bluuebunny/crossref_metadata_2025 huggingface dataset:
Wet Night Visibility of Pavement Markings
Authors: Gibbons Ronald B. , Andersen Carl , Hankey Jonathan
Published: January 2019

Thirty-three participants, all 60 years of age and older, evaluated the visibility of six different pavement marking materials under a simulated rain system operating at 0.8 in. (20 mm) of rain per h at night. Evaluation consisted of counting the number of skip lines visible from both a sedan and truck tractor, under headlight illumination only. Participants also evaluated markings from the sedan under dry conditions at night. Visual observations were compared with measured retroreflectivity of pavement marking materials, measured luminance of pavement marking materials at 30 m, and calculated retroreflectivity at 30 m, on the basis of measured luminance and illuminance provided by vehicle headlights. Data showed a high degree of correlation between the visibility distance of a marking material and the log of both the measured retroreflectivity and the calculated retroreflectivity. A definitive level of retroreflectivity required to meet drivers’ needs in wet night conditions was not found in the investigation and is now the subject of further study. There was also a high degree of correlation between measured and calculated values of retroreflectivity under simulated rain and measurements with the use of two current ASTM test methods, E2176 and E2177. In a second experiment, six original participants evaluated the visibility of the pavement marking materials for a 10-min interval following cessation of simulated rain. Results of the second experiment indicated significant differences in the time required for the visual performance of a pavement marking material to recover from rain for paint and bead products versus that of other pavement marking materials under evaluation.
FHWA's Maintenance Decision Support System Project
Authors: Mahoney William P. , Bernstein Ben , Wolff Jamie , Linden Seth , Myers William L. , Hallowell Robert G. , Cowie Jim , Stern Andrew D. , Koenig George , Phetteplace Gary , Schultz Paul , Pisano Paul A. , Burkheimer Dennis
Published: January 2019

The Federal Highway Administration's Office of Transportation Operations Road Weather Management Program began a project in FY 1999 to develop a prototype winter road maintenance decision support system (MDSS). The MDSS capabilities are based on feedback received by the FHWA in 2001 from maintenance managers at a number of state departments of transportation (DOTs) as part of an initiative to capture surface transportation weather decision support requirements. The MDSS project goal is to seed the implementation of advanced decision support services provided by the private sector for state DOTs. This has been achieved by developing core software capabilities that serve as a basis for these tailored products. After the 2001 user needs assessment was completed, the MDSS program was extended with the objective of developing and demonstrating a functional prototype MDSS. Field demonstrations of the prototype MDSS were conducted in Iowa between February and April 2003, and during the winter of 2004. The performance of the prototype MDSS was much improved during the second winter. The weather and road condition predictions were more accurate, and the treatment recommendations generated by the system were reasonable given the predicted conditions. Iowa garage supervisors actively considered the treatment guidance, and on occasion they successfully used the recommended treatments without modification. This paper describes the status of the MDSS project, results and lessons learned from the field demonstrations, and future development efforts.
Inverse Estimation of Friction Coefficients of Winter Road Surfaces
Authors: Nakatsuji Takashi , Hayashi Ikuko , Kawamura Akira , Shirakawa Tatsuo
Published: January 2019

This study is an extension of a method developed in a previous paper. The major concern remains one of how to estimate the friction coefficient of a winter road surface indirectly with the use of vehicular motion data. Similarly, in this paper, there is no change in the central structure of the argument; the friction coefficient is estimated as the solution to an optimization problem in which a tire model describing the interaction between tire and road surface is integrated into a genetic algorithm. The tire model differs from the previous method. The one-degree-of-freedom (1-DOF) model that formulated only longitudinal motion is replaced by a 3-DOF model, in which lateral and angular motions have also been taken into account. This revised method was applied to data measured at three sites: at intersections on a test track, on curved sections of the same test track, and at intersections on arterials in Sapporo, Japan. The friction coefficients estimated by the method were in relatively good agreement with those actually measured. Lateral and angular motions have contributed to the improvement.
Improvement of Concrete Cracking Resistance and Joint Load Transfer through Coarse Aggregate Selection
Authors: Chupanit Punya , Roesler Jeffery R.
Published: January 2019

The ability to transfer load across concrete pavement cracks and the concrete cracking resistance can be improved by careful selection of the concrete constituents, such as the coarse aggregate. The fracture energy from the wedge splitting test was used to represent the cracking resistance of the concrete material, and the power spectral area parameter was used to represent the concrete surface roughness and indicate its ability to transfer load across a crack. Three aggregate types (limestone, river gravel, and trap rock), two aggregate top sizes (25 and 38 mm), and two aggregate gradations (dense and gap gradation) were used in this research to cast six concrete mixes. The experimental results showed that concrete mixes with strong aggregates (i.e., trap rock) had greater cracking resistance and load transfer ability than concrete mixes with weak aggregate (i.e., limestone). Concrete mixes with larger aggregate top sizes (38 mm) had improved mechanical properties relative to smaller aggregate top sizes (25 mm). The aggregate gradation was found to have little effect on the cracking resistance and shear load transfer ability of cracks for 25-mm river gravel aggregates. The wedge split fracture energy test better differentiated the mechanical properties between concrete mixes that contained varying aggregate types and sizes compared with the compressive strength test.
Simple Methods to Estimate Inherent and Stress-Induced Anisotropy of Aggregate Base
Authors: Kim Sung-Hee , Little Dallas N. , Masad Eyad
Published: January 2019

Simple methods to estimate cross-anisotropic properties of unbound aggregate assemblies on the basis of aggregate physical properties are presented. A regression model for the cross-anisotropic material properties was developed from a database consisting of aggregates from six sources. Aggregate specimens from each source were tested with the use of different gradations and compaction moisture contents. The results demonstrate that aggregate shape and gradation influence the level of anisotropy, which has a substantial effect on the pavement responses that affect pavement design. The level of anisotropy, defined as the ratio of the horizontal modulus to the vertical modulus, was calculated from the regression model and compared with the results from a micromechanics model. This micromechanics model accounted for the effect of particle orientation and the ratio of the normal contact stiffness to shear contact stiffness among particles on inherent anisotropy. Horizontal-to-vertical modulus ratios ranging from 0.4 to 1.0 were calculated with the micromechanics model. However, the experimental results and regression model show that the level of anisotropy can drop to as low as 0.15 because of the additional anisotropy induced by repeated loading. The effect of this increased anisotropy on the performance of a pavement with an unbound aggregate base is substantial.
Testing of Unbound Materials in the Nottingham Asphalt Tester Springbox
Authors: Edwards Paul , Thom Nick , Fleming Paul R. , Williams John
Published: January 2019

The current trend in mechanistic (analytical) pavement design is to use the mechanistic properties of pavement materials to optimize design. This is compatible with the move toward performance-based specifications and away from traditional empirically based design methods and recipe specifications. Other drivers—such as the Europeanwide adoption of aggregate mixture standards, which no longer differentiate on source, but moves toward sustainable construction—mean that a wide range of recycled, secondary, and primary aggregate sources can potentially be used in highway construction. The requirement for accelerated, performance-based testing is therefore coming to the fore. The U.K. Highways Agency has funded an accelerated testing program across a range of unbound capping and subbase materials. The performance parameters assessed, over a range of moisture and soaking conditions, are resistance to permanent deformation and resilient stiffness. The apparatus used during the unbound mixture assessments is the newly developed Springbox, which uses the standard Nottingham Asphalt Tester loading frame and software. This follows a simplification of the K-mold test and facilitates repeated loading of 170-mm cubic specimens under variable confinement. Samples are compacted into stainless steel liners. If required, samples can then be soaked before placement within the Springbox apparatus for testing. The following are discussed: the aggregate mixture performance parameters being measured, sample preparation procedures, the Springbox equipment and test procedures, a testing program of unbound capping and subbase materials, and results. The performance of the Springbox apparatus is discussed, and conclusions on the relative performance of the aggregates are presented.
Reliability of Piezocone Penetration Test Methods for Estimating the Coefficient of Consolidation of Cohesive Soils
Authors: Abu-Farsakh Murad Y. , Nazzal Munir D.
Published: January 2019

The current piezocone penetration test (PCPT) interpretation methods were evaluated for their capability to estimate the vertical coefficient of consolidation (c v) of cohesive soils reasonably by using the piezocone dissipation tests. Seven PCPT methods were evaluated. Six sites in Louisiana were selected for this study. At each site, in situ PCPT tests were performed, and soundings of cone tip resistance, sleeve friction, and pore pressures at different locations were recorded. Piezocone dissipation tests also were conducted at different penetration depths. High-quality Shelby tube samples were collected close to the PCPT tests and were used to carry out a comprehensive laboratory testing program. The (c v) values predicted by the different interpretation methods were compared with the reference values determined from the oedometer laboratory tests. The results of this study showed that two methods can estimate cv better than the other prediction methods.
Simplified Laboratory Assessment of Subgrade Performance Parameters for Mechanistic Design of Pavement Foundations
Authors: Frost Matthew W. , Edwards J. Paul , Fleming Paul R. , Arnold Stuart J.
Published: January 2019

With the increasing agenda for sustainability, the United Kingdom is attempting to move away from the empirical design of pavement foundations to develop a performance specification approach that facilitates analytical design. The measurement of the subgrade performance parameters of resilient modulus and resistance to permanent deformation is required for analytical design. These parameters ideally should be assessed concurrently under loading and environmental conditions similar to those the materials will experience in the field. To date, measurement of these parameters is largely confined to research laboratories using cyclic triaxial testing with advanced on-sample strain measurement. This apparatus is considered too complicated for routine commercial use; hence, the implementation of laboratory performance evaluation for routine pavement foundation design is potentially limited. A previous program of cyclic triaxial testing on clay subgrades indicated a series of useful correlations between strength and permanent deformation behavior (via a threshold stress) and material resilient modulus at this threshold. The previous work is reviewed; with these correlations, data from tests performed on three different clay materials to develop simplified equipment and procedures for the routine measurement of the required design parameters are presented. Simple pseudostatic tests can measure a subgrade modulus for a simplified performance-based design. The previous data (in the light of the recent work) were reevaluated to show a boundary correlation that may allow a shear strength–based parameter to control (in design) the onset of permanent deformation, and the ways long-term subgrade water content changes can be accommodated are detailed.
Using Repeated-Load Triaxial Tests to Evaluate Plastic Strain Potentials in Subgrade Soils
Authors: Puppala Anand J. , Chomtid Suppakit , Bhadriraju Venkat
Published: January 2019

The design and the analysis of flexible pavement systems depend on soil layer characterization, traffic loads, and number of passes. The current AASHTO design method for flexible pavements uses resilient characteristics of subsoils to characterize and determine the structural support of each layer and to design the thickness of the layers. This moduli property, however, does not fully account for the plastic strain or rutting potentials of subsoils, as in the cases in which silt and mixed soils undergo high plastic deformations but possess high resilient properties. A study was initiated to establish a test procedure to use a repeated load triaxial device to measure plastic strain potentials of subgrade soils. Laboratory-compacted soil specimens were subjected to a repeated deviatoric load, determined as a percentage of static deviatoric load at failure under un-consolidated undrained conditions. The plastic strains were monitored during 10,000 repeated load cycles, and the accumulated plastic deformations were determined. The test procedure and test results conducted on two types of soils, a coarse sand and silty sand, are presented. Effects of soil type, compaction moisture content, dry unit weight, confining pressure, and deviatoric stresses on the plastic strains were addressed.
Guidelines for Prime Coat Usage on Low-Volume Roads
Authors: Cross Stephen A. , Voth Michael D. , Shrestha Pramen P.
Published: January 2019

Prime coat has a purpose in the pavement construction process, yet many times prime is misused or eliminated during the project. Although most of the time no harm appears to occur to the roadway, and thus this practice may be viewed as acceptable, technical guidance is warranted to ensure appropriate usage. The objective of this study was to produce a prime coat guide for Central Federal Lands Highway Division project development and field personnel to provide decision-making guidance. The study consisted of a literature search, which focused on handbooks and technical reports, and a review of agency construction specifications. A phone survey of state departments of transportation in the region was undertaken to provide information on current practice. Finally, a review of both the potential harmful and the positive environmental effects of the prime coat process, including the various bituminous products used, was undertaken. On the basis of the information collected, a guideline for project development and field personnel was developed. The guideline provides guidance on how to use, when to keep, and when to eliminate prime coats.
Can Spring Load Restrictions on Low-Volume Roads be Shortened without Increasing Road Damage?
Authors: Kestler Maureen A. , Berg Richard L. , Haddock John E.
Published: January 2019

Major highways are designed to withstand heavy vehicles and high volumes of traffic year round. However, low-volume roads in seasonal frost areas are highly susceptible to damage from trafficking by heavy vehicles during spring thaw. Conventional practice is to place partial or full spring load restrictions on low-volume roads during spring thaw. This practice reduces road damage significantly. However, companies whose livelihood depends on trucking can suffer major economic losses as they await the removal of load restrictions. Using reduced tire pressure constitutes a less conventional technique that can reduce springtime damage. Reducing tire pressure generally appears to be less effective than reducing load. Nevertheless, it does appear that the load restriction window can be shortened in duration by implementing a reduction in tire pressure for a few weeks, starting toward the latter part of the standard spring load restriction period. With a mechanistic pavement design and evaluation model for seasonal frost areas, a critical combination of load and tire pressure reduction was developed; it contributes to optimizing the balance between minimizing springtime road damage and minimizing disruption to local economies caused by load restrictions. This analysis constitutes the first step in the development of simplified, general application guidelines for shortening the springtime load restriction window for a variety of pavement structures.
Validation of Enhanced Integrated Climatic Model Predictions with New Jersey Seasonal Monitoring Data
Authors: Ahmed Zubair , Marukic Ivana , Zaghloul Sameh , Vitillo Nick
Published: January 2019

Environment is one of the essential factors that influence pavement material behavior and consequently its performance. The variation of climatic patterns from region to region, coupled with the variation of site-specific conditions across North America, makes it difficult to develop standard models to account for seasonal variation in material properties that apply for all regions. Consequently, the need to develop regional models becomes an essential requirement for most transportation departments. The enhanced integrated climatic model (EICM) was evaluated to determine its suitability in predicting subsurface temperature and moisture conditions within New Jersey sites. The validation of the model used environmental data collected through pavement instrumentation of a large-scale research study under the sponsorship of the New Jersey Department of Transportation. Site-specific data were input to the model, and the model output parameters were compared against field-measured values. The results of the validation for two of the instrumented sites are reported. Results of the study do not indicate a high correlation between field-measured values and EICM-predicted temperature and moisture profiles for the various pavement layers.
Using Fiber Bragg Grating Sensors to Monitor Pavement Structures
Authors: Wang Jian-Neng , Tang Jaw-Luen
Published: January 2019

A new high-resolution temperature and strain sensor with fiber Bragg grating (FBG) technology was developed. The FBG sensor consists of a reference fiber grating and a grating pair scheme that could offer the potential of simultaneous measurement of strain and temperature for monitoring pavement structures. Experimental results showed that measurement errors of ±μ∈ and ±0.13°C for strain and temperature could be achieved, respectively. Feasible applications of this sensor for monitoring pavement structures were investigated. The reliability and long-term stability tests for this sensor were examined by mounting it on the surface of two kinds of specimens, asphalt and concrete, and several temperature cycles with a designed working temperature range up to 110°C were applied for at least 24 h. An electronic thermocouple and a long-period optical fiber grating (LPG) sensor with similar function were used to compare the performance. Small root-mean-squared temperature variations (better than 1°C) and excellent long-term stability (within 2%) were obtained. The maximum variations in temperature for 48 h were only 1.94% and 2.32% for asphalt and concrete specimens, respectively. Results indicated that although the performance of this FBG sensor was comparable with that of the conventional thermocouple, its long-term stability was four times better than its counterpart, the LPG sensor. This type of simple and low-cost fiber-optic sensor is expected to benefit the developments and applications of new paving materials, mix design procedures, or the enhancement of pavement management systems.
Framework for Real-Time Three-Dimensional Modeling of Infrastructure
Authors: Teizer Jochen , Kim Changwan , Haas Carl T. , Liapi Katherine A. , Caldas Carlos H.
Published: January 2019

Modeling transportation infrastructure assets in three dimensions (3D) is becoming increasingly necessary for good management. Condition assessment, maintenance, operations, and construction activities are exploiting 3D models for improved visualization, communications, and process control. Acquiring 3D models rapidly can improve safety and productivity and is becoming feasible through approaches based on sparse range point clouds; however, although this approach has contextual advantages, it is ultimately limited in speed. Emerging Flash laser detection and ranging (LADAR) technology is opening up the possibility of 3D modeling at rates better than 1 Hz (real time). A framework for 3D modeling is presented that includes the dimension of time. In particular, the performance of the Flash LADAR technology is examined, and potential applications are explored. Technologies such as Flash LADAR will play an important role in real-time modeling of infrastructure assets in the near future.
Analysis of Global Stability, Anchor Spacing, and Support Cable Loads in Wire Mesh and Cable Net Slope Protection Systems
Authors: Sasiharan Navaratnarajah , Muhunthan Balasingam , Shu Shanzhi , Badger Thomas C.
Published: January 2019

Wire mesh and cable net slope protection have been in use for more than 50 years along North American highways to control rockfall on actively eroding slopes. The basic design of these systems is comparatively similar throughout North America. It consists of a top horizontal cable suspended by regularly spaced anchors, typically a perimeter or widely spaced grid of horizontal and vertical support cables, and double-twisted, hexagonal wire mesh laced to the support ropes. To date, the design of the slope protection systems has been based primarily on empirical methods, engineering judgment, and experience. Although these systems generally perform well, there is some consensus among geotechnical specialists that some elements in the system may be overdesigned or even unnecessary. In addition, system failures under a variety of loading conditions within the past few decades indicate that certain design elements may in fact be underdesigned for their desired application. Analytical and numerical models to evaluate the stability of slope protection systems are presented. The inclusion of interior horizontal support ropes in addition to the top horizontal rope does not reduce the stress within the mesh and accordingly provides no mechanical benefit. Results also show that the stresses on the vertical support rope are much smaller than the top horizontal support rope. Therefore, the vertical ropes do not need to be as strong as the top horizontal rope. Further, some useful design charts for the design of slope protection system are presented.
Aggregate-Based Modulus of Elasticity for Florida Concrete
Authors: Yazdani Nur , McKinnie Bryant , Haroon Saif
Published: January 2019

The current empirical model for the Florida Department of Transportation (FDOT) concrete modulus of elasticity (E) is a function of concrete compressive strength and unit weight. Recent testing shows that this model consistently underestimates E for FDOT concrete. This underestimation may lead to construction problems caused by the overprediction of camber and the deflection of concrete structural members. E values for the typical concrete mix used in FDOT projects were experimentally determined at various concrete ages. Regression analyses were used to find the E models that best fit the generated data, and such models were compared with existing E models from the literature. It was found that the aggregate type and specific gravity play significant roles in influencing the E value of concrete. The best-fit E models for FDOT concrete, together with suggested modification factors for various aggregate types, are recommended.
Comparative Study of Cumulative Damage to Pavement Concrete under Splitting Tensile, Variable Amplitude Fatigue Loadings
Authors: Yun Kyong-Ku , Kim Dong-Ho , Jeong Won-Kyong , Won Chimoon
Published: January 2019

The purpose of this study was to compare the cumulative damage to pavement concrete under splitting tensile, variable amplitude fatigue loadings by splitting tensile and flexural tensile tests. The cumulative damage theories adapted in this study included the linear damage theory, the nonlinear damage theory, and the equivalent damage theory. The results were as follows. The sums of the cumulative damage were greater by the flexural tensile test than by the splitting tensile test, even though the difference between them was small in each load case. The sums of the cumulative damage at higher stress levels showed values farther from one than those at lower stress levels. This suggested that Miner's rule might be applied to plain concrete with little error, provided that the stress level remained low. The cumulative damage obtained by the nonlinear damage theory was closer to one than that obtained by the linear damage theory in all load cases except one. This indicated that nonlinear cumulative damage could consider the effects of the magnitude and the sequence of variable amplitude fatigue loadings. The theoretical results calculated from the equivalent damage theory were similar to the experimental results except in one case, even though the equivalent damage theory was simple. The results obtained by the splitting tensile test were equivalent to or better than those obtained by the flexural tensile test for application to the equivalent damage theory. Thus, the splitting tensile test and the equivalent damage theory could be used to estimate the damage and the remaining life of pavement concrete under variable amplitude fatigue loadings.
Evaluation of Use of Lithium Nitrate in Controlling Alkali-Silica Reactivity in Existing Concrete Pavement
Authors: Tuan Christopher Y. , Kelly Michael T. , Sun Haosu , Buss Mark E.
Published: January 2019

The study presents the findings from a 2-year field trial in which lithium nitrate was applied at a rate of 0.006 gal/ft2 twice a year on an existing concrete pavement in Norfolk, Nebraska, in an attempt to arrest ongoing alkali–silica reaction (ASR) distress. Various destructive and nondestructive means were used to measure the effectiveness of the treatments. Concrete cylinders were cored for petrographic examination and split tension testing. Powder samples were taken to determine the lithium content. Nondestructive evaluations used crack mapping, a Schmidt hammer, a velocity meter, and an impact echo apparatus. The amount of lithium that penetrated into the pavement by gravity soaking has been limited. The results to date have not shown a definitive benefit of application of the lithium material in controlling or mitigating the ASR process; presumably, the pavement has not reached the state of deterioration optimal for lithium penetration. The feasibility and effectiveness of other application techniques on hardened concrete, such as electrolysis, surface pressurization, and vacuum impregnation, should be investigated for comparison with the feasibility and effectiveness of gravity soaking.
Performance of Low-Slump Underwater Concrete Incorporating Antiwashout Admixtures
Authors: Nakhla Dina Adel , Abou-Zeid Mohamed Nagib
Published: January 2019

Antiwashout admixtures (AWAs) are among the agents recently used to minimize the adverse effects associated with underwater concrete placement. However, relatively little work on the influence of AWAs on the performance of underwater concrete and evaluation of the validity of the conventional and nondestructive test methods used has been conducted. Thirty mixtures were prepared with several water-to-cementitious material ratios, admixture types, and dosages. Concrete specimens were placed in air and at two underwater depths. The testing program involved fresh and hardened concrete testing as well as nondestructive testing. A simple method was used to assess the concrete and the corrosion damage on exposure to wetting and drying cycles in aggressive saline solution. The impacts of the type and the dosage of the AWAs admixtures, mix proportions, and placement depth on fresh and hardened concrete properties are highlighted. The results suggest that the quality of the surface of underwater concrete is inferior to that of its core and that there is a need to adjust and calibrate the nondestructive testing methods when such concrete is evaluated. Underwater AWA concrete exhibited relatively high degrees of susceptibility to damage when it was exposed to saline solutions.
Virginia Department of Transportation Early Experience with Self-Consolidating Concrete
Authors: Ozyildirim Celik
Published: January 2019

This paper summarizes the work conducted by the Virginia Department of Transportation on self-consolidating concrete (SCC). Initially, a laboratory study with locally available materials was conducted to develop and evaluate the properties of SCC, including flow, segregation, strength, permeability, resistance to cycles of freezing and thawing, and drying shrinkage. Studies at two precast plants followed. Then, one of the precast plants furnished SCC for an arch bridge. The other plant fabricated two bulb T-beams with SCC. Studies also were conducted with cast-inplace SCC. A structures pad at the FHWA Turner—Fairbank Highway Research Center, a median on I-64, and a column in Norfolk, Virginia, were constructed with SCC. The results show that SCC can be produced successfully and provide many benefits to transportation agencies and the construction industry.
Instrumentation and Analysis of High-Performance Concrete Bridge Decks
Authors: D'Ambrosia Matthew D. , Lange David A. , Grasley Zachary C. , Roesler Jeffery R. , Lee Chang Joon , Altoubat Salah A.
Published: January 2019

The use of high-performance concrete (HPC) for transportation structures was the subject of a 3-year study that involved field investigation, laboratory experiments, analysis, and modeling. The field study involved instrumentation and analysis of six HPC bridge decks. The laboratory component characterized early-age thermal, shrinkage, creep, and cracking behaviors. A three-dimensional finite element model was used in conjunction with material models to analyze and predict creep and shrinkage behavior and to investigate structural and material interactions. This paper focuses on the field component of the project and discusses the instrumentation, deformation measurements, and analysis of bridge decks in Illinois. The bridges were instrumented to understand the development of shrinkage and thermal stress in concrete bridge decks with the use of various materials and structural components. The results indicate that the stress development due to daily temperature cycles and long-term temperature changes are relatively small compared with the stress development due to drying shrinkage. According to model simulations, a 15% to 40% reduction in shrinkage would reduce the stress level enough to prevent most cracking. Although drying shrinkage is the major driving force for stress development, the interaction of concrete shrinkage and structural restraint influences the magnitude of the stress and is linked to the propensity for early-age cracking.
Customers' Reactions to the Introduction of High-Speed Rail Service
Authors: Suh Sunduck Daniel , Yang Keun-Yul
Published: January 2019

Korean Train Express (KTX) of South Korea introduced high-speed commercial rail service on April 1, 2004. It currently has two lines covering 661.1 km (413.2 mi), and its trains achieve speeds of 300 km/h (186 mph). KTX's offering represents the first phase of a scheduled two-phase introduction due to be completed in 2010. This paper documents the service changes of external transportation operators during the first 3 months of KTX operation and details the initial reactions of KTX customers. KTX reduced rail travel time between major cities by almost half. By offering 128 daily services, it increased seat supply by 33% among the major cities and increased revenue by nearly 100% for the Seoul–Busan line, as compared with the same April–June period the previous year. KTX achieved one million passengers in 14 days and 10 million passengers in 142 days of operation. Although these numbers are significant, they represent only about half the demand forecasted. Three major causes of this discrepancy are an inability to provide fully implemented KTX services, low Korean economic activity, and a degraded level of service on conventional passenger rail systems. The expected service level of passengers and the initial marketing strategies used appear to have negatively affected the successful introduction of KTX. However, demand trends show continued increases after the initial response. As a whole, KTX strengthened the viability of Korean rail travel and is expected to contribute to the building of a more balanced national transportation system.
Options for Improving the Energy Efficiency of Intermodal Freight Trains
Authors: Lai Yung-Cheng (Rex) , Barkan Christopher P. L.
Published: January 2019

Intermodal trains are typically the fastest trains operated by North American freight railroads. Ironically, these trains tend to have the poorest aerodynamic characteristics. Because of constraints imposed by equipment design and diversity, intermodal trains incur greater aerodynamic penalties and increased fuel consumption than other trains. Improving the loading patterns of intermodal trains has the potential to improve aerodynamic characteristics and thus fuel efficiency. Train aerodynamics and resistance analyses were conducted on several alternative intermodal train-loading configurations. Matching intermodal loads with cars of an appropriate length reduces the gap length between loads and thereby improves airflow. Filling empty slots with empty containers or trailers also reduces aerodynamic resistance and improves energy efficiency, despite the additional weight penalty and consequent increase in bearing and rolling resistance. Depending on the particular train configuration, train resistance can be lowered by as much as 27% and fuel savings by 1 gal/mi per train.
Improved Destressing of Continuous Welded Rail for Better Management of Rail Neutral Temperature
Authors: Kish Andrew , Samavedam Gopal
Published: January 2019

Maintaining high, stable rail neutral temperatures helps prevent the buckling of continuous welded rail (CWR) track. Rail neutral temperatures are typically set high during installation (90°F to 110°F), but the large variations that develop during revenue service often lead to buckling-prone conditions. Readjusting or correcting for these variations requires CWR to be destressed with the use of procedures that do not always restore the desired target neutral temperature. As part of the Federal Railroad Administration's Track Systems Research program, the U.S. Department of Transportation's Volpe Center is investigating rail force and neutral temperature influences on track buckling. An analytic model for field applications has been developed to improve destressing and readjustment of CWR in both winter and summer conditions. The model has been validated in several field tests on instrumented CWR test segments under both high tensile and compressive force conditions. Both wood and concrete tie tracks were tested, and the rail longitudinal movement, rail gap, rail force distributions after rail cutting and welding, and readjusted neutral temperature were measured and correlated with the model predictions. The model and test results were used to develop a field tool for more effective destressing and readjustment of CWR. The tool provides the required removal lengths of anchors/fasteners, the rail gap size requirements when mechanical loads (rail-pullers) are used to adjust to the desired neutral temperature, and the required amounts of steel removal in summer when cutting rail out for stress relief.
Interchange Critical Movement Analysis for Planning and Preliminary Design Applications
Authors: Bonneson James A. , Zimmerman Karl
Published: January 2019

A procedure that can be used to compare a variety of common interchange types or make decisions about their design is described. The technique is based on the critical movement analysis approach traditionally used for signalized intersection analysis. This approach defines the rules for quantifying the sum of critical flow ratios for various interchange types. The concept of interchange delay is defined, and an equation for quantifying it is described. Simulation data are used to calibrate a series of models that relate the sum of critical flow ratio to interchange delay. A procedure that describes how these models can be used to obtain a quick estimate of the delay associated with a particular interchange type, given specific volume levels, lane assignments, and ramp separation distances, is documented.
Driver Assessment of Service Quality on Urban Streets
Authors: Flannery Aimee , Wochinger Kathryn , Martin Angela
Published: January 2019

This paper presents the results of a study that compared drivers’ assessments of the performance of urban streets with objective measures of performance, including level of service (LOS). The purpose of the study was to test the ability of LOS to predict drivers’ perceptions of service quality. Seventy-seven automobile drivers rated the service quality of half-mile segments of urban streets as depicted on videotaped scenes from the driver's perspective. Drivers rated 12 to 15 video segments on a six-point scale from very satisfactory to very unsatisfactory. After rating all segments, the drivers selected and ranked from a list of 36 factors the three factors that they considered the most important to quality. The results show that the mean driver rating had statistically significant correlations with operational and design characteristics and aesthetics, including the following variables: travel time, average travel speed, number of stops, delay, number of signals, lane width, the presence of trees, and the quality of the landscaping. LOS, calculated by the Highway Capacity Manual methodology, predicted 35% of the variance in mean driver rating. This finding suggests that LOS does not completely represent drivers’ assessments of performance because drivers perceive the quality of urban street segments in several dimensions, including travel efficiency, sense of safety, and aesthetics.
Capacity at Intersections without Traffic Signals
Authors: Brilon Werner , Miltner Thorsten
Published: January 2019

Two-way stop control is a form of intersection operation in widespread use. Calculations of the level of service are usually based on gap acceptance theory. In the American Highway Capacity Manual, the influence of pedestrians is considered an impedance factor, whereas in the German guideline the influence of pedestrians and bicyclists has not been considered so far. To close this gap, an alternative calculation method, called the conflict technique, has been developed. This method allows consideration of the influence of nonmotorized road users on the traffic performance of motor vehicles. Moreover, the method provides a significant simplification of the entire theoretical approach. Different modalities of operation, such as a zebra crossing at the entries to an intersection, can be considered, as can the fact that some road users do not comply with the priority rules. It is possible to calculate the capacity for one movement from the minor stream from a single equation. To calibrate the calculation method, traffic at several intersections was observed by video and analyzed for traffic volumes, delays, compliance with priority rules, and other parameters. With these field measurements, the calculation method was calibrated to actual road-user behavior. Comparison of the conventional calculation concept based on gap acceptance and the new conflict technique showed that they provide similar results. In particular, the consideration of pedestrians and limited priority effects is a considerable benefit of the new method.
Comparison of Methods for Sensitivity and Uncertainty Analysis of Signalized Intersections Analyzed with the Highway Capacity Manual
Authors: Ji Xiaojin , Prevedouros Panos D.
Published: January 2019

Most users of the Highway Capacity Manual (HCM) would prefer to have confidence intervals around the estimate of delay, but no procedure measures the uncertainty in delay and level of service. Four sensitivity analysis methods-partial differential analysis (PDA), partial correlation coefficient analysis, standardized regression coefficient analysis, and the Fourier amplitude sensitivity test (FAST)-and four uncertainty analysis methods-first-order analysis (FOA), Monte Carlo simulation (MCS), FAST, and the point estimate method (PEM)-were investigated. They were applied to data from an actuated signalized intersection. All input variables in the delay model except for the duration of analysis period were considered uncertain, for consistency with HCM. Day-to-day variation was the source of errors. Progression factor, cycle length, green time, and saturation flow are the most sensitive parameters. The incremental delay and upstream metering factors are the least sensitive. Volume and peak hour factor fall in between. The four uncertainty methods produced similar results for the mean, standard deviation, and confidence intervals of control delay for the base case. When the standard deviations of input parameters were doubled, MCS, FAST, and PEM produced similar results. PDA and FOA appear to be less suitable for sensitivity and uncertainty analysis, respectively, of the HCM delay model for signalized intersections.
Effect of Pedestrian-Related Factors on Intersection Performance
Authors: Kim Hoe Kyoung , Hunter Michael P.
Published: January 2019

The Manual on Uniform Traffic Control Devices (MUTCD) contains the national standard for installing and maintaining traffic control devices on all streets and highways. The 2003 MUTCD contains numerous corrections, revisions, and updates to the millennium edition (2000). One update is related to the definition of crossing distance at signalized intersections, where the crossing distance is extended to the far-side curb rather than the center of the farthest traffic lane. This study investigated the sensitivity of intersection performance to crossing distance and walking speed, critical constraints in the determination of the minimum green time. Three crossing distance standards and four walking speeds are considered. With Highway Capacity Manual (HCM) procedures, the impacts of the given crossing distance definitions and walking speeds on intersection operations were tested on two intersection configurations over a range of cycle lengths and traffic volumes. The effect on intersection performance was found to be most significant at low cycle lengths, in some instances with the delay increased manyfold. However, when cycle lengths were increased to account for the pedestrian constraints, optimal delay rarely increased by more than a few seconds. Additionally, as the discrepancy between the critical lane traffic volume on the main and cross streets was increased, the impact of pedestrian green times on vehicle delay also increased. It was seen that as the cycle length increased, pedestrian minimum green times no longer governed, so the impact of pedestrians on intersection performance became increasingly insignificant, often with a minimal impact on the optimal performance.
Effects of U-Turns on Capacities of Signalized Intersections
Authors: Liu Pan , Lu Jian John , Fan Jingjing , Pernia Juan C. , Sokolow Gary
Published: January 2019

In Florida, the increased use of restrictive medians and directional median openings has generated many U-turns at signalized intersections. There is no widely accepted procedure for estimating the effects of U-turning vehicles on signalized intersection capacity. In the 2000 edition of the Highway Capacity Manual, U-turns are treated as left turns for estimation of saturation flow rates. However, the operational effects of U-turns and left turns are different. This study analyzed the effects of U-turning vehicles on the left-turn saturation flow rate. Data were collected at three signalized intersections in the Tampa Bay area in Florida. In total, the study team recorded the queue discharge times for 260 queues, including 571 U-turning vehicles and 1,441 left-turning vehicles. On the basis of the data collected in the field, a regression model was developed to estimate the relationship between the average queue discharge time for each turning vehicle and the various percentages of U-turning vehicles in the left-turn traffic stream. Adjustment factors for various percentages of U-turning vehicles were also developed by using the regression model. The adjustment factors developed in this study can be directly used to estimate the capacity reduction due to the presence of various percentages of U-turning vehicles at a signalized intersection.
Headway Compression during Queue Discharge at Signalized Intersections
Authors: Lin Feng-Bor , Thomas Daniel R.
Published: January 2019

Current methodologies for estimation of intersection capacity are based mainly on the concept of saturation flow. Saturation flow is the steady maximum queue discharge rate after the green light is turned on. According to the U.S. Highway Capacity Manual, this steady maximum rate is generally reached after the fourth queuing vehicle is discharged. Two recent studies conducted in Hawaii and Taiwan, however, have found that queue discharge headways tend to undergo compression for a considerable time as more vehicles in the same queue are discharged. Consequently, queue discharge rates often kept rising even after the 15th vehicle has entered the intersection. If this queue discharge characteristic is common in the United States, then there is a need to assess the implications of con-tinued use of the traditional concept of saturation flow rate for capacity analysis of signalized intersections. To provide insight into this potential problem, this study examines the queue discharge characteristics at three intersections on Long Island, New York. The queue discharge characteristics at all three intersections were found to be similar to those observed in Taiwan and Hawaii.
Calibrating and Validating Deterministic Traffic Models
Authors: Paulo Rui Miguel Batista , Lin Jiong , Rouphail Nagui M. , Sacks Jerome
Published: January 2019

Calibration and validation of traffic models are processes that depend on field data that are often limited but are essential for determination of inputs to the model and assessment of its reliability. Quantification and systematization of the calibration and validation process expose statistical issues inherent in the use of such data. Formalization of the calibration and validation process naturally leads to the use of Bayesian methodology for assessment of uncertainties in model predictions that arise from a multiplicity of sources, especially statistical variability in estimation and calibration of the input parameters and model discrepancy. The general problem was elucidated in an earlier paper; this paper carries out the full calibration and validation process in the context of a widely used deterministic traffic model, namely, the Highway Capacity Manual model for control delay at signalized intersection approaches. In particular, the reliability of the model was assessed through quantification of the uncertainty in the estimation of model parameters, predictions of model delay, and predictions obtained by adjusting the data used in the model. While the methods are described in a specific context, they can be used generally but are inhibited at times by computational burdens that must be overcome.