bluuebunny/crossref_metadata_2025 huggingface dataset:
Factors Affecting Overlay Ride Quality
Authors: McGhee Kevin K.
Published: April 2007

A study was conducted to identify the predominant factors that affect the achievable smoothness of asphalt overlays. The subject was approached from the perspective of a contracting entity (state highway agency). The basis of the study was a roughness survey that incorporated 4270 lane-km (2,650 lane-mi) and two full construction seasons with hot-mix asphalt concrete paving. Among the variables found to be related to the achievable smoothness were the functional classification (highway system), original surface roughness, and a special provision for smoothness. Variables that were found to be not significantly related to the smoothness achieved included surface mix type, the application of additional structural layers, the use of milling, and time-of-day restrictions on construction activities (i.e., nighttime paving).
Study of Compaction Density in Closed Form
Authors: Huh Jung D. , Nam Young K.
Published: April 2007

As a common description of the compaction process, density versus number of roller passes (coverage) is often found in the literature and is subsequently used in the field. The closed formula is introduced to quantify such a relationship. Variables considered are compaction density, mix viscosity, temperature, frequency, and amplitude, in addition to the number of roller passes. Their effects are included in the proposed formula. The experimental data found in the literature are used to verify the equation. Excellent prediction of the data confirms the success of the formulation. As the result of this mathematical modeling, the minimum number of passes required to finish a certain compaction job and the maximum compaction density achievable by a certain compaction operation are suggested. The equation and its features will be an effective tool for using rolling compaction in an effort to construct better roadway pavements.
Method to Model Performance Relationships and Pay Schedules
Authors: Weed Richard M.
Published: April 2007

Performance-related specifications require mathematical models to link construction quality to expected life and, ultimately, to value expressed in the form of pay schedules. Although ongoing research efforts continue to advance the state of the art, the type of data needed to develop accurate and precise models may not become available for several years. In the interim, present engineering and mathematical knowledge can be used to create rational and practical models that will perform effectively until better models are available. Several examples are presented to illustrate how both analytical data and survey data can be used to develop realistic performance models and pay schedules useful for statistical construction specifications. The issue of the proper method that can be used to combine the effects of multiple deficiencies is also addressed.
Cold-Weather Cast-in-Place Segmental Construction for Long-Span Bridges
Authors: Burgess Christopher J.
Published: April 2007

An innovative heating and monitoring method was developed and used for wintertime casting of the Wabasha Street Bridge in Saint Paul, Minnesota. The bridge’s twin 384-m (1,260-ft) box-girder structures slope 5 percent from atop Saint Paul’s bluffs on the Mississippi River’s north side down to the lower portion of Saint Paul. Each box girder is composed of two 122-m-long (400-ft-long) center spans and two 70-m (230-ft) approach spans. The deck width of 14.54 m (47 ft 8 in.) contains two 3.66-m (12-ft) travel lanes, two shoulders of 0.92 m (3 ft) and 1.83 m (6 ft) with a 3.36-m (11-ft) sidewalk, and 1.11 m (3 ft 8 in.) to account for the barriers. The superstructure consists of 4.88-m (16-ft) typical-length segments that are 6.10 m (20 ft) deep over the piers and 2.44 m (8 ft) deep at midspan and the abutments. The bridge was constructed in balanced cantilever fashion with form travelers. The contractor, the local concrete supplier, the city, and the Minnesota Department of Transportation worked together to develop an innovative mix that would withstand the frigid temperatures and also achieve 24 115 kPa (3,500 lb/in.2) compressive strength in less than 24 h to allow the stressing of the post-tensioning. To insulate and protect the curing concrete, reinforced plastic enclosures surrounding the form travelers housed three 316 761-kJ (300,000-Btu) propane heaters. A layer of plastic and a double layer of insulating blankets covered the top slab. Thermocouples in the segments provided temperature readings, which the contractor used to monitor the effectiveness of the cold-weather procedures. The forms, reinforcing steel, and previous concrete were heated above 10°C (50°F) by using plastic enclosures, propane heaters, and insulating blankets. The concrete arrived from the batch plant at approximately 21°C (70°F) and was still above 13°C (55°F) when it was pumped into the segments. Multiple thermocouples indicated that the top slab cured above 38°C (100°F) for several days, whereas the bottom slab and webs were about 11°C warmer. The contractor ran the propane heaters for 5 days after each pour or until the segments reached a 28-day strength of 41,340 kPa (6,000 lb/in.2). The segments reached the required 24 115 kPa (3,500 lb/in.2) strength for post-tensioning on the day after each pour, including pours made on days as cold as −28°C (−19°F). Only 3 working days were lost because of the cold, and the bridge was completed on time. The method of heating and protection used at the Wabasha Street Bridge proved that the segmental cast-in-place construction method is a viable option in cold-weather climates on major long-span bridges.
Determining Minimum Contract Time for Highway Projects
Authors: Shr Jin-Fang , Thompson Benjamin P. , Russell Jeffrey S. , Ran Bin , Tserng H. Ping
Published: April 2007

An increasing number of state highway agencies (SHAs) are using A (cost) + B (time cost) bidding ( A + B bidding) for highway construction. The A + B bidding concept is designed to shorten the total contract time by allowing each contractor to bid the number of days in which the work can be accomplished, in addition to the traditional cost bid. The SHA is then presented with the problem of determining a reasonable range of contract time submitted by the bidders. Most SHAs do not currently restrict the range of B. However, several problems may arise from an unrestricted range of B. First, if no minimum is set for B, a bidder may inflate the cost bid and submit an unreasonably low B, using the excess cost bid to cover the disincentives charged for exceeding the time bid. Second, if no maximum is set for B, then a bidder with a high B and a low-cost bid may be awarded the job and make an unreasonable amount of money from incentive payments. This study develops a quantified model of the price-time bidding contract. A construction cost-versus-time curve is developed from Florida Department of Transportation (DOT) data. The contractor’s price-versus-time curve is then combined with the road-user cost to determine the optimum lower limit to be set on B. Finally, several projects completed by the Florida DOT will be used to illustrate this model.
Behavior of a Sandy Silt Reinforced with Discontinuous Recycled Fiber Inclusions
Authors: Murray J. J. , Frost J. D. , Wang Y.
Published: April 2007

Laboratory compaction and triaxial compression tests were performed to assess the compaction characteristics and load deformation response of a sandy silt reinforced with randomly oriented recycled carpet fibers. Discrete, randomly distributed fiber inclusions significantly increase the peak shear strength, reduce the postpeak strength loss, increase the axial strain to failure, and, in some cases, change the stress-strain behavior from strain softening to strain hardening for a sandy silt. Fiber inclusions also impede the compaction process, causing a reduction in the maximum dry density of reinforced specimens with increasing fiber content. The strength losses associated with in-service saturation are significantly reduced with fiber reinforcement. It is suggested that large volumes of recycled waste fibers can be used as a value-added product to enhance the shear strength and load deformation response of soils.
Critical Review of Coupled Flow Theories for Clay Barriers
Authors: Olsen Harold W. , Gui Shengxiang , Lu Ning
Published: April 2007

Coupled flow theories and systems, introduced from the 1960s to the 1990s, are critically reviewed in relation to their applicability for investigating the coupled migrations of groundwater and dissolved species through clay barriers. Most of these theories and systems are based on irreversible thermodynamics. Katchalsky and Curran developed theories for noncharged and electrolyte solutes in discontinuous systems consisting of a membrane separating solutions of a single solute dissolved in water. Olsen developed an experimental system to investigate the applicability of the force-flux relationships in Katchalsky and Curran’s electrolyte theory for soil. Greenberg et al. and Yeung and Mitchell derived theories for continuous systems with noncharged and electrolyte solutes that are based on most of the thermodynamic concepts and assumptions in Katchalsky and Curran’s theories. Alshawabkeh and Acar developed a theory based on the kinetics of ion diffusion, electrodiffusion, and advection; a phenomenological relationship for advection in response to hydraulic and electric gradients; and the mechanisms by which electric charge is transferred between carbon electrodes and solutions. This review shows that the abilities of these theories to analyze the migration of groundwater and dissolved species through clay barriers are limited. A more general coupled flow theory is needed that takes into account multiconstituent pore fluids, ion exchange, and all the coupling mechanisms involved. This model should be developed from irreversible thermodynamics and should consider the simultaneous fluxes of liquid, solutes, and electric charge in response to hydraulic, solute concentration, and electric potential gradients.
Remediation and Transformation of Kaolin by Plasma Magmavication
Authors: Celes Josepha D. , Mayne Paul W.
Published: April 2007

In situ plasma magmavication is a powerful and expedient technique for melting soil that subsequently cools to form a glassy igneous rock. A nontransferred arc plasma torch provides temperatures exceeding 4000°C that can be positioned within boreholes as a means of ground improvement or for environmental restoration of contaminated soils. The process is similar to in situ vitrification by embedded graphite electrodes, yet the nontransferred arc is a considerably more efficient process. The artificial rock can be left in place or, alternatively, may be exhumed and stored. The effectiveness of plasma remediation on uncontaminated and contaminated kaolin was investigated through a preliminary series of laboratory chamber tests with small dosages of chemical, biological, and nuclear surrogates. It is believed that the process pyrolizes organic contaminants, while locking the inorganic contaminants within the glass matrix. Measurements in compressive strength, stiffness, porosity, and mass density verified the transformation of soil to rock with improved material characteristics.
In Situ Investigation of Liquefiable Gravels
Authors: Koester Joseph P. , Daniel Chris , Anderson Michael L.
Published: April 2007

A series of dynamic in situ penetration tests was performed in deep alluvial gravel deposits at Seward, Alaska, that were shaken and apparently liquefied by the March 27, 1964, Alaska earthquake. Both a U.S. standard penetration test split spoon and a larger-diameter drive sampler were used, and dynamic cone penetrometers of two sizes were also driven into the gravels near the mouth of the Resurrection River that had exhibited settlement and lateral spreading as a result of earthquake shaking. Two safety hammers were used [nominally 623 N (140 lb) and 1334 N (300 lb)], and the energy delivered with various hammer and penetrometer combinations was measured throughout all tests. Limited measurements of hammer velocity were also made by a radar system developed for that purpose to allow for kinetic energy determination. Soils recovered in the split spoon samplers were sent to the U.S. Army Engineer Waterways Experiment Station Soils Research Facility in Vicksburg, Mississippi, where they were evaluated for classification (gradation and index properties). The sampling and testing procedures used at the Seward site, as well as preliminary analysis of the various penetration test results, are summarized. Comparisons are made with penetration resistance measurements made by the Alaska Highway Department immediately after the 1964 earthquake. Results of this investigation will be adapted to guide future practice for in situ determination of liquefaction resistance in coarse alluvial soils.
Characterizing Granular Material Coarseness and Micromechanical Properties with a Small-Diameter Penetrometer
Authors: Johnson Jerome B.
Published: April 2007

A micromechanical theory and data from a penetrometer with a small base area were used to characterize the average microstructural and micromechanical properties of snow, a granular material composed of ice. The micromechanical theory also was used to describe penetration in soil and successfully explains the dependence of penetration resistance for granular materials on penetrometer base area. Material coarseness (microstructural element dimension), elastic modulus, and compressive strength were determined by interpreting penetration resistance measurements by the micromechanical theory. Predictions of the macroscale (continuum) mechanical properties for the snow were made by the micromechanical measurements and theory. The average microstructural dimensions for snow were 3.6 mm (coarse grained) and 1.45 mm (fine grained). Micromechanical strength and modulus of elasticity of snow depend on internal structure and bonding at grain boundaries; grain size by itself was not a good indicator of the mechanical properties for snow. The accuracy of determining micromechanical and microstructural properties for individual microstructural elements decreases as the ratio of the penetrometer base area to the microstructural element cross-sectional area increases. Average micro-and macroscale structural and mechanical properties of a granular material can be determined by interpreting penetration resistance data with a micromechanical penetration theory. The resolution of measurement of material properties increases as the size of the penetrometer tip decreases.
Risk Analysis Techniques for Safety Evaluation of Highway Work Zones
Authors: Elias Ana Maria , Herbsman Zohar J.
Published: April 2007

Construction sites or work zones create serious disruptions in the normal flow of traffic, resulting in major inconveniences for the traveling public. Furthermore, these work zones create safety hazards that require special consideration. Current legislation and programs, at both state and national levels, emphasize the need for a better understanding of work zone problems to address work zone safety. This reality—coupled with the temporary closure of more miles of highway every year for rehabilitation and maintenance—makes the analysis of safety at construction sites a serious matter. A summary of a comprehensive study associated with the development of a new practical approach to address highway safety in construction zones is presented. Because empirical models require sample sizes that are not attainable due to the intrinsic scarcity of construction zone accident data, the problem was studied from the point of view of risk analysis. Monte Carlo simulations were used to develop risk factors. These factors are meant to be included in the calculations of additional user costs for work zones, or simply applied as risk measurements, to optimize the length and duration of closures for highway reconstruction and rehabilitation projects. In this way, it will be possible to assess the danger of work zones to the traveling public and minimize adverse effect of work zones on highway safety.
Effect of the Work Zone Double-Fine Law in Texas
Authors: Ullman Gerald L. , Carlson Paul J. , Trout Nada D.
Published: April 2007

Results of research conducted to investigate the short-term effects of the double-fine law in work zones implemented in Texas on January 1, 1998, are presented. Field studies of traffic speeds in several work zones were performed before and after the law was implemented. Traffic citation data for these same work zones were also obtained from the Texas Department of Public Safety. Analyses showed that traffic speeds in the work zones 4 to 6 months after the law was enacted were essentially unchanged from before the law was enacted. Similarly, citation frequency and fines levied were not significantly higher than they were before enactment of the law. The data suggested that a higher proportion of drivers who were issued citations after the law was implemented chose to take defensive driving training and to have the ticket subsequently dismissed. However, researchers could not determine whether this was due to the increased fine or to other external reasons.
Intrusion Accidents on Highway Construction Projects
Authors: Bryden James E. , Andrew Laurel B. , Fortuniewicz Jan S.
Published: April 2007

Two hundred and ninety intrusion accidents were reported on New York State Department of Transportation construction projects from 1993 through 1998. Characteristics of intrusion accidents and the locations where they occur were investigated, and intrusions were compared with other traffic and construction accidents. Overall, intrusions into the work and buffer space are a relatively small proportion of all accidents. Intrusion accidents accounted for nearly 10 percent of all work-zone traffic accidents and about 8 percent of serious injury accidents. Four fatalities and 60 serious injury accidents occurred. About two-thirds of intrusion accidents involved a vehicle entering an area defined by channelizing devices, including the transition area, buffer space, and work space. About 20 percent involved moving operations. Most intrusions resulted in a collision between the intruding vehicle and work vehicles, equipment, or roadway features. Pedestrian workers were involved in less than 10 percent of the intrusions but were at greater risk for serious injury than workers in vehicles or equipment. Excessive speed was a major factor, identified in about one-fourth of all intrusion accidents. Driver incapacity—due to alcohol use, lack of sleep, medical problems, vehicle failure, or roadway conditions—was involved in another one-fourth of intrusion accidents. Based on circumstantial evidence in the accident reports and a substantial number of impacts on highly visible arrow panels, it appears that driver inattention is also a significant factor.
Special Flashing Warning Lights for Construction, Maintenance, and Service Vehicles: Are Amber Beacons Always Enough?
Authors: Ullman Gerald L.
Published: April 2007

Ways to improve the Texas Department of Transportation’s (TxDOT’s) current vehicle warning light policy were researched. Tasks included a survey of motorist perceptions of different warning light color combinations and also field studies of the effect of selected color combinations on traffic behavior. The motorist survey, conducted at driver licensing stations in Dallas–Fort Worth, San Antonio, and Houston, indicated that the combination of blue and amber lights implied a slightly greater sense of hazard to motorists than did the amber light alone. However, this greater sense of hazard did not necessarily translate into differences in how motorists believed they needed to respond. Field studies conducted at freeway locations in San Antonio and Houston investigated the effect of selected, alternative vehicle warning-light color combinations on vehicle speeds, lane choice, and braking activity. Researchers found significant reductions in speeds at a few sites—but not all—for the amber and blue warning light color combination when compared with speeds observed when only an amber warning light was used. In addition, the data suggested a trend toward increased brake usage for the red, amber, and blue light configuration compared with the amber-light-only configuration. There also was evidence that the amber-and-blue light configuration slightly increased the frequency of brake applications. Furthermore, the use of a law enforcement vehicle during testing resulted in significantly more brake-light activations than did a TxDOT courtesy patrol vehicle outfitted with the same warning light colors.
Public Perception of Pavement-Marking Brightness
Authors: Loetterle Francis E. , Beck Richard A. , Carlson Jim
Published: April 2007

The Minnesota Department of Transportation (MnDOT) conducted research to establish a threshold value of retroreflectivity for use in its pavement-marking management program. Members of the general public were invited to drive MnDOT automobiles on a driving course of state and county roads. An interviewer rode along with each study participant asking questions about the brightness (or luminance) of pavement markings within predetermined sections of roadway. The interview was conducted after dark with the car’s headlights at low beam. For each section of roadway, study participants were asked to grade the visibility of the pavement markings; the edge line and the centerline were evaluated individually. The average scores received from all study participants for a specific section were compared with retroreflectivity data taken by MnDOT’s mobile retroreflectometer. Analysis of the data revealed an apparent correlation between the readings taken by the retroreflectometer and the rating scores provided by the study participants. This analysis also suggested that the threshold value of acceptable retroreflectivity versus unacceptable retroreflectivity was between 80 and 120 mcd/m2/lx when using the Laserlux® retroreflectometer. In its continuing effort to improve “customer service,” MnDOT has committed to providing durable pavement markings that are visible year-round and is purchasing equipment and training personnel to implement this program. As a result of the market research project, MnDOT will use 120 mcd/m2/lx as the threshold between acceptable retroreflectivity and unacceptable retroreflectivity when developing the new pavement-marking management program. The establishment of a threshold retroreflectivity value also will allow cost-benefit and life-cycle analyses of different pavement-marking materials and help MnDOT to grade itself on how well it is meeting customer expectations.
Minimum In-Service Retroreflectivity of Pavement Markings
Authors: Zwahlen Helmut T. , Schnell Thomas
Published: April 2007

Minimum in-service retroreflectivity values for pavement markings are presented based on visibility computations performed with the CARVE (Computer-Aided Road-Marking Visibility Evaluator) computer model. CARVE accurately computes all geometric and photometric relationships for each headlamp separately; applies the human visual luminance contrast threshold database from Blackwell (Part III, 1946) adjusted by a field factor function that has been obtained from a number of pavement marking visibility field experiments; and provides retroreflectivity values for the pavement markings for any selected single-point geometry (e.g., ASTM 30-m geometry, observation angle = 1.05°, entrance angle = 88.7°). Based on the CARVE computation results, a set of in-service pavement marking retroreflectivity values are derived for fully marked, dark, straight, and dry roads using paint-and-beads pavement markings. The derived minimum retroreflectivity values for fully marked roads without raised pavement markers (RPMs) are highly speed dependent, because the computations are based on a constant minimum preview time of 3.65 s (3.0 s true preview and 0.65 s for eye-fixation duration). A separate set of minimum retroreflectivity values, based on a constant preview time of 2.0 s, is provided for fully marked roads with RPMs in good working order. It was found that the minimum retroreflectivity requirements for pavement markings could be substantially relaxed if RPMs (in good photometric working condition) were used. The proposed minimum retroreflectivity values are based on a 62-year-old driver (about the 85th percentile of the licensed driver population, about the 95th per-centile of the nighttime driver population based on trip frequency data as a function of the time of day).
Evaluating Runway Pavements at Seattle-Tacoma International Airport: Continuous Deflection Profiles Measured with the Rolling Dynamic Deflectometer
Authors: Bay James A. , Stokoe Kenneth H. , McNerney Michael T. , Soralump Suttisak , Van Vleet David A. , Rozycki Dan K.
Published: April 2007

The rolling dynamic deflectometer (RDD) is a relatively new tool for assessing the condition of pavements. Continuous deflection profiles, rather than deflections at discrete points, are measured with the RDD. The results of RDD tests on two runways at the Seattle-Tacoma International Airport (Sea-Tac) are presented. These results illustrate how continuous deflection profiles can be used to assess the condition of pavements without the use of backcalculation. Continuous deflection profiles allow sections of pavement exhibiting large or anomalous deflections to be quickly and easily identified. The extent to which pavements are damaged and degraded can be determined by comparison of the deflections of intact, lightly trafficked pavements with the deflections of the pavements in question. The condition and load transfer capacity of all transverse joints and cracks in rigid pavements can be determined by observation of the measured deflections as the RDD approaches and crosses each joint or crack. The RDD is a valuable tool for rapidly identifying regions of pavement requiring rehabilitation. Critical regions of pavement identified with the RDD for possible rehabilitation can be studied further with use of traditional discrete testing methods. These capabilities make the RDD a valuable tool in airfield pavement management.
Effect of Moisture on Modulus Values of Base and Subgrade Materials
Authors: Ksaibati Khaled , Armaghani Jamshid , Fisher Jason
Published: April 2007

Moisture in the base and subgrade layers of pavement can significantly decrease the modulus values of these layers. Recently, a study was performed on several Florida state roads for the purpose of evaluating the decrease in moduli of bases and subgrades due to the proximity of the water table. Dynaflect and falling weight deflectometer (FWD) tests were performed on pavement test sections throughout Florida for the purpose of backcalculation of the modulus values of the different layers. Testing was performed at different times of the year, and the water table fluctuations were recorded throughout the study. The Dynaflect and FWD deflections, water contents, depths to water table, layer thicknesses, pavement temperatures, and air temperatures were recorded on all test sections over a 5-year period. EVERCALC was used for back-calculation of modulus values on the basis of FWD tests. The Dynaflect data were also used for calculation of layer properties on the basis of a procedure developed by the Florida Department of Transportation. Both Dynaflect and FWD showed that the water table had a significant negative impact on the modulus values of the base and subgrade materials. Such results are extremely beneficial aids for establishing acceptable embankment depths so that the effects of moisture on the modulus values of pavements may be reduced.
Temperature Correction on Falling Weight Deflectometer Measurements
Authors: Chen Dar-Hao , Bilyeu John , Lin Huang-Hsiung , Murphy Mike
Published: April 2007

Repeated falling weight deflectometer (FWD) tests were conducted at three sites. The tests were conducted at regular intervals for 2 to 3 consecutive days per location, and also done during different seasons in order that the widest possible range of temperatures could be obtained. The influence of cracks on temperature correction was also investigated. Temperature correction equations for deflection and moduli were developed so that users could be allowed to input their own reference temperatures. For all test pads, only the W1 and W2 deflections were found to be significantly affected by temperature. Comparisons with other reported temperature correction equations showed close agreement for deflection, but not for moduli. Tests were also run on cracked locations. Temperature did not affect the response of the cracked pavement as much as it did the intact pavement. Due to the different temperature-dependent characteristics of intact and cracked locations, the equations developed from the intact locations may not be used on cracked locations.
Curvilinear Behavior of Base Layer Moduli from Deflection and Seismic Methods
Authors: Tawfiq Kamal , Sobanjo John , Armaghani Jamshid
Published: April 2007

The reality of curvilinear relationships of stiffness versus deformation is usually neglected when moduli values from seismic methods are compared with those of deflection methods. On the basis of extensive field testing, results showed that moduli values for the base layers from deflection methods did not conform to those of seismic methods. Deflection testing techniques were signified by the falling weight deflectometer (FWD) and the Dynaflect methods. Seismic testing was carried out by use of the seismic pavement analyzer (SPA) method. The SPA test results yielded moduli values higher than those obtained from the deflection methods. Utilizing pavement parameters obtained from the SPA data, researchers determined surface deflections by use of frequency response functions of signals from the two groups of sensors used in the testing setup. Because of the types of hammers in the SPA testing, two different deflection basins were obtained at each testing point. Comparison of surface deflections from these methods indicated that deflection amplitudes from the FWD method were about 100 times higher than those obtained from the high-frequency hammer of the SPA. At certain pavement sections, deflections from the Dynaflect method were comparable to those obtained with the SPA low-frequency hammer. Accordingly, curvilinear relationships between surface deformation versus stiffness values were derived. These relationships can be used to determine moduli values at all surface deflections, including those from service loads.
Performance Prediction of Louisiana Accelerated Loading Facility Test Sections
Authors: Djakfar Ludfi , Roberts Freddy L.
Published: April 2007

Using the accelerated loading facility (ALF), the Louisiana Transportation Research Center recently conducted an accelerated pavement test of nine test sections that consisted of the same asphalt wearing course but had different types and thicknesses of crushed stone and soil cement bases and subbases. One of the aims of the project was to compare observed field performance with that predicted with use of the VESYS 3A-M mechanistic prediction model, which predicts the development of rutting, cracking, and roughness, along with serviceability [present serviceability index (PSI)] over time. It was found that VESYS provided a reasonable prediction of observed rutting and PSI—albeit an underestimation—but a poor estimate of surface cracking. This was probably related to the fact that the observed cracking was due to shrinkage of the soil cement rather than fatigue cracking under the load, and also to the fact that VESYS is generally used to model unbound granular materials that have a modulus no greater than 690 MPa (100 ksi). The modulus of soil cement material tested by ALF was 105 MPa (150 ksi) and its behavior under load would be different from that of an unbound granular material. More research is needed into the behavior of soil cement bases, their influence on the cracking of asphalt surfacings, and the most appropriate input into VESYS to model this behavior.
Accelerated Pavement Testing of Rutting Performance of Two Caltrans Overlay Strategies
Authors: Harvey John , Popescu Lorina
Published: April 2007

Results of accelerated pavement tests (APT) at elevated temperatures on dense graded asphalt concrete and gap-graded asphalt rubber hot mix (ARHM-GG) are presented. APT testing was performed by use of a Caltrans heavy vehicle simulator. The overlays were placed on previously untrafficked sections of an existing flexible pavement. Variables included in the experiment were overlay type, ARHM-GG overlay thickness, tire/wheel type (dual/bias-ply; dual/radial, wide-base single, aircraft), and pavement temperature (40°C, 50°C, at 50 mm depth). Results presented include the rut development for the different variables, changes in layer thickness, and changes in air-void content. Analyses were performed for evaluating the relative contributions of shear deformation and densification to rut development.
Performance of Superpave Mixtures Under Accelerated Load Testing
Authors: Wu Zhong , Hossain Mustaque , Gisi Andrew J.
Published: April 2007

The performances of two Superpave® test sections, constructed with 12.5 mm (0.5 in.) nominal maximum size Superpave mixture (SM-2A) with varying percentages of river sand at the Kansas Accelerated Testing Laboratory (K-ATL), are described. A 150-kN (34-kip) tandem axle with dual wheels and 620-kPa (90-psi) tire pressure was used for loading. After 10,000 repetitions, the sections were loaded by 160-kN (36-kip), 150-kN (34-kip), and 144-kN (32.5-kip) tandem axles and 98-kN (22-kip), 90-kN (20-kip), and 80-kN (18-kip) single axles, for estimating relative pavement damage due to different axle loads and configurations. Critical pavement responses were measured on each test section with the transverse strain gauges and soil pressure cells under both K-ATL tandem axle and falling weight deflectomter (FWD) loads. The pavement responses were also estimated from a multilayer elastic analysis program, ELSYM5. Laboratory fatigue tests were conducted on the SM-2A beams. Fatigue and rutting damage analyses were then conducted. The results indicated very little fatigue damage on these sections. The Superpave mixtures appeared to be less susceptible to fatigue damage, presumably due to better aggregate structure and higher binder content than the traditional asphalt mixtures. Rutting on the section with 15 percent river sand was mainly due to consolidation of the SM-2A and/or other layers since no significant flow of the Superpave mixture was evident. The AASHTO load equivalency factors were found to be much higher than those calculated in this study.
Truck Travel Time Around Weigh Stations: Effects of Weigh in Motion and Automatic Vehicle Identification Systems
Authors: Benekohal Rahim F. , El-Zohairy Yoassry M. , Wang Stanley
Published: April 2007

Weigh in motion (WIM) technology may provide an efficient and cost-effective complement to static weighing. An evaluation of the effectiveness of an automated bypass system around a weigh station in Illinois is presented. The system combines the use of automatic vehicle identification (AVI), high-speed weigh in motion (HSWIM), and low-speed weigh in motion (LSWIM) technologies to facilitate preclearance for trucks at the weigh station. The preinstallation conditions were compared with post-installation conditions of WIM/AVI so that the effects and benefits of the system could be evaluated. During preinstallation, average delay was 4.9 min/truck, and 7 percent of trucks had delays of more than 10 min. The station was intermittently closed to prevent the truck queue from backing up onto the Interstate highway, allowing 15 to 51 percent of trucks to bypass the station without being weighed. In postinstallation, the delay for trucks equipped with transponder and allowed to bypass on the freeway was reduced by 4.17 min. The delay for trucks equipped with transponders and allowed to bypass inside the weigh station was reduced by 2.02 min. The delay for trucks that reported to the weigh station decreased by 1.25 min. On the other hand, less than 1 percent of trucks that have been observed in after-study were able to bypass on the freeway. With greater numbers of trucks being checked, fewer trucks on the road may exceed the allowable weight limits. Consequently, electronic screening minimizes road deterioration and risks to public safety and levels the playing field for illegally operating carriers and carriers who operate in compliance with the law.
Using a Road Surface Analyzer to Explain Noise Characteristics of Portland Cement Concrete Pavement Surface Texture
Authors: Kuemmel David A. , Sonntag Ronald C. , Jaeckel John R. , Crovetti James A. , Becker Yosef Z. , Satanovsky Alex
Published: April 2007

Uniformly spaced, transverse-tined portland cement concrete (PCC) pavements have been in extensive use in the United States since the early 1970s. Recent research by the Wisconsin Department of Transportation (WisDOT) and FHWA has led to an interim guideline for randomization of the tining pattern, with spacings varying from 10 to 40 mm and 50 percent of the spacings at or below 25 mm. At least five states have experimented with this random pattern. A six-state research study, funded by WisDOT and FHWA, was completed in 2000 by Marquette University and the HNTB Corporation. This study investigated 57 different PCC pavement textures, including a wide range of transverse and longitudinal tining patterns. One goal was to explain noise differences within and between various textures as well as to document noise and texture differences. The laser-based road surface analyzer (ROSAN), developed cooperatively by the Turner Fairbanks Research Center and private industry, was utilized for surface textural measurements. Before the advent of laser-based texture measurement devices, large studies of this type would have relied on manual volumetric (sand patch) measurements to quantify surface textural differences, making virtually impossible the determination of reasons for differences in noise characteristics of various textures. The use of ROSAN is described, tools developed to analyze textural variations and noise characteristics of tined pavement surfaces are presented, and correlations between ROSAN outputs and other variables, including noise level and sand patch measurements, are provided. Examples of simple and more subtle causes of noise discrepancies on random transverse tined PCC pavements are presented by use of ROSAN outputs. A great variation in surface texture, including tine spacing, width, and depth, was found among different PCC pavement sections constructed to identical tining specifications. Significant variations were also noted within any given test section in all states. A low correlation between ROSAN estimated texture depth and noise was observed. A more significant correlation between depth and width of tining was observed with use of ROSAN outputs. Recommendations include the need for quality control of tine depth, the need for a wet pavement accident study to determine tining depth requirements, and the development of an improved measurement device for measuring longitudinally tined PCC pavements.
Method for Identifying Factors Contributing to Driver-Injury Severity in Traffic Crashes
Authors: Chen Wan-Hui , Jovanis Paul P.
Published: April 2007

Numerous driver, vehicle, roadway, and environmental factors contribute to crash-injury severity. In addition to main effects, interactions between factors are very likely to be significant. The large number of potentially important factors, combined with the complex nature of crash etiology and injury outcome, present significant challenges to the safety analyst, who must select from a large number of factors and specify a comprehensive but feasible set of main factors and interactions for testing in statistical models. In addition, some factors contain a relatively large number of categories (e.g., weather conditions), and the selection of cut-off points for categorization of continuous factors may not be readily obvious (e.g., driver age). It is also important that statistical tests underlying these analyses accurately address the frequent problem of data sparseness. The development and testing of a variable-selection procedure to address each of these problems is the stated objective. Bus-involved crash data for Freeway 1 in Taiwan from 1985 through 1993 were used to screen a set of 39 possible influential factors, along with interactions. The final log-linear model shows that late-night or early-morning driving increases the risk for bus drivers of being severely injured, particularly when the drivers caused the accident or when the drivers were involved in rear-end accidents. Bus accidents involving large trucks or tractor-trailers also increase the risk. An assessment of the importance of considering interactions in crash models is presented as a conclusion.
Guidelines for Identification of Hazardous Highway Curves
Authors: Persaud Bhagwant , Retting Richard A. , Lyon Craig
Published: April 2007

Curve-warning treatment can be extremely cost-effective because of the low cost of treatments, such as curve warning signs or markings, and the potentially large number of target crashes. However, measures are needed to identify and prioritize treatment of potentially hazardous rural curves. An empirical Bayes-based procedure is presented for prioritizing potential treatment sites on the basis of crashes that may be classified as occurring because of the presence of curves. The attractiveness of the procedure is enhanced by the fact that the data and calculations are also a part of the evaluation of treatment that may be applied to sites identified. Alternative levels of the procedure can be selected, depending on the data available. Ontario data were used to calibrate supporting models. It is hoped that experience gained from using the guidelines can lead to the development of procedures that can be incorporated into the U.S. Department of Transportation’s Manual on Uniform Traffic Control Devices.
Tools to Identify Safety Issues for a Corridor Safety-Improvement Program
Authors: Breyer Jerome P.
Published: April 2007

The Arizona Department of Transportation (ADOT) recognizes that a new paradigm in highway safety evaluation was brought about by the advent of advanced technologies such as photo log, geographic information systems (GIS), and global-positioning satellite systems. Whereas these technologies are known to serve distinct singular purposes in a highway agency, ADOT has endeavored to explore the possibilities of integrating these technologies for the purpose of providing an all-encompassing perspective of crash history and roadside characteristics in a multimedia display of GIS maps and related photo imagery. The research provides the account of an analytic tool-development process aimed at improving the recognition of highway safety hazards. These hazards might otherwise be apparent if not for the relative complexity of existing relational databases and spatial GIS infrastructure at ADOT. Previous methods of mining data from the ADOT crash databases were limited in functionality as well as in reliability. By promoting the “visualization” of highway safety conditions, the advanced technologies open a wealth of new opportunities in identifying problematic roadside conditions and crash histories. This is expected to lead to an improved economy of implementing safety improvements that are designed properly to mitigate the “real” conditions that can be identified. The research is a companion to the larger, FHWA-sponsored research into establishing a corridor safety-improvement program for Arizona (FHWA Report FHWA-AZ 98-458).
Injury Effects of Rollovers and Events Sequence in Single-Vehicle Crashes
Authors: Krull Kimberly A. , Khattak Asad J. , Council Forrest M.
Published: April 2007

The effect that rollovers and tripping-event sequence surrounding rollover crashes have on the severity of driver injury was explored. Three-year crash and inventory data from Michigan ( N = 35,447) and Illinois ( N = 24, 296) were analyzed to explore the effect of rollover, while controlling for roadway, vehicle, and driver factors. The results show that 9 percent of single-vehicle crashes are either fatal or cause incapacitating driver injuries (K + A injuries). Significantly more fatalities and incapacitating injuries occur in rollover crashes. Logistic regression models of fatal and incapacitating injuries (K + A) versus other injuries and noninjuries (B + C + 0) were estimated separately and together for the two states. The results show that the effects of independent variables are largely consistent across the two states. Driver-injury severity increases with rollovers; failure to use a seat belt; passenger cars (as opposed to pickup trucks); alcohol use; daylight; rural roads (as opposed to urban); posted speed limit; and dry pavement (as opposed to slick pavement). Restricting the injury models to rollover crashes only, it was determined that hitting point objects or longitudinal objects before rolling over resulted in a more severe injury than rolling over first. The policy implications of the findings for restraint use, crash-testing, and roadside design and hardware are discussed.
Analytical Modeling of Driver-Guidance Schemes with Flow Variability Considerations
Authors: Kaysi Isam , Hage Ali Nadine
Published: April 2007

The role that advanced traveler information systems (ATISs) are likely to play in alleviating traffic congestion is explored. The impacts of and benefits from traveler guidance systems that are based on instantaneous as well as predictive information are assessed by developing an analytical formulation for a simple prototypical network. Previous research introducing day-to-day flow variability with both compliance and market-penetration considerations is reviewed, and the case in which traffic flow varies within the day is developed. Two strategies for determining route-guidance directives are considered in the case of predictive information. Also, the integration of ATIS and traffic control through open-loop coordination measures is introduced, with the objective of finding the optimal signal control to maintain user equilibrium on alternate routes. The superiority of predictive information in maintaining guidance validity and mitigating the potential adverse impacts of information is demonstrated.
Effect of Speed, Flow, and Geometric Characteristics on Crash Frequency for Two-Lane Highways
Authors: Garber Nicholas J. , Ehrhart Angela A.
Published: April 2007

Although during the past several years significant progress has been made in improving safety on U.S. highways, the frequency and severity of crashes continue to be of concern. A better understanding of the factors associated with crashes will facilitate the identification of suitable countermeasures that could further reduce the occurrence of crashes. Results are presented from a study that determines how the characteristics of speed, flow, and geometry affect the crash rates for two-lane highways. Deterministic models that relate the crash rate with the mean speed, standard deviation of speed, flow per lane, lane width, and shoulder width are presented. The multivariate ratio of polynomials method was used to develop the models. Research was limited to two-lane roadways in Virginia with speed limits of 89 km/h (55 mph). The data were obtained from speed-monitoring stations established by the Virginia Department of Transportation and from police accident reports from January 1993 to September 1995.