bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of Resilient Modulus for Lime- and Cement-Stabilized Synthetic Cohesive Soils
Authors: Achampong Francis , Usmen Mumtaz , Kagawa Takaaki
Published: April 2007

The effects of deviator stress, molding moisture content, stabilizer type and content, curing period, and soil type on the resilient modulus (Mr) of lime- and cement-stabilized cohesive soils were investigated by using Hydrite R (kaolinite) and sodium bentonite (montmorillonite) blends. It was found that Mr increases with decreasing deviator stress, increasing lime and cement content, and extended curing period. Moisture variations around optimum had little effect on Mr with higher lime contents. Multiple regression analyses and Student's t-tests indicated that all the factors investigated were significant and could be related to Mr by predictive regression equations. For a given stabilizer type and content, the low-plasticity clay (CL) soil produced the best results. The cement-stabilized CL soil normal cured for 28 days produced the highest Mr value. However, cement stabilization was not found to be very effective for the high-plasticity clay (CH) soil. Mineralogical composition has a marked effect on the Mr of lime and cement-stabilized cohesive soils. Kaolinitic CL soils work better than montmorillonitic CH soils with both lime and cement.
Stabilization of Shallow Slope Failures with Lime Piles
Authors: Rogers C. D. F. , Glendinning S.
Published: April 2007

Lime piles essentially consist of boreholes filled with lime. They have been used to stabilize slopes in many countries worldwide but have not been adopted as a standard means of stabilization in any country. The literature on the subject makes several claims about the way lime piles stabilize the soil. However, the reported results of experimental work are in some cases contradictory and are too few to facilitate appropriate engineering judgment of the stabilizing mechanisms. Research at Loughborough University, United Kingdom, has investigated the use of quicklime piles in the context of stabilization of shallow slope failures in clay slopes. The stabilizing mechanisms observed in a series of laboratory and field investigations are ( a) increased strength of an annular zone of clay surrounding the pile caused by lime-clay reaction, ( b) clay dehydration, ( c) generation of negative pore-water pressure, ( d) over-consolidation of the soil in the shear plane, and ( e) pile strength. The idea of lateral consolidation of the clay surrounding the pile as a result of physical pile expansion has been shown not to occur in the case of augured quicklime piles sealed with a clay plug at the surface. Data are presented to quantify each of the stabilization mechanisms and advice is given on how to use the data in design. It is concluded that lime piles provide a potentially valuable addition to the techniques available for shallow slope stabilization and are particularly suitable for sites with access problems.
Theoretical Evaluation of Poisson's Ratio and Elastic Modulus Using Indirect Tensile Test with Emphasis on Bituminous Mixtures
Authors: Mirza M. Waseem , Graul Richard A. , Groeger Jonathan L. , Lopez Aramis
Published: April 2007

The theoretical fundamentals used in evaluating Poisson's ratio and elastic modulus of materials using the indirect diametral tensile test are evaluated. With the current state of practice (ASTM D4123), the material properties are evaluated by the two-dimensional stress equations for a circular element supporting short-strip loading along the vertical diameter. Because of the inability of these equations to study misalignment of the specimen, the planar solution is analyzed. The analysis of the above two approaches indicates that the material properties predicted are relatively insensitive to specimen size and misalignment. However, the influence of aggregate inclusions in the vertical plane may cause significant propagation of errors in the vertical measurements outside the central half-radius that significantly affects the value of the predicted Poisson's ratio. The influence of aggregate inclusions in the horizontal plane does not appear to be a significant factor contributing in the horizontal displacement variations. Thus, determination of the elastic modulus from horizontal displacements alone has great potential in providing consistent, reasonable results with an assumed Poisson's ratio. In addition, a means of estimating the magnitude of the displacements and the required sensitivity of the measuring devices based upon expected Poisson's ratio and gauge length is presented. Finally, test control parameters based upon the ratio of vertical to horizontal deformations have been developed to check if the material being tested is within the elastic range as the test progresses.
Full-Scale Rutting Tests of Large-Stone Asphalt Mixtures
Authors: Coree Brian , Button Joe W.
Published: April 2007

Repetitive loaded-wheel tests were conducted on three large-stone mixtures: (a) a dense mixture designed using a new method that guarantees stone-on-stone contact, (b) a dense mixture designed to exhibit poor stone-on-stone contact, and (c) an open-graded mixture commonly used by the Indiana Department of Transportation (INDOT). All three mixtures had 38-mm (1.5-in.) nominal maximum size aggregate. Test pads 76-mm (3-in.) thick, 1.5-m (5-ft) wide, and 6.1-m (20-ft) long were constructed by a local contractor using a batch plant, a conventional paver, and a static steel wheel roller. No serious difficulties were experienced during placing or compacting the mixtures. The compacted surfaces were quite rough due to the large particle sizes. This rough texture apparently introduced significant variability in the density of the compacted test pads. The finer mixture designed to have poor stone-to-stone contact gave the highest density. Five thousand repetitions of a 4082-kg (9,000-lb) force were applied to each pavement through dual truck tires inflated to 620 kPa (90 psi). Cross-section profiles were measured periodically throughout testing. Rut depths measured in the mixture designed using the new design (Texas coarse) were significantly less than those in the other two mixtures. The mixture made purposely with poor stone-on-stone contact (Texas fine) exhibited the highest rut depths, which were similar to those measured in conventional binder coarses in the INDOT data base. This indicates that large stones floating in a matrix of conventional mix will have little effect on resisting rutting. The INDOT No. 2 open-graded mixture exhibited more rutting than the Texas coarse mixture but less than the Texas fine mixture. The use of this open-graded mixture as a surface coarse may have allowed unnatural displacement of large aggregate near the surface at the sides of the applied loads, which contributed to greater-than-expected rut depths.
Long-Term Oven-Aging Effects on Fatigue and Initial Stiffness of Asphalt Concrete
Authors: Harvey John , Tsai Bor-Wen
Published: April 2007

An investigation of the effects of long-term oven aging (LTOA) on initial stiffness and fatigue of asphalt concrete was made using two typical California asphalts, known to have different aging characteristics, in mixes with one aggregate. Asphalt content, air-voids content, and days of LTOA were varied independently. Stiffness and fatigue were evaluated using the controlled-strain flexural beam test developed by the Strategic Highway Research Program Project A-003A. The results indicated that both mixes exhibited an increase in initial stiffness with LTOA periods of up to six days. The sensitivity of beam fatigue life to LTOA depended on the asphalt. Beams containing Valley asphalt had virtually no change in fatigue life due to LTOA, whereas beams with Coastal asphalt showed some sensitivity to LTOA. For both asphalts, the average reduction in fatigue life from 6 days of LTOA was less than that caused by a 3 percent increase in air-void content or a 1 percent decrease in asphalt content. Simulations of thick and thin pavement structures were performed to reconcile the effects of LTOA, asphalt content, and air-void content on mix fatigue life and stiffness by evaluating their combined effects on predicted pavement fatigue life. The simulations indicated that aging, as induced by LTOA, increased fatigue life for all cases except one.
Comparison of Coarse Matrix High Binder and Dense-Graded Hot-Mix Asphalt
Authors: Izzo Richard P. , Button Joe W. , Tahmoressi Maghsoud
Published: April 2007

Coarse matrix high binder (CMHB) is a gap-graded hot mix consisting of a large proportion of coarse aggregate with an asphalt binder-filler mastic. CMHB and dense-graded mixtures were compared in terms of their resistance to rutting (permanent deformation), moisture damage, aging, and water permeability. A static creep test was performed to evaluate relative rutting susceptibility. Moisture damage was assessed with the tensile strength ratio (TSR) and a boiling-water test. The effects of aging were evaluated with indirect tensile strength and resilient modulus testing. Penetration and complex shear modulus ( G*) of the recovered, aged asphalt were measured. Permeability was determined with Darcy's Law for flow through saturated, porous media. The static creep test did not indicate that CMHB mixtures were consistently more resistant to rutting in comparison with dense-graded mixtures. CMHB mixtures were found to be more resistant to moisture damage, which was indicated by higher TSR values and less visible stripping than corresponding dense-graded mixtures. The dense-graded mixtures exhibited higher resilient moduli and indirect tensile strengths after short-term and long-term aging. Penetration of binder extracted from aged CMHB mixtures was greater than that from dense-graded mixtures. Binder extracted from aged dense-graded mixtures exhibited higher G* values. The permeability of CMHB mixtures was greater than that of the dense-graded mixtures with comparable air voids.
Study of Speed-Flow Relationships on Individual Freeway Lanes
Authors: Hurdle V. F. , Merlo Mark I. , Robertson Doug
Published: April 2007

Many researchers have examined the form of the relationship between speed and flow on freeways. However, these researchers have concentrated on relationships for the freeway as a whole instead of on individual lanes. In this study, the relationship was examined for each of the three lanes at two locations on Highway 401 in metropolitan Toronto. It proved possible to accurately describe the mean speed in each lane with simple linear functions over the range of flows of most practical interest. Cubic functions provided comparable results over a wider range of flows, but it appears unlikely that the very high and very low flows are of sufficient interest to justify the added complexity. When an attempt was made to examine the relationship between speed and flow for the entire roadway, the linear functions were not adequate, but cubic functions performed reasonably well. However, the details of the full roadway curves are quite different from those of the curves described in the 1994 Highway Capacity Manual. In particular, the curves described in the manual are much steeper than the Highway 401 curves at high flows, implying a much more rapid loss of performance as flow approaches capacity than was observed. The full roadway curves are also surprisingly different from the curves for the individual lanes.
Calibration of FRESIM To Achieve Desired Capacities
Authors: Payne Harold J. , Thompson Stephen , Chang Gang-Len , Ge Wenhong
Published: April 2007

Selection of input parameters for the FRESIM freeway traffic simulator is addressed. Methods are presented for calibrating key parameters to achieve desired freeway capacities during incident and incident-free simulation runs. The impacts of these parameters on freeway capacity are explored through systematic variation of the parameters for selected traffic scenarios.
Empirical Assessment of a Markovian Traffic Flow Model
Authors: Lan Chang-Jen , Davis Gary A.
Published: April 2007

Previous research efforts on developing traffic flow models to account for traffic flow dynamics over transportation networks have centered on macroscopic high-order models. It is unclear whether traffic flow dynamics can be well described using a high-order model formulation, but for real-time traffic control, it is important to have tractable yet accurate models. Described here is a set of tractable traffic flow models based on the Markovian compartment concept. The basic models can be further modified to produce effects analogous to high-order models in capturing unstable traffic behavior during congestion. Special treatments are also made to account for the effects of conflicting flow on the predicted turning exit flow at intersection approaches. The proposed models are evaluated using field data. The results indicate that all the model parameters, including traffic flow parameters and gap acceptance parameters, are reasonably estimated, and the underlying models provide good fits to the field data.
Long-Term Network Performance: Function of Pavement Management System Maintenance Selection Policy
Authors: Rohde Gustav T. , Pinard Michael I. , Sadzik Elzbieta
Published: April 2007

Most road agencies operate under a scenario in which the maintenance need exceeds the available maintenance funds. In this environment pavement managers are forced to select maintenance and rehabilitation actions on the basis of a defined methodology. This is typically done through a ranking process or through modern optimization routines. In the ranking process the maintenance priority of a road is determined on the basis of the importance and condition of the road. Projects with a high priority rating are carried out first, and projects are then carried out until the available funds are depleted. The more sophisticated pavement management systems use optimization routines that allow for interproject trade-offs when generating a maintenance plan. The importance of the choice of maintenance selection methodology for the long-term network condition is described. Data from an actual road network were used and were subjected to various ranking and optimization functions. This included policies such as fix worst first, use priority index, maximize asset value, minimize transportation costs, and the traditional maximization of area under a condition curve approach. The outcome was evaluated in terms of network condition, network asset value, overall transportation costs, and road user cost. It is shown that the maintenance policy should be compatible with agencies’ long-term maintenance objectives.
Expert Project Recommendation Procedure for Arizona Department of Transportation’s Pavement Management System
Authors: Flintsch Gerardo W. , Zaniewski John P.
Published: April 2007

The Arizona Department of Transportation (ADOT) uses a network-level pavement management system to determine budget requirements for its annual pavement preservation program. Although this is a valuable tool for preservation programming, it does not assist the engineers with the selection of projects and rehabilitation treatments. The documented research was designed to enhance the capability of ADOT’s pavement management system to include project selection. An automatic project recommendation procedure was developed and implemented in a user-friendly, modular computer program. This automatic system is expected to reduce considerably the effort required to develop the preservation programs. It should improve the consistency of the decision process. The analysis starts with a section delineation procedure that delineates uniform roadway sections. It then computes the remaining service life of each uniform section by using linear performance equations and trigger points defined for each condition indicator. An artificial neural network simulator is used to screen and recommend roadway sections for the preservation program. The trained artificial neural network prepares a list of candidate sections, using the criteria learned from past selections and the current condition of all pavement sections. This preliminary list of candidate sections is further analyzed by a project recommendation procedure. This procedure recommends a preservation treatment, assigns a priority rating to each section in the list, and sorts the projects by priority. Funding is assigned to the highest-priority sections within each roadway group until the budget recommendation provided by the network optimization process is reached.
Prediction of Highway Performance Monitoring System’s Present Serviceability Rating for Local Agencies Using San Francisco Bay Area Pavement Management System
Authors: Mok Hei-Tat , Smith Roger E.
Published: April 2007

Several local agencies in the San Francisco Bay Area use the Metropolitan Transportation Commission (MTC) pavement management system (PMS) that requires a pavement condition index (PCI) as the primary condition measure. This PCI is based on distress types, severities, and quantities. However, several of these local agencies must also submit present serviceability rating (PSR) data on a sample of their network for use in the Highway Performance Monitoring System (HPMS). Currently, these agencies use a trained rater to determine a subjective PSR value for each HPMS section to report to FHWA and another set of trained raters to inspect the pavement for surface observable distress from which the PCI is calculated. A study was performed to develop mathematical models to relate the PCI used in the MTC PMS to the subjective PSR submitted by local agencies for FHWA’s HPMS reports. Regression equations were developed to predict the PSR values, as defined for HPMS, from Bay Area PCI values and subcomponents of the PCI. These equations have R2 values that show moderate to strong relationships between the HPMS PSR and the MTC PCI. They provide reasonable values at or near the boundaries of the PSR scale. The local agencies using the Bay Area PMS can use these equations to estimate a PSR value from the inspection required for the PMS without inspecting pavement sections a second time.
Geographic Information System Applied to Pavement Evaluation by Video-Laser Road Surface Tester Multifunction Device
Authors: Del Río Ramón Crespo , De Madrid Pedro Aliseda Pérez , Herrero Eva Garcinuño
Published: April 2007

The methodology used in the production of a geographic information system for the management of 20 000 km (14,247 mi) of highways in Spain is explained. Pavement evaluation systems provide an exhaustive amount of information about highways. A multifunction device provides information about international roughness index, rutting, megatexture, macrotexture, microtexture, cracking, curve radius, longitudinal, and cross slope. Some of these parameters break down into data such as those relative to both wheel tracks or into different intermediate levels. Additionally, all of these data can be taken at a very high sampling rate, a rate as high as one every 10 cm (4 in.). All of this information, which is useful for having detailed knowledge of the highway’s condition, can be useless (because of unmanageability) if the right tools that permit highway administrators to perform a quick overall analysis of the highway network are not applied. These tools should be capable of grouping data of different types, depending on the study to be performed, and should also be able to represent the data in graphical form. These groups should be significant for each type of data, average value, variance, maximum value, minimum value, and so forth. Maps and graphics have been demonstrated to be good analytical tools that allow a quick and easy overall view of the whole network, making it easier to locate questionable or bad areas and their extent. Once these areas are found, a more detailed analysis on a smaller scale can be made by reanalyzing the data. At the same time the system is capable of integrating various types of information (traffic, deflections, etc.). To do this, the reference system is flexible, permitting its use with different types of data and different scales. The reference system used is the arch/node system. Accordingly, the highway network is divided into sections. The end of a section, which will be the beginning of the following section or an intersection where different sections converge, is designated a node. This system allows data on a specific point (accidents, signals, etc.) to be perfectly referenced in a section at a distance from the node of origin. It also allows lineal data along a segment to be referenced by situating the node in a section starting at a distance from the origin and with a specific length. This reference system can be very well adapted to the Spanish highway network, which is entirely referenced by means of kilometer posts.
Assessment of Long-Term Pavement Performance Program Manual Distress Data Variability: Bias and Precision
Authors: Rada Gonzalo R. , Bhandari Rajesh K. , Elkins Gary E. , Bellinger William Y.
Published: April 2007

The use of manual survey methods within the Long-Term Pavement Performance (LTPP) program for the collection of distress data has drastically increased both in intensity and in coverage over the past couple of years. Because these surveys are conducted by individual raters whose biases can lead to variability between raters, it was hypothesized that distress data variability existed and that it could potentially be quite large. Thus, the purpose of the presented study was to quantify manual distress data variability, with special emphasis on the bias and precision of the data. Results from seven LTPP program distress rater accreditation workshops conducted during the period from 1992 to 1995 were used as the only source of data. On the basis of analyses of these data, both the apparent bias and the precision for the common distress type-severity level combinations were quantified. It was also concluded from this study that individual rater variability for any given distress type-severity level combination is typically large and increases as the distress quantity increases; however, when all distress type-severity level combinations are viewed in terms of a single composite number such as the pavement condition index value, there is excellent agreement between the individual raters, the group mean, and the ground truth value, and individual rater variability is also quite small. Because LTPP program distress data are to be used in the development of pavement performance prediction models, improvements in variability are highly desirable to ensure that they serve their intended purpose. Recognizing that the LTPP program distress raters are experienced individuals, such improvements are not envisioned to come through additional training. It is the authors’ contention that the only way of achieving the desired improvement is through the conduct of group consensus surveys.
Accuracy of Estimates of Mean Daily Traffic: A Review
Authors: Davis Gary A.
Published: April 2007

A location’s mean daily traffic (MDT) is the expected traffic volume on a “typical” day, and AASHTO’s Guidelines for Traffic Monitoring Programs identifies 22 different uses for estimates of MDT. The problem of quantifying the “precision and bias” of short-count estimates of MDT is reviewed, with particular attention to the different sources of estimation errors. It is argued that early attempts to estimate the likely error of short-count estimates did not include errors from using incorrect seasonal or day-of-week adjustment factors. It is also indicated that incorrect adjustment can produce very substantial increases in estimation errors. Research on managing such adjustment errors is reviewed, leading to the conclusion that seasonal counts, rather than simple coverage counts, may be needed to produce accurate estimates of MDT when solid prior information concerning appropriate adjustment factors is lacking.
Workload, Response Rate, and Data Yield: Experiments with Long-Distance Diaries
Authors: Axhausen K. W. , Köll H. , Bader M. , Herry M.
Published: April 2007

Workload, response rate, data yield, and data quality of travel diaries are interacting variables. It has long been suspected that it is impossible to maximize all variables at the same time. Still, empirical work trying to improve understanding of the trade-offs among them has been rare. Results are reported of experiments with long-distance diaries, which aim to clarify some of the possible relationships. The object of experimentation is surveys of long-distance travel behavior, which are currently of particular interest in Europe and elsewhere. The development of the tourism industry, deregulation of the long-distance modes, and infrastructure concerns require improved data about long-distance travel, both in improved inventories and in improved behavioral understanding. The experiments undertaken varied the workload of the respondents by varying the number of items to be reported about any long-distance journey, the duration of the survey period, and the temporal orientation of the survey. The results indicate that the response rate and the data yield, that is, the number of reported journeys and stages, change systematically with changes in the experimental variables (reduced response rates for prospective surveys, reduced number of reported journeys, and stages for retrospective surveys). Detailed results for these trade-offs are given. The trade-offs force the designer of such surveys to choose carefully and to invest time and effort in correcting for the potential biases resulting from this systematic behavior.
Using Voice Recognition to Collect License Plate Data for Travel Time Studies
Authors: Washburn Scott S. , Nihan Nancy L.
Published: April 2007

The use of portable computers for performing travel time studies has become commonplace with many transportation agencies. Whereas data entry has historically been done via the keyboard, a new method of data entry is being proposed that should make license plate data collection with portable computers more efficient and convenient. This new method uses voice recognition to allow the user to dictate license plate data into a microphone. These data are then directly entered into the computer and time-stamped. The authors have developed a standalone Windows program for performing license plate data collection using voice recognition. Preliminary testing has indicated that this technology has the capability to provide entry accuracy rates in excess of 95 percent, as well as to provide sample sizes comparable to or larger than those obtained through keyboard entry. Additionally, this technology has the capability to reduce personnel requirements for situations typically using two data-collecting people per station, such as those in which one person using binoculars reads the license plates aloud to another person doing the data entry. The results of this preliminary testing are definitely promising and have indicated that this method for license plate data collection is feasible at this time.
Innovative Prestressed Steel Composite Short-to Medium-Span Bridges
Authors: Burroughs Dan , Lockwood James , Price Kenneth
Published: April 2007

Methods for combining both prestressing, high-performance steel and composite concrete decks to improve bridge performance, construe-tibility, aesthetics, and economy are reviewed. The designs are part of a study sponsored by the American Iron and Steel Institute. Five bridge concepts have been developed to the preliminary design phase, including plan details and cost comparisons. Single- and two-span bridges with span lengths of between 24.4 and 54.9 m (80 and 180 ft) have been studied. The alternates developed use prestressing both longitudinally in the main structural components and transversely in the deck. Alternates include a modular space truss, a twin warren truss, a composite steel box, and steel girders. All alternates have either a cast-in-place or a precast concrete deck. Advantages include improved durability and reduced maintenance with the use of prestressing in the deck, which eliminates deck cracking. The use of corrosion-resistant steel eliminates painting requirements. Elimination of deck joints and use of integral piers and abutments also improve durability. Economy can be improved with the combined efficient use of steel, prestressing, and concrete; with the use of jointless bridges and integral abutments and piers; and by increasing shipping lengths, reducing the number of splices, and optimizing construction methods, which are integrated into the design. Construction issues are reviewed to reduce fabrication costs and to simplify bridge erection.
Fatigue of Diaphragm-Girder Connections
Authors: Stallings J. M. , Cousins T. E. , Tedesco J. W.
Published: April 2007

Distortion-induced fatigue cracking has occurred at hundreds of diaphragm-girder connections in multigirder steel bridges in Birmingham, Alabama, in recent years. Repairs have been ineffective in some cases. The goal of the reported research was an improved strategy for repair and maintenance of the bridges so that the potential for future cracking is minimized. The investigation included field measurements of distortion-induced stresses at connections, field measurements of the effects of removing diaphragms from two in-service bridges, structural evaluations and finite-element method analyses of typical bridge designs, and laboratory testing of bolted connections. The results indicate that interior diaphragms can be removed from many existing bridges without significant negative effects. A new bolted diaphragmgirder connection was designed, installed in the field, and tested. Tests confirmed that the new design performed better than the original design. Recommendations for maintaining the Birmingham bridges include removing unneeded diaphragms and repairing old connections with the new design at needed diaphragms.
Experimental Verification of Shakedown Approaches for Bridge Design
Authors: Leon Roberto T. , Flemming Daniel J.
Published: April 2007

Recently, it has been suggested that the lives of many deficient short-span composite bridges could be extended significantly if these structures were allowed to enter into the inelastic range for a low number of cycles. This limit state is known as the shakedown or incremental collapse limit. The results of one test with a half-scale, two-beam, two-span composite bridge aimed at clarifying some important aspects of composite behavior related to shakedown are reported. The test is unique in that various amounts of composite action (50 and 80 percent) were used in the two spans and in that actual moving loads were used to load the structure. The experimental and theoretical load calculations for the test compared favorably after the actual material properties were used in the section capacity calculations. The results indicate that for spans with 80 percent or greater interaction, the members are capable of sustaining a large number of cycles without significant strength deterioration. Although the slip at the beam-slab interface increased with cycling, strain hardening and redistribution of forces were sufficient to allow the system to reach its theoretical elasto-plastic capacity. In the span with 50 percent interaction, however, the maximum load achieved during the test was 30 percent lower than the theoretical prediction. This implies that if 50 percent or less of the required shear connection is provided, one should not expect the structure to carry cyclic loads into the inelastic range.
Diagnostic Load Testing for Bridge Load Rating
Authors: Fu Gongkang , Pezze Frank P. , Alampalli Sreenivas
Published: April 2007

Diagnostic load testing uses field-measured data for bridge load rating without requiring certain information or the assumptions needed for analytical rating, and it can help arrive at more-reliable load ratings. It usually consists of three steps: preparation, execution, and analysis of the results. It is critical to estimate the probability of success in the preparation step before the execution step. A case of such a test for a steel highway bridge is presented. The bridge’s fascia beams were given a low rating because their cover plates were removed. Diagnostic load testing was used to obtain more reliable load ratings for the fascia beams. Under the test loads covering service loads, the support-fixity of the bridge was confirmed. It was identified as reserve strength and was not taken into account in the original analytical rating. Thus, it was concluded that no strengthening is needed for the fascia beams, and their rating factor was recommended to be increased from 0.7 to 1.4 on the basis of the measured load effects.
Field Evaluation of Steel Girder Bridge
Authors: Saraf Vijay K. , Nowak Andrzej S.
Published: April 2007

The objective of the study was to verify the load-carrying capacity of an existing steel girder bridge. The selected structure was a 70-year-old deteriorated bridge in Michigan. The load-carrying capacity of the bridge was in question because of extensive corrosion of the steel girders. An initial rating indicated that the bridge had a marginal operating rating factor for 11-axle two-unit trucks, which are the heaviest vehicles allowed in Michigan. To avoid the load limit posting, it was decided that investigators would verify by nondestructive testing whether the bridge is safe to carry normal truck traffic. The test procedures used on the selected bridge included tests for obtaining stress histogram measurements and weigh-in-motion measurements and a proof load test. The methodology and the results are described.
Asphalt Plug Joint Usage and Perceptions in the United States
Authors: Bramel Brian K. , Puckett Jay A. , Ksaibati Khaled , Dolan Charles W.
Published: April 2007

The University of Wyoming is developing design guidelines for asphalt plug joint use and application under the sponsorship and guidance of the Wyoming and Colorado departments of transportation. As a first step in this research a survey of 50 state departments of transportation was conducted to assess use, perceptions, and installation guidelines. Fifty states responded. The survey results are presented and the trends are summarized.
Load Reduction on a Rigid Pipe: Pilot Study of a Soft Cushion Installation
Authors: Liedberg N. Sven D.
Published: April 2007

In a project involving the construction of a new link of European Freeway E18, an 800-mm pipe was to be founded on a cushion of expanded polystyrene under an embankment fill of 9.3 m. In a pilot study measurements were taken of soil-pipe contact earth pressures around the circumference of the pipe, vertical earth pressures in the soil above the crown, relative diameter changes of the pipe in the vertical and the horizontal directions, and pipe settlements into the cushion. The design of the complete structure was partly done by using the active design program SPIDA (Soil Pipe Interaction Design and Analysis). The results indicate that the safety margin in the design was greater than first expected because the reinforced standard pipe, designed for only 5 m of fill, was uncracked, even though the height of fill was 9.3 m. The measured deformations of the pipe were smaller than those expected for the concrete to crack. The earth pressure measurements showed a pronounced soil arching effect in the soil above the pipe.
Influence of Traffic Signal Timing on Red-Light Running and Potential Vehicle Conflicts at Urban Intersections
Authors: Retting Richard A. , Greene Michael A.
Published: April 2007

Motor vehicle crashes at traffic signals are a major source of injuries and property damage, especially in urban areas. Many crashes result from vehicles entering the intersection after the onset of a red light, a traffic violation that may be affected by the duration of the change interval (the yellow and all-red periods of the traffic signal). The purpose of this study was to examine short-term and sustained effects on red-light compliance and potential vehicle conflicts as a result of an increase in change intervals to values associated with the Institute of Traffic Engineers (ITE) proposed recommended practice for determining vehicle change intervals. Data were collected during an experiment in an urban location involving changes in signal timing at some 10 intersections. Observations included the proportion of signal cycles with vehicles entering on a red light and the proportion of vehicles exiting the intersection after the onset of a conflicting green signal. Results indicate that change intervals set closer to ITE’s proposed recommended practice can reduce red-light violations and potential right-angle vehicle conflicts and that such safety benefits can be sustained.
Provincial-Wide Travel Speed and Traffic Safety Study in Saskatchewan
Authors: Liu Guo Xin , Popoff Al
Published: April 2007

The latest speed limit increases in the United States have brought about debates about the relationship between travel speed and traffic safety. The relationship between travel speed and collision severity is clear: Increase in travel speed leads to a dramatic increase in collision severity. However, the relationship between speed and collision involvement is more complicated. Examined here is the relationship between travel speed and collision involvement on Saskatchewan provincial highways. Saskatchewan data indicate that the most prevalent source of human error contributing to collisions may be speed-related. The study of the relationship between vehicle speed and collisions therefore is fundamental for developing countermeasures to achieve compliance with speed regulations and to reduce the number of collisions. According to nine provincial-wide speed surveys and corresponding accident data from the last 26 years, traffic casualties and casualty rates on provincial highways are closely correlated to the surveyed average travel speed. This finding is not surprising, considering the fact that about 60 to 80 percent of all collisions on provincial highways are single-vehicle collisions. The relationship indicates that casualties will be reduced by about 7 percent for every 1-km/hr (0.62-mph) reduction in average travel speed on provincial highways. Casualty rates on provincial highways are closely correlated to speed differentials—higher speed differentials lead to higher casualty rates. Some difficult issues relating to speed and safety are also discussed.
Development and Intermediate Findings of a Level III Heavy-Truck Collision Study
Authors: Hildebrand Eric D. , Wilson Frank R.
Published: April 2007

The development, implementation, and intermediate results of a Level III (on-scene) study of heavy freight vehicle collisions are presented. The University of New Brunswick’s Accident Research Team, under contract with Transport Canada, has conducted over 50 in-depth investigations over a 3-year period. Although the present findings are based on a relatively small sample, a number of common, and perhaps surprising issues have been identified. Many of the cases highlight the need for increased safety regulations targeted at the design and operation of these vehicles and the infrastructure over which they operate. The most common problems identified include the propensity of heavy trucks to roll over, load security, and inadequate crash protection afforded to the occupant compartment. The issues related to the establishment of an intense investigation protocol are discussed in this paper, as are the findings of the investigations that have occurred over a 3-year period. Recommendations are presented that are directed toward the refinement of a Level III protocol for further heavy-vehicle investigations. In addition, changes are proposed to existing Canadian Motor Vehicle Safety Standards as they apply to heavy trucks.
Commercial Driver Rest and Parking Requirements: Making Space for Safety
Authors: Davis Robert E. L.
Published: April 2007

The research described in this paper sought to address a perceived need for additional commercial vehicle parking space along U.S. Interstate highways by generating ( a) a nationwide description of truck parking spaces at public rest areas, ( b) detailed models of trucker demand for and utilization of public rest area parking spaces, and ( c) an evaluation of the ability of privately owned truck stops throughout the country to accommodate parking needs. Most commercial drivers, motor carriers, and even some privately owned truck stop operators acknowledged that there are parking shortages at some locations at certain times. The research projected a current shortfall of 28,400 truck parking spaces in public rest areas nationwide. It also projected that about one-third of privately owned truck stop operators plan to expand their parking facilities over the next 3 years, increasing total projected capacity at truck stops by about 28,000 spaces. Although some of the shortfall at public rest areas might be satisfied by private expansion efforts, variations in survey methodologies precluded any conclusive determination of substitutability. In addition, the truck drivers surveyed did not appear to substitute privately owned truck stops for public rest areas. The two appear to serve different functions and meet different needs. Although just over half of the sampled drivers expressed a preference for public rest areas for short-term needs, two-thirds indicated a preference for privately owned truck stops for overnight or long-term rest needs. The apparent shortfall of truck parking spaces nationwide is a problem requiring creative resolution by both the public and private sectors to ensure that commercial drivers needing a safe place to stop and rest can find one.
Evaluation of Dynamic Earth Pressure Cells for Subgrade
Authors: Selig Ernest T. , Zhang Jian , Ebersöhn Willem
Published: April 2007

Two types of commercially available dynamic earth pressure cells were tested to determine their suitability for measuring traffic-induced stresses in subgrade. The main consideration was how well the gauges could be calibrated for accurate representation of soil stresses. Tests were conducted with fluid pressure applied directly to the cells and with cells buried at various depths in a soil test chamber. The effects of soil type, proximity of adjacent cells, major principal stress direction, and temperature were investigated. Results indicate linearity, hysteresis, sensitivity, conformance, and accuracy. The two cells performed differently, but one was much more accurate than the other.
Measurement of Stress and Strain in an Unsurfaced Haul Road at a Soft Clay Site in Scotland
Authors: Dawson A. R. , Little P. H.
Published: April 2007

Strain coil sensors and pressure cells were installed in relatively large numbers in a trial haul road, constructed in Scotland, that was subjected to controlled trafficking. The instruments and their installation are described and their operation is discussed. The strain coils are shown to give a reasonably good measurement of both transient and plastic strains when placed in both unbound aggregate and cohesive subgrade soil, and data collection is shown to be facilitated by a new electronic apparatus. Sensors also have good survivability and are cheap to make and install. Pressure cells performed somewhat less well, because of apparent environmental survivability defects and inherent difficulties of installation and operation resulting from inhomogeneity generated in the surrounding ground. The cells were unable to monitor any (small) self-weight stresses.
Performance Problems of Open-Graded Drainage Layers Under Continuously Reinforced Concrete Pavements in Illinois
Authors: Heckel Laura
Published: April 2007

Illinois has constructed 14 pavements that contain open-graded drainage layers (OGDLs). The pavement types include continuously reinforced concrete pavements (CRCPs), jointed pavements, and full-depth asphalt concrete pavements. Three of the CRCPs have begun to show a higher level of distress than would be expected from pavements of that cross section and age. An in-depth investigation into the cause of the distress has begun and is expected to be completed early in 1997. The investigation includes visual distress surveys, core analysis, analysis of Shelby tube samples, deflection tests, and inspection of slabs removed in patching operations. The state has placed a moratorium on the construction of new OGDLs pending the outcome of the investigation. The investigation indicates that possible causes of the problems are the incompatibility of the OGDL and CRCP, the lack of a separation layer on two of the three sections, the cement content in the OGDL, the percentage of reinforcing steel and epoxy-coating of the steel in the slab, and the design of the CRCP and shoulders. The current maintenance plan includes patching and undersealing of problem areas. No recommendations for the future use of OGDLs can be made until the investigation narrows the possible causes.
Role of Deicing Salt in Pavement Deterioration by Frost Action
Authors: Doré Guy , Konrad Jean-Marie , Roy Marius
Published: April 2007

Frost action is a major cause of pavement deterioration in cold climates. Thermal cracking, differential heaving, and loss of bearing capacity during spring thaw are often identified as the main mechanisms involved. Except for thermal cracking, frost-susceptible subgrade soils are generally considered to be the source of the problems. Field observations suggest that frost action within the pavement granular layers could also contribute to pavement deterioration. Differential freezing conditions associated with the contamination of the base material by deicing salt are believed to be the cause of this problem. Indeed, field observations of heaved pavement surfaces near discontinuities, such as cracks or pavement edges, suggest that an ice enrichment process is occurring in pavement granular layers during the freezing season. In a laboratory testing program, salt concentration gradients reproduced in freezing temperature create conditions favorable to an ice enrichment process and contribute to a substantial increase in the frost susceptibility of granular materials. Under steady isothermal cooling conditions, samples placed in layers of increasing salinity have exhibited heave at rates as high as 6 mm/day. Normal freezing tests on the same material free of salt have shown no significant segregation potential. Surface heave resulting from ice enrichment can be highly detrimental to pavement performance. Induced distortion contributes to rapid deterioration of the pavement surface. When occurring along transverse cracks, the phenomenon may seriously alter the ride quality of the pavement.