bluuebunny/crossref_metadata_2025 huggingface dataset:
Real-Time Detector-Free Adaptive Signal Control with Low Penetration of Connected Vehicles
Authors: Feng Yiheng , Zheng Jianfeng , Liu Henry X.
Published: August 2018

Most of the existing connected vehicle (CV)-based traffic control models require a critical penetration rate. If the critical penetration rate cannot be reached, then data from traditional sources (e.g., loop detectors) need to be added to improve the performance. However, it can be expected that over the next 10 years or longer, the CV penetration will remain at a low level. This paper presents a real-time detector-free adaptive signal control with low penetration of CVs ([Formula: see text]10%). A probabilistic delay estimation model is proposed, which only requires a few critical CV trajectories. An adaptive signal control algorithm based on dynamic programming is implemented utilizing estimated delay to calculate the performance function. If no CV is observed during one signal cycle, historical traffic volume is used to generate signal timing plans. The proposed model is evaluated at a real-world intersection in VISSIM with different demand levels and CV penetration rates. Results show that the new model outperforms well-tuned actuated control regarding delay reduction, in all scenarios under only 10% penetrate rate. The results also suggest that the accuracy of historical traffic volume plays an important role in the performance of the algorithm.
Effects of Maintenance Human Factors in Maintenance-Related Aircraft Accidents
Authors: Dorn Matthew D.
Published: August 2018

To help prevent maintenance-related aircraft accidents the complex factors behind previous accidents must be understood. Maintenance-related aircraft accidents were studied to determine the effects of maintenance human factors. A taxonomy of causal factors was developed and used to classify the causes of 101 military and civilian accidents and to determine the frequency of occurrence for each factor. The taxonomy identifies elements, such as people and hardware, interfaces between elements (i.e., human factors), and maintenance processes comprised of elements and interfaces. Human factors were found to have a significant effect in the 86 military and 15 civilian maintenance-related accidents studied. Whereas investigation boards were found to focus most heavily on element failures, a majority of the failures were found to occur at the process level. Maintenance instructions and their interfaces with the maintainers and inspectors who use them were the most frequently failed elements and interfaces, respectively. Recommendations are made to guide further research, and ideas are provided for improving process analysis by maintenance units and investigation boards.
Effects of Air Traffic Congestion Delays under Several Flow-Management Policies
Authors: Glockner Gregory D.
Published: August 2018

Air traffic delays occur when demand for airports or airspace exceeds available capacity. Consequently, these delay effects can be lessened by increasing capacity or by modifying the air traffic demand. Increasing capacity is an important solution, but it is a long-range option involving major changes such as facility construction, fundamental procedural changes, and improvements in navigational equipment. For short-term decision making a tactical-optimization model can suggest alternative flight plans to reduce delays. However, a tactical-optimization model is extremely complex because of the uncertainty in airport-capacity forecasts, which primarily depend on weather. A practical implementation of a tactical-optimization model must therefore make approximations so that a solution may be computed quickly and be of good quality. A practical model framework for the congestion-delay problem is given; this model framework is a generalization of several other flow-management models. Congested situations are simulated, to compare the practical performance of this model to other air traffic management tactics.
Indiana Subdrainage Experience and Application
Authors: Hassan Hossam F. , White Thomas D. , McDaniel Rebecca , Andrewski David
Published: August 2018

The applications of pavement subdrainage in the state of Indiana are presented. A recent study evaluated pavement subdrainage systems and measured and predicted moisture conditions underneath various types of pavements. Camera systems were used for internal inspection of the edge and geocomposite drains. Pavement instrumentation included moisture blocks, pressure transducers, temperature probes, rain and outflow tipping buckets, and a data acquisition system. Ongoing research using a test site on I-469 at Fort Wayne, Indiana, is aimed at finding the optimum location and layer configuration in flexible pavement; it uses those instruments as well as a TDR system, neutron probes, resistivity probe trees, and an enhanced data acquisition process. The research is a long-term project that will build on the data base of material hydraulic characteristics and performance. Indiana Department of Transportation has formed a committee to address issues related to use of subdrainage. Some of the recommendations from the committee were to abandon geocomposite drains, use bigger concrete protector walls at outlet pipes, and implement a routine inspection and maintenance program for drainage systems.
Innovative Approaches to Regional Freight Transportation Planning: Case Study of Monterey Bay Region
Authors: Fischer Michael J. , Constantine Elena K.
Published: August 2018

How a California metropolitan planning organization (MPO) overcame data limitations and developed innovative solutions to regional agricultural freight transportation problems is described. Data from government agencies and trade groups on annual fruit and vegetable production, fish landings, and wine production were combined with survey data on truck volumes and loading practices to develop novel approaches for estimating truck and rail trips. Similar methods were used to project future freight volumes by using key population, income, and agricultural productivity indexes to project agricultural production volumes and employment forecasts in the processed food industries and thereby forecast freight volumes in their industries. To identify problems and deficiencies in the system, new performance indicators such as number of internal truck trips per outbound line-haul trip, wait time per pickup, comparisons of hourly inbound and outbound line-haul truck trip distributions, and truck trips as a percent of total traffic volume on roadways with poor level of service were used. It was concluded that poor logistics planning, lack of coordinated information and communications about load availability, poor load consolidation practices, and inadequate truck parking and driver waiting facilities were among the biggest problems facing the region. A proposed freight logistics center, which may be developed as a public-private partnership, is now under consideration. The methods and programs developed in this study may have applications in other small to medium-sized MPOs.
Benefits of Electronic Clearance for Enforcement of Motor Carrier Regulations
Authors: Titus Matthew J.
Published: August 2018

The transparent borders concept of the Federal Highway Administration's Intelligent Transportation System for Commercial Vehicle Operations program could enhance regulatory efficiency by improving motor carrier compliance and reducing the costs of compliance. Discussion focuses on the cost of enforcement for motor carriers, which is one of the components of compliance cost. Motor carrier regulations are typically enforced concurrently with weight and safety enforcement efforts. To determine the burden, the amount and value of time spent by motor carriers on enforcement activities was estimated. Recognizing that differences among trucking firms exist, burdens were estimated separately for truckload and less-than-truckload carriers. Values were based on labor and opportunity costs. Time requirements were taken from existing literature. Current weight enforcement efforts cost the industry between $167 and $283 million annually. Furthermore, over 99.4 percent of the burden is borne by compliant carriers. Technologies and enforcement strategies that would greatly reduce the proportion of compliant vehicles subjected to enforcement are currently available and should be pursued. Complying with current safety enforcement efforts costs the industry between $14 and $25 million annually. Compliant carriers bear over 44 percent of this cost. Analysis of safety data indicates that a statistical relationship exists between out-of-service rates and accident rates. Therefore, it is possible to develop a system that would increase the proportion of noncompliant vehicles subjected to inspection relative to compliant vehicles.
Applications of Economic Value of Freight Flows to Transport Planning
Authors: Rico Alfonso , Mendoza Alberto , Mayoral Emilio
Published: August 2018

As in most developing countries, the resources available in Mexico for improving the infrastructure of the transportation system and its services are frequently insufficient. This situation has led the Mexican Transport Institute (MTI) to develop strategies for optimizing the allocation of resources among the various necessities of the system. The use of the economic value of the freight flows for identifying and planning improvement projects to be undertaken for a specified time period on basic surface transportation networks (roads and railways) is proposed. This parameter can also be used for assessing the relative importance of the components of such networks. The methodology suggested for assessing the economic value of the freight flows is presented. The basis of the use of the criterion proposed including its greater convenience than other commonly used criteria (of the benefit/cost type) is described. Based on the suggested criterion, several considerations are raised for the Mexican road and railroad networks. The belief of some policy makers that freight is of paramount importance for planning improvements to the transportation systems is applied and facilitated by the applications described.
Surface Transportation and Administrative Law: Growing up Together in the 20th Century
Authors: Kussy Edward V. A.
Published: August 2018

The concurrent development of administrative law and America's modern transportation system is no accident. Both reflect the technological and societal changes that have defined what the United States is today. The importance of transportation is reflected by the fact that so many of the important events, statutes, and court decisions in the history of 20th century administrative law have involved transportation. The first really powerful administrative agency, the Interstate Commerce Commission, was created to regulate railroads and, later, interstate trucking. The Federal-Aid Highway Program, which can trace its roots to 1893, has been the largest federal grant program for much of this century. The statutory framework for this program, established by the Federal Road Act of 1916 and the Federal-Aid Highway Act of 1921, became the model for all federal grant programs. The Interstate system and other highway programs helped shape the great economic expansion that followed World War II. The effects of these vast new road systems were among the most important factors leading to the growth of modern environmental law in the 1960s and 1970s. In the years ahead, with the accelerating integration of new technology into the transportation system, further concurrent change in transportation and administrative law is inevitable.
NCHRP Report 350 Crash Test Results for Connecticut Truck-Mounted Attenuator
Authors: Carney John F. , Dougan Charles E. , Lohrey Eric C.
Published: August 2018

The results of four full-scale crash tests performed on the Connecticut Truck Mounted Attenuator (CTMA) are summarized. The tests were conducted in accordance with the guidelines of NCHRP Report 350 for Test Level 2 devices. NCHRP Report 350 specifies two required and two optional tests. The four crash tests passed all requirements of NCHRP Report 350. No repeat tests were required, and the results were uniformly excellent. The successful CTMA test series is the first of several NCHRP Report 350 test programs that are anticipated to gain compliance for various impact attenuation systems designed and developed in Connecticut.
Assessment of Guardrail-Strengthening Techniques
Authors: Rosson Barry T. , Bierman Mark G. , Rohde John R.
Published: August 2018

Guardrail-strengthening techniques were assessed by full-scale crash testing according to Service Level 2 conditions of NCHRP Report 230 and by BARRIER VII computer simulation. The Kansas Department of Transportation's standard W-beam with steel posts guardrail was strengthened by nesting the W-beam and by reducing the post spacing. Computer simulations with BARRIER VII were used to assess the various strengthening techniques for guardrails with standard and extended post lengths installed in clay and sand. The soil-post stiffness parameters used in the program were obtained by conducting 21 post impact tests with a 1388-kg bogie striking a post at 33 km/hr. The guardrails constructed with W6 × 8.5 steel posts and 15.2 × 20.3-cm timber posts behaved similarly under all test conditions. The density of the clay has a profound effect on the lateral dynamic deflections. Nesting the W-beam to strengthen the guardrail provides very little benefit, whereas reducing the post spacing by half provides the greatest benefit.
Approach Guardrail Transition for Single-Slope Concrete Barriers
Authors: Faller Ronald K. , Soyland Ketil , Sicking Dean L.
Published: August 2018

An approach guardrail transition for use with the single-slope concrete median barrier was developed and crash tested. The transition was constructed with 3.43-mm-thick (10-gauge) thrie-beam rail and was supported by nine W6 × 9 steel posts. Post spacings consisted of one at 292 mm (11.5 in.), five at 476 mm (1 ft 6.75 in.), and three at 952 mm (3 ft 1.5 in.). A structural tube spacer block (TS 7 × 4 × 3/16) was also developed for use with the thrie-beam rail. Two full-scale vehicle crash tests were performed, and the system was shown to meet the Test Level 3 requirements specified in NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features.
Crack Sealing in Flexible Pavements: A Life-Cycle Cost Analysis
Authors: Ponniah Joseph E. , Kennepohl Gerhard J.
Published: August 2018

Pavement cracks are usually sealed to prevent water from entering base course layers. Experience suggests that water in pavement layers hastens pavement deterioration and, therefore, increases rehabilitation costs. Initially the Ministry of Transportation, Ontario (MTO), Canada, had limited success in sealing cracks because inappropriate materials and installation procedures were used. This setback during the initial stages of development in crack sealing raised questions about the effectiveness of crack sealing in reducing the rate of pavement deterioration. In the 1970s and 1980s MTO carried out several field studies to develop an effective crack sealing procedure and to study the influence of crack sealing on pavement distress and performance. The cost-effectiveness of this treatment was investigated as well. The results of the studies indicate that sealing cracks is a viable and cost-effective preventive maintenance treatment and can extend the service life of asphalt pavements by at least 2 years. However, for optimum benefits the crack sealing program must be implemented according to guidelines proposed. The guidelines provide a basis for the selection of suitable pavements and cracks, sealant materials, and application procedures.
Hot Mix Asphalt Rubber Applications in Virginia
Authors: Maupin G. W.
Published: August 2018

Four test sections using asphalt rubber hot mix were placed in Virginia from 1990 to 1993. These installations were to familiarize contractors and Virginia Department of Transportation personnel with the construction process and compare the performance of different types of mixes containing ground tire rubber. The MacDonald and Rouse wet processes were used successfully. Dense graded surface mixes, a gap-graded surface mix, and a base mix were manufactured. A stress-absorbing membrane interlayer was also used on one project in an attempt to deter or eliminate various types of cracking. The asphalt rubber mixes have performed as well as the conventional mixes over the short term. More evaluation time is needed to determine if long-term performance of the asphalt rubber mixes is superior to conventional mixes. The asphalt rubber mixes cost 64 to 102 percent more than conventional mixes. This cost would probably decrease if substantial quantities were placed.
Effects of Mineral Fillers on Properties of Stone Matrix Asphalt Mixtures
Authors: Mogawer Walaa S. , Stuart Kevin D.
Published: August 2018

Stone matrix asphalt (SMA) is a gap-graded hot mixture that has higher proportion of coarse aggregate, lower proportion of middle-size aggregate, and higher proportion of mineral filler than a dense-graded mixture. Because of the high quantity of mineral filler, the type and quantity of this fraction should play a major role in the properties of these mixtures and their mastics. Determination of whether mastic and mixture properties can distinguish good mineral fillers from bad ones is the objective. Eight mineral fillers with known performance were obtained from three European countries. Mastics were tested for stiffness using a bending beam rheometer (AASHTO TP1), a dynamic shear rheometer (AASHTO TP5), and softening point of bitumen using the ring-and-ball apparatus (AASHTO T53-92). None of the tests distinguished among mastics with good and bad mineral fillers. Mixtures were tested for draindown of mastic using the National Center for Asphalt Technology draindown test, rutting using the French pavement rutting tester, low-temperature cracking using the indirect tensile test, workability using the U.S. Corps of Engineers gyratory testing machine, and moisture susceptibility using the ASTM D 4867 method. None of the tests distinguished among SMA mixtures with good and bad mineral fillers.
Investigation of Stone Matrix Asphalt Mortars
Authors: Brown E. Ray , Haddock John E. , Crawford Campbell
Published: August 2018

The use of stone matrix asphalt (SMA) has continued to increase in the United States since its initial application in 1991. This preference for SMA has been linked to its ability to withstand heavy traffic without rutting. The antirutting capability of SMA is normally accredited to the presence of a stone-on-stone aggregate skeleton in the mixture. However, the mortar in an SMA mixture is also important. The mortar is composed of fine aggregate, filler, asphalt cement, and a stabilizing additive. Work to characterize SMA mortars is detailed. For testing purposes, the mortar was broken into separate phases, total mortar and fine mortar. The fine mortar was tested using the Superior Performing Asphalt Pavements system (Superpave) binder tests. The total mortar was tested using the bending beam rheometer, resilient modulus, indirect tensile test, and Brookfield vis-cometer. The results indicate that the fine and total mortars are closely related. In addition, it was determined that at least some of the Superpave tests can be used to characterize SMA mortars. It is recommended that further testing be completed and specification criteria be established for the mortar.
Impact of Concrete Placing Method on Air Content, Air-Void System Parameters, and Freeze-Thaw Durability
Authors: Hover Kenneth C. , Phares Roger J.
Published: August 2018

Approximately 76 m3 (100 yd3) of ready-mixed, air-entrained concrete were placed in a parking lot and driveway at the Schwing America Manufacturing facility in White Bear, Minnesota, on June 21, 1994. This concrete was placed by means of a pump, crane and bucket, and truck-mounted conveyor, and came directly from the chute of ready-mix trucks. Pump configurations were used that allowed unrestricted free-fall of the concrete; a kink in the rubber hose at the end of the line created a slight back pressure and slowed the descent of the concrete. After placement, the concrete was consolidated by an immersion vibrator in some locations and struck off with no further consolidation in other locations. Air content of the fresh concrete was measured by ASTM C231 pressure meters at the truck chutes and at the point of placement. Air content and air-void system parameters of the hardened concrete were determined in accordance with ASTM C457. Actual freeze-thaw performance was evaluated by ASTM C666 for concrete sampled from the truck chute and sampled from the pavement after placement by the various methods. Twenty-four tests of the air content of concrete from six successive truckloads of concrete showed that the variation in truck-to-truck air content was frequently greater than the within-truck variation because of different methods of handling the concrete. Tests of the fresh concrete after pumping, conveying, chuting, and free-fall from the concrete bucket showed reduced air content. From analysis of the hardened concrete, it was observed that the air bubbles remaining in the pumped concrete were smaller than in the concrete as delivered. The air-void spacing factor was not significantly altered by pumping. In ASTM C666 freezing and thawing tests, the specimen experiencing the greatest loss of air content as a result of pumping was determined to have the lowest total air content of all specimens tested (before vibration), yet had the highest durability of all specimens tested.
Mechanical Properties of Concrete with Ground Waste Tire Rubber
Authors: Fedroff David , Ahmad Shuaib , Savas Banu Zeynep
Published: August 2018

Because used tires represent an increasingly serious environmental problem in the United States, this study was undertaken to examine the feasibility of using finely ground rubber in Portland-cement concrete. Various percentages of rubber, by weight of cement, were added to a control mix and the effects on the plastic and hardened properties of concrete were investigated. Workability of the mixes was affected, but it was controllable. For hardened concretes, the tests were conducted for compressive strength, split-cylinder strength, modulus of elasticity, and flexural strength. Stress-strain response was also investigated. The strength and stiffness characteristics were markedly reduced for rubcrete mixtures.
Kansas Water-Cement Ratio Meter: Preliminary Results
Authors: Hossain Mustaque , Koelliker James , Ibrahim Hisham , Wojakowski John
Published: August 2018

The water-cement ratio of fresh concrete is recognized as the one factor that affects the strength and durability of an adequately compacted concrete mix. Although water-cement ratio is the predominant factor affecting strength of hardened concrete, currently no widely used, reliable method is available for measuring water-cement ratio in the field. A prototype device has been developed to measure the water-cement ratio of a plastic concrete mix. The method is based on the measurement of turbidity of water-cement slurry separated out of a concrete mixture by pressure sieving. Consistent results were obtained for air-entrained and non-air-entrained concrete. Statistical analyses of the test results have shown that this meter can measure the water-cement ratio of fresh concrete with an accuracy of ±0.01 on the water-cement ratio scale for a single test at a 90 percent confidence interval. The equipment will cost less than $10,000. If the method works as well in the field as it does in the laboratory, accurate determination of water-cement ratio could dramatically improve the ability of the concrete industry to ensure the quality of concrete construction.
Geotextiles to Mitigate Frost Effects in Soils: A Critical Review
Authors: Henry Karen S.
Published: August 2018

The use of geotextiles to mitigate frost effects in soils has been studied, but few techniques have been developed. Guidelines developed for the placement of granular capillary barriers are presented to serve as preliminary guidelines for geotextile capillary barriers. Laboratory research shows that pore size distribution, wettability, and, for some geotextiles, thickness influence capillary barrier performance in a given soil. Geotextiles that easily wet do not reduce frost heave and may even exacerbate it. On the basis of the literature reviewed, guidance for selection of geotextile capillary barriers in field trials is given. If geotextiles function as capillary barriers during freezing and reinforce or separate and filter the subgrade at the base course interface during thaw, then the potential exists for their use in a combination of functions to reduce frost-related damage in geotechnical structures. It was found that properly designed geotextiles have the potential to reduce frost heave by functioning as capillary barriers, they can be filters for capillary barriers, and they can provide reinforcement or separation or filtration (or all of these) of the subgrade soil to reduce thaw-related damage.
Temperatures of Insulated Landfill Liner
Authors: Benson Craig H. , Olson Michael A. , Bergstrom Wayne R.
Published: August 2018

Five methods for insulating the side slope of a landfill liner were evaluated in a field test. The insulations consisted of leachate collection sand, leachate collection sand and chipped tires, polyurea foam, polystyrene boards, and encapsulated fiberglass geoinsulation panels. Results of the study indicated that tire chips are an effective means of insulating landfill liners, whereas sand alone is inadequate. Of the three geoinsulations tested, the encapsulated fiberglass and extruded polystyrene worked best. The polyurea foam performed poorly, although its performance would have been better had it been thicker. The results of the study also indicated that freezing of the liner can occur near gaps between geoinsulation panels and at corners where the panels are joined if the overlaps or seaming methods are inadequate.
Construction and Instrumentation of Geosynthetically Stabilized Secondary Road Test Sections
Authors: Brandon Thomas L. , Al-Qadi Imad L. , Lacina Bruce A. , Bhutta Salman A.
Published: August 2018

Nine instrumented flexible pavement test sections were constructed in a rural secondary road in southwest Virginia. The nine test sections, each 15 m (50 ft) long, were built to examine the effects of geogrid and geo-textile stabilization. Three test sections were constructed with a geogrid, three were built with a geotextile, and three were nonstabilized. The test section base course thicknesses ranged from 10.2 cm (4.0 in.) to 20.3 cm (8.0 in.), and the hot-mix asphalt (HMA) thickness averaged 8.9 cm (3.5 in.). Geosynthetic stabilization was placed on top of the subgrade layer. The pavement test sections were heavily instrumented with two types of pressure cells, soil and HMA strain gauges, thermocouples, and soil moisture cells. In addition, strain gauges were installed directly on the geogrid and geotextile. An extensive instrumentation infrastructure was constructed to locate all instrumentation, cabling, and data acquisition facilities underground. Instrument survivability has ranged from 6 percent for the strain gauges mounted on the geotextile to 100 percent for the soil moisture blocks after 8 months of operation. The majority of instrument failures occurred either during construction or the first few weeks of operation. The data acquisition system is triggered by traffic passing over piezoelectric sensors and operates remotely. The corresponding data are transferred via modem to Virginia Polytechnic Institute and State University for processing. It is planned that the performance of the pavement test sections will be monitored for a minimum of 3 years.
Relationships between Molecular Weights and Rheological Properties of Asphalts
Authors: ranthaver Jan F. B , Robertson Raymond E. , Duvall John J.
Published: August 2018

It is known that the rheological properties of mixtures of organic compounds are functions of molecular weight distributions. However, with respect to asphalts, which are composed of many different compounds and compound types, molecular weights are difficult to measure. This difficulty occurs because the molecular associations that form are held together by forces of varying strengths and are partly broken up by heat and solvents. In theory, the strongest molecular associations in asphalts should have the greatest influence on the rheological properties of asphalts. These associations would be expected to be the major contributors to the asphalt's behaving as if it were a relatively high molecular weight material. Asphalt molecular associations should be isolatable by means of size exclusion chromatography. Several fractions of varying molecular weights (measured by membrane osmometry and vapor phase osmometry) were isolated from Strategic Highway Research Program (SHRP) asphalt AAD-1 by preparative size exclusion chromatography. Molecular weights of these fractions ranged from approximately 2,000 daltons to over 40,000 daltons. When these fractions were independently mixed with asphalt AAD-1 solvent moiety, mixtures were obtained whose rheological properties were a function of the molecular weights and concentrations of the associated materials. These results support the microstructural model of asphalt proposed during SHRP. The results also suggest that the unusual rheological properties of some asphalts may be explained by measuring molecular weight distributions. This type of information may be useful for modification of asphalts to achieve desirable rheological properties.
Characterization of Fracture in Asphaltic Mixes Based on a Molecular Approach
Authors: Jacobs Maarten M. J. , Hopman Piet C. , Molenaar André A. A.
Published: August 2018

In contradiction to the fracture mechanics approach, the fundamental absolute rate theory (ART) model describes the macroscopic behavior of processes on the molecular level. Attention is given to the theoretical background of the ART and its application to describing the crack growth process in asphalt concrete mixes. From the analyses, it is concluded that in the crack propagation phase, three parallel processes are distinguished: cohesive crack growth, adhesive crack growth, and a crack-retardant process. In the crack initiation phase, only cohesive crack growth is present. The difference between the mixes is specified by the free activation energy Qa: increase in crack growth resistance increases the Qa-value. This Qa-value, determined from mechanical tests, is close to the energy that bonds the bitumen to the aggregate, determined from chemical tests.
Characteristics of Polymers and Polymer-Modified Binders
Authors: Bonemazzi F. , Braga V. , Corrieri R. , Giavarini C. , Sartori F.
Published: August 2018

The properties of a number of polymers commonly proposed for polymer-modified bitumens (PMBs) were studied to suggest a way to select the polymer suitable for the required application; the prediction of the performance in the final application would allow bypass of the tests on PMBs and asphalt mixtures. Rheological and mechanical tests were performed on both raw materials and PMBs containing 5 percent polymer. Tensile dynamic mechanical test analyzer hardness, tensile properties, and tension set tests were conducted on polymers; the tendency of the polymers to absorb aromatic oil was also determined to simulate their swelling in the PMBs. Rheometer dynamic tests, R&B, penetration, and elastic recovery were carried out on PMBs. Rheometer dynamic parameters, R&B, penetration, and elastic recovery were measured on the bitumen. The experimental data confirm that selected tests on polymers can give good information about the polymer contribution to PMBs' performances.
Differential Scanning Calorimetry Study of Asphalt Crystallinity
Authors: Daly William H. , Qiu Zhaoyao , Negulescu Ioan
Published: August 2018

Eight asphalt samples with grades ranging from AC10 to AC30 from four different sources were examined using NMR, FTIR, and differential scanning calorimetry. The crystallization process of asphalt is very time dependent. Slow heating or annealing before analysis to experimentally realize a near-equilibrium state is necessary to study the system with more thermodynamic rigor. Indeed, the annealing method developed in this work resolves a number of low-temperature transitions characteristic of a given crude and/or refinery source; thus, comparison of thermograms from an unknown source with reference thermograms from documented sources allows one to identify the unknown source. The crystallization process of a selected AC-20 asphalt, ACB, was systematically studied by doping with the following pure crystalline hydrocarbons: octadecene-1, eicosane, and octacosane. The impact of doping on the crystalline fractions in asphalt varies from asphalt to asphalt. The crystalline components in asphalt exhibit distinct endothermic patterns that depend on their chemical structure, the interactions with the amorphous phase, and among themselves. The most significant endothermic effect is produced by cocrystallization of components with similar crystalline chain lengths. For example, the crystalline components of asphalt ACB do not interact with octadecene-1, but do cocrystallize with eicosane and octacosane.
Laboratory Aging and Annealing of Asphalt Binders by Microwave Radiation
Authors: Bishara S. W. , McReynolds R. L.
Published: August 2018

A household microwave oven with a frequency of 2.45 × 103 ±13 MHz and an output power of 1000 W is used to simulate short- and long-term aging of asphalt, and for annealing, prior to sampling, to remove steric (isothermal) hardening. A quartz petri dish holds the asphalt during microwave treatment, at atmospheric pressure. To simulate thin film oven (TFO) aging, a 10-g sample is microwaved for a total of 33 min. For 11 asphalts, the average difference in G*/sin δ, at limiting high temperature, between TFO and microwave aging is ±0.68 kPa. Simulating rolling thin-film oven (RTFO) aging is possible by microwaving for a total of 63 min. For 18 asphalts, the average difference in G*/sin δ, at limiting high temperature, between RTFO and microwave aging is ± 1.19 kPa. Aging by RTFO + pressure aging vessel (PAV) and TFO + PAV is simulated by microwaving for a total of 158 min. Microwave aging marginally underestimates long-term aging. For 18 asphalts, the average difference in intermediate temperature obtained after RTFO + PAV versus microwave aging is −2.8°C; for TFO + PAV versus microwave aging, the average difference is −2.7°C. Annealing for 2 hr at 150°C in a convection oven (conductive heating) is simulated by microwaving for a total of 27 min. The average difference in G*/sin δ between the two methods is ±0.24 kPa. Molecular size index (MSI, the ratio of first to second fraction from size exclusion chromatography) correlates with stiffness at low temperature. At intermediate temperature, tan δ remains practically unchanged until MSI reaches a minimum, then increases sharply. At limiting high temperature, G* does not correlate with MSI.
Weigh-in-Motion Data Quality Assurance Based on 3-S2 Steering Axle Load Analysis
Authors: Ott W. C. , Papagiannakis A. T.
Published: August 2018

An innovative method is offered for conducting the quality assurance of weigh-in-motion (WIM) data by analyzing the variation in the measurements of five-axle semitrailer (3-S2) truck steering-axle loads. Confidence-interval limits for those measurements are established on the basis of their historic mean static loads adjusted for the effect of air resistance and their combined variation from two sources, the variation within a fleet of 3-S2 trucks and the variation due to axle dynamics at a WIM site. The first variation was determined by analyzing historic 3-S2 load data obtained by FHWA using static scales. The second variation was established through dynamic vehicle simulations of a “typical” 3-S2 truck using vehicle model VESYM and the roughness profile at a particular WIM site. The method was tested with data from four WIM systems in the state of Washington, two bending-plate systems and two piezoelectric systems. The proposed method resulted in clear indications of the performance of the scale versus time by the number of confidence interval violations observed.
Study of Aircraft Accident Related to Asphalt Runway Skid Resistance
Authors: Thenoux Guillermo , Allen Wendy , Bell Chris A.
Published: August 2018

On February 20, 1991, a brand-new British Aerospace BAE 146-200 aircraft, operated by a commercial airline, landed at Guardiamarina Airport in Port Williams, Chile. The aircraft landed under good weather conditions on an asphalt surface treatment runway and skidded more than 1,000 m into the Beagle Channel. It was a charter flight with 60 tourists on board; 40 survived. A long investigation provided evidence on why the aircraft skidded off the end of the runway.
Evaluation of Videowindows Photolog Laser Videodisc Viewing System
Authors: Hudson John H. , Seitz Robert L.
Published: August 2018

A low-cost alternative to the photolog laser videodisc (PLV) retrieval station is described. A video-overlay-board-based PLV viewing system or mini-PLV provides virtually the same functionality and acceptable image resolution for all applications described previously with the pavement rating. Not only does the mini-PLV lower hardware costs by almost two-thirds, from $31,000 to $11,000, but it also significantly reduces the system footprint, thereby providing a true desktop image-retrieval system.
User Perceptions of SmarTraveler Advanced Traveler Information System: Findings from Second-Year Evaluation
Authors: Englisher Larry S. , Juster Richard D. , Bregman Susan , Koses David G. , Wilson Alicia Powell
Published: August 2018

SmarTraveler was implemented as an operational test of an advanced traveler information system in the Boston metropolitan area. Users call the service from cellular or conventional telephones to receive realtime, route-specific traffic and transit information free of charge (except for any telephone company charges). Several evaluations were conducted since the service began in January 1993, to assess public acceptance of the information provided by SmarTraveler. Findings on user perceptions of and response to the program during its second year of operation, from April through December 1994, are summarized. Calling frequency increased during this period. Calls from cellular telephones made up 61 percent of the total calls received, even though cellular telephone callers were in the minority of the user population. Users were found to be quite satisfied with the service, especially in comparison with broadcast media traffic reports. In particular, they found SmarTraveler easy to use and were pleased with its availability on demand, its up-to-the-minute information, and its coverage of major routes. Two-thirds of current users said that SmarTraveler helped reduce anxiety. Although virtually all users said they would continue calling SmarTraveler in the future, users indicated substantial sensitivity to the potential imposition of a service fee.
Dynamic Decision Making for Commercial Fleet Operations Using Real-Time Information
Authors: Regan Amelia C. , Mahmassani Hani S. , Jaillet Patrick
Published: August 2018

The application of intelligent transportation system technologies to freight mobility requires dynamic decision-making techniques for commercial fleet operations, using real-time information. Recognizing the productivity-enhancing operational changes possible using real-time information about vehicle locations and demands coupled with constant communication between dispatchers and drivers, a general carrier fleet management system is described. The system features dynamic dispatching, load acceptance, and pricing strategies. A simulation framework is developed to evaluate the performance of alternative load acceptance and assignment strategies using real-time information. Real-time decision making for fleet operations involves balancing a complicated set of often conflicting objectives. The simulation framework provides a means for exploring the trade-offs between these objectives. Results suggest that reductions in cost and improvements in service quality should result from the use of dynamic dispatching (assignment) strategies in addition to traditional planning tools. These results and the overall simulation framework are discussed.
Computational Study of a Path-Based Algorithm and Its Variants for Static Traffic Assignment
Authors: Sun Carlos , Jayakrishnan R. , Tsai Wei K.
Published: August 2018

Recent research has indicated that advances in computer memory have made the use of path-based algorithms in urban traffic networks a possibility. The path-based gradient projection (GP) offers significant benefits in computation times over the conventional Frank-Wolfe algorithm and may be especially suited for real-time applications. The computational results from applying GP to networks of up to 4,900 nodes, as well as the performance of different variants of GP, are discussed. Also discussed is the sensitivity of the results to parameters such as the number of destinations and the level of congestion. The variants of the basic GP algorithm examined are intended to further improve the per-iteration performance of the algorithm for larger networks. These variants include a GP version with a modified first derivative update and different versions that use line-search techniques, including a boundary stopping method. The results establish that GP indicates substantial benefits even for larger networks. The modifications, while they do improve the computation times per GP iteration, affect the convergence quality of the algorithm, indicating that the earlier GP algorithm is a better alternative for both large and small networks.
Bicycle and Pedestrian Level-of-Service Performance Measures and Standards for Congestion Management Systems
Authors: Dixon Linda B.
Published: August 2018

The Gainesville Mobility Plan Prototype was developed as the congestion management system plan for Gainesville, Florida, and incorporated level-of-service (LOS) performance measures for bicycle and pedestrian facilities. The LOS evaluations describe the degree of bicycle and pedestrian accommodation in a transportation corridor. The bicycle LOS measures are designated basic facility provided, conflicts, speed differential, motor vehicle LOS, maintenance, and provision of transportation demand management programs or intermodal links. Pedestrian LOS criteria are similar and incorporate specific pedestrian features. The Gainesville bicycle and pedestrian LOS performance measures use a point scale resulting in an LOS rating system of A through F. The scoring system was developed with sensitivity to characteristics that may be mutually exclusive or inclusive to determine all possible combinations of points. The methodology hypothesizes that there is a critical mass of variables that must be present to attract nonmotorized trips. The methodology is applicable for corridor evaluations on arterial and collector roadways in urban or suburban areas. The criteria include measures of programmatic and off-street projects such as rail-trails, bicycle parking, bikes-on-transit, employer-based programs, and so forth, in addition to traditional on-street facility improvements. By measuring such improvements recommendations for more diverse projects can be supported. This analysis was applied to several roadways with promising results that generally corresponded to user perceptions of the facilities. LOS evaluation was used as a tool of the congestion management system to develop project recommendations and priorities, but it may also be useful in concurrency and long-range transportation planning.
Examination of Washington State Department of Transportation Transfer Functions for Mechanistic-Empirical Asphalt Concrete Overlay Design
Authors: ahoney Joe P. M , Pierce Linda M.
Published: August 2018

A review of transfer functions for mechanistic-empirical design procedures is addressed. Specific emphasis is placed on those transfer functions currently used by the Washington State Department of Transportation (WSDOT) and shift factors that relate estimates of laboratory to field fatigue cracking. To achieve this goal, brief discussions about how the WSDOT transfer functions were developed or chosen are presented. A comparison of WSDOT with South African transfer functions is presented. This comparison is of special interest because the South African transfer functions have been updated recently and are in part based on extensive accelerated pavement testing. Finally, mechanistic-empirical overlay designs have been performed by WSDOT for more than 10 years, and a selection of prior overlay projects is reviewed to examine fatigue cracking shift factors. Only projects exhibiting fatigue cracking or its early manifestation are used. The annual visual distress surveys contained in the WSDOT Pavement Management System make this review a bit easier because all pavement sections on the WSDOT route system have been systematically monitored for the preceding 26 years. The conclusion is that the laboratory-based tensile strain relationship currently used by WSDOT must be shifted to predict field fatigue cracking. Such shift factors appear to fall most commonly into a range between 4 and 10.
Viscoelastic Analysis of Full-Scale Pavements: Validation of VEROAD
Authors: Nilsson R. N. , Oost I. , Hopman P. C.
Published: August 2018

VEROAD, a linear viscoelastic multilayer computer program, takes the time dependence of road building materials into consideration. VEROAD calculates the responses (displacements, stresses, and strains) of a pavement structure subjected to a moving, sliding load. The validation of VEROAD (for longitudinal and transversal strain results) is described. The calculated strains were compared with measured strains from two full-scale pavement tests: the road track machine test in Denmark and the linear tracking apparatus test in the Netherlands. Measurements from these tests indicate distinct viscoelastic strain curves, that is, time retardation and asymmetry. The study indicates that VEROAD is able to calculate the pavement behavior (both longitudinal and transversal strains) as it was measured in these two full-scale tests. VEROAD-calculated strain curves have the same shape as the measured curves.
SAPSI-M: Computer Program for Analyzing Asphalt Concrete Pavements under Moving Arbitrary Loads
Authors: Chatti Karim , Yun Kyong K.
Published: August 2018

A new solution for the dynamic analysis of asphalt concrete pavements subjected to moving fluctuating loads has been developed. The method builds on an existing model for stationary loads, SAPSI, which uses the complex response method of transient analysis with a continuum solution in the horizontal direction and a finite-element solution in the vertical direction. The structural model is an n-layered damped-elastic medium. The subgrade can be modeled as either a rigid base or a semi-infinite half space. The loads are surface pressure loads, and the analysis is under axisymmetric conditions. The moving loads are modeled as a series of pulses with a duration equal to the time required for the wheel to pass a fixed point in the pavement. The proposed method of analysis in the new version of the program, SAPSI-M, is an improvement over the existing methods because (a) it treats moving fluctuating loads on an n-layered damped-elastic system; (b) it incorporates such important factors as wave propagation, inertia, and damping effects of the medium, as well as frequency-dependent asphalt concrete properties; and (c) it can handle any load configuration, thus making possible the modeling of multiple wheel configurations of truck axles and airplane landing gears. Theoretical results have shown that the effect of vehicle speed is significant, in part due to the frequency-dependent properties of the asphalt concrete. Comparison with field strain data from full-scale pavement tests has shown excellent agreement.