bluuebunny/crossref_metadata_2025 huggingface dataset:
New Jersey Statewide Rail Right-of-Way Study: Toward a Framework for Planning and Preservation
Authors: Ledger Matt
Published: April 2007

Right-of-way (ROW) preservation is one of the 15 factors of the Intermodal Surface Transportation Efficiency Act, but scant attention is paid to prioritizing which corridors to preserve. In light of increasingly scarce planning, operating, and capital resources, as well as high expectations for the expansion of rail services, transit operators and other decision makers need a tool to priority rank the preservation of abandoned rail corridors. The NJ Transit rail ROW study responded to a state legislative mandate to identify, analyze, and priority rank abandoned rail corridors for preservation and possible service expansion. A methodology to screen out unusable rail ROW is developed, and the remaining ROW is ranked in terms of its initial potential to generate transit ridership. NJ Transit staff completed an inventory of all active and known abandoned rail lines within New Jersey. The ROW was passed through successive screens that eliminated ROW with “fatal flaws” (environmental sensitivity, major development encroachments, etc.) and ROW that would provide redundant transit service. The remaining ROW was ranked in terms of the number of journey-to-work (JTW) trips to likely rail destinations, JTW trips per mile, and household density in communities that the ROW serves. This preliminary investigation of ROW identified its potential suitability for various modes of transportation as well as intermodal opportunities.
Traffic Flow Characteristics on a Three-Lane Rural Highway in Finland: Results from Empirical Studies and Simulations
Authors: Enberg Åsa , Pursula Matti
Published: April 2007

The traffic-flow characteristics on an experimental, 20-km-long three-lane highway section in Finland were studied. The sections of highway that have a separate passing lane consist of three lanes. The central lane is assigned alternately to each direction as a passing lane with a length of 1.05 to 1.70 km. The lengths of the no-overtaking zones between successive passing lanes are 1.5 to 4.0 km. The traffic-flow characteristics on the three-lane highway have been observed by comprehensive before-and-after field studies and complementary simulations. Because it was possible to use passing lanes, the number of overtakings on the three-lane highway was remarkably higher than on the former two-lane highway. The overall average travel speeds were slightly higher, and the speed decreased a little more slowly with increasing flow on the three-lane compared with the two-lane highway. Overall platooning and mean platoon lengths decreased as a result of platoon dispersal on the passing lanes. The speeds used in the passing lanes were clearly higher than in the basic lanes. According to the simulation results, the optimum length for a single passing lane was between 0.5 and 2.5 km depending on flow rate and measure of effectiveness. For the actual three-lane highway conditions, passing lanes 1.0 to 1.5 km long seemed to bring the most benefits.
Development of Passenger Car Equivalents for Freeways, Two-Lane Highways, and Arterials
Authors: Elefteriadou Lily , Torbic Darren , Webster Nathan
Published: April 2007

Passenger car equivalents (PCEs) have been used extensively in the Highway Capacity Manual to establish the impact of trucks, buses, and recreational vehicles on traffic operations. PCEs are currently being used for studying freeways, multilane highways, and two-lane highways. A heavy-vehicle factor is directly given for the impact of heavy vehicles at signalized intersections (and indirectly along arterials). These PCE values are typically based on a limited number of simulations and on older simulation models. In addition, the impact of variables such as traffic flow, truck percentage, truck type (i.e., length and weight/horsepower ratio), grade, and length of grade on PCEs has not been evaluated in depth for all facility types. The methodology for developing PCEs for different truck types for the full range of traffic conditions on freeways, two-lane highways, and arterials is described. Given the scope of this research and the variability of traffic conditions to be examined, simulation was selected as the most appropriate tool. The resulting PCE values for freeways, two-lane highways, and arterials indicated that some variables, such as percentage of trucks, do not always have the expected effect on PCEs, whereas other variables, such as vehicle type, are crucial in the calculations. Generally, major differences in PCEs occurred for the longer and steeper grades. There was great variability in PCE values as a function of the weight/horsepower ratio as well as of vehicle length.
Validation of Generalized Delay Model for Oversaturated Conditions
Authors: Engelbrecht Roelof J. , Fambro Daniel B. , Rouphail Nagui M. , Barkawi Aladdin A.
Published: April 2007

With today’s ever-increasing traffic demand, more and more signalized intersections are experiencing congestion for longer periods of time. To better quantify oversaturated conditions, it is necessary to accurately estimate oversaturation delay. The generalized delay model, proposed for inclusion in the next update of the U.S. Highway Capacity Manual (HCM), is introduced here. The generalized delay model differs from the model in the 1994 edition of the HCM as it is sensitive to the duration of the analysis period and is not restricted to degrees of saturation less than 1.2. The TRAF-NETSIM microscopic simulation model was used to verify the generalized delay equation for oversaturated conditions. A simulation model was used, because it is extremely difficult to measure oversaturated delay in the field. The study was designed to cover as much of the domain of oversaturated traffic operations as possible. The variability in simulated delays was investigated, and an equation was developed to predict the standard deviation of oversaturated delay estimates. It was found that delays estimated by the proposed generalized delay model are in close agreement with those simulated by TRAF-NETSIM. On average, simulated delays are overestimated slightly, but the error is small compared with actual delays. The proposed generalized delay model is expected to provide a good estimate of actual oversaturation delays that occur in the field.
Review and Evaluation of Methods for Analyzing Capacity at Signalized Intersections
Authors: McGhee Catherine C. , Arnold Eugene D.
Published: April 2007

Capacity analysis is a critical activity in traffic engineering and planning divisions of state departments of transportation across the nation. The Highway Capacity Manual (HCM) provides a methodology for capacity analysis that is commonly accepted and often required by state departments of transportation. The variety of computer programs that exist to aid transportation professionals in conducting capacity analyses has led to questions regarding the best methods to use under various conditions. Several computer programs other than the Highway Capacity Software (HCS) that are commonly used in evaluating capacity at signalized intersections were evaluated to determine which ones provide acceptable results. The results obtained from a simulation model were also evaluated to determine whether the model could be used to determine the operational characteristics of signalized intersections. The study results, although based on limited data, provided valuable information about the programs evaluated. HCS, SIGNAL94, HCM/Cinema, and the simulation model TRAF-NETSIM are all acceptable for capacity analysis at isolated intersections. SIGNAL94, HCM/Cinema, and TRAF-NETSIM provide reasonable estimates of queue length at isolated intersections. However, at isolated intersections where congested, oversaturated conditions exist, TRAF-NETSIM provides more accurate measures of delay and queue length. At nonisolated intersections where queueing and spill-back are potential problems, simulation analysis with TRAF-NETSIM is recommended instead of capacity analysis to determine the operational characteristics of the corridor.
Driver Memory Retention of In-Vehicle Information System Messages
Authors: Hanowski Richard J. , Kantowitz Barry H.
Published: April 2007

Memory retention of drivers was tested for traffic- and traveler-related messages displayed on an in-vehicle information system (IVIS). Three research questions were asked: ( a) How does in-vehicle visual message format affect comprehension? ( b) How does message format affect memory retention? and ( c) What impact does driver age have on recall of in-vehicle visual messages? Nine younger (less than 30 years old) and nine older (65 years old or older) drivers participated in the experiment. As subjects steered the Battelle Automobile Simulator, an IVIS presented traveler-related messages. Two types of messages, symbols and text, were presented. Message recognition was tested immediately or 50 sec after the message left the IVIS. Except for low comprehension symbols, driver recognition scores on both text and symbol messages were similar. Younger drivers scored higher than older drivers in identifying the meaning of messages, particularly in the 50-sec question delay condition. Latency to respond to the questions and confidence in the responses were also affected by question delay, with longer response latencies and lower self-rated confidence scores for the longer delay conditions. Message presentation did not degrade vehicle control.
Behavioral Aspects of Automatic Vehicle Guidance: Relationship Between Headway and Driver Comfort
Authors: De Vos Alexander P. , Theeuwes Jan , Hoekstra Wytze , Coëmet Michèle J.
Published: April 2007

Automation of road traffic has the potential to greatly improve the performance of traffic systems. The acceptance of automated driving may play an important role in the feasibility of automated vehicle guidance (AVG), comparable to automated highway systems (AHS). Because decreasing headways could mean a large increase in road capacity, a study was conducted concerning the acceptability of short headways in an automated traffic system. In one part of a driving simulation experiment, subjects gave ratings on comfort regarding the headway in an automated lane; in another part of the experiment, subjects were allowed to adjust the headway setpoint to a comfortable level. Subjects also rated the comfort level when driving under manual control in a number of traffic conditions. Results showed that to equal the comfort level that people experience daily in dense traffic on the freeway network in rush hours, the AVG headway should be no less than 0.86 sec. If a comfort level that people experience daily during incident situations (not uncommon in unstable traffic flow) would be acceptable, the AVG headway could be as short as 0.29 sec. The AVG headways as set by the subjects correspond to the values observed in normal traffic (on average 1.1 sec).
Driver Backing-Behavior Research: Implications for Backup Warning Devices
Authors: Lerner Neil D. , Harpster Jeffrey L. , Huey Richard W. , Steinberg Geoffrey V.
Published: April 2007

Collisions during backing maneuvers are a common accident type and cause a significant number of injuries and fatalities. Backup warning systems are among the intelligent vehicle warning applications being developed. Designing effective warning criteria and display characteristics is a serious challenge because little is known about how drivers behave during backing maneuvers. Drivers often intentionally back their vehicles into close proximity to objects, and backing speeds vary greatly, so appropriate conditions for warning a driver are unclear. A series of experiments was conducted to provide a basis for the design of effective vehicle-based backup warning devices. The experiments concerned driver behavior, perceptions, and responses to warning signals. One experiment measured common behaviors and vehicle control aspects during backing maneuvers. Another experiment measured driver brake reaction time and stopping distance to an acoustic signal during various backing maneuvers. A third experiment required participants in a car that was backing toward an object to identify the point at which they would want to receive cautionary and imminent crash warnings. Key findings are highlighted and their implications for the design of backup warning systems are discussed. Findings suggest the most effective design is a two-level warning system using acoustic signals as the primary mode and time to collision as a primary means of recognizing probable driver errors. Although preliminary, a time to collision of approximately 1.5 to 2.0 sec appears to be a reasonable criterion for an imminent crash warning, based on joint consideration of normal maneuver characteristics, driver reaction times, and driver judgments of appropriate warning times.
Potential of Procedural Knowledge to Enhance Advanced Traveler Information Systems
Authors: Deakin Ann K.
Published: April 2007

The closure of a portion of the Santa Monica Freeway following the 1994 Northridge earthquake afforded the opportunity to study the behavior of motorists as they found their way around the collapsed bridges along alternate and detour routes. In this study, 502 motorists, many of whom were displaced from the damaged Santa Monica Freeway, responded to a mailed questionnaire asking about changes in travel patterns, factors affecting alternate route choice, way-finding strategies used, difficulty in following alternate routes, attitudes toward the neighborhoods containing alternate routes, and attitudinal changes regarding the risk of traveling city freeways. A factor analysis of the responses revealed a procedural knowledge factor, indicating that motorists found landmarks, street signs, and written directions to be helpful aids in following alternate and detour routes. Procedural knowledge, the stored sequence of decisions about how to get from one place to another, is part of the spatial knowledge acquisition process. It is suggested that cues supporting a procedural level of knowledge could be used to enhance Advanced Traveler Information Systems (ATIS). Alternate and detour route information could include more emphasis on landmarks and street signs and be conveyed in the form of written or verbal directions.
Evaluation of A16 Motorway Fog-Signaling System with Respect to Driving Behavior
Authors: Hogema Jeroen H. , van der Horst Richard
Published: April 2007

On the A16 Motorway in the Netherlands, the Dutch Ministry of Transport implemented an automatic fog-signaling system to elicit safer driving behavior during fog. Along a road section 12 km (7.4 mi) long, 20 sensors were placed to continuously measure the visibility range. During fog, the system displays an explicit fog warning on overhead matrix signs together with a maximum speed limit that depends on the actual available visibility range. An evaluation study in terms of driving behavior was carried out for a period of more than 2 years. Continuous traffic measurements for individual vehicles were obtained via inductive loop detectors at six locations (four experimental and two control locations). Data on the local visibility conditions and on the messages displayed on the matrix signs were available on a 1-min basis. The results reveal that the system has a positive effect on speed choice in fog: on top of a lower mean speed caused by the reduced visibility, the system results in an additional decrease of speed of about 8 to 10 kph
Driver Acceptance of Weather-Controlled Road Signs and Displays
Authors: Rämä Pirkko , Luoma Juha
Published: April 2007

This study was designed to investigate driver acceptance of the weather-controlled road signs and displays on Finland’s southern coast where road condition changes are particularly frequent and rapid. There were 36 variable speed limit signs and five variable message displays to warn about hazardous conditions on the 14-km-long experimental road section. Local weather and road surface conditions were monitored automatically from road weather stations; the information gathered was used for determining appropriate speed limit, as well as for controlling variable slippery road signs and temperature displays. Five hundred ninety drivers were interviewed 3, 4, 11, and 13 months after the introduction of this new road section. The results showed that drivers recalled the variable signs very well. Furthermore, 81 percent of the drivers said that the posted speed limit was appropriate, and 95 percent of the drivers stated that the variable speed limits were useful. However, only a relatively small proportion of drivers estimated that the slippery road sign or temperature display influenced their behavior. The main implication of this study is that the concept of the weather-controlled road signs and displays is a promising one. However, objective data will be collected in order to estimate the effects of the weather-controlled road signs and displays on driver behavior and to evaluate the profitability of the system.
Driver Age as a Factor in Comprehension of Left-Turn Signals
Authors: Drakopoulos Aris , Lyles Richard W.
Published: April 2007

An experiment to measure driver comprehension of left-turn signal and sign configurations was conducted as part of a study to investigate the performance of left-turn signals used in various signal strategies. The responses of 191 individuals to 81 stimuli simulating left-turn signal phases were analyzed for the effect of signal message on driver comprehension. Stimuli included 17 left-turn signal displays used for permitted, protected, and protected/permitted left-turn strategies as well as left turns during nighttime or emergency flashing signal operations. Comprehension in the original study was based on a correct versus incorrect dichotomy: if the subject’s response agreed with a predetermined subset of possible answers, the answer was correct; all other answers were considered incorrect. These data are reanalyzed with three principal variations: ( a) individuals’ answers are based on a three-level correctness concept whereby answers considered incorrect in the previous study were further categorized into minor errors and serious errors depending on whether subjects incorrectly chose to “give away” their right-of-way or to violate other drivers’ right-of-way, respectively; ( b) signal message is introduced in the analysis as an explanatory variable of driver comprehension; and ( c) emphasis is placed on older drivers. Youngest, oldest, and female subjects were found to drive fewer kilometers per year than middle-aged males. Comprehension was found to deteriorate with driver age in terms of both higher serious error rates and lower correct answer rates. Flashing signals were the least well understood, whereas change and red interval stimuli were understood best by all age groups.
Minimum Luminance of Highway Signs Required by Older Drivers
Authors: Graham Johnny R. , Fazal Anwar , King L. Ellis
Published: April 2007

No standard for a minimum level of highway sign luminance or retroreflectivity exists. The purpose of this research was to establish such a level. Because of the increasing number of older drivers and their diminished visual capabilities, the focus is on sign luminance requirements of these drivers. Forty-two subjects 65 years of age or more and 19 subjects 25 years of age or less participated in this project. All subjects had a valid driver’s license and wore corrective lenses during the field test if they normally wore them while driving. The field study determined the minimum sign luminance required for the subjects to read a sign with black numerical data on a yellow background. The subjects viewed seven yellow warning signs on a simulated roadway in a large asphaltpaved parking lot. The signs were viewed at distances of 30, 40, 50, 60, 70, 80, and 90 m (32.7, 43.6, 54.5, 65.4, 76.3, 87.2, and 98.1 yd). The sign luminance was varied by using signs of differing retroreflectivity. All tests were conducted at night with low-beam headlights and no fixed roadway lighting. The sign luminance requirements for the two groups has been determined and compared.
Fiber Optic Sensing of Prestressed-Prism-Reinforced Continuous-Composite Concrete Beams for Bridge Deck Application
Authors: Nawy Edward G. , Chen Benxian
Published: April 2007

This investigation involves the identification and use of a novel type of fiber optic sensor in nondestructive testing and monitoring of the deformation behavior of critical sections of structural concrete elements and transforming them into smart systems. Deformational behavior of high-performance-concrete continuous-composite beams reinforced with prestressed prisms was studied and instrumented using fiber optic Bragg grating sensors. Such elements are useful as components of continuous bridge decks where prevention of cracking in the negative moment regions is essential to maintaining the integrity of a bridge. An experimental technique using Bragg grating sensors to evaluate the behavior of the investigated elements at service load stages and the potential of this technique for on-line, real-time monitoring of existing constructed concrete structures are presented. Four continuous beams 5791 mm (19 ft) long with two equal 2743-mm (9-ft) clear spans were tested to failure. High-performance concrete with compressive strength fc’ in excess of 90 MPa (13,000 psi) was used for both the precast prestressed prisms and the main beams cast in situ. Experimental results were compared with theoretical evaluations obtained from nonlinear analysis. Parametric study was conducted to further identify the primary variables that affected the structural performance of such composite T-sections.
Nondestructive Determination of Response of Shear Keys to Environmental and Structural Cyclic Loading
Authors: Hlavacs George M. , Long Todd , Miller Richard A. , Baseheart T. Micheal
Published: April 2007

Adjacent box girder bridges use grouted shear keys to share loads among beams. These keys tend to crack and leak. A full-scale portion of an adjacent box girder bridge is being used to test the performance of grouted shear keys under environmental and cyclic loads. The pulse velocity method is employed to find cracks in the shear keys. Two separate tests were conducted. In the first, shear keys that were grouted in late autumn cracked soon after casting, before any load had been applied. Data from instruments embedded in the beams and shear keys showed large discontinuities in strain caused by freezing temperatures. The strains were much larger than strains that occurred under loads corresponding to the weight of an HS20-44 truck. The beams were subjected to 41,000 cycles of loading, simulating HS20-44 wheel loads. No new cracking occurred from the loading, but cracks caused by temperature propagated under loads. In the second test, the keys were grouted in summer. Higher temperatures caused by the sun’s heat on the top of the beams again caused large thermal strains, which cracked the shear keys. These keys were subjected to 1,000,000 cycles of load corresponding to an HS20-44 wheel load. As in the first test, the load itself did not cause new cracks but the existing thermal cracks propagated under the load.
Control of Cracking with Shrinkage-Reducing Admixtures
Authors: Shah Surendra P. , Marikunte Shashidhara , Yang Wei , Aldea Corina
Published: April 2007

Shrinkage cracking can be a critical problem in concrete construction, especially for flat structures such as highway pavements, slabs for parking garages, and bridge decks. One way to reduce the shrinkage cracking is to provide reinforcement in the form of wire mesh to resist tensile forces. In recent years, short, randomly distributed fibers have been used to control shrinkage cracking. The efficiency of shrinkage-reducing admixtures (SRAs) in controlling restrained shrinkage cracking of concrete is reviewed. A ring-type specimen was used for restrained shrinkage cracking tests. The SRA selected for this investigation was a propylene glycol derivative, which was used at 1 and 2 percent by weight of cement. Free (unrestrained) shrinkage, weight loss, compressive strength, and fracture toughness were also investigated. The results of SRA concretes were compared with that of plain concrete with the same water-to-cement ratio. A theoretical model based on nonlinear fracture mechanics was developed for predicting transverse cracking of the concrete ring specimen caused by drying shrinkage. The model prediction of time to cracking compared well with the experimental data. The model can be extended to different geometries and dimensions than those considered in this research.
Future Research Trends in High-Performance Concrete: Cost-Effective Considerations
Authors: Hwang Chao-Lung , Lee Long-Sherng
Published: April 2007

High-performance concrete (HPC) prepared on the basis of eugenic considerations (cost-effectiveness and life-cycle length) is proposed to resolve actual concrete problems. HPC is safe, durable, workable, economical, and ecologically sound. Concrete in Taiwan is always designed with large amounts of water and paste (even though it is generally accepted that the concrete will tend to crack and deteriorate). Therefore, HPC with fewer problems is the target of ongoing research. Eugenic HPC is produced from ordinary concrete, superplasticized concrete, pozzolanic concrete, and high-flowing concrete. Without the drawbacks of past forms of concrete, eugenic HPC is a better construction material on the basis of individual material characteristics. The characteristics of eugenic HPC are presented and illustrated by two high-rise buildings in Taiwan constructed with high-flowing HPC.
Investigation of Fiber-Reinforced Concrete for Use in Transportation Structures
Authors: Ozyildirim Celik , Moen Cristopher , Hladky Shannon
Published: April 2007

Results are presented of a laboratory investigation to determine the properties of fiber-reinforced concretes (FRCs) with steel (hooked-end), polypropylene (monofilament and fibrillated), and the recently introduced polyolefin fibers (monofilament) for application in pavements and bridge deck overlays. Concrete properties in the unhardened and hardened states were evaluated and compared. Although the ultimate splitting tensile strength, compressive strength, and first-crack strength were higher in most of the FRCs, when strength values were adjusted for changes in air content, only a few batches had higher strengths. The addition of fibers resulted in great improvements in flexural toughness and impact resistance. Three FRC pavement overlays were applied in Virginia in 1995. The FRCs used in the projects were similar to those used in the laboratory investigation, with similar fiber volumes, types, and sizes. To implement the findings of the study successfully, the performance of the FRC pavement overlays is being monitored.
Applying Statistical Methods for Further Improvement of High-Performance Concrete for New York State Bridge Decks
Authors: Bajorski Peter , Streeter Donald A. , Perry Robert J.
Published: April 2007

A new concrete mixture designated “Class HP” for high-performance has been developed for bridge decks in New York State. A modification of the state’s standard Class H concrete, it has better handling and workability characteristics, reduced permeability, and greater resistance to cracking and displays little or no surface scaling. These improvements have potential to result in twice the previously expected concrete service life. The mixture incorporates substitutions for cement of 20 percent Class F fly ash and 6 percent microsilica. It has now been established as the required concrete mixture for all decks built by the New York State Department of Transportation. Its successful implementation has triggered further research toward an even better mixture. An experiment was designed and performed to investigate the effects on cracking and permeability of microsilica and fly ash content, as well as the effects of total weight of cementitious materials. Experimental designs allowed investigation of a broad range of possible combinations while only a limited number of mixtures were tested. Statistical analysis of experimental data is presented and some concrete mixes are recommended for further study, especially those having 10 to 25 percent fly ash, 11 to 12 percent microsilica, and 327 to 375 kg/m3 (550 to 630 lb/yd3) of cementitious materials, and also those with 20 to 35 percent fly ash, 4 to 6 percent microsilica, and 392 to 428 kg/m3 (660 to 720 lb/yd3) of cementitious materials.
Relative Costs of Various Concrete Pavement Features
Authors: Cole Lawrence W. , Hall Michael J.
Published: April 2007

The design and construction of portland cement concrete pavement involves the selection, specification, and construction of a number of concrete pavement features. Concrete pavement features can significantly affect pavement construction costs. In this study, the relative effect on pavement construction cost of several concrete pavement features was investigated, including concrete pavement thickness, foundation, shoulders, cross-section thickness variation (trapezoidal section), joint spacing, transverse joint load transfer, and transverse joint sealant. Careful consideration and study should be given the cost effects of various features when designing and specifying concrete pavement. The ideal pavement design is one that selects the least costly pavement section that will perform to the expected level over the life of the facility. The least costly pavement section is that with the least life-cycle costs.
Criteria for Opening Expedited Bonded Concrete Overlays to Traffic
Authors: Delatte N. J. , Fowler D. W. , McCullough B. F.
Published: April 2007

For rehabilitation of concrete pavements, resurfacing with a bonded concrete overlay (BCO) may provide significantly longer life and reduced maintenance costs. Two important issues to consider in rehabilitation are bonding and rapid reopening of resurfaced sections. The purpose of accelerated or expedited concrete paving is to limit the duration of lane closure and inconvenience to the public. Expedited BCOs offer an economical method for substantially extending rigid pavement life. Research for expedited BCOs in El Paso and Fort Worth, Texas, has been carried out for the Texas Department of Transportation by the Center for Transportation Research at the University of Texas. Results of previous expedited BCO construction are reviewed. Laboratory testing for this project included a high-early-strength mix design, bond development of that mix design, and early-age fatigue strength of half-scale BCO models. A 122-m-long test strip was cast with eight different expedited BCO designs, and accelerated traffic loading was imposed at 12 hr. Recommendations are made for construction and quality control of BCOs for early opening to traffic.
Vibration Study for Consolidation of Portland Cement Concrete
Authors: Tymkowicz Shane , Steffes Robert F.
Published: April 2007

The Iowa Department of Transportation has discovered an increase in the occurrence of excessively vibrated portland cement concrete (PCC) pavements. The overconsolidation of PCC pavements has been observed in several projects across the state. Overconsolidation is also believed to be a factor in acceleration of premature deterioration of at least two pavement projects in Iowa. To address the problem, a research project in 1995 documented the vibratory practices of PCC slipform paving in Iowa in order to determine the effect of vibration on consolidation and air content of pavement. Paver speed, vibrator frequency, and air content relative to the location of the vibrator were studied. The study concluded that the Iowa Department of Transportation specification of 5,000 to 8,000 vibrations per minute (vpm) for slipform pavers is effective for normal paver speeds on the three projects that were examined. Excessive vibration was clearly identified on one project where a vibrator frequency of 12,000 vpm was discovered. When the paver speed was reduced to half the normal speed, hard air contents indicate that excessive vibration was beginning to occur in the localized area immediately surrounding the vibrator at a frequency of 8,000 vpm. The study also indicates that the radius of influence of the vibrators is smaller than has been claimed.
Performance Factors and Quality Control/Quality Assurance for Porous Pavements
Authors: Dunn Kimberly D. , Hicks R. Gary , Gower Jeff
Published: April 2007

Open-graded hot mixes have been used as road surfaces in Oregon since 1978. Since 1989, they have been used on all Interstate and primary highways in western Oregon; they are used less extensively in eastern Oregon. The Oregon Department of Transportation (ODOT) has pay-adjustment factors for dense-graded mixes based on an evaluation of constituents, including asphalt content, gradation, compaction, and moisture content. As a part of a larger research effort, a survey was administered to various national and international agencies inquiring about their knowledge of and experience with porous pavements. Administration of this survey was sponsored by ODOT; the purpose of the larger research effort was to develop an improved specification for porous pavements that would contain pay incentives and disincentives. Findings from this survey are reported. Of the 28 individuals contacted, responses were received from 24, providing an 86 percent response rate. Because this study was conducted to determine appropriate pay factors for open-graded mixtures, the survey was designed to learn about how other agencies were dealing with specifications and adjustment factors for porous pavements. The findings from the survey are presented with respect to (a) the respondents’ experiences with construction of open-graded asphalt during the past 5 years, (b) the factors that contribute most to the performance of open-graded mixes, (c) the most common types of failures for these mixes, (d) the primary causes of failures of the various types, and (e) the use of specifications that contain provision for pay adjustment.
Applicability of New Flexible Pavement Smoothness Specification for Asphalt Overlays
Authors: Fernando Emmanuel G.
Published: April 2007

The Texas Department of Transportation plans to implement smoothness specifications based on profilograph testing for all asphalt concrete paving projects as part of its construction quality control/quality assurance program. Smoothness specifications have been developed for newly constructed asphalt and portland cement concrete pavements. In a move to develop a similar specification for asphalt concrete overlays, the Texas Transportation Institute was asked to evaluate the applicability of the existing flexible pavement smoothness specifications for the quality control and quality assurance of pavement rideability on overlay construction projects. This study was intended to provide the state with the information necessary to evaluate the improvement in ride quality that may be expected from placement of asphalt overlays, particularly for thin overlays [38 to 51 mm (1.5 to 2 in.)], which are generally constructed in Texas. To collect data to determine whether the existing specification can be implemented for overlay construction work, TTI monitored a number of overlay projects during the 1994 calendar year. Profilograph measurements were made during these projects before any surface preparation, after surface preparation, and after placement of the asphalt concrete overlay. All of the projects monitored involved thin overlays. The data collected indicate that the existing smoothness specifications can be implemented on overlay projects, provided that appropriate surface preparations (e.g., milling, level-ups) are conducted to correct existing surface distresses before placement of the overlay.
Using Ground-Penetrating Radar and Dielectric Probe Measurements in Pavement Density Quality Control
Authors: Saarenketo Timo
Published: April 2007

Ground-penetrating radar and capacitance-based dielectric surface probe measurements are used to measure fluctuations in voids, bitumen content, or both, in newly asphalted pavements without causing structural damage. Both methods rely on the compaction of asphalt to reduce the proportion of low-dielectricity air in the material, which increases the volumetric proportions of high-dielectricity bitumen and rock and thus results in higher asphalt dielectricity values. Ground-penetrating radar enables pavement thickness to be measured rapidly from a moving vehicle and information on variations in pavement voids content to be collected simultaneously on the basis of dielectricity fluctuations. The results can be calibrated against real void content by material sampling or by comparison of dielectric value with voids content values determined beforehand for the same material under laboratory conditions. This means that the subcontractor can be informed quickly of any values that exceed or fall below the norms and can take immediate steps to rectify such defects. Other advantages offered by the technique are the rapidity of the measurements and the immediate availability of the results. In addition, the one measurement provides simultaneous information on pavement and base thicknesses and the quality of the latter. The dielectric probe based on capacitance measurements lends itself to use in asphalt mass proportioning examinations performed at the laboratory stage, which enables the values to be used directly for monitoring in situ pavement compaction. The advantages of the dielectricity probe are rapidity of measurement, low-cost meters, and the avoidance of radiation. Thus far, the probe has been excessively sensitive to variations in the roughness of pavement surfaces. The theory behind these research methods is discussed, the methods are described, and the results of laboratory tests conducted at the Texas Transportation Institute in 1994–1995 and field tests performed in Finland in 1995 are presented.
Finite-Element Modeling of Red Maple Glued-Laminated T-Beams and Bridge Behavior
Authors: Witmer Ray W. , Manbeck Harvey B. , Janowiak John J.
Published: April 2007

Finite-element modeling methods are presented using an existing finiteelement program to (1) predict the stiffness increase, due to the addition of deck panels, for red maple glued-laminated (glulam) T-beam assemblies relative to beams with no deck panels; and (2) predict the midspan beam deflection for a red maple glulam longitudinal stringer–transverse deck bridge for two loading conditions (one lane loaded and two lanes loaded). The red maple T-beam stiffness increase was determined for T-beams assembled with and without gaps between deck panels. The T-beam stiffness increase was predicted to within 5 percent for T-beams assembled with gaps between deck panels and to within 3 percent for T-beams assembled with no gaps between deck panels. Red maple glulam longitudinal stringer–transverse deck bridge maximum midspan beam deflections were predicted to within 6 percent for one-lane loading and to within 7 percent for two-lane loading.
Developing QC/QA Specifications for Hot Mix Asphalt Concrete in Illinois
Authors: Patel Arti , Thompson Marshall , Harm Eric , Sheftick William
Published: April 2007

The Illinois Department of Transportation (IDOT) has recently undertaken a quality management program to improve the quality of construction, allow more innovation, and reduce IDOTs management of industry construction programs. The Asphalt Concrete (AC) Quality Control/Quality Assurance (QC/QA) program is a significant part of this quality management program. IDOT accredits the success of the AC QC/QA program to gradual implementation and contractor and industry involvement. In 1991, four projects were constructed under a newly developed QC/QA specification. After reviewing and evaluating feedback from the contractors and IDOT personnel, the specification was revised for use on 1992 projects. In 1992, IDOT let 30 QC/QA projects, and in 1993, 65 QC/QA projects. In 1994 and 1995, most AC projects containing over 225 metric tons (250 tons) of hot-mix asphalt (HMA) were designated as QC/QA projects. In conjunction with this effort on AC quality, an aggregate certification program was implemented. The program ensures that aggregate gradation is highly controlled and is acceptable for incorporation into the mixture. Training programs for contractor QC and aggregate certification were also implemented. Analysis of the data indicates an increase in uniformity of the HMA, potentially leading to a 15 percent increase in fatigue life. IDOT is now examining the implications of developing end-result and performance-related specifications (ERS/PRS) for the AC QC/QA program. In the summer of 1996, one QC/QA project was shadowed and evaluated based on newly developed ERS/PRS.
Comprehensive Quality Control of Portland Cement Concrete With Seismic Methods
Authors: Nazarian Soheil , Yuan Deren , Weissinger Eric , McDaniel Mark
Published: April 2007

The feasibility of seismic methods for determining the quality and thickness of portland cement concrete layers was recently studied. The study consisted of performing nondestructive laboratory seismic tests on cylinders that were laboratory-cured for 2 to 90 days. The cylinders were then subjected to appropriate strength tests (such as compressive and splitting tensile). Reasonably high correlations were found between static modulus, compressive strength, or tensile strength and seismic modulus. Seismic moduli were also found to be repeatable, as the coefficients of variation for different lots were generally less than 2 percent. Similar tests were also performed on cores retrieved from a site constructed with similar concrete. Before coring the slabs, nondestructive seismic tests were also performed on the concrete. Seismic moduli from laboratory and field tests were close and repeatable. The coefficients of variation for the seismic tests were generally less than 3 percent and 4 percent for the laboratory and field tests, respectively. The curing patterns observed in both the field and the laboratory were very different. Regardless of the methodology used, the correlations based on the laboratory specimens appear not to be representative of the field behavior. A focus on the use of nondestructive field methods for quality control/quality assurance may be necessary.
Improving Conceptual Estimating Methods Using Historical Cost Data
Authors: Walton Jennifer R. , Stevens James D.
Published: April 2007

Growing needs for the highway system are causing great concern, considering that federal and state funding cannot possibly support all the demands. To maximize the benefit of each allotted dollar, a dependable method for forecasting costs is needed. In 1993, the Federal Highway Administration and the Kentucky Transportation Cabinet authorized a study of current estimating methods for highway projects and the development of a better method, if possible. The research led to the development of a computer program, KYEstimate. It uses historical cost data and project length to calculate a unit cost (cost/kilometer or cost/mile), and promises to improve conceptual estimates for highway projects. KYEstimate is most beneficial in the planning stages of a project; the estimate produced should be viewed as a preliminary estimate only. The program has been designed to complement the skills of an estimator, and should make the conceptual estimating process easier and less time consuming. KYEstimate also provides justification and documentation for the estimate. Using their own historical data, other states could also benefit from this type of conceptual estimating.
Long-Term Highway Revenue Forecasting for Indiana
Authors: Varma Amiy , Sinha Kumares C.
Published: April 2007

Increased emphasis is being placed on improved financial control and planning within state transportation agencies because of shifts in revenue sources; escalation of construction, maintenance, and operating costs; instability of revenue bases; and mandates of the Intermodal Surface Transportation Efficiency Act of 1991. A summary of the highway revenue analysis and highway revenue forecasting done for the state of Indiana as part of an investigation conducted by the Joint Highway Research Project, Engineering Experiment Station, Purdue University, in cooperation with the Indiana Department of Transportation and the Federal Highway Administration, is provided. A long-term highway revenue forecasting methodology was developed with emphasis on ease of data input, simplicity of internal model relationships, and responsiveness to changes in socioeconomic, technological, energy, environmental, financial, and legislative factors.
Urban Transportation Policies and Practices in the United States and Its Peer Countries
Authors: Vuchic Vukan R. , Eun Shin Yong , Bruun Eric C. , Krstanoski Nikola
Published: April 2007

All developed countries experience similar trends and problems in urban transportation: growth of cities and affluence result in an increase in car dependency. Increased volumes of car travel lead to congestion and many negative effects, often termed as the “collision of cities and cars.” A review of urban transportation policies and their implementation in the United States and its peer countries—Australia, Canada, and countries in Western Europe and East Asia—indicates that all peer countries except Great Britain place major emphasis on maintaining the human orientation of cities. They pursue policies aimed at achieving multimodal transportation systems and preventing automobile dominance. The United States, after significant strides in that direction up to 1980, has returned to policies favoring car travel and reducing support for alternative modes—transit, bicycles, and walking. This trend largely ignores the spirit and mandates of the Intermodal Surface Transportation Efficiency Act of 1991. The gap between the United States and its peer countries is increasing. Present U.S. policies are likely to aggravate this situation. An example is presented: New York is compared with its peer cities in accessibility for long-distance travel. Its competitiveness in this respect is lagging. This trend cannot be ignored. As its peers learned from the U.S. experiences in highway and traffic engineering in the past, the U.S. should now learn from its peers how to avoid total car dependence and implement multimodal transportation systems to improve the livability of its metropolitan areas.
Use of Work Group Technology in Transportation Agencies: Current Experience and Opportunities
Authors: Vlahos Nicholas J. , Harrison Frances D.
Published: April 2007

In recent years, information technologies have emerged that are geared toward helping groups to work together more productively and effectively. These technologies are dramatically changing the way people work by breaking down spatial, temporal, and organizational barriers that have limited communication in the past. Work group technologies can address a critical need for improved efficiency and teamwork in transportation agencies. Transportation organizations are an ideal environment for application of these technologies and have a substantial number of processes (both internal and cross organization) that are logical candidates for piloting work group technologies. Various types of work group information technologies are surveyed, relevant application areas in transportation agencies where significant benefits could be realized are described, and examples of three current applications are provided. Key implementation considerations are discussed.