-equipped vehicles travel the roadways, they can share information on network traffic conditions, and regional traffic information can soon be established. Decentralized systems avoid potential single-point failures that a TMC-based system might have and are capable of covering roadways that do not have embedded loop detectors. Several techniques are investigated on the way traffic information can be collected, processed, and shared in a decentralized IVC-based traffic information system. These techniques vary from simple blind averaging between all participating vehicles, to more sophisticated techniques using decay factors or filtered estimation. Simulation experiments have been carried out with the use of a unique integrated vehicle-traffic–network-communication tool to analyze the efficacy of decentralized IVC-based traffic information systems, on which each estimation technique has been rigorously evaluated.
Extracting Roadway Background Image
Authors: Zheng Jianyang , Wang Yinhai , Nihan Nancy L. , Hallenbeck Mark E.
Published: May 2018

Traffic monitoring cameras are widely installed on streets and freeways in U.S. metropolitan areas. Video images captured from these video cameras can be used to extract many valuable traffic parameters through video image processing. A popular way to capture traffic data is to compare the current traffic images with the background image, which contains no vehicles or other moving objects, just background such as pavement. Once the moving vehicle images are separated from the background image, measurements of their number, speed, and so on can be obtained. Typically, background images are extracted from a video stream through image processing because it may be hard to find a frame without any vehicles for normal traffic streams on urban streets. This paper introduces a new method that can quickly extract the background image from traffic video streams for both freeways and intersections in a variety of prevailing traffic conditions. This method has been tested with field data, and the results are promising.
Probes as Path Seekers
Authors: Demers Alixandra , List George F. , Wallace William A. , Lee Earl E. , Wojtowicz Jeffrey M.
Published: May 2018

In a recent field experiment, a fleet of Global Positioning System—equipped vehicles shared real-time data about network travel times over a wireless network and had their path choices automatically updated accordingly. This paper describes the behavior of these 200 vehicles during the 3-month experiment and illustrates the kind of information that can be derived from the data archive that the vehicles created. Much can be learned about real-time traffic-responsive path choice, travel times, compliance, and more. Planners, designers, and system operators can learn much about the way a system behaves and can sharpen their ability to create systems that work effectively and efficiently under all ranges of use. True path seeking by probe-equipped vehicles will arise when such vehicles become a common part of the vehicle fleet.
Calculation of Travel Time Variability from Loop Detector Data
Authors: Oh Jun-Seok , Chung Younshik
Published: May 2018

Travel time variability has recently become an important measure in transportation system management and has begun to be treated as a major factor influencing travel decisions. The main purpose of this study is to develop a database to help understand traffic variability of point measures and route-level measures by incorporating existing traffic surveillance systems. This study develops an integrated geographic information system database for traffic analysis in Orange County, California, and reports temporal and spatial traffic variability as measures of travel reliability. The database is to provide the analysis framework to study travel time variability at both the section level and the route level. In many cases, traffic data are used for traffic operations without the data being stored. The archived traffic data can play an important role as a way of measuring freeway performance. Such historic data make it possible to analyze such travel time variability from a long-term perspective. The database developed in this study is expected to help researchers and practitioners understand travel time variability as a measure of transportation system reliability by providing the analysis framework.
Accuracy Assessment of Traffic Monitoring Devices Vehicle by Vehicle
Authors: Gillmann Ralph
Published: May 2018

Traffic monitoring devices count or classify vehicles or measure characteristics such as vehicle speed to portray traffic movement. The accuracy of these devices is often assessed by a comparison of aggregate or binned outputs with reference values. However, this process overlooks errors in the detection or measurement of individual vehicles. If vehicle-by-vehicle data are available, the accuracy analysis may be improved. Several methods are presented to assess traffic monitoring devices with vehicle-by-vehicle data. The approach taken is to use measures of agreement based on a frequency table, called a confusion matrix, which cross-classifies the data from traffic monitoring devices and a reference standard. In addition to the overall accuracy, several forms of the kappa statistic with and without weighting are presented. Prevalence is treated by normalization. Findings are illustrated by data from a study of automatic vehicle classifiers.
Characterization of Truck Traffic in California for Mechanistic–Empirical Design
Authors: Lu Qing , Harvey John T.
Published: May 2018

Truck traffic information is one of the key inputs in the design and analysis of pavement structures. Until relatively recently, truck traffic data typically were aggregated into equivalent repetitions of a standard axle load for pavement design. The mechanistic pavement design procedures being developed for the California Department of Transportation by the University of California Pavement Research Center will make use of axle-load spectra and other more detailed truck traffic information when incremental design and incremental–recursive design approaches are used. It is necessary to develop traffic inputs in different regions in the state to support the new pavement design procedures. With the weigh-in-motion data collected in California, the truck traffic characteristics were studied for developing default traffic inputs. Traffic composition, temporal and spatial distribution of truck volume, traffic growth rate, vehicle speed, and axle-load spectra were analyzed by intensive and unbiased sampling. Cluster analysis was applied to multivariate responses (e.g., axle-load spectrum) to extract the structure of highway sections in terms of traffic characteristics, which ensured the preservation of useful information during analysis.
Identification and Correction of Dual-Loop Sensitivity Problems
Authors: Cheevarunothai Patikhom , Wang Yinhai , Nihan Nancy L.
Published: May 2018

Freeway traffic speed and bin volumes for different vehicle categories are typically collected by dual-loop detectors. Good quality dual-loop detector data are crucial for effective real-time traffic management systems and traveler information systems. However, loop detectors are subject to various malfunctions that can result in erroneous measurements. Previous studies indicated that loop sensitivity-level discrepancies between two single loops forming a dual-loop detector and unsuitable sensitivity levels of the single loops are two major causes of quality degradation in dual-loop data. This paper presents an algorithm and its implementation for identifying and correcting such loop sensitivity problems. The algorithm identifies dual-loop sensitivity problems using individual vehicle data extracted from loop event data and corrects dual-loop sensitivities through a two-step procedure: (a) remove the sensitivity discrepancy between the two single loops and (b) adjust their sensitivities to the appropriate level. Elimination of dual-loop sensitivity problems significantly enhances the reliability of dual-loop detectors and improves the quality of traffic speed and bin volume data.
Identifying Lane-Mapping Errors at Freeway Detector Stations
Authors: Lang Lixin , Coifman Benjamin
Published: May 2018

With several loop detectors, numerous junctions, and site-specific configuration files, many opportunities exist for errors at a freeway detector station in mapping from a loop detector input to its physical location and lane in the freeway. If these configuration errors are not caught, they propagate to the station's data and any control decisions based on those data. Great care is necessary to prevent such errors, yet they persist in the field even with the added expense of trying to prevent them. This paper develops and tests two algorithms to identify such errors without using a priori knowledge about the detector station configuration. By correlating events between two loop detectors, the first algorithm tests all active detectors to match pairs from dual-loop detectors and to identify any single-loop detectors at the station. The second algorithm uses a hypothesis-test-based K-means method to group lanes from common directions based on time series velocity. Both algorithms exhibited good performance; they were tested over many days and detector stations. Although the analysis focuses on loop detectors, the methodology should also apply to emerging technologies that mimic loop detectors, such as wayside-mounted microwave radar.
Visually Improving Construction Contract Administration
Authors: Sturgill Roy E. , Vorster Michael C.
Published: May 2018

The construction industry runs into many claim and dispute issues. Often these can be associated with the contractual conditions. What if the conditions themselves or the people writing them are not causing the problems? The blame may fall on the actual reading of the complex conditions and the inability of the human brain to comprehend all the information read. The field of psychology can be used to support this claim as well as to support the potential solution of use of flowcharts to illustrate contract conditions. The flowcharts provide a visual framework to complement and organize the text of the conditions. A project was designed with the Virginia Department of Transportation and the Virginia Polytechnic Institute and State University to collaborate and investigate flowchart usage. Flowcharts depicting general conditions were produced, and the outcomes of the project support the claim that a greater understanding can be achieved with the creation and use of flowchart-based conditions complementing the text format.
Quantity-Based Approach to Preliminary Cost Estimates for Highway Projects
Authors: Chou Jui-Sheng , Peng Min , Persad Khali R. , O'Connor James T.
Published: May 2018

The preliminary cost estimate heavily influences the fate of a transportation project, yet it can be up to an order of magnitude off the final bid amount. Poor prediction of costs in state departments of transportation can lead to less-than-optimal project selection at the front end and delays later when funding is not adequate to cover planned projects. A demonstration is made of the potential to separate quantity uncertainty from price uncertainty. If item quantities can be predicted early, then readily available unit prices can be applied to create a semidetailed preliminary estimate. Compared with the typical practice of applying a gross cost per lane mile, the proposed approach provides a more detailed basis for tracking the effects of changes during project development. This methodology is being tested for implementation by the Texas Department of Transportation.
Sample Size Requirements for Seismic and Traditional Testing of Concrete Pavement Strength
Authors: Velivelli Lakshmi K. , Gharaibeh Nasir G. , Nazarian Soheil
Published: May 2018

The strength of portland cement concrete (PCC) is one of the major acceptance quality characteristics in most existing specifications and quality assurance programs for PCC pavement. A statistical method is provided for determining the sample size requirements for reliable estimates of PCC parameters for pavement strength. These parameters include compressive strength from cylinders, flexural strength from beams, and dynamic seismic modulus from both portable seismic pavement analyzer and the free–free resonant column seismic nondestructive testing (NDT) methods. The sample size, which refers to the number of tests or measurements for each quality characteristic taken randomly from a lot, is a function of specifications tolerance, buyer's (i.e., agency's) risk, seller's (contractor's) risk, and the standard deviation of the test parameter under consideration. In practice, sample size typically is set on the basis of practical considerations and engineering judgment. Although practicality is an important consideration, there is a need to verify the adequacy of these practices on the basis of sound statistical analysis. The cost of sampling and testing is also discussed. The results of the study reveal that the sample size used in FAA's Item P-501 (which is four beams or cylinders per lot) is relatively small and needs to be increased. A larger sample size can be most cost-effectively achieved if seismic NDT is used because of the rapid and nondestructive nature of these testing methods.
Quality Assurance of Hot-Mix Asphalt
Authors: Turochy Rod E. , Willis J. Richard , Parker Frazier
Published: May 2018

Quality assurance is the process by which highway construction elements are sampled and tested to ensure compliance with specifications and other project requirements. The results of contractor-performed tests, originally performed for quality control purposes, are increasingly used in the acceptance decision in many states. The Georgia Department of Transportation (GDOT) uses contractor-performed tests in the acceptance decision on acceptable corroboration of GDOT-performed tests. Statistical analyses were performed to assess differences between tests conducted on hot-mix asphalt concrete by GDOT and its contractors during the 2003 construction season. Measurements of gradation and asphalt content taken by both parties were compared both across all projects and on a project-by-project basis for projects large enough to meet sample size requirements for this type of analysis. Both tabular and graphic representations of data are used to interpret the results. Statistically significant differences occur in some cases; these differences are much more common when comparing variability of these measurements than with the means. At the project level, on most projects in which statistically significant differences occur, the GDOT value typically is larger.
Probabilistic Procedure for Analyzing Construction Pay Adjustment Systems
Authors: Vidalis Sofia M. , Kopac Peter A. , Najafi Fazil T.
Published: May 2018

Statistical quality assurance specifications containing pay adjustment provisions for quality let the contractor decide what levels of quality to target during construction. A procedure and accompanying computer program have been developed to address the optimization of target quality levels. This dual-purpose procedure will help contractors intelligently set target quality levels and help highway agencies validate their quality assurance specifications and pay adjustment provisions. By using the proposed procedure, a contractor can answer the question, “What target quality levels will lead to maximum profit in my specific situation?” The informal procedure contractors currently use does not consider probability and risk. Also, by following the same proposed procedure by using its own data, an agency can answer the question, “What quality levels are the specifications forcing our contractors to deliver?” This important question must be properly answered for the agency to determine the impact of its pay adjustment provisions on contractors. An exercise is presented to compare the current and proposed procedures. The two procedures may identify different optimal target values, leading to sizeable differences in a contractor's profit.
Mathematical Modeling Procedures for Performance-Related Specifications
Authors: Weed Richard M.
Published: May 2018

Performance-related specifications (PRS) that depend on quantified relationships between various construction characteristics and performance provide one of the best means for achieving both effectiveness and fairness in the administration of highway construction contracts. But if this approach is to be used to its fullest advantage, current knowledge must be synthesized into a simple and straightforward process that can be easily understood and applied by engineers having only a basic back-ground in statistics, mathematics, and computer science. A previous paper described how several approaches used successfully by the New Jersey Department of Transportation can form the basis for such a process. A logical continuation of this work has resulted in two important refinements. The first allows high and low failures of a two-sided requirement to be treated as separate quality measures, when appropriate, and the second provides a more general mathematical model to allow greater flexibility in developing multicharacteristic performance relationships. An extensive series of tests necessary to validate performance models derived by this procedure is described. The complete developmental process is offered as a practical alternative for agencies that want to develop their own versions of PRS.
Estimating Percent within Limits for Skewed Populations
Authors: Burati James L. , Weed Richard M.
Published: May 2018

Computer simulation, using samples of size 3, 5, and 10, was used to evaluate the percent within limits (PWL) estimates for populations with skewness coefficients from 0.0 to ±3.0. The average bias and variability were then determined for the 10,000 PWL estimates. The analyses show that even a moderate amount of skewness in the underlying population can affect both the accuracy (bias) and the variability of individual lot PWL values. The amount of bias increased as the amount of skewness increased, and the bias also increased as the sample size increased. The results show that with two-sided specifications the bias varies not only in its magnitude but also in its sign, that is, positive or negative, depending on the split of defective material outside the lower and upper limits (the PDL/PDU split). The amount of variability also increases as a greater percentage of the defective material is on the long tail of the distribution. Increased variability means that errors in individual lot estimates will be larger and thereby create a greater spread in the pay factors on a project. If skewness is present, the population cannot be identified only by its PWL value. It will also be necessary to consider what percentage of the defective material is outside each of the specification limits. The analyses indicate that erroneous results for a population's PWL value can be obtained if the population is only moderately skewed. For this reason it is important to monitor process data to ensure that they are from an approximately normal population.
Evaluating Specification Limits
Authors: Burati James L.
Published: May 2018

The results of a study to evaluate the existing South Carolina Department of Transportation (SCDOT) hot-mix asphalt quality assurance specification are presented. When the existing specification was developed, assumed values were used for the standard deviations needed to establish the specification limits. Acceptance test results from 39 different projects were analyzed to determine standard deviation values that were being obtained for asphalt content, air voids, voids in mineral aggregate, and density. For each project, standard deviation values were calculated for each lot, and these were then pooled to obtain a typical value for the project. The target miss variability, that is, the ability of contractors to center their processes on the target, was also determined for each acceptance characteristic. The project and target miss values were then used to establish a typical process standard deviation value for each of the four acceptance characteristics. All these standard deviation values proved to be smaller than those initially assumed and resulted in the SCDOT narrowing the specification limits for each of the acceptance characteristics. The project standard deviation values justified that these changes were made to reflect the actual variability that was present and not simply to tighten the specifications.
Finite Difference Modeling of Misaligned Dowel Bars and Their Effects on Joint Performance
Authors: Leong Patrick , Tighe Susan , Rothenburg Leo , Hein David
Published: May 2018

This paper presents an analysis of the potential impact of misaligned dowel bars on concrete pavement joint performance. The performance and efficiency of a concrete pavement joint is assessed through the ability of the joint to expand and contract under temperature variations. With the finite difference method, the pullout force and stress distribution resulting from various dowel bar misalignment combinations are compared to propose an acceptable misalignment value. It was found that the stress within the concrete is acceptable for dowel bar misalignments of 20 mm, and cracking is expected to occur if a dowel bar is misaligned by more than 25 mm.
Seismic Testing to Determine Quality of Hot-Mix Asphalt
Authors: Celaya Manuel , Nazarian Soheil
Published: May 2018

Existing practices for acceptance of hot-mix asphalt are based on parameters such as adequate density, adequate thickness, and adequate air voids of the placed and compacted materials. Current mechanistic routines for structural design of flexible pavements consider mainly the modulus of each layer. Therefore, a procedure to measure the modulus of each pavement layer shortly after placement is highly desired. Laboratory tests on specimens prepared from material retrieved during construction, such as the simple-performance tests, can be used to determine these moduli. However, these methods are time-consuming, and the equipment costs are high. In addition, prepared specimens may not be representative of as-placed materials. Seismic tests are more practical because they are rapid to perform and are nondestructive, immediate results are obtained, and the material is tested in its natural state. The portable seismic property analyzer (PSPA) is an example of such a device. The PSPA is presented as a real-time nondestructive method with which to assess the hot-mix asphalt quality in the field.
Thermal Imaging of Hot-Mix Asphalt Paving Projects in Connecticut
Authors: Henault John W. , Larsen Donald A.
Published: May 2018

Results of a study on thermal segregation of hot-mix asphalt (HMA) during pavement construction are presented. The significance of thermal segregation to pavement performance should not be overvalued, because it is not only possible but probable that other factors play more significant roles. For example, the idea is presented that density achieved is more dependent on HMA temperature (T) than temperature differentials (ΔT). It is surmised that thermal segregation has a negligible effect until cold-area temperatures drop below certain threshold values. This reasoning is based on results of a 5-year pavement condition survey that demonstrated little, if any, relationship between temperature differentials located with an infrared camera during HMA construction and subsequent damage to a pavement's surface. Although 5 years may be too short a period for some distresses to develop, extensive reflective cracking was observed at some locations; this demonstrates reflective cracking played a more prominent role than ΔT. Comparisons of asphalt contents and grain-size distributions between cold areas and their surrounding normal-temperature pavements demonstrated no significant differences, suggesting that temperature differentials in HMA during construction are not necessarily indicative of particle segregation. Finally, definitions for the terminology associated with HMA construction and infrared thermography are presented.
Field Trial of Infrared Joint Heater to Improve Longitudinal Joint Performance in New Hampshire
Authors: Daniel Jo Sias , Real William L.
Published: May 2018

Longitudinal joint cracking is one of the most prevalent forms of distress in asphalt concrete pavements. The joint area does not achieve the same density as the mat because of an unconfined edge on the initial pass and a cold joint during the second pass. The lower density allows water to penetrate, and the material cracks, usually within a year of construction. There are many techniques for constructing longitudinal joints; one is to preheat the joint before paving the second lane. A field study conducted in New Hampshire used an infrared joint heater on the base, binder, and surface layers of a full-depth hot-mix asphalt pavement. Thermocouples were embedded in the pavement to determine the extent of heat penetration from the infrared heaters. Cores were taken along the joint and in the travel lanes for both control and infrared test sections. Density and strength measurements taken on the cores show some statistically significant improvements in the joint constructed by using the infrared heater. Permeability measurements along the control and test joints were performed and show average differences between the two sections. Cracking surveys on the binder and surface layers performed 1 year after construction showed that the section of pavement where the infrared heater was used has significantly less cracking than the control section.
Evaluation of the Effect of Sampling Location on Laboratory-Measured Quality Control Parameters
Authors: Turner Pamela , West Randy C.
Published: May 2018

The sampling of hot-mix asphalt (HMA) is an important part of the quality control testing process. The quality of the sample can have a significant effect on the test results. When a sample of HMA is taken, the technician's goal should be to obtain a sample that is representative of the mixture that will be placed on the pavement and is not segregated or contaminated by foreign materials. Several possible choices exist for sampling locations. Samples may be taken from the back of the haul truck at the plant with either a shovel or a robotic sampling device. Samples can be taken at the paving site directly behind the spreader after the mix has been released from the screed but before the first roller has passed over it. Samples can also be taken with cores being cut from the compacted roadway. Each of these methods has its advantages and disadvantages. For this study, samples of two mixes were taken at various locations (truck by shovel, truck by robotic device, behind the spreader, and cores) for a period of several days and tested for asphalt content, gradation, and percent air voids. The results were compared to determine what, if any, effect sampling location has. Overall, although there is little statistical difference in the laboratory properties due to sampling location (except for percent asphalt content), it does appear that segregation may be occurring in the samples obtained from the truck by using a shovel (finer gradation, higher asphalt content, and lower percent air voids). Use of the remote truck sampling device appears to result in properties that more closely match the properties of the mix sampled behind the spreader for Mix 2.
Characterizing Strain Induced by Environmental Loads in Jointed Plain Concrete Pavements
Authors: Wells Steven A. , Phillips Brian M. , Vandenbossche Julie M.
Published: May 2018

The focus of this study is to provide a detailed analysis of the strain that develops as a result of environmental loads. The study characterizes slab response immediately after construction (first 72 h after paving) and also addresses seasonal effects over the first 10 months following construction. A heavily instrumented test section was constructed on SR-22 in Murrysville, Pennsylvania, to help characterize slab response to environmental loads better. Static strain and climatic data collected through the first 10 months after construction (August 2004 through June 2005) were analyzed to interpret pavement response to environmental loads as a function of location with respect to joint proximity, depth within the slab, and level of restraint applied to the slab. Many things were also learned about the strain that develops in the slab over the first 10 months after construction. The average strain in the fall was around –450 μstrain, whereas the average strain in the winter was –600 μstrain. The ambient temperatures increased during the spring and summer; this resulted in a decrease in the average strain to –250 μstrain. Thermal strain was found to be twice as high as the drying shrinkage the first winter after construction. A substantial amount of drying shrinkage occurred within the first 50 days after construction. Variations in drying shrinkage occur not only through the depth of the slab but also across the surface of the slab.
Jointed Plain Concrete Pavement Model Evaluation
Authors: Wang Weijun , Basheer Imad , Petros Katherine
Published: May 2018

The mechanistic–empirical pavement design guide developed under NCHRP Project 1–37A employs mechanistic models to calculate pavement primary responses for predicting pavement performance. Therefore, it is imperative that the primary response models be evaluated in relation to their prediction accuracy. In this study, both theoretical accuracy verification and comparison with field measurement were employed to judge the prediction quality of three primary response models commonly used in concrete pavement analysis, namely, ISLAB2000, JSLAB2004, and EverFE2.22. The theoretical evaluation involved simulations, sensitivity trials, and comparisons of calculated slab stress, strain, and deflection responses of a number of hypothetical pavement systems. The field evaluation involved direct comparison of model-simulated responses against those measured from the SHRP Ohio test section. It was found that the agreement between analytical solutions and those obtained by the three analysis programs was affected by the load location, location of the desired response, and consideration of slab self-weight in the analysis. The study also showed that the three analysis models were fairly able to simulate field-observed responses by using both the multiple-step and one-step approaches. For the pavement section analyzed in this study, the average percentage relative deviation of peak predicted responses from corresponding measurements (deflection and strain) was estimated as 16.2%, 17.6%, and 22.9% for ISLAB2000, JSLAB2004, and EverFE2.22, respectively. Because the evaluation of the three programs was conducted against one pavement structure, additional verification is required through the use of pavement structures with different materials and layer thicknesses. Besides accuracy, the user's selection of a specific analysis program will depend on run time, ease of use, cost, and ability to incorporate the base and subbase layers of pavement structures.
Effect of Slab Curling on Movement and Load Transfer Capacity of Saw-Cut Joints
Authors: Jeong Jin-Hoon , Lee Jae-Hoon , Suh Young-Chan , Zollinger Dan G.
Published: May 2018

The effect of slab curling on the development of cracking at saw-cut notches and long-term joint movement in the concrete pavement sections of the Korea Highway Corporation test road was investigated in addition to joint deflections and load transfer efficiency (LTE) at the joints. During paving operations, 50 joints were saw-cut immediately after the occurrence of a random crack in the concrete pavement. The location and the time of the uncontrolled cracking were observed by a comparison of the tensile strength of the concrete with the tensile stress developed by the slab curling because of the temperature difference between the top and bottom of the slab. The development of cracking and movement of the saw-cut joints and random cracks were observed over a 2-year period after construction. The relationship between the initial and long-term joint movements is presented. The deflections and LTE at the joints and random cracks were measured by using the falling weight deflectometer 2 years after concrete placement. The effect of slab curling due to a permanent built-in temperature difference on the deflection at the joint is described. In addition, the effect of dowel locking due to the upward slab curling on the load transfer capacity of the joint is presented.
Measurement and Analysis of Early-Age Concrete Strains and Stresses
Authors: Nam Jeong-Hee , Kim Seong-Min , Won Moon C.
Published: May 2018

The early-age behavior of continuously reinforced concrete pavement (CRCP) in terms of concrete strains and stresses due to environmental loading was extensively investigated. The strains measured with strain gauges in the actual CRCP cannot be used simply to calculate the concrete stresses by multiplying the elastic modulus of concrete because the measured strains include both the stress-dependent and -independent strains. In situ stress-independent strains were measured with vibrating wire gauges embedded in the modified half-cylinders developed in this study and in small beams. The total strains in the concrete were measured with vibrating wire gauges at different depths in both the longitudinal and transverse directions at the crack-induced area and the surrounding areas in several test sections. The crack width variation through the depth of the pavement was also measured with the gauges installed at the crack-induced area. The in situ coefficient of thermal expansion and drying shrinkage of concrete were successfully measured with the developed measurement devices, and these measured values were used to calculate the stress-dependent strains. The concrete stresses were then calculated from the stress-dependent strains and the calculated stresses were finally verified by comparison between the calculated stress at the instant of cracking and the measured strength.