bluuebunny/crossref_metadata_2025 huggingface dataset:
Potential Applications of Intelligent Transportation Systems to Road Freight Transport in Mexico
Authors: Mendoza Alberto , García Antonio
Published: April 2007

In the past few years, tools have been developed based on different communication means with the purpose of achieving a safer, more efficient, and environment-friendly operation of vehicular flows in the transport systems. Some of the early means generally involved a very strong human participation. In the course of time and with the rapid progress made in electronics, telecommunications, and computer systems, such processes have become automated until generating a series of technologies that currently are incorporated into the single generic term of intelligent transportation systems (ITS). This research has multiple purposes. First, some characteristics of road freight transport in Mexico are presented. Then, with such characteristics under consideration, the ITS technologies with the largest potential for application to that transportation type are described. A vision of future implementation is shown. Finally, some conclusions are presented.
Decision-Making Process in Intermodal Transportation
Authors: Tsamboulas Dimitrios A. , Kapros Seraphim
Published: April 2007

A methodological framework with models is provided, which correlates behavioral and perceptual issues related to the use of intermodal transportation with the commonly used physical and economic criteria in modal choice approaches. With factor analysis, key variables and common decision patterns related to the choice of intermodal transportation are identified. Factor analysis is applied to capture the actors’ perception of the importance of variables affecting the decision-making process. With multiple regression analysis, models simulating the decision-making process are developed for actor groups, utilizing actual quantitative data of cost and performance of intermodal transportation services. Three decision patterns and the respective actor groups’ profiles are identified. The first group consists of actors who decide almost exclusively according to the cost criterion; these actors are intensive users of intermodal transportation. The second group has actors who decide according to both quality and cost criteria; using intermodal transportation by this actor group constitutes a minor portion of its total transport volumes. The third group consists of actors who are influenced in their decisions by specific logistics needs, beyond the physical transportation activity itself. The offer of third-party end-haul operations or refrigerated storage areas is an example of such services, necessitating specific logistic support. For each actor group a model is developed, which associates values of the quantitative variables affecting the decision-making process with the share of intermodal transportation in the total volume of transport handled by the group. The application of the model defines the extent to which changes in the values of relevant variables may shift a decision toward the use of intermodal transportation.
Color Night Vision for Navigation and Surveillance
Authors: Das Sanjoy , Zhang Yunlong
Published: April 2007

Fusion of registered images of night scenery that are obtained from cameras tuned to different band-widths will be a significant component of future night-vision devices. A new algorithm for such multispectral image fusion is described. The algorithm performs gray-scale image fusion using a method based on principal components. The monochrome fused image is then colored by means of a suitable pseudocoloring technique to produce the fused color output image. The approach can easily be used for any number of bandwidths. Examples illustrate the algorithm’s use to fuse an intensified low-light visible image with another image obtained from a single forward-looking infrared camera. The algorithm may be implemented readily in hardware for use in night-vision devices as an important aid to surveillance and navigation in total darkness. The applicability of the technology to transportation is also discussed.
Advanced Prediction of Train Arrival and Crossing Times at Highway-Railroad Grade Crossings
Authors: Estes R. Matthew , Rilett Laurence R.
Published: April 2007

There are many issues related to highway–railroad grade crossings. For historic and practical reasons, trains have the right-of-way at grade crossings, which results in delays to motorists. In addition, the differential in size, speed, and stopping ability between motor vehicles and trains raises many serious safety concerns. Historically, the methods used to address these delay and safety problems at grade crossings have been reactive in nature. For example, the Manual on Uniform Traffic Control Devices specifies a minimum of 20 s of warning time for active warning devices at grade crossings. Intelligent transportation system (ITS) technology offers potential solutions for increasing the warning time at grade crossings. Advanced on-board devices and off-track detection equipment can allow train position and speed to be monitored. This information can be shared through wireless and wireline telecommunications equipment being deployed for ITS. Transportation management center personnel can then predict the arrival and crossing times of trains at grade crossings. It is hypothesized that if the warning time could reliably be increased, the traffic-operation strategies in the vicinity of grade crossings could be more proactive, reducing delay to motorists and increasing safety for both trains and automobiles. The research focuses on a second-generation technology approach to an advanced prediction of train arrival and crossing (gate-up and gate-down) times at highway–railroad grade crossings, including problems faced at grade crossings, background on detection and prediction technology for grade crossings, the train monitoring system used as the test bed for the research, the development of the methodology, the results of the analysis, and the conclusions of the research and potential applications for the model.
Considerations for Providing Subsurface Drainage in Jointed Concrete Pavements
Authors: Mallela Jagannath , Titus-Glover Leslie , Darter Michael I.
Published: April 2007

Design considerations for pavement subsurface drainage in new or reconstructed jointed concrete pavements are outlined for all components of a permeable base system (permeable bases, separator layers, edgedrains, and outlets). Discussion topics—including guidelines for determining drainage needs, permeable base system components, hydraulic design of permeable base systems, structural design of permeable bases and separator layers, and economic considerations for providing drainage—are arranged to provide a comprehensive picture of the subject area. For topics with established procedures, such as the hydraulic design of permeable bases, a synthesis of information is presented. Where there is a lack of information or a clear consensus among researchers on a topic, new ideas and concepts are proposed.
Finite-Layer Approach to Pavement Response Evaluation
Authors: Siddharthan Raj V. , Krishnamenon Nadaraja , Sebaaly Peter E.
Published: April 2007

The following aspects of the proposed continuum-based finite-layer model are presented: (1) theoretical basis, (2) applicability in evaluating pavement response, and (3) verification of predictive capability. The model incorporates important pavement response factors such as noncircular contact area, complex contact stress distributions (normal and shear), vehicle speed, and viscoelastic material characterization. The proposed model is much more computationally efficient than the moving-load models based on the finite-element method. A verification study, undertaken to validate the predictive capability of the proposed approach and its ensuing computer program, is also presented. The validation study includes (1) verification using results from ELSYM5, a widely used pavement response model, and (2) laboratory verification using two foam rubber models. Very good agreement was observed in both cases. Applicability of the proposed approach has also been demonstrated using realistic pavement loading. The proposed finite-layer approach is therefore an ideal tool for modeling the behavior of asphalt concrete layer and for studying the effects of vehicle speed and complex tire-pavement interface stresses on pavement response.
Stone Interlayer Pavement Design
Authors: Rasoulian Masood , Becnel Byron , Keel Gary
Published: April 2007

A project was initiated to evaluate the pavement performance of an alternative pavement design, referred to here as stone interlayer or inverted pavement. The test section consisted of a 4-in. (102-mm) layer of stone base on top of 6 in. (152 mm) of in-place cement stabilized base. The control section consisted of 8.5 in. (216 mm) of cement-stabilized base layer on top of prepared subgrade (standard design). A 3.5-in. (99-mm) layer of flexible pavement was placed over both sections. The objective of the study was to evaluate reflective cracking reduction through the asphaltic pavement as well as overall pavement performance. The project took place in Acadia Parish, Route LA-97, near Jennings, Louisiana. LA-97 is considered a low-volume rural highway, with average daily traffic of 2,000 vehicles. The pavement was monitored for 7 years after construction. During the evaluation period, annual crack survey, ride, and deflection measurements were collected. Additionally, as part of the Louisiana Transportation Research Center accelerated pavement testing research program, the same pavement design was tested to failure using the Accelerated Loading Facility device. Results of the investigation showed that the stone interlayer had significantly reduced the amount of reflective cracking. The ride characteristics and structural capacity of both sections were similar during the evaluation period. Accelerated testing results also verified the superior performance of the stone interlayer pavement system. The cost analysis showed initial construction costs for the stone interlayer system may be as high as 20 percent more than standard design. However, the life of the stone interlayer pavement system is increased to almost five times that of the standard soil cement pavement as tested under accelerated loading.
Pavement Distress and Roadway Damage Caused by Subsurface Moisture and Freezing Temperatures; Case Histories from Alaska
Authors: Tart Rupert G.
Published: April 2007

Since 1992 Golder Associates has been working with the municipality of Anchorage, Alaska, to evaluate the causes of pavement distress throughout the municipality. Design and construction changes have been recommended and implemented. The performance of pavements both before repair and after redesign has been monitored and evaluated. Surficial heave rates have been measured, ground temperature variations have been documented, crack patterns have been mapped, and soil profiles have been noted at various sites around the municipality. In locations where drainage and insulation recommendations have been implemented, improved pavement performance has been observed. This research presents case histories outlining the conditions initially observed in the distressed pavements. It also traces the performance of the pavements after their being rebuilt according to recommendations.
Seasonal Variation of Moisture and Subsurface Layer Moduli
Authors: Janoo Vincent , Shepherd Kent
Published: April 2007

In 1995 the Montana Department of Transportation initiated a study on the seasonal variation of pavement strength, with an emphasis on spring thawing. Ten sites representing a cross section of Montana subgrade soil and pavement structure were selected and instrumented with moisture and temperature sensors. Field measurements of surface deflections, moistures, and temperatures were initiated in autumn 1996 and continued through the spring of 1997. The moisture and deflection data were used to determine the thaw-weakening characteristics of the sites and to develop subgrade modulus values for use in the future design of pavement structures using AASHTO mechanistic design methodology. Results indicated that in several areas not only the subgrade but also the base course layers were prone to thaw weakening. The length of thaw weakening varied from 4 days to a 3-week period. In addition, it was found that in almost all cases the subsurface moisture content began to increase rapidly when the subsurface temperature rose to around–2°C during the spring. In some cases it was found that when the subsurface temperature finally warmed to 0°C, the moisture content had reached its prefreeze value. This research provides a general description of the test sites and measurements; it quantifies the effects of thaw weakening on typical roads in Montana based on deflection and surface and subsurface moisture and temperature.
Modeling Four-Directional Pedestrian Flows
Authors: Blue Victor J. , Adler Jeffrey L.
Published: April 2007

The objective of this study is to explore the modeling of multidirectional pedestrian flows. The complex interactions between flow entities within m-directional space present challenges that cannot be readily handled by existing bidirectional flow models. A cellular automata microsimulation model for four-directional flow is prescribed. This model, built on previous bidirectional models developed by the authors, additionally seeks to manage cross-directional conflicts. Performance of this function in the simulation of unidirectional, bidirectional, cross-directional, and four-directional flows is presented. The applications extend to m-directional terminal facility design and to four-directional street corners, a vital component in any network model of pedestrians.
Car-Following and Collision Constraint Models for Uninterrupted Traffic: Reexamination Using High-Precision Global Positioning System Data
Authors: Khan Sarosh , Maini Pawan , Thanasupsin Kittichai
Published: April 2007

In the last few decades several car-following models have been proposed and tested using mainly vehicle location data. The use of high-precision Global Positioning System (GPS) data to test several car-following and collision constraint models is reported, with a critical evaluation of these models and proposal of a modified collision constraint formulation. GPS receivers typically report time-stamped location or position fixes and velocity. For a pair of leading and following vehicles, location and velocity data were used to examine estimates of acceleration, velocity, and headway by Pipes’s; modified Pitt’s, or FRESIM; CARSIM; and INTELSIM car-following models. The important aspects of collecting accurate GPS data are also highlighted.
Predictive Time-Based Feedback Control Approach for Managing Freeway Incidents
Authors: Sawaya Omar B. , Doan Dung L. , Ziliaskopoulos Athanasios K.
Published: April 2007

A feedback control approach is introduced that produces dynamic control strategies in the form of alternate routes around freeway incidents and in response to the prevailing traffic conditions. The approach is based on the equalization of predictive travel times on alternate routes. The methodology is intended to be used as a decision-aid tool for real-time traffic management applications, more specifically for route guidance via variable message signs. The approach is implemented and tested computationally on an example network in a simulated environment under various scenarios of system disturbances. The results indicate that the performance of this approach is fairly robust to uncertainties in demand, compliance rate, and incident severity. It also performs better than an anticipatory approach and an instantaneous time–based feedback control approach.
Experimental Verification of Time-Dependent Accumulation Predictions in Congested Traffic
Authors: Smilowitz Karen R. , Daganzo Carlos F.
Published: April 2007

With experimental traffic data from a 4-mi (6.44-km) long congested road, it is shown that traffic delays and vehicle accumulations between any two generic observers located inside the road section can be predicted quite accurately from the traffic counts measured at the extremes of the section. Predictions can be made with a streamlined version of the kinematic wave theory that does not rely on ambiguous traffic stream characteristics such as density. The predictions were found not to require recalibration on the day of the experiment and to work well despite what appeared to be location-specific driver behavior.
Characterizing and Modeling Observed Lane-Changing Behavior: Lane-Vehicle-Based Microscopic Simulation on Urban Street Network
Authors: Wei Heng , Meyer Eric , Lee Joe , Feng Chuen
Published: April 2007

Key findings are discussed regarding characteristics of lane-changing behavior based on observations of an urban street network. An in-depth exploration of observed lane-changing behavior and its modeling were conducted using vehicle trajectory data extracted from video observations using VEVID, a software package developed by the authors, integrated with a video-capture system. As a result, rules for modeling lane-changing behavior are proposed with respect to various types of lane changes. A lane-changing model consists of three components: a decision model, a condition model, and a maneuver model. Drivers’ decisions to change lanes depend on travel maneuver plans, the current lane type (i.e., the relationship between the current lane and the driver’s planned route), and traffic conditions in the current and adjacent lanes. A lane-changing condition model is the description of acceptable conditions for different types of lane changes. A lane-changing maneuver model describes a vehicle’s speed and duration when a certain type of lane change occurs. All of these models are established in a heuristic structure.
Theory of Breakdown Phenomenon at Highway Bottlenecks
Authors: Kerner Boris S.
Published: April 2007

On the basis of an empirical study of congestion occurring at a freeway bottleneck, it is shown that the congested regime can exist under a large variation of the discharge flow rate downstream of the bottleneck. This variation can be from about 1,600 to 1,700 vehicles/h to 2,600 to 2,700 vehicles/h per lane. A criticism of the application of queuing theories for the description of traffic pattern features is given. An explanation is given of the features of a congested regime on the basis of the recently discovered properties of synchronized flow as a new traffic phase.
Weaving Area Analysis in Year 2000 Highway Capacity Manual
Authors: Roess Roger P. , Ulerio Jose M.
Published: April 2007

The development of weaving area analysis procedures for the next edition of the Highway Capacity Manual, which is to be published in 2000, is described. Weaving has proved to be one of the most complex types of operation to analyze consistently. Although many studies and investigations have examined weaving areas, no single comprehensive research document exists that has resulted in an analysis procedure that has withstood the test of time and application, despite many attempts to do so. As the publication of the Highway Capacity Manual for the Year 2000 (HCM 2000) nears, weaving analysis procedures continue to be influenced by a variety of historic studies and documents and by several databases. None of these is statistically adequate given the number of variables involved. Thus, procedures continue to require the application of the professional judgment of the members of the Committee on Highway Capacity and Quality of Service of the Transportation Research Board. Documentation for the analyses and judgments that support the analysis procedure as it is recommended to appear in the HCM 2000 is given in this paper.
New Insights into Freeway Capacity at Work Zones: Empirical Case Study
Authors: Al-Kaisy Ahmed , Zhou Miao , Hall Fred
Published: April 2007

A construction project in Ontario, Canada, provided the opportunity to use field data to investigate freeway capacity at long-term lane closures due to rehabilitation work. Data from two lane closures at the same construction site (eastbound and westbound) were examined. The site is located on the Gardiner Expressway in the southern part of downtown Toronto. Data were collected during 4 days, totaling around 53 h of congested traffic operations. Results showed significant variation in freeway capacity in the work zones. Despite this variation, average capacity values are reasonably close to the corresponding values provided in the Highway Capacity Manual. Four intervening variables were investigated; all exhibited significant but different effects on freeway work-zone capacity. These variables included temporal variation (which is thought to relate to driver characteristics), grade, day of week, and weather conditions. The results confirmed the pressing need for more extensive field data that will allow better identification of the effect of various control variables on work-zone capacity.
Freeway Facility Methodology in Highway Capacity Manual 2000
Authors: Eads Brian S. , Rouphail Nagui M. , May Adolf D. , Hall Fred
Published: April 2007

The next edition of the Highway Capacity Manual (HCM 2000) will contain for the first time an operational analysis procedure for directional freeway facilities up to 20 to 25 km long. At the simplest level, this procedure integrates the proposed HCM 2000 methods for the analysis of basic, ramp, and weaving segments to enable the analysis of an entire facility. But the proposed facility methodology goes much further. It allows the user to analyze multiple, contiguous time intervals with timevarying demands and capacities. It can handle both undersaturated and oversaturated traffic conditions (with some limitations). In the latter case, both the spatial and time extent of congestion are estimated. Finally, the method permits the investigation of the effect of many traditional and intelligent transportation system–based freeway improvement strategies such as full or auxiliary lane additions, ramp metering, incident management, and a limited set of high-occupancy-vehicle designs on facility performance. Described here is the conceptual model for and computational steps of the methodology, with emphasis on the components for analysis of oversaturated conditions. The scope and limitations of the methods are also highlighted. Reference is given to a companion paper that describes how the results of the method were validated in the field and how they compared with those obtained from widely used freeway simulation models.
Validation of Left-Turn Delay at Two-Way Stop-Controlled Intersections
Authors: Simpson Sarah A. , Matthias Judson S.
Published: April 2007

Control delay for left-turning vehicles at unsignalized intersections was observed in the field and compared with average control delay calculated from the methodologies presented in the 1997 update of the Highway Capacity Manual (HCM). Unsignalized intersections with two-way left-turn lanes on the major street were observed in the peak and offpeak hours, and control delays were recorded for the one-stage and twostage left-turn processes. Next, the methodologies presented in the HCM were used to calculate the control delay for both processes and compared with the observed data. These comparisons were used as the basis for validation of the HCM methodologies regarding left-turn control delay at unsignalized intersections. From the comparisons, the calculated delay closely corresponds with the observed data, with a total approach volume at the intersection of approximately 2,500 vehicles per hour or less. Once the total approach volume increases above this level, the calculated values rapidly increase and the actual observed control delays gradually increase at a much lower rate. As a result, the observed and calculated delays are different when the intersection handles more than 2,500 approach vehicles in an hour. Statistical analyses were performed on the data to determine if the average observed control delay was related to the calculated control delay. Statistically, the observed control delay and the calculated control delay at the 95 percent confidence level show that the two data sets yield similar results for off-peak conditions. However, during the peak hour, when the total approach volumes are higher, the 95 percent confidence interval yields different results. Hence, the HCM procedures produce, on average, greater control delay estimates than the field observations when the total approach volumes are high.
Comparison of Queue-Length Models at Signalized Intersections
Authors: Viloria Fadhely , Courage Kenneth , Avery Donald
Published: April 2007

Several measures of effectiveness (MOEs) are associated with the queuing process at traffic signals, including delay, number of stops, fuel consumption, emissions, and queue length. The focus in this study is on queue length in general and on the storage requirements for left turns in particular. Queue length is an important MOE because queues that overflow the available storage space have an adverse effect on the overall operation of the intersection. Many traffic models now provide queue-length estimates, but the procedures used by these models are based on different queue definitions and have different computational approaches that lead to different results. A classification framework is developed for the existing models, their behavior is compared with that of the proposed Highway Capacity Manual (HCM) 2000 queue model, and queue conversion factors are provided for translating the various model outputs to their HCM 2000 equivalent. The proposed HCM 2000 model and its parent model from the Signalized and Unsignalized Intersection Design and Research Aid (SIDRA) provide a comprehensive treatment of the queuing process, accounting for control parameters such as controller type and progression quality as well as for the random and overflow effects associated with traffic flow. As such, the queue-length estimates from these models are more analytically defensible than those of the simpler theoretical models. The SIDRA and HCM 2000 queue estimates are generally higher than those of most other models and are somewhat higher than what conventional wisdom would suggest. It is suggested as a result of the comparisons presented that the queue estimates from some models are unduly optimistic when demand approaches capacity and that a goal of 90 percent confidence in the adequacy of left-turn storage lanes may be difficult to achieve under these conditions.
Mating Habits of Slugs: Dynamic Carpool Formation in the I-95/I-395 Corridor of Northern Virginia
Authors: Spielberg Frank , Shapiro Phillip
Published: April 2007

The availability in the Shirley Highway corridor in Northern Virginia of an uncongested high-occupancy vehicle (HOV) lane restricted to vehicles carrying three or more persons has led to the development of significant dynamic ridesharing activity. Each day, drivers of vehicles carrying too few occupants to qualify for HOV lane use (known as “bodysnatchers”) stop at informally established but well-known locations to seek additional passengers (known as “slugs”). As part of a study whose purpose was to quantify the likely effects of changing the HOV lane eligibility rule from three or more persons per vehicle to two or more persons per vehicle, data were collected on the patterns of dynamic carpool formation. These data were used in the examination of the hypothesis that an important factor contributing to the long-term success of dynamic ridesharing is that a single passenger need never ride with a lone driver: the 3+ occupant HOV rule ensures that there will always be two passengers in addition to the driver. Analysis of carpool formation patterns by number and gender revealed that slugs come in pairs. Changing the HOV occupancy rule would result in fewer vehicles seeking riders, but most slugs would still find acceptable rides. The primary effect on ridesharing would result from increased congestion in the HOV lanes.
Construction Productivity and Constraints for Concrete Pavement Rehabilitation in Urban Corridors
Authors: Lee Eul-Bum , Ibbs C. William , Harvey John T. , Roesler Jeff R.
Published: April 2007

A constructability analysis tool was developed to help the California Department of Transportation (Caltrans) determine which rehabilitation and construction strategies were the most feasible in an urban environment to maximize production and minimize traffic delay. With the assistance of California concrete paving contractors, the constructability analysis explored the effects of the following parameters on the construction production of concrete pavement rehabilitation in California: pavement thickness, concrete material, curing time, number and capacity of resources, number of lanes to be paved, type of construction scheduling, and alternative lane closure strategies. The constructability analyses indicated that the proposed Caltrans strategy to rebuild 6 lane-km within a 55-h weekend closure period had a low probability of success. The analyses showed that the concrete curing time was not the most critical activity for the overall production. Material delivery resources, such as dump trucks for demolition and concrete delivery trucks, were the major constraints that limited production. An increase in the concrete slab thickness from 203 to 305 mm reduced the level of production by about 50 percent. A concurrent-construction working method was more productive than a sequential-construction working method. The number of lanes to be paved affected the production capability. Continuous closures were more productive and less inconvenient to the public than weekend-only closures.
Comparative Analysis of Volumetric Properties for Superpave Gyratory Compactors
Authors: Yildirim Yetkin , Solaimanian Mansour , McGennis Robert B. , Kennedy Thomas W.
Published: April 2007

The experience with the original Superpave gyratory compactors (SGCs) introduced into the paving industry in 1994 was very positive. Consequently, since 1995 several additional manufacturers have developed SGCs to meet the growing demand for such devices. Although these units generally meet the broad requirements of the original SGC specification developed by FHWA, their basic designs are somewhat different. To ensure a systematic means for evaluation of the compactors, FHWA developed a standard protocol, designated AASHTO PP35. This procedure was used to evaluate various gyratory compactors. By using the discriminating value of 0.010 for difference in bulk specific gravity ( Gmb), the compactors were evaluated in terms of Gmb. The five gyratory compactors evaluated were the Rainhart, Test Quip, Troxler Electronic Laboratories, Inc. (Troxler), Model 4141, Pine Instrument Company (Pine) Model AFG1A, and Interlaken compactors. These compactors were compared with either Pine Model AFGC125X (Pine 1) or Troxler Model 4140 (Troxler 1) SGCs, which were used as reference compactors. In addition, the project included a comparison of two Pine compactors (Pine 1 and Pine 2) of the same model (AFGC125XS) with each other. A total of 336 specimens (48 specimens for each compactor) were prepared for all the compactors to fulfill the comparison. Eleven comparisons of each candidate compactor and the reference compactor were made during a 12-month period. All of the candidate compactors compared favorably with an existing SGC. It was found that all seven compactors would provide the same results within the given tolerance range under the rigid conditions of the AASHTO PP35 protocol.
Construction-Related Temperature Differentials in Asphalt Concrete Pavement: Identification and Assessment
Authors: Mahoney Joe P. , Muench Stephen T. , Pierce Linda M. , Read Steven A. , Jakob Herb , Moore Robyn
Published: April 2007

Numerous Washington State Department of Transportation (WSDOT) paving projects have experienced a cyclic occurrence of premature failure of open-textured asphalt concrete (AC) pavement sections by fatigue cracking, raveling, or both, generally called “cyclic segregation” or “endof-load segregation.” This resulted in an initial study in which mat temperature differentials were observed during laydown. In turn, this led to the current study and the reported results. Pavement temperature differentials result from placement of a cooler portion of the hot-mix mass into the mat. This cooler mass generally constitutes the crust, which can develop during hot-mix transport from the mixing plant to the job site. Placement of this cooler hot mix can create pavement areas near cessation temperature that tend to resist proper compaction (they may also exhibit tearing or roughness or appear to be open textured). These areas were observed to have decreased densities and a higher percentage of air voids (higher air voids). Four 1998 WSDOT paving projects were examined to determine the existence and extent of mat temperature differentials and associated material characteristics. An infrared camera was used to identify cooler portions of the mat, which were then sampled along with normal-temperature pavement sections. Gradation and asphalt content analysis showed no significant aggregate segregation within the cooler areas. However, these cooler portions of the mat consistently showed higher air voids than the surrounding pavement. On the basis of numerous studies that have related AC deterioration and high air voids in a mix, it is known that the areas of a mat with higher air voids may experience premature failure compared with the time to failure of the mat as a whole.
Development of Composite Quality Measures
Authors: Weed Richard M.
Published: April 2007

Statistical construction specifications based on multiple quality characteristics frequently use pay equations that include a separate term for each of the quality characteristics so that the resultant pay adjustment is a function of the combined effect of all quality measures. An alternate method that can be used to accomplish the same purpose is to base the pay equation on a single quality measure that is a composite of the individual quality measures. The latter approach, because it keys the various decision-making steps to a single performance indicator, simplifies the procedure and offers several practical advantages. It is believed that this approach makes significant strides toward the ultimate goal of developing quality assurance procedures that are at the same time technically sound, fair and effective, and easy to understand and apply. Examples of a two-variable case for hot-mix asphalt pavement and a general three-variable case are presented.
Nonparametric Approach to Managing Materials Quality
Authors: Benson Paul E. , Chong Y. Sam , Samaniego Francisco J.
Published: April 2007

The normal distribution was tested for its goodness of fit to quality control data from 25 California Department of Transportation projects. The binder content and relative compaction of asphalt concrete were studied. In a significant number of cases, the assumption of normality was rejected. Closer examination of the observed distributions revealed instances of skewed, truncated, and bimodal distributions. Indications of nonnormality were found for a third of the asphalt content cases and nearly half of the relative compaction cases. An alternative nonparametric procedure for estimation of the percentage of material outside specification limits (POL) is proposed. Comparisons with the current methodology, which assumes that the data are normally distributed, indicated that somewhat lower, but arguably more accurate, estimates of POL are obtained by the nonparametric approach. Issues of accuracy and precision were addressed through a simulation study. The nonparametric method offers considerably greater statistical accuracy and power than the parametric approach when the data are not distributed normally and a performance comparable to that of the parametric approach when they are.
Partnering on a Design-Build Project: Making the Three-Way Love Affair Work
Authors: Ernzen Jim , Murdough Ginger , Drecksel Debra
Published: April 2007

The partnering process used by the Arizona Department of Transportation in the execution of an $89 million design-build reconstruction of an urban freeway through a congested section of Phoenix is described. The project is changing 6 lanes into 10 lanes by adding a high-occupancy vehicle lane, along with auxiliary lanes, between the entrance and exit ramps over a 13-km (8-mi) stretch of freeway. It involves the demolition and replacement of two bridges that carry major arterial roads over the freeway by using single-point urban interchanges along with several kilometers (miles) of sound walls, new freeway lighting, and an automated freeway management system. Design-build by its nature lends itself to the partnering concept. The partnering concept ideas of increased communication, alignment of goals, and development of a dispute resolution system fit perfectly with design-build’s overarching theme of single-point responsibility for the owner. Increased pressure because of schedule compression typical of most design-build projects makes partnering a vital necessity. Several innovative partnering ideas used on the design-build project to overcome the problems inherent in a complex, high-profile, fast-paced construction project are described.
Asphalt Trackbed Technology Development: The First 20 Years
Authors: Rose Jerry G. , Brown E. Ray , Osborne Monica L.
Published: April 2007

The evolution of hot-mix asphalt (HMA) trackbed technology is documented as presently practiced in the United States. Criteria used in selecting sites for and the attendant benefits of HMA trackbeds, based on long-term performance evaluations, are discussed. Prevailing practices for selecting ideal HMA mix parameters, trackbed section designs, and application procedures are described in detail. Primary attention is directed at the “underlayment” procedure in which the HMA serves as a premium subballast layer within the track structure to enhance the support, waterproofing, and confinement properties of the subballast. The roadbed or subgrade materials underlying the HMA mats maintain near-optimum moisture content. The HMA appears to undergo little if any weathering or deterioration in the trackbed environment. The resultant benefits are decreased maintenance costs, fewer slow orders, fewer operational interferences, and improved operational efficiency of the rail network overall.
Cost Comparisons of Remedial Methods to Correct Track Substructure Instability
Authors: Chrismer Steven , Davis David
Published: April 2007

The effectiveness and costs of various remedies for stabilizing track over a soft clay subgrade were tested and compared. To date, the techniques of repeated tamping, increasing granular layer thickness, and placing a geoweb layer have been tested under 39-kip (170-kN) wheel-load traffic. Using typical industry cost figures, economic analysis shows that the most cost-effective selection depends on traffic volume. For the heavy-axle load conditions studied at the Facility for Accelerated Service Testing (located at FRA’s Transportation Technology Center, Inc., near Pueblo, Colorado), analysis indicates that continued tamping of the ballast can be the best choice when the annual tonnage is less than about 40 million gross tons (MGT; 360 GN). For annual tonnage levels greater than 50 MGT (450 GN), fixing the problem by use of a remedial technique is less costly. Of the two remedies tested, increasing the granular layer thickness appears to be the lower cost option, mainly because of the lower material cost compared with geoweb. The intent of this analysis is to help railroads decide whether to make temporary repairs with low initial costs or more permanent remediation with higher initial costs.
Cost-Benefit Analysis of Sleeper Replacement Strategies: Simulation Model
Authors: Lake Maree R. , Ferreira Luis , Murray Martin H.
Published: April 2007

A simulation model predicts the condition of a section of timber-sleepered railway track, including the clustering patterns of the defective sleepers and the cost of replacement under a given strategy. These results are used to perform a cost-benefit analysis of the different possible strategies for the replacement. For the simulation model, it is assumed that the life of a timber sleeper is represented by the Weibull distribution. User-controlled inputs include the length of track and the number of years to be simulated. Results generated from the model include the percentage of defective sleepers, the average life remaining, the number of clusters of various sizes, the number of sleepers replaced, and the total cost of the strategy. Investigation was conducted into the length of track that should be simulated. The length depends on the required reliability of the model. The simulated replacement strategies are compared on the basis of cost and resulting track condition.
Austrian Track Testing and Recording Car EM 250: Source for Wheel-Rail Interaction Analysis
Authors: Presle Gerard , Hanreich Werner , Mittermayr Paul
Published: April 2007

The dynamic behavior and ride quality of railway vehicles are influenced by track quality. Monitoring riding comfort and safety is a major task of the Austrian Federal Railway’s Infrastructure Division. The track testing and recording car EM 250 provides a proven measuring instrument for modern track maintenance. Equipped with an inertial measuring system and an optical track gauge measuring system, the track testing and recording car can measure the track alignment and rail profiles at speeds of up to 220 km/h. The measurements, taken every 25 cm, provide binary data files that can be processed offline. Track quality parameters are measured as functions of vehicle acceleration and are stored in a database from which they can be easily retrieved from any computer in the company. The Bureau for Applied Mechanics and Mathematics was commissioned by the Austrian Federal Railways to develop the SIMULAT program for analyzing rolling stock dynamics. In developing the model, special consideration was given to the exact mathematical description of all elements affecting vehicle dynamics. Using an optical measuring system, the track testing and recording car determines the rail cross section on the basis of readings at individual points. The simulation program links the curve with the track data, allowing the analysis of the impact of worn profiles on running stability. For the simulation, the line layout and the track geometry deviations excite the model of track and vehicle. In a followup phase, the vector of generalized degrees of freedom is evaluated, and the results are displayed with a visualization program. The simulation results were compared with data recorded during a test run and showed satisfactory correspondence.
Technology Transfer of Tools for Passenger Rail Environmental Analysis
Authors: Duffey Marilyn , Freytag David
Published: April 2007

It is time to transfer the advanced technology and processes specifically developed for conducting the environmental analysis of high-speed rail (HSR) corridors to other large-scale infrastructure projects. Because HSR projects cover thousands of miles and traverse multiple geographic and land use conditions, the most advanced electronic tools available have conveyed vast amounts of information into quantitative, tabular, and graphic format for analysis. A geographic information system allows comprehensive analysis of multiple layers of information in formats compatible with the electronic files used to engineer the alignment. A global positioning system can verify previously recorded data and locate and record new data, transferring information to a comprehensive database readily accessible to technical analysts and agency staff. Digital photographs and digital files of geographic contours, combined with engineering plans and profiles, provide the information needed to create a video simulation of HSR for public presentations. These tools have been used effectively in information exchange and decision making during environmental reviews for HSR projects, and they are compatible with personal computers and the Internet for transfer of information to potential users. The Florida HSR project and the ongoing California HSR project have used these tools effectively to streamline environmental review and to produce information in electronic formats for other projects in the same area. These advanced technological tools for HSR projects should be shared with the rest of the transportation industry, specifically for the environmental analysis of other planned passenger rail projects in the United States.
Boarding Aid Devices for Disabled Passengers on Heavy Rail: Evaluation of Accessibility
Authors: Dejeammes Maryvonne
Published: April 2007

Because railway networks are widely developed in Europe, facilitating access to disabled passengers is a pressing issue. Steps and gaps at the entrance doors are barriers to people in wheelchairs and to people with walking difficulties. Because of the difference between platform and car floor heights, level access is not available, and boarding aid devices are necessary for disabled passengers to bridge steps or gaps. A literature survey is presented, the practices of European railways are discussed, and relevant factors for choosing the most appropriate and convenient devices for boarding and alighting train cars are analyzed. Recommendations are suggested for near-term enhancements.
Slope Stabilization with Recycled Plastic Pins
Authors: Loehr J. Erik , Bowders John J. , Owen Jacob W. , Sommers Lee , Liew Willie
Published: April 2007

A scheme to stabilize minor slope instabilities is currently being developed. The scheme uses a distributed network of “pins” fabricated from recycled plastics and other waste materials to provide positive reinforcement of a soil mass. Although the application is similar to stabilization of slopes with soil nails or micropiles, significant modifications to conventional design and construction are necessary to account for the reduced strength and increased ductility and creep exhibited by plastic materials compared with concrete and steel. Using recycled plastics has the advantage of providing reinforcing members with low susceptibility to degradation and provides a market for materials that otherwise might be buried in a landfill. An extensive investigation is under way to evaluate the potential for using recycled plastic pins (RPPs) to stabilize minor slope failures. This evaluation includes quantification of appropriate material and engineering properties of RPPs, evaluation of RPP resistance to degradation in various environments, development and evaluation of suitable mechanisms for installing RPPs, evaluation of RPP resistance to driving stresses, development of a design procedure that accounts for the reduced structural capacity of RPPs compared with steel or concrete members, and installation and monitoring of several full-scale field demonstration sites. The ongoing evaluation program that is described focuses on laboratory tests to determine fundamental engineering and material properties, field driving trials to evaluate potential driving mechanisms, and preliminary development of a suitable procedure for designing RPP stabilization schemes.