bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Temperature Stresses and Fracture Analysis of Asphalt Overlays
Authors: Shalaby A. , Halim A. O. Abd El , Easa S. M.
Published: August 2018

Thermal cracking of asphalt overlays is a leading cause of pavement deterioration. The thermoelastic response of a multilayered pavement structure is modeled using a transient thermal analysis followed by a quasi-static stress analysis at discrete time intervals using finite element analysis. Numerical analysis of two- and three-dimensional cracking problems is performed. Based on a fracture mechanics approach, the potential of thermal cracks to propagate through the overlay is examined using both a displacement formula and an energy-balance principle. The interaction between multiple cracks and the effect of bond between layers on crack propagation are examined. The proposed numerical methods for analysis of pavement thermal cracking provide a means to characterize and optimize different evolving materials and innovative pavement reinforcement techniques.
Plasticity Modeling Applied to the Permanent Deformation Response of Granular Materials in Flexible Pavement Systems
Authors: Bonaquist Ramon , Witczak Matthew W.
Published: August 2018

Mechanistic design methods for flexible pavements are usually based on limiting only two critical pavement responses: tensile strain at the bottom of the asphalt layer for fatigue damage and vertical compressive strain at the top of the subgrade for overall pavement rutting. Rutting in granular base and subbase layers is assumed to be small for all cases. Research was conducted to develop a fundamental method for incorporating rutting of granular base and subbase layers in flexible pavement thickness design. The research concentrated on investigating the potential for using constitutive relationships based on the flow theory of plasticity to limit permanent deformations in granular layers of pavement systems. The flow theory of plasticity is the most popular of the three plasticity theories that have been applied to soils and granular materials. The total strain is viewed as the sum of the reversible elastic component and the irreversible plastic component. A yield function is introduced to differentiate between elastic and plastic behavior. This yield function is a function of the stress state and may change on loading and unloading to describe cyclic hardening behavior. To use a flow theory model to predict the response of a granular pavement layer requires relatively complex finite-element analysis and sophisticated laboratory testing that may not be warranted for normal pavement design. A method is presented for using the yield surfaces from a flow theory model as a design criterion for limiting permanent deformations in granular layers. Only the results of triaxial strength tests are needed to implement the method.
Rolling Weight Deflectometer with Thermal and Vibrational Bending Compensation
Authors: Johnson R. F. , Rish J. W.
Published: August 2018

A pavement deflectometer has been developed for continuous measurement of airfield pavements under a rolling load wheel. The rolling weight deflectometer (RWD) measures pavement deflection using a new method of laser triangulation. It also compensates for bending of the beam on which the sensors are mounted. This compensation allows accurate measurement of deflection in the presence of motion and thermal effects. The deflection measurement incorporates data from four equally spaced pavement sensors mounted on a beam. The method requires the sensors to remain in a straight line at all times. This method was previously plagued with measurement errors caused by thermal and vibrational effects. The RWD uses a laser beam to monitor the state of bending of the physical beam in real time. The bending data are used with pavement sensor data to produce accurate deflection measurements in the presence of any amount of beam bending. The bending-compensated RWD produces deflection measurements on 0.3-m (1-ft) intervals with an accuracy of 40 microns (0.0015 in.) while moving at 10 km/hr (6 mph). The RWD is composed of a towed trailer, a networked data-acquisition system, and a load platform. Its essential elements consist of a horizontally transported beam, strategically placed pavement sensors, sensors to measure beam bending, an odometer, and a data-acquisition computer. A brief history of pavement deflection methods is presented along with a description of the RWD. Preliminary field results include a comparison between data obtained by a falling weight deflectometer and the RWD.
Application of Falling Weight Deflectometer Data for Analysis of Superheavy Loads
Authors: Chen Dar-Hao , Fernando Emmanuel , Murphy Michael
Published: August 2018

Permitting superheavy loads may increase the rate of pavement damage and the cost of maintenance. An analysis of a proposed superheavy load route (FM519) to evaluate the potential pavement damage caused by a planned superheavy load move is presented. Falling weight deflection (FWD) tests and backcalculations of layer moduli were performed on the FM519. FWD tests and backcalculation of layer moduli were performed on the pavement before and after the superheavy load was moved. ELSYM5 and BISAR were used to evaluate the pavement responses using the backcalculated layer moduli from FWD data. The predictions of surface deflections from ELSYM5 and BISAR were close to (within 10 percent of) the measured deflections from FWD tests. The FWD data and analyses show that the existing pavement structure is adequate for the planned superheavy load move. Finally, the permit was issued with the condition that the transport vehicle should be kept within the travel lanes and away from the shoulder whenever possible. FWD tests were conducted after the superheavy load move and comparisons with before superheavy load move were made. T-tests were performed to check for significant difference at the 95 percent confidence level. T-tests showed that there is no significant difference between before and after superheavy load move. Also, no significant distresses due to this superheavy load were observed after the move, and the pavement condition is consistent with the analysis performed to issue the permit.
Prediction of Pavement Fatigue for California Department of Transportation Accelerated Pavement Testing Program Drained and Undrained Test Sections
Authors: Long Fenella , Harvey John , Scheffy Clark , Monismith Carl L.
Published: August 2018

The use of laboratory testing and mechanistic analysis to predict the fatigue life of the California Department of Transportation accelerated pavement testing (CAL/APT) heavy vehicle simulator (HVS) test sections is investigated. Two pavement structures are investigated: a drained pavement that includes an asphalt-treated permeable base layer and an undrained conventional asphalt concrete pavement. The fatigue life under HVS accelerated loading for both sections is predicted using the laboratory testing procedure from SHRP A-003A, which is based on tests of actual pavement samples using the flexural fatigue beam test. This fatigue life is compared with predictions from the SHRP A-003A surrogate equation for flexural testing, the Shell model, and the Asphalt Institute model. The critical tensile strains for the fatigue calculations using the models investigated were determined using linear elastic theory. Ranges of moduli for the pavement layers were determined from extensive material testing, and 24 moduli combinations were made. The effect of pavement type, changes in moduli, and the HVS loading conditions on the tensile strain and fatigue life predictions between the models is discussed. Reasons for differences between predicted fatigue lives and their implications are also discussed. Predicted fatigue life is compared with actual performance under HVS loading for the drained pavement.
Use of Visual Methods to Investigate Influence of Installation Procedure on Pipe-Soil Interaction
Authors: Rogers C. D. F. , Fleming P. R. , Talby R.
Published: August 2018

The results of four laboratory tests on a very flexible pipe (standard dimension ratio of 83) buried in sand are reported. Photographs of sand particles and the pipe in the plane of the cross section were taken through the glass face of the test rig. The measured displacements during installation and subsequent surcharge loading were compared with measurements of circumferential pipe wall strains to determine the effects of installation on pipe performance. Two installations involved sand being placed carefully around the pipe profile, one with compaction of the sand in layers and the other without compaction. The final two installations concerned sand either being scattered uniformly around the pipe or being heaped (uncompacted) on one side before leveling. The results indicate that pipe performance is greatly affected by the installation procedures used. In particular, asymmetrical filling and compaction result in lateral displacement and a difference in pipe support on either side of the pipe. Lack of haunch support because of poor material distribution during initial sidefilling results in a tendency to displacement, and hence strain concentration, at these points. Thorough compaction of the side-fill at the spring lines was found to cause the pipe to be raised from its bedding, with the pipe subsequently deforming into the void thus formed. The pipe wall strain profiles were shown to correlate well with the displaced pipe profile, and predictions of deformed shape can thus be made with care. The movement of individual sand particles indicates well the way in which the soil support is derived.
Analysis of Reinforced Concrete Culvert considering Concrete Creep and Shrinkage
Authors: Oswald Charles J.
Published: August 2018

Measurements made on a long span reinforced concrete arch culvert under 7.3 m (24 ft) of silty clay backfill were compared with results from finite-element analyses of the soil-structure system using the CANDE finite-element code. The culvert strains and deflections and the soil pressure on the culvert were measured during construction and during the following 2.5 years at three instrumented cross sections. The CANDE program was modified to account for the effects of concrete creep and shrinkage strains after it was noted that the measured postconstruction culvert deflection and strains increased significantly whereas the measured soil pressure on the culvert remained relatively constant. Good agreement was generally obtained between measured and calculated values of the culvert strain and deflection and the soil pressure during the entire monitoring period after the code was modified.
Reconstruction of Aquarium Station
Authors: Highfill Steven , Shah C. K. , Brenner Brian , Formosa John
Published: August 2018

This paper discusses the analysis and design for the reconstruction of the Massachusetts Bay Transit Authority (MBTA) Aquarium subway station in downtown Boston. This unusual design includes rebuilding and extension of the Blue Line rapid transit station, and construction of the new I-93 Central Artery highway tunnel directly above it. All construction work will be performed while the existing I-93 viaduct remains in service overhead, the MBTA subway operations are ongoing, and surface street vehicular and pedestrian traffic is maintained.
Effects of Removing Diaphragms from Steel Girder Bridge
Authors: Stallings J. M. , Cousins T. E. , Stafford T. E.
Published: August 2018

Many multigirder steel bridges built before the 1980s are experiencing distortion-induced fatigue cracking at diaphragm-girder connections. A means of eliminating the cyclic stresses that cause those fatigue problems is to remove the interior diaphragms (diaphragms not at the girder supports). The effects of removing all interior channel diaphragms from an existing simple-span bridge with rolled-steel girders were evaluated based on field measurements of girder stresses and deflections made before and after the diaphragms were taken out. Results from tests with trucks of known weight indicate that removing the diaphragms resulted in increases between 6 and 15 percent in the maximum bottom flange stresses experienced by the most heavily loaded girder. Results for loading by trucks of unknown weight in normal traffic indicate that the most heavily loaded girder may carry up to 17 percent more load as a result of removing the diaphragms.
Performance Evaluation of Asphalt Overlays on Broken and Seated Concrete Pavements
Authors: Arudi Rajagopal S. , Minkarah Issam , Kandula Krishna , Gosain Archana
Published: August 2018

Evaluating the effectiveness of breaking and seating concrete pavements prior to asphalt overlay is a subject of great importance for pavement rehabilitation. A number of studies reported that breaking and seating delayed reflection cracking, but some indicated that, after 4 to 5 years, the cracking of the asphalt overlays on broken and seated sections increased and was about the same as in the other sections. Structural analysis of these pavements confirmed a significant loss of structural support. A controlled experimental project in Ohio investigated the effectiveness of breaking and seating jointed reinforced concrete pavements before asphalt overlay. Four miles of in-service composite pavements carrying heavy traffic were rehabilitated by milling the original asphalt layer, breaking and seating the concrete slabs, and constructing new asphalt overlays. Four more miles of the same sections were constructed in the same way except for breaking and seating. After 2 ½ years of study, the results confirm the previous findings regarding the effectiveness of breaking and seating in delaying reflection cracks and reduction in structural capacity, increase in surface deflection, and loss of flexural strength. This study indicates that the type of breaking equipment used and the extent of breaking are the most significant factors affecting the performance of these pavements.
Round-Robin Study of Asphalt-Concrete Content by Ignition
Authors: Brown E. R. , Mager Stuart
Published: August 2018

The National Center for Asphalt Technology (NCAT) has developed a test method to determine the asphalt content of hot-mix asphalt (HMA) mixtures by ignition. In the ignition method, an HMA sample is subjected to heat of 538°C (1,000°F) in a furnace to ignite and burn the asphalt cement (AC) from the aggregate. The difference in weight of the sample before and after is used to determine the asphalt content of the mixture. The aggregate recovered after ignition testing may then be used for gradation analysis. A round-robin study was completed by NCAT to determine the accuracy and precision of the ignition method. The round-robin test program is discussed, as well as the accuracy and precision values determined for the measured AC content and gradation using the ignition method. The results of the round-robin study indicate that the ignition method can measure the AC content of HMA mixtures with greater precision than solvent-extraction methods, without significantly affecting the gradation of the aggregate. This test method has shown excellent potential for replacing existing test methods for measuring asphalt content.
Structural Modeling for Reconstruction of Arch Bridge
Authors: Hill James J.
Published: August 2018

When a 70-year-old multiarch concrete bridge was to be reconstructed by removing the deck and vertical spandrel columns down to the arch, analysis was necessary for unloading and reloading. The arch bridge, located on TH-55 over the Minnesota River, was of world-record length for such a structure when it was originally constructed in 1926 through 1928. The amount of steel reinforcement in each of the two support arches was only 32 No. 9 bars of 28.6-mm (1.125-in.) diameter. The deck, which was 18.3 m (60 ft) wide and supported at 9.1 m (30 ft) by columns, was designed as a patented panel system. This involved the use of only 250 kg (550 lb) of reinforcement in each deck panel. The slab did not possess upper reinforcement in the center areas, so removal operations could not allow the slab to cantilever in these areas. As a result of the minimal steel reinforcement in the deck and arches, removal operations needed to be planned safely and effectively. At no time during the removal process could the arches be placed in flexural stress above their very limited carrying capacity. Prospective contractors were advised of this condition and were given 2 weeks beyond the original deadline to submit bids accordingly. The proposal and plans given to each prospective contractor for bidding showed a possible deck removal method using a crane. Structural modeling by the contractor's consultant and the Minnesota Department of Transportation using Staad III finite element analysis was necessary for the contractor's bridge deck removal and replacement method. The existing slab removal and replacement with a wider, 27.4-m (90-ft) deck was successful and the bridge was reopened to traffic in October 1994.
Design of Flowable Fill: Waste Foundry Sand as a Fine Aggregate
Authors: Bhat S. T. , Lovell C. W.
Published: August 2018

Flowable fill is generally a mixture of sand, fly ash, a small amount of cement, and water. Sand is the major component of most flowable fill mixes; consequently, using a waste material as a substitute for natural sand results in the beneficial use of the waste material. Waste foundry sand (WFS) was used as a fine aggregate in this study. Three green sands from ferrous foundries and two Class F fly ashes were used. A natural river sand was used for comparison. The flow behavior, hardening characteristics, and ultimate strength behavior of flowable fill were investigated. The penetration resistance necessary to sustain walkability as the fresh flowable fill hardens was determined, and the time necessary to achieve this penetration resistance was defined as “walkable time.” The unconfined compressive strength at 28 days appeared to correlate well with the water-to-cement ratio. The 90-day compressive strength test results indicate that a maximum rise of 25 to 30 percent in long-term strength with respect to 28-day strength can be expected. The permeability of hardened flowable fill was found to be low (around 10−6cm/sec). The pH of pore solution of hardened flowable fill indicated that the potential for corrosivity is low. The toxicity tests indicated that some WFSs are environmentally safe. The concepts explained are not necessarily restricted to flowable fill containing WFS; they can be generalized as being applicable to all flowable fills.
Condition Assessment of Installed Timber Piles by Dispersive Wave Propagation
Authors: Chen Shunyi , Kim Y. Richard
Published: August 2018

Timber piles are widely used for supporting bridges, piers, wharves, and other marine structures. As they age, it becomes critical that their in situ condition be assessed so their remaining service life can be evaluated. Current inspection methods involving visual examinations and sounding tests are unable to quantitatively disclose a pile's degree of deterioration, depth of penetration, or remaining load-bearing capacity. Years of exposure to wood-decomposing fungi and weathering may have substantially decreased a pile's effective cross-sectional area, so that the pile can no longer function as originally intended. A study was conducted in which nondestructive dispersive wave propagation tests were applied to both laboratory pile models and field timber piles. The laboratory models consisted of acrylic cylinders having different wall thicknesses to simulate various levels of internal deterioration and timber posts with drilled holes to simulate damage created by marine borers. Seven installed and two uninstalled field timber piles were tested. Laboratory experiments indicated that the dispersive wave propagation test is an excellent means for evaluating the degree of hollowness and borer damage. Field experiments further verified the applicability of the dispersive wave propagation in finding the condition of the installed timber piles. The approaches found to be promising for the condition assessment were (a) phase velocity comparison between the first pass and the return pass and (b) wave speed versus test location. The general trend of the dispersion field in condition assessment is the higher the wave speed, the better the condition.
Evaluation of Pavement Bearing Characteristics Using Florida Limerock Bearing Ratio Test
Authors: Ping W. Virgil , Ge Ling , Yu Zhiliang
Published: August 2018

A laboratory study performed to evaluate pavement bearing characteristics by the Florida limerock bearing ratio (LBR) test is presented. The LBR is a modification of the California bearing ratio test and has been widely used in Florida for the design of pavement structures. The LBR evaluation is part of a larger research project studying existing pavement conditions in Florida. A field experimental program was recently conducted on 20 selected pavement sites across the state of Florida. The LBR test was performed on pavement soils obtained from the field test sites. The LBR test results were analyzed and compared with the field test results. The AASHO Road Test layer coefficient values (a2) and soil support values (SSVs), which have become classic reference values over more than two decades, were evaluated by using the LBR and field test results. It was concluded that the LBR values could be used to estimate the SSVs for the design of flexible pavements in Florida. The correlation relationships between the LBR values and SSVs were evaluated to better characterize the pavement structures in Florida.
Effects of Aging on Freshly Deposited or Densified Calcareous Sands
Authors: Al-Sanad Hasan A. , Ismael Nabil F.
Published: August 2018

The effect of aging on the strength and compressibility of calcareous desert sands was examined by laboratory and field tests. The field tests included standard penetration and dynamic cone penetration tests on freshly deposited loose calcareous sand at one site in Kuwait City. The laboratory tests included direct shear, consolidation, and California bearing ratio tests on reconstituted compacted specimens from a naturally cemented sand. These tests were conducted at zero time and after aging for different periods in the laboratory. The results indicate an increase in the shear strength and a reduction in compressibility at a decreasing rate with time. The penetration resistance increased by 100 to 200 percent as a result of aging over a period of 1 year. The changes in strength and compressibility are attributed to mechanical effects resulting from particle interlocking, reorientation, and dispersion and increased friction at a constant effective stress.
Development of Cyclic Triaxial Apparatus with Broad Frequency and Strain Ranges
Authors: Gookin W. B. , Riemer M. F. , Boulanger R. W. , Bray J. D.
Published: August 2018

A cyclic triaxial testing system capable of measuring very small to large strain properties on a single specimen has been developed by combining a wide variety of existing instrumentation, including piezoceramic bender elements, internal displacement measurement devices (both contact and noncontact), local displacement measurement devices, a sensitive internal load cell, and an external load cell. The bender elements provide information on soil properties in the nearly linear elastic (very small strain) range. Local and noncontact internal displacement measurements provide information about small strain range properties, whereas more traditional internal displacement measurements provide information in the small to large strain range. In addition, this apparatus can be used over a wide range of loading frequencies to investigate the effect of frequency on dynamic soil properties. By combining this equipment in a single testing system, a number of tests may be run on one specimen, eliminating the effects of variability. The broad variety of displacement measuring instruments also allows direct comparisons of these techniques on a single specimen.
Low Strain Dynamic Shear Modulus of Cemented Sand from Cone Penetration Test Results
Authors: Puppala Anand J. , Acar Yalcin B. , Tumay Mehmet T.
Published: August 2018

Low strain dynamic shear modulus property is generally used to subclassify soil strata, determine elastic settlements under geotechnical structures, and characterize the dynamic nature of soils. Several methods to interpret the dynamic shear modulus of sands from in situ friction cone test results have been developed. These methods used calibration chamber test data of clean sands. Therefore, these methods are not valid for interpreting the shear modulus of cemented sands. Introduced here is an interpretation method to estimate the shear modulus of cemented sand. Thirty-seven friction cone penetration tests (CPTs) were conducted on artificially cemented sand specimens of relative densities ranging from 45 percent to 85 percent and confining pressures ranging from 100 to 300 kPa in a laboratory stress-strain-controlled calibration chamber. Cementation levels of 1 and 2 percent were used in preparing cemented specimens. Resonant column tests were also conducted on the same sand with identical cementation levels. The CPT and resonant column test data are used in developing an interpretation method that includes semiempirical correlations. Simple interpretation charts are also provided to directly estimate the low strain shear modulus of cemented sand from tip resistance, unconfined compressive strength, and relative density data. Comparisons between predictions of the proposed interpretation method and the present measured shear modulus test data indicate that the interpretation charts have provided reasonable predictions. The comparisons also indicate that the predicted results on clean sands obtained by different researchers are in agreement with each other.
Visual and Ecological Environmental Quality Model for Transportation Planning and Design
Authors: Burley Jon Bryan
Published: August 2018

Landscape aesthetics and environmental quality have both become central investigatory areas in transportation planning and design. Environmental designers are interested in applying research-based models to study the effects of specific transportation design treatments on the built and natural landscape. The development of a perception-based visual quality predictive equation is investigated for application in both naturalistic and designed landscapes for transportation planning and design projects. The prediction model contained total area of noospheric features and total area of motorized vehicles; presence of humans, wildlife, utility structures, and foreground flowers; total area of distant nonvegetation landscape features such as mountains and buttes; perimeter of intermediate nonvegetation; total area of foreground vegetation; and openness, mystery, and environmental quality indexes (p < 0.0001 for the overall regression, p ≤ 0.05 for each regressor using Type II sums of squares, and multiple. R-square of 0.67). Other variables such as motorized boats, nonflowering foreground herbaceous plants, a greenness index, fire, total area of exposed foreground substrate, smoke, water, smoothness, and the Shafer index were not significant regressors. By using a graph plotting the 95 percent confidence limits for the equation, an investigator can predict the statistical differences between a pair of images at a 90 percent confidence level.
Measuring Driver Performance in Braking Maneuvers
Authors: Koppa Rodger J. , Fambro Daniel B. , Zimmer Richard A.
Published: August 2018

A simple, reliable instrumentation package with an on-board computer for installation in a test vehicle or the test driver's own vehicle is described. This package was used in a research project recently completed, an empirical investigation of stopping sight distance. Selected data on perception-response time (PRT) and braking performance under artificial and simulated on-the-road emergency conditions are presented. PRTs were less than the AASHTO assumed constant of 2.5 sec even at the 95th percentile. Braking performance in terms of steady deceleration was greater than −0.32 g at the 95th percentile.
Driving Simulator Validity: Some Considerations
Authors: Kaptein Nico A. , Theeuwes Jan , van der Horst Richard
Published: August 2018

The validity of driving simulators for behavioral research is discussed. The concept of validity is introduced and explained, and a survey of validation studies follows, in the TNO driving simulator and others, comparing field and simulator study results. Results for mid-level driving simulators show that generally absolute validity of route choice behavior is obtained and relative validity of speed and lateral control behavior is obtained. There is evidence suggesting that for a number of applications the presence of a moving base and possibly a higher image resolution might increase the validity of a driving simulator.
International Tourist Guidance Needs and Understanding of Selected Guide Signs in Florida
Authors: Dudek Conrad L. , Huchingson R. Dale , Trout Nada , Chester Dana
Published: August 2018

The Florida Department of Transportation initiated a research study to determine whether existing guide signing in large cities in Florida is adequately accommodating international tourists and, if not, to determine the types of problems international tourists are experiencing and to recommend changes so that tourists will not become confused or lost. Results from two surveys conducted to assess the highway guidance needs for international tourists are presented. The first survey was conducted as part of a critical incident analysis. International tourists were asked to provide a general critique of Florida signing practices and asked to comment on what would make these signs easier to understand and follow. Two hundred nineteen comments or suggestions were obtained. The most commonly reported criticisms were the need for better advance notice of exits, the presence of confusing messages, poor visibility and lighting, and the need for better signing guidance to major destinations. A follow-up study was conducted to assess certain signing issues relative to guide-sign designs for international tourists. Four hundred eighty-six international tourists participated in studies. Among the findings relative to international tourists were that certain abbreviations of International Drive are understood and others are not; the Manual on Uniform Traffic Control Devices aircraft symbol is often taken to mean any airport, rather than an international airport; the question mark for “tourist information” is not understood; and destination information is important on guide signs, especially when the cardinal direction conflicts with the compass direction.
Determining Detailed Origin-Destination and Travel Time Patterns Using Video and Machine Vision License Plate Matching
Authors: Shuldiner Paul W. , D'Agostino Salvatore A. , Woodson Jeffrey B.
Published: August 2018

Examples are presented of the use of machine vision technology for reading and processing vehicle license plate images acquired in the field by video camcorders. Applications include travel time and microscale origin-destination pattern analyses for a freeway interchange in Tampa and the road network serving Houston's Intercontinental Airport, and high-occupancy vehicle lane performance measurements in Seattle. It is concluded that video and machine vision analysis of license plates is an effective and efficient means of conducting a wide variety of traffic engineering and traffic management studies.
Origin-Destination Survey Data Dissemination in Metropolitan Context: A Multimedia Experience
Authors: Chapleau Robert , Trέpanier Martin , Lavigueur Pierre , Allard Bruno
Published: August 2018

Since the early 1970s, the Montreal Urban Community Transit Commission has held a series of six major origin-destination surveys in the greater Montreal area. These studies, which include approximately 50,000 households per survey, benefit from a totally disaggregate approach. This framework permits the spatialization of each trip end at the x-y coordinate level and associates multiple variables to every recorded trip. The dissemination of such a vast quantity of data requires different levels of resolution with respect to processing methods and software, zonal aggregation, itineraries, and sociodemographic variables. In this context, two tools have been created for public use: MADEOD (Origin-Destination Survey Data Disaggregate Analysis Model) and MADGEN (Trip Generator Disaggregate Analysis Model). Because of the recent and rapid evolution of multimedia technology, these tools have been developed in an interactive Microsoft Excel worksheet format and in hypertext markup language for the Groupe MADITUC's World Wide Web site on the Internet. Stand-alone multimedia presentations and a Windows help file have also been developed for tutorial use.
Determination of Timings in Signal Systems with Traffic-Actuated Controllers
Authors: Skabardonis Alexander
Published: August 2018

Many traffic control systems on urban arterials and grid networks include signals with actuated controllers. However, commonly used signal timing computer programs have been designed for fixed-time signals and cannot directly optimize the timing of coordinated actuated signals. Users have to apply techniques designed for pretimed signals and then translate the optimal fixed-time plans into settings for the actuated controllers. The development of improved procedures for applying the MAXBAND, PASSER, and TRANSYT-7F timing programs to arterials and grid networks with actuated controllers is described. These procedures determine the yield points, force-offs, and maximum green times from the fixed-time plans on the basis of simple analytical relationships. The proposed procedures were applied on 14 representative real-world arterials and grid networks with different characteristics, and their performance was evaluated with the NETSIM microscopic simulation model. The results indicated that the proposed procedures improved traffic performance compared with the commonly used approaches that directly use the optimal fixed-time splits and offsets to set the actuated controller settings. Based on the study findings, guidelines were formulated and documented for timing coordinated actuated signals.
Implementation Vision for Distributed Control of Traffic Signal Subsystems
Authors: Bullock Darcy
Published: August 2018

The developments that have led to the construction of the 2070 controller are reviewed. The intelligent transportation system community has proposed many features and user services that will likely use this new controller. In general, many of the functions proposed for this controller, such as emergency vehicle preemption, transit priority, weather monitoring, dynamic lane assignment, enhanced malfunction diagnostics, and adaptive algorithms, are all technically feasible. To achieve widespread deployment of systems that integrate several advanced traffic management system features, however, a systematic method for integrating a variety of distributed computing subsystems must be thoughtfully defined. The fundamental benefits of adopting a distributed control model for traffic signal subsystems are described and summarized.
Evaluation of Bus Priority Signal Strategies in Ann Arbor, Michigan
Authors: Al-Sahili Khaled A. , Taylor William C.
Published: August 2018

With the emergence of intelligent transportation system technologies there has been a renewed interest in the bus priority signal (BPS). The effect of providing the BPS treatment on the Washtenaw Avenue Corridor in Ann Arbor, Michigan, was studied. The NETSIM graphic animation feature was used to detect the bus arrival and award preemption. The signal timing plan was then restored to the original signal setting in subsequent cycles. The model was calibrated using field data, and the sensitivity of the model to several variables was tested. The corridor's signal timing was first optimized using the TRANSYT-7F model. The green extension and red truncation with and without compensation, the skip phase with and without compensation, and the conditional preemption plans were evaluated. It was found that in all cases signal preemption disrupts traffic progression and, thus, increases overall vehicle delay. The results of preemption were analyzed at each intersection as well as over the entire simulation network. The most appropriate preemption strategy for each intersection was determined and used in the simulation. Bus travel time and delay were reduced when this optimal BPS plan was used.
NETSIM-Based Approach to Evaluation of Bus Preemption Strategies
Authors: Khasnabis Snehamay , Karnati Rajashekar R. , Rudraraju Rama K.
Published: August 2018

Preemption techniques are designed to provide preferential treatment to buses at signalized intersections. Uncertainties resulting from variations in passenger boardings and unboardings at bus stops make the prediction of the exact arrival times of buses at intersections extremely difficult. A preemption strategy, if properly designed, can provide continuous green phases to buses at successive intersections. It is unfortunate that a validated technique that can be used to assess the possible consequences of signal preemption is not available. The authors present the application of a simulation model, NETSIM, to make such an assessment. NETSIM was selected because of its ability to microscopically simulate vehicular movements on a street network and its ability to track an individual vehicle from the source to the sink by the use of an animation feature. A major bus route in Ann Arbor, Michigan, was used as the experimental site. The major conclusions are that NETSIM, when properly validated, can generate delay and queue-related measures of effectiveness that are compatible with field data and that the animation feature of NETSIM can be used to assess the operational consequences of bus preemption on a series of intersections on a bus route. For the volume levels studied in the project, savings in delay along the bus route resulting from preemption exceed the increases in delay along the cross street. Further research is needed to determine whether the net savings in delay, when balanced against the costs of installing and maintaining the system and the inconvenience to motorists along the cross street, make the system worthwhile.
Comparability and Transferability of Commuter Behavior Characteristics between Cities: Departure Time and Route-Switching Decisions
Authors: Jou Rong-Chang , Mahmassani Hani S.
Published: August 2018

Extensive diary surveys of commuter behavior were conducted in Dallas and Austin. These surveys provide data to characterize the day-today dynamics of commuter decisions, including departure time and route, for both morning and evening commutes. The data were used to develop user decision models that relate route and departure time switching patterns to socioeconomic characteristics, workplace conditions, and traffic system characteristics. Comparisons were made to assess the extent of transferability of behavioral findings and model parameters. Remarkable similarity was found in the general commuting behavior patterns observed in the two cities, such as greater switching activity in the evening than in the morning commute and greater frequency of departure time switching relative to route changes. Differences between the two cities appear to be primarily due to the larger size of Dallas.
Artificial Neural Network–Based Approach to Modeling Trip Production
Authors: Faghri Ardeshir , Aneja Sandeep
Published: August 2018

Accurate and reliable estimates of trip production of a study area are important for an accurate forecast from the four-step travel demand forecasting procedure. In the trip generation step, trip production estimates are considered more accurate, and trip attractions are adjusted while keeping the productions constant. This means that more accurate trip production rates will result in more reliable forecasts. Improving the accuracy of forecasts requires an extensive and reliable data base or improvement in the modeling techniques. Since data base enhancement is costly and time-consuming, an alternative methodology is proposed and examined for trip production prediction using artificial neural network (ANN) concepts and techniques. The data base used was made available by the Delaware Department of Transportation. The data were collected for 60 sites throughout Delaware between 1970 and 1974 and are based on field counts and home interviews. Twenty-six regression models were calibrated on these data. In addition, 18 ANN architectures were developed, and their predictions were compared with those from regression models. Comparisons indicate that the ANNs have the capability to represent the relationship between the trip production rate and the independent variables more accurately than regression analysis at no additional cost of increasing the data base.
Traffic Platoon Dispersion Modeling on Arterial Streets
Authors: Manar Abdelaziz , Baass Karsten G.
Published: August 2018

Platoon dispersion is a key element in traffic simulation models designed to measure arrivals at traffic signals. One of the most popular models is contained in the TRANSYT program. In this program, dispersion is defined by the platoon dispersion factor, which is given for three types of conditions in relation to external friction. This study demonstrates that platoon dispersion depends not only on external friction but also on internal friction between vehicles in the platoon. As volumes and densities increase, platoon dispersion increases up to a maximum, which is attained at half the capacity. As volumes and densities increase further, dispersion decreases and reaches a minimum value at volumes around maximal capacity. Experimental analysis on eight arterial sites in the city of Montreal (Quebec, Canada) has confirmed this relationship between dispersion and traffic volumes. Mathematical models (having a parabolic shape) relating platoon dispersion to internal and external friction were developed for three different categories of arterial streets representing low, moderate, and heavy friction levels. These models could be introduced into signal coordination programs and could contribute to a better simulation of arriving platoons at intersections as volumes change in relation to time.
Passing Sight Distance and Overtaking Dilemma on Two-Lane Roads
Authors: Liu Chiu , Herman Robert
Published: August 2018

The overtaking dilemma involving two small vehicles was discussed by Herman and Lam in 1972. The formulation in a dynamical moving frame of the overtaken vehicle is extended by taking into account the pertinent variables for an overtaking scenario, such as vehicle acceleration and deceleration characteristics, roadway frictional characteristics, drivers' responses, and speeds of the overtaking vehicle and the oncoming vehicle in relation to the overtaken vehicle. A general framework dealing with overtaking is introduced, and analytic expressions for safe passing and aborting sight distances are derived for frictional roadway characteristics from the AASHTO guide. This formulation is further extended to other situations, namely, overtaking that involves a small and a long vehicle and overtaking that involves two long vehicles. Comparisons among our results, the AASHTO guide, the Manual on Uniform Traffic Control Devices on design for safe passing sight distances (PSD), and other related works are given for various overtaking situations. The overtaking scenario in which the vehicle overtaken is “fast” is addressed. Finally, the previous literature associated with the development of PSD is discussed.
Submerging Kittler
Authors: Jue Melody
Published: August 2018

This article imaginatively submerges the media theory of German scholar Friedrich Kittler into the ocean in order to show how the ocean changes how one might theorize computational media. Beginning with a description of XL Catlin Seaview Survey’s oceanic ‘Street View’, it plunges into several examples from Kittler’s own work that engage sound and the sea. I argue that natural media are always already co-present with digital media; and we have only recently and retrospectively been able to see natural media as media through the lens of analogous technical media for storage, transmission, and recording. The ocean leads to a more comprehensive account of the networked power of computational media and their contemporaneity with natural media. Attention to the role of environment in this way suggests a mischievous inversion of Kittler’s claim that ‘media determine our situation’. Perhaps the possibilities of our media are determined by the materiality of distinct environmental situations.
Maximizing Versus Satisficing: Negative Correlation Between Maximizing Attitude and School Domain Satisfaction
Authors: Beja Edsel L.
Published: August 2018

The study uses a projection method to identify maximizing and satisficing individuals in a sample of college students from the Philippines. The study defines a maximizing individual as one who sketches a full glass that is filled up to the brim and a satisficing individual as one who sketches a full glass that is filled below the brim. The study also uses data on school domain satisfaction of the college students. The analysis finds that individuals who maximize also experience lower school domain satisfaction.

JEL Classifications: I31, C91
The Earnings Disadvantage of 21st Century Immigrants in the United States
Authors: Gill Fahad , Ahmad Waseem
Published: August 2018

This article provides a comprehensive analysis of the earnings disadvantage of 21st century immigrants in the United States. The study is the first to decompose the earnings disadvantage faced by recent immigrants to present the channels through which immigrants lag behind their native counterparts. The decomposition of the earnings disadvantage reveals that the time spent in the United States is the key determinant of the earnings disadvantage. Other important sources of the earnings disadvantage of immigrants are the levels of English-language proficiency and educational attainment. The decomposition analysis also suggests that low levels of human capital cause an even larger disadvantage for immigrants in the years following the 2008-2009 recession as compared with the corresponding relative returns of the prerecession period. The decomposition analysis and trends in returns to human capital variables highlight the merits of a selective immigration system that favors young, English-speaking, and highly educated individuals.

JEL Classifications: J1, J3, J6
Politics of Active Representation: The Trade-off Between Organizational Role and Active Representation
Authors: Yun Changgeun
Published: August 2018

The translation of passive into active representation assumes that bureaucrats are willing to serve the interest of their social group when developing and implementing policies. However, the assumption does not account for organizational socialization—the process of being taught what is important in an organization. In addition, there is a comparative paucity of theoretical and conceptual frameworks to explain why and how bureaucrats decide to become active representatives. In this study, I develop a framework for analyzing the decision to engage in active representation. The framework recognizes that active representation conflicts with organizational role and is based on the assumption of public choice theory that humans are utility maximizers. Bureaucrats are not totally devoted to active representation, but instead find an optimal point at which their self-interest is maximized in interrole conflict.