bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluating Particulate Emissions from Jet Engines: Analysis of Chemical and Physical Characteristics and Potential Impacts on Coastal Environments and Human Health
Authors: Boyle Karleen A.
Published: August 2018

The results of this study suggest that the range of size of particulate emissions from some jet engines clusters below 1.5 µm and that the emissions contain heavy metals. Therefore, jet exhaust particulates (JEPs) have the potential to adversely affect both the environment and human health. Little is known about the particulate component of jet engine emissions. Baseline physical and chemical data on JEPs were obtained to evaluate their potential effects on the environment. Particles collected from the exhaust stream of two types of jet engines were examined using scanning electron microscopy. Analysis indicated that 100 percent of the particles collected were below 1.5 µm in size. Particles in this size range can penetrate to the alveoli of human lungs. Chemical analyses of jet engine exhaust were conducted in an attempt to identify chemical fingerprints that would distinguish aviation emissions in the environment from other anthropogenic emissions. Certain heavy metals, especially vanadium, were found in jet exhaust and may be useful chemical fingerprints. Analysis of JP-5 fuel standards revealed a suite of alkylbenzene hydrocarbons, which may also aid in fingerprinting aviation emissions. Sediment samples taken at coastal wetlands near airports indicated the presence of the same heavy metals as those found in jet exhaust samples. Field sites exposed to higher volumes of air traffic contained higher levels of sediment heavy metals, supporting the hypothesis that aerial deposition of heavy metals is occurring in areas near some airports.
North American Airline Mergers: Strategic Response to Imperfectly Competitive International Markets
Authors: Clougherty Joseph A.
Published: August 2018

The wave of domestic mergers among North American airlines during the late 1980s and the subsequent reduction in competition increased the risk of higher domestic prices for airline tickets. Why then have the North American governments allowed this consolidation to occur? Research to date has focused on these mergers as a domestic phenomenon, but they occurred in response to imperfectly competitive international aviation markets as well. The North American nations and their international airlines could garner the lion's share of the supranormal profits to be had in these imperfectly competitive markets by cutting the costs of their international carriers. Matching international routes with domestic-route networks and establishing a global hub-and-spoke system lower the cost of providing international flight service. Domestic airline mergers are a means to creating significant domestic-route networks, cutting costs, and allowing international carriers to increase profit shares in international markets. Economic incentive for airline mergers is established and provides a basis for consideration of the political sphere; findings indicate that these mergers are beneficial to private interests and are also in the public welfare. Private interest and public-welfare political rationales are often in opposition both in political literature and in practice, but in this case they coincide. Empirical tests support domestic airline consolidation in North America as a contributing factor in competitive gains in international markets for both the nations and the airlines.
Age-Related Changes in Selected Status Variables in General Aviation Pilots
Authors: Harkey Julie Anne Yates
Published: August 2018

Nine status variables were analyzed in an attempt to narrow the focus of where, within the active pilot population, to look for some of the factors that may be associated with increase in risk of becoming involved in a general aviation accident. Epidemiological analysis of general aviation pilots indicates that there is a significant rise in the accident rate for pilots after age 39. An analysis was made of changes in the frequency of occurrence of selected status variables between pilots in the 35 to 39 and those in the 40 to 44 age groups who were involved in general aviation accidents in 1992, 1993, and 1994; between pilots in the 35 to 39 and those in the 40 to 44 age groups in the active pilot population; and between accident-involved pilots and those in the active pilot population. Status variables analyzed were Federal Aviation Administration pilot and medical certificates, instrument rating, flight time, pilot occupation and gender, and purpose of the accident flight. The two age groups of accident-involved pilots differed on only one variable. However, examination of the data showed two distinct differences between accident-involved pilots and the active pilot population. The most substantial finding for both age groups was that accident-involved pilots were significantly different from the active pilot population. Second, with the exception of class of FAA medical certificates, accident-involved pilots did not differ significantly with age whereas the active pilot population differed significantly over five status variables.
Comparison of Pavement Drainage Systems
Authors: Hagen Mark G. , Cochran George R.
Published: August 2018

Pavement drainage systems have become a common addition to construction and reconstruction plans. Several types of transverse and longitudinal drains that vary in shape, size, and cost are often included in designs, although little is known about their performance. The drainage characteristics and pavement performance of four drainage systems under jointed portland cement concrete pavement are described and evaluated. Included are the Minnesota Department of Transportation (Mn/DOT) standard dense-graded base, two dense-graded base sections incorporating tranverse drains placed under the transverse joints, and permeable asphalt-stabilized base—a design that reflects current Mn/DOT drainable-base thinking. All sections contain longitudinal edge drains. Experiment variables include drainage flows, percent of rainfall drained, time to drain, base and subgrade moisture content, and pavement and joint durability. Two primary conclusions were reached. First, although all systems appear capable of removing drainable water from the pavement base, the permeable asphalt-stabilized base usually drained the most water within 2 hr after rainfall ended, while providing the driest pavement foundation and the least early pavement distress. Second, sealing the longitudinal and transverse joints temporarily reduced all rain inflow. After about 2 wk inflow resumed, although the joint sealants appeared to be intact.
Evaluation of Pavement Edge Drains and Their Effect on Pavement Performance
Authors: Fleckenstein L. John , Allen David L.
Published: August 2018

Research was conducted on pavement edge drains between 1991 and 1995 in Kentucky by the Kentucky Transportation Center. The study was initiated in an attempt to determine the effectiveness of these systems in improving pavement performance. Each edge drain system was evaluated on the basis of construction, maintenance, and performance of the edge drain backfill and geotextile and the lateral effectiveness of pavement edge drains across the pavement structure determined, to verify that pavement edge drains improve pavement performance and to determine their cost effectiveness. The initial findings indicate that if the edge drains are properly installed, edge drain systems in most cases will add significant life to pavement structure.
Review of Studies concerning Effects of Unbound Crushed Concrete Bases on PCC Pavement Drainage
Authors: Snyder Mark B. , Bruinsma James E.
Published: August 2018

Recycled concrete aggregate (RCA) products are sometimes used as replacements for virgin aggregate products in concrete pavement structures. Recent concerns have centered on the deposit of RCA-associated fines and precipitate suspected of reducing the drainage capacity of RCA base layers and associated drainage systems. Environmental concerns have focused on the relatively high pH of the effluent produced by untreated RCA base layers. Several studies have examined these concerns and others; the results of some of these studies have not been published or publicized. The most relevant of these studies are summarized herein. These research efforts demonstrate that calcium-based compounds are present in most recycled concrete aggregates in quantities sufficient to be leached and precipitated in the presence of carbon dioxide. Precipitate potential appears to be related to the amount of freshly exposed cement paste surface. Thus, selective grading or blending with natural aggregates can reduce, but not eliminate, precipitate problems. It was also noted that insoluble, noncarbonate residue makes up a major portion of the materials found in and around pavement drainage systems. Washing the RCA products before using them in foundation layers appears to reduce the potential for accumulation of dust and other fines in the drainage system, but probably has little effect on precipitate potential. Field studies have shown that precipitate and insoluble materials can significantly reduce the permittivity of typical drainage fabrics but that attention to drainage design details can minimize the effects of these materials on pavement drainage.
Collecting Usage Data for Analyzing a Heavy-Vehicle, Divisible-Load Permit System
Authors: Meyburg Arnim H. , Saphores Jean-Daniel M. , Schuler Richard E.
Published: August 2018

The collection of truck usage data for performing a benefit-cost analysis of the New York State Divisible-Load Permit System is described. To motivate the data collection requirements, the procedures used for estimating both infrastructure costs and economic benefits are briefly described. The survey procedure is summarized, as are data gathered on permitted vehicles, operator characteristics, and truck usage. Advantages and shortcomings of the methodology for collecting data are reviewed from the perspective of analyzing divisible-load permit systems for heavy vehicles. The overall study is one of the first attempts to assess the economic impact of permit systems based on actual usage data provided voluntarily by truck operators through seasonal mail surveys. As illustrated by the authors in a 1994 report, the economic benefits of a permit system for trucks hauling heavy divisible loads can be substantial. The collected survey data were adequate for providing order-of-magnitude estimates of benefits and costs although bridge damage and accident costs could not be evaluated because of a lack of data. Results should therefore be of interest to transportation officials throughout the country for use in evaluating the merits of allowing extra-heavy vehicles on the roads.
Mobile Data Communication and Electronic Data Interchange Technology in European Road Freight Operations: Evaluation of Pilot Applications
Authors: Giannopoulos G.A.
Published: August 2018

The results of a 3-year research work that investigated the impact of the introduction of mobile data communications (MDC) and electronic data interchange (EDI) on road freight operation is presented. Pilot applications were set up throughout Europe and evaluated for a number of months for both MDC and EDI. A total of 63 trucks belonging to five transport operators were equipped with MDC equipment, while five EDI liaisons were established to deal with transport order handling, contract status reporting, and ferryboat booking. A comprehensive evaluation of these pilot applications followed, and the results are presented and discussed. For MDC, tangible benefits were identified that can recover costs of the complete installation within 3 to 6 years. Specific benefits included an increase of about 2–3 percent in productive vehicle-kilometers, savings in fuel costs of 1–3 percent, and reductions in dispatch times of 5–6 percent. For EDI, certain preconditions for success were found to be necessary before tangible benefits occur: There must be a certain minimum of business done by EDI compared to the total business of the company—about 15–20 percent of all transactions—and there must be an overall acceptance and use of EDI in the business environment as a whole, in other words, a “critical mass” of wider EDI use. The integration of MDC and EDI within the same company will help maximize the benefits from both systems. In the pilot applications presented here, the EDI installation payback period was not positive, but several points regarding the conditions under which positive results could be obtained are made and actions are recommended.
Statewide Truck Transportation Planning: Methodology and Case Study
Authors: Smadi Ayman , Maze T. H.
Published: August 2018

An alternate approach for truck transportation planning at the state level is presented using a case study application in the State of Iowa. The method was based on some freight modeling concepts and available freight data sets. However, the model takes advantage of two concepts: unconstrained highway capacities and the decomposition of commodities, resulting in manageable data and modeling requirements. Identification of significant economic sectors, selection of appropriate productivity measures, estimation of truck freight volumes for each sector individually, and estimation of routing of truck traffic on major highway routes are major elements of the planning method. The case study used two industrial sectors—food and kindred products, and machinery products—which accounted for the largest portion of state employment in nonservice sectors and the largest truck traffic generated in the state. A simplistic transportation network was used to demonstrate the modeling procedure. The analysis uses county-level employment and population to estimate zonal freight tonnage. The truck share of generated freight was estimated as the total freight generated less the freight tonnage shipped by rail. A gravity model was used to distribute the truck tonnage among origin-destination pairs, using travel time as the impedance on highway links. Estimated truck flows were converted to vehicle trips on least time highway routes using typical vehicle equivalent weights.
Ohio Motor-Carrier Preferences for Intelligent Transportation Systems/Commercial Vehicle Operations Innovations
Authors: McCord Mark R. , Hidalgo Dario
Published: August 2018

The results of a survey sent to 400 motor carriers registered with the Ohio Trucking Association are reported. The survey was designed to lend insight on motor-carrier preferences for seven innovations of intelligent transportation systems (ITS) that deal with the interface between government agencies and commercial vehicle operators. A rating scale was used and interpreted in such a way that it allowed for more meaningful and theoretically acceptable analyses than have been seen to date in the field of ITS/commercial vehicle operations (CVO). The 93 responses to the survey showed a marked preference for the innovations. The respondents preferred innovations facilitating application processes to those reducing en route time. Within the category of application processes they preferred one-stop operations to electronic data interchange concepts. Within the one-stop operations category they preferred the model most difficult to implement from an institutional perspective, one in which the government agencies would consolidate their authority in a single motor-carrier agency. The results did not depend on the size of the carrier or on the carrier's status as private or for-hire. The importance and limitations of these findings are discussed, as well as why they are surprising.
Computerized Heavy-Vehicle Size and Weight Regulations Data Base
Authors: Fekpe Edward S. K.
Published: August 2018

Policy, management, and technical decisions affecting highway infrastructure, truck operations, and regulatory enforcement, among other factors affecting the trucking industry require information on the types and operating characteristics of heavy vehicles. This information is contained in the set of regulations governing the sizes and weights of these vehicles and is traditionally provided in print medium. The results of a novel attempt to computerize these regulations and store them in a data base are presented. The platform used for the data base is user friendly, flexible, easily accessible, and interactive; sketches of vehicles can be included and information can be protected through definition of user passwords. It is demonstrated that even though industry regulations are complex, specific to jurisdiction, and varied in a number of respects, it is possible to capture the most important variables in a data base. It is also possible to enhance the utility and scope of the data base by interfacing with a geographic information system and to include other variables, such as the dynamic and operational performance attributes of heavy vehicles. The data base has limitations, among them that it cannot capture all descriptive details of the set of regulations and that it serves as an information base only and cannot be used as a legal document.
Incorporating Energy Criteria in Intermodal Transportation Policy Decisions
Authors: Bester Nancy L.
Published: August 2018

Regional and local governments are collectively responsible for maintaining the economic health of their communities and managing traffic congestion, air quality, land use, and other related growth-management issues. Yet global climate change and air quality problems result from the consumption of energy in the production of goods and services that help sustain the economy. Public policy solutions to such problems are often difficult to design because of the interrelated nature of the environment, economic activities, and the infrastructure that links them together. A conceptual framework for thinking about the market behavior of consumers and producers as cost minimizers and offering a new way to design public policies using economic and energy efficiency goals is presented for the use of public-policy makers. Production theory can be used to explain how land, vehicles, infrastructure, and energy are combined to produce transportation goods and services. Heat and waste by-products from the production process act as the precursors of air pollution and other global climate-change problems. If public policies are designed to minimize such problems, policy analysis methods need to include those factors that help determine the cost and benefits of prospective policy alternatives, as well as information on how the net benefits of such policies are redistributed in society. A list of criteria to use in selecting analysis methods for this purpose is suggested.
Strategic Planning Model for Marine Oil Transportation in the Gulf of Mexico
Authors: Li Huan , Iakovou Eleftherios , Douligeris Christos
Published: August 2018

The development of a comprehensive model of the marine oil transportation in the Gulf of Mexico is presented; it solves for oil flow distribution in a competitive multimodal and multiproduct network on the basis of systemwide optimization. It is a high-level strategic decision-making tool that will be used to interface with a risk analysis model, which is under development, to identify weak links in the system and evaluate alternative routing and shipping scenarios. It may also be used to provide suggestions for the designation of lightering zones, which will enable the United States to draw from the general world supply of tanker capacity and reduce oil transportation costs and risks.
Introducing Evidence of Contamination and Offsetting Cost of Remediation in Determining Fair Market Value for Eminent Domain Awards: A Review of Interrelationship between Environmental and Acquisition Law
Authors: Jochnowitz Leona D.
Published: August 2018

The issue is whether evidence of contamination is admissible and remediation costs may be offset in determining fair market value in eminent domain proceedings. The answer will depend on an analysis of methods of valuation and local acquisition statutes; economic impact of environmental regulation; effectiveness of attempts to resolve issues of environmental liability in the context of eminent domain proceedings; preclusive or nonpreclusive effect of the determination of value on future liability for environmental remediation; and use of the property. To understand these issues, an acquiring agency should view an eminent domain proceeding from the clear vantage point of a potential defendant or plaintiff in an environmental case. How these questions can be decided consistently with both local acquisition law and the other bodies of state and federal environmental law is the subject of a variety of recent court decisions. The theme that arises from the cases is that it appears fair to discount the valuation of property if the owner's procedural rights are satisfied, including determinations as to liability and third-party actions. Nevertheless, once payment is discounted, it is critical that the transferee does not have to pay twice for the same remediation but should be liable under the environmental laws for new or newly discovered contamination. A partial indemnification may be appropriate. In addition, issues regarding just compensation may be raised when an acquiring agency not only values a compensation award at zero but also seeks compensation for remediation costs that exceed the value of the property. Alternatives should be explored for escrowing the remediation costs, inviting the owner to clean up the property now or indemnifying the owner to the extent of the discount against future liability. One solution will not fit all cases, but these and other alternatives will make owners and states more thoughtful when property is acquired and better able to plan for the uncertainties that can arise in environmental liability.
Overview of Innovative Financing: Highway and Transit
Authors: Vaccari Michael A.
Published: August 2018

An overview of innovative finance activity in highway and transit programs is presented. It is hoped that readers are given enough information to assess the usefulness of a particular financing device for their agencies. The financings are grouped into five categories: lease-structured financings; structures that achieve more with less money; cross-border leases; derivatives; and miscellaneous. Each of the financings is assessed to determine which of FTA's goals for innovative financing are achieved, that is, whether the financing reduced the costs of capital projects or provided better management of cash flow.
Development of Metal-Cutting Guardrail Terminal
Authors: Pfeifer Brian G. , Sicking Dean L.
Published: August 2018

A crashworthy terminal for strong-post W-beam guardrail systems was developed at the Midwest Roadside Safety Facility at the University of Nebraska—Lincoln. The terminal incorporates an impact head that is placed over the end of a tangent section of W-beam rail. The impact head is designed to be pushed down the rail and to dissipate impact energy by cutting the W-beam along the peaks and valley to produce four essentially flat strips of steel. These flat strips are then deflected out of the path of the vehicle, striking the end of the rail. Static and dynamic component tests as well as full-scale developmental crash tests conducted during the development of this system are described. Finally, the results of the three full-scale compliance crash tests are presented and discussed. The metal-cutting guardrail terminal was shown to meet NCHRP Report 230 safety performance standards.
NCHRP Report 350 Compliance Tests of the ET-2000
Authors: Ross Hayes E. , Menges Wanda L. , Bullard D. Lance
Published: August 2018

The ET-2000 is one of the end treatments currently approved for use with W-beam guardrail systems. The ET-2000 has successfully met all evaluation criteria set forth in NCHRP Report 230. However, with the adoption of NCHRP Report 350 by FHWA as the official guidelines for crash testing of roadside safety features, it became necessary to reevaluate the ET-2000 to the new guidelines. It is noted that one of the design test vehicles specified in NCHRP Report 230, the 2044-kg passenger car, was replaced by a 2000-kg pickup truck (2000P) under NCHRP Report 350 guidelines. The purpose of the crash tests was to evaluate the ET-2000 according to NCHRP Report 350 guidelines. The ET-2000 met NCHRP Report 350 criteria for Performance Level 3 without any design modifications. All findings in this study demonstrate that the impact performance of the ET-2000 was satisfactory.
Severity Indexes for Roadside Objects
Authors: Council Forrest M. , Stewart J. Richard
Published: August 2018

An attempt was made to develop severity indexes (SIs) for various fixed objects that are struck when vehicles leave the roadway. The objectives of the study included both the development of new indexes with recent data from two states and the exploration of methodological issues related to statistical modeling and unreported crashes. Both severe injury and cost-based SIs were developed for a wide range of crash situations by using data from both North Carolina and Illinois with which injury could be more precisely linked to the specific object stuck. Although the final SIs developed were not categorized by exactly the same control variables for the two states, the values of the indexes were, in general, moderately consistent between states and with earlier Texas-based work. However, the three state's SIs were not consistent with the SIs found in the AASHTO Roadside Design Guide. In the limited sample of airbag-related impacts with guardrails, trees, and utility poles, it appears that the airbag significantly reduces the value of the SI. Additional future research on the effects on SIs of both airbag-related and unreported crashes is needed.
Instrumentation for Determination of Guardrail-Soil Interaction
Authors: Rohde John R. , Rosson Barry T. , Smith Richard
Published: August 2018

A series of steel posts (W150 × 12.6) and timber posts (15.2 × 20.3 cm) were instrumented with soil pressure transducers to assess the soil-post load response to a 1,388-kg bogie striking the post at 33 km/hr. Soil pressure measurements demonstrated the dramatic effects of soil shear strength and modulus on the responses of both timber and wood posts. The differences in the failure mechanisms between stiff and soft cohesive soils and noncohesive soils are demonstrated by both stress distributions and total stresses measured by the pressure transducers. The measurement system has potential applications for measurement of loads during impact testing of guardrail systems and as a tool for developing more appropriate models of soil behavior during impact loading.
Crashworthiness Simulations with DYNA3D
Authors: Schauer Dale A. , Hoover Carol G. , Kay Gregory J. , Lee Anthony S. , De Groot Anthony J.
Published: August 2018

Current progress in parallel algorithm research and applications in vehicle crash simulation is described for the explicit, finite-element algorithms in DYNA3D. Two challenging algorithm research problems are addressed: problem partitioning methods and parallel algorithms for contact at material interfaces. Two prototype parallel contact algorithms have been developed for treating the cases of local and arbitrary contact. Demonstration problems for local contact are crashworthiness simulations with 22 locally defined contact surfaces and a vehicle-barrier collision modeled with arbitrary contact. A simulation of crash tests conducted for a vehicle striking a U-channel small signpost embedded in soil has been run on both the serial and parallel versions of DYNA3D. A significant reduction in computational time has been observed when running these problems on the parallel version. However, to achieve maximum efficiency, complex problems must be appropriately partitioned, especially when contact dominates the computation.
Finite-Element Modeling of G2 Guardrail
Authors: Hendricks Bart F. , Wekezer Jerry W.
Published: August 2018

A finite-element model of the AASHTO G2 guardrail (weak-post W-beam) was developed and analyzed under vehicle impact conditions by using LLNL-DYNA3D, a nonlinear, explicit, three-dimensional, public-domain, finite-element code. The modeling procedures and problems encountered are described, and suggestions for further research are given. W-beam and S3 × 5.7 steel post mesh optimization procedures and results are described. A suitable point of fixity for the posts to account for soil effects is determined. W-beam-to-post connections were investigated by three different methods. Impact influence lengths and problems associated with modeling flexible barriers are discussed. The steps taken to assemble a model, including a prebuilt vehicle model, are given. The G2 guardrail was struck with the 820C vehicle model, developed by FHWA, at a speed of 26.69 m/sec (59.7 mph) and an angle of 15.4 degrees.
Characterizing Guardrail Steel for LS-DYNA3D Simulations
Authors: Wright Amy E. , Ray Malcolm H.
Published: August 2018

Finite-element models have three parts: geometry, connections, and material properties. As the visible parts of a model, geometry and connections are generally carefully considered. Material properties often are not chosen with the same degree of care although they are equally important to obtaining good results. Accurate simulations of vehicles striking roadside hardware require an understanding of both the material behavior and the mathematical material models in LS-DYNA3D. A method for comparing LS-DYNA3D simulations with typical ASTM materials tests is described. The behavior and modeling parameters of guardrail steel (AASHTO M-180 Class A Type II) are examined in this study. Experimental and simulation results of quasistatic coupon tests are compared for AASHTO M-180 Class A Type II guardrail steel, and parameters for guardrail steel are recommended.
Nonlinear Finite-Element Analysis of Dual Support Breakaway Sign
Authors: Paulsen Gene W. , Reid John D.
Published: August 2018

Breakaway supports are common devices used for dual support signs located along the roadway. Design of these systems often involves several costly vehicle crash tests to ensure their effectiveness. It is believed that mathematical modeling can be used to help develop new sign systems in a more timely and cost-effective manner. To this end, a dual support breakaway sign system was successfully modeled using LS-DYNA3D, a nonlinear, large deformation finite-element package. Small component models were first constructed on critical parts of the breakaway sign system. The component models were compared with physical component tests to aid in the development process, as well as to validate the results. The components were then assembled into a complete system model. Very few changes were made in the complete sign model, because problems were worked out in component modeling. Results from two full-scale vehicle crash tests were used to validate the system model. With successful results, the model can now be used to study various sign modifications and configurations.
Repeatability of Full-Scale Crash Tests and Criteria for Validating Simulation Results
Authors: Ray Malcolm H.
Published: August 2018

A method of comparing two acceleration time histories to determine whether they describe similar physical events is described. The method can be used to assess the repeatability of full-scale crash tests and it can also be used as a criterion for assessing how well a finite-element analysis of a collision event simulates a corresponding full-scale crash test. The method is used to compare a series of six identical crash tests and then is used to compare several finite-element analyses with full-scale crash test results.
Traffic Control at Flagger-Operated Work Zones on Two-Lane Roads
Authors: Shibuya Shuetsu , Nakatsuji Takashi , Fujiwara Takashi , Matsuyama Eiji
Published: August 2018

To clarify the traffic flow characteristics and the signal timings at work zones controlled by flaggers, traffic flows at some work zones were measured. Using the measurement data a computer simulation program based on the microscopic traffic flow model was developed. The simulation results were in accordance with the measured results. Using the simulation program traffic behavior was analyzed for various work-zone conditions under the assumption that no heavy vehicles were mixed with the traffic. First, the delay characteristics at short work zones less than 200 m long were investigated. The summed delay of the acceleration delay and the speed-decrease delay was between 35 and 40 percent of the total delay. This suggests that those delays cannot be ignored in estimates of delay at short work zones. Next, three methods for estimating the green intervals under flaggers' control were presented: nomograph, regression equation, and analytical optimization. The first two methods were obtained directly from the simulation results, whereas the third was derived by describing both the queuing and the acceleration delays with a regression equation and minimizing the total delay. The analytically optimized green intervals diverged from the simulated ones as the traffic became heavier. The signal timings produced by a nomograph and a regression equation can be installed in pretimed traffic lights as a substitute for flaggers, and the optimized ones can be installed in actuated lights combined with traffic detectors.
Queuing and Natural Diversion at Short-Term Freeway Work Zone Lane Closures
Authors: Ullman Gerald L.
Published: August 2018

Research conducted to explore the effects of natural diversion on traffic conditions and travel patterns upstream of temporary work zone lane closures on high-volume urban freeways in Texas is described. Specific objectives were to explore how natural diversion affects traffic volumes at the exit and entrance ramps upstream of the lane closures and the interrelationships between the freeway and frontage road operating conditions that develop at a closure and the amount of natural diversion that occurs. The field studies showed that the rate of queue growth upstream of the short-term lane closures diminished significantly after the first hour at each site. Eventually, the queues approached a balanced state in which the upstream end of the queue became almost stationary. This stabilization was due to significant reductions in entrance ramp volumes both upstream of the freeway queue and within the limits of queuing, as well as to changes in exit ramp volumes within the queue. As a result of these ramp volume changes the constrained flow rate within the queue increased as a function of the distance upstream of the actual lane closure. Using the theory of shock waves in a traffic stream it was shown that the changes in ramp volumes and resulting impact on constrained freeway flow rates within the queue were consistent with the queue stabilization process observed at each site.
Capacity for North Carolina Freeway Work Zones
Authors: Dixon Karen K. , Hummer Joseph E. , Lorscheider Ann R.
Published: August 2018

Work zone capacity values for rural and urban freeways without continuous frontage roads were defined and determined. Data were collected using Nu-Metrics counters and classifiers at 24 work zones in North Carolina. The research included analysis of speed-flow behavior, evaluation of work zone sites based on lane configuration and site location, and determination of the location within the work zone where capacity is lowest. It was shown that the intensity of work activity and the type of study site (rural or urban) strongly affected work zone capacity. The data suggested that the location where capacity is reached is also variable based on the intensity of work. For heavy work in a two-lane to one-lane work zone configuration, the capacity values proposed at the active work area are approximately 1,200 vehicles per hour per lane for rural sites and 1,500 vehicles per hour per lane for urban sites. It is recommended that two distinct volumes be used when queue behavior in a freeway work zone is analyzed. The collapse from uninterrupted flow (designated work zone capacity) and the lower queue-discharge volume both should be considered.
Development of Work Zone Lighting Standards for Nighttime Highway Work
Authors: Ellis Ralph D. , Amos Scott J.
Published: August 2018

The results of a study to develop illumination guidelines for nighttime highway work are presented. Nighttime highway construction activities were identified and the seeing-task visual requirements for work activities were determined. Suggested illumination levels and lighting configurations were developed. In addition, hazard glare-control counter-measures were developed. A limited field demonstration of the suggested guidelines was conducted and the results are presented.
Analysis of Crash Rates at Interstate Work Zones in Indiana
Authors: Pal Raktim , Sinha Kumares C.
Published: August 2018

The aging Interstate system in the United States requires extensive rehabilitation and maintenance, which results in the closure of a significant portion of the system each year to accommodate work zones. These work zones not only cause travel delay, they also create safety hazards. An analysis of crash rates at Interstate work zones in Indiana is presented. Crash rates in work zones were found to be higher than those on comparable highway sections without work zones. It is believed that lane closure strategies also may influence crash potential at work zones. An analysis of the relative safety effects of two commonly used lane closure strategies, partial lane closure and crossover, is presented.
Pavement Marking Retroreflectivity Requirements for Older Drivers
Authors: Graham Johnny R. , Harrold Joseph K. , King L. Ellis
Published: August 2018

Traffic pavement markings serve to regulate, guide, and channelize traffic and supplement other traffic-control devices. Because of their retroreflective properties pavement markings are critical for guidance at night, when reference objects near the edge of the roadway are difficult to see. Nighttime luminance levels provided by pavement markings that may be adequate for younger drivers may be less than adequate for older drivers. Both subjective evaluations and quantitative measures of in-place roadway markings were made to determine minimum marking retroreflectivity levels required for older drivers. In the field study more than 85 percent of subjects aged 60 years or older rated a marking retroreflectance of 100 mcd/m2/lx as adequate or more than adequate for night conditions. This base value does not include the effects of windshields and headlights that are less than clean or the variability of individual vehicle headlight performance. A comparison between the results for older drivers and the results of a similar 1989 study of younger drivers was also made. It was found that whereas the average subjective ratings were similarly distributed relative to the retroreflectivity of pavement markings, there was a significant difference in the subjective ratings made by older and younger drivers. Older drivers consistently rated the retroreflectivity of markings lower than did younger drivers.
Field Test of a Portable Retroreflectometer for Retroreflective Raised Pavement Markers
Authors: Ullman Gerald L. , Rhodes Lewis R.
Published: August 2018

The results of an evaluation of a portable retroreflectometer used to monitor the reflectivity of retroreflective raised pavement markers (RRPMs) installed at field test sites in Texas are presented. The correlation achieved between field and laboratory readings of RRPM reflectivity is described, and the degree of correlation achieved as a function of marker type and amount of reflectivity available is explored. Six different RRPM manufacturers provided a total of 17 different types of markers for evaluation. Over 2 years the retroreflectometer achieved an aggregate correlation value of 0.938 with the Texas Department of Transportation (TxDOT) laboratory measurements. However, the degree of correlation was not identical for all types of RRPMs. Whereas the correlation coefficient exceeded 0.90 for 13 of the 17 markers tested, coefficient values of only 0.755 to 0.852 were achieved by the other 4 marker types. In addition, the correlation between retroreflectometer and laboratory data was not necessarily consistent over the entire range of reflectivity values examined. Instead, the retroreflectometer achieved a lower correlation coefficient with the laboratory data at higher coefficient of luminous intensity (RI) values (greater than 148 mcd/lx) than at lower RI values (less than 148 mcd/lx). Nonetheless, the evaluation indicated that portable retroreflectometers have improved sufficiently that TxDOT now is confident using them to determine compliance with specifications.
Strain and Age Effects on Behavior of a Concrete Pavement Joint Sealant Material
Authors: Gurjar Ashok , Zollinger Dan G. , Tang Tianxi
Published: August 2018

A one-part self-leveling silicone joint sealant material was experimentally investigated in the laboratory. It was found that strain and age had apparent effects on the relaxation modulus of the material. Relaxation tests were conducted under different strain levels. The test samples were exposed to ultraviolet radiation and moisture for artificial aging before testing. For this largely deformable material, finite strain formulas were used in analysis of experimental data. Strain and age effects were successfully normalized in the relaxation master curve by using the superposition principle. On the basis of the master curve, a material model of the generalized Maxwell model in parallel type was constructed. The real time was scaled to the reduced time by time-strain shift and time-age shift factors so as to characterize the strain and age effects. This model is mathematically simple and can be easily applied in finite element programs for concrete pavement joint analysis.
Evaluation Systems for Crumb Rubber Modified Binders and Mixtures
Authors: Troy Kenneth , Sebaaly Peter E. , Epps Jon A.
Published: August 2018

The use of crumb rubber modified (CRM) asphalt mixtures has been increasing steadily. The reasons for this increase in use are twofold: the Intermodal Surface Transportation Efficiency Act of 1991 mandate and the potential of better performance. The technology of testing, design, and evaluation of CRM binders and mixtures has not yet caught up. Therefore, there is a need for establishing standard procedures for the design and evaluation of CRM mixtures. The outcome of a recent research project sponsored by the Nevada Department of Transportation (NDOT) is presented. The binder testing system concentrated on the newly developed Strategic Highway Research Program (SHRP) performance grading system and its applicability to CRM binders. It was concluded that the standard SHRP system will not work for CRM binders containing coarse rubber particles. The plate and cup system will have to be used for such CRM binders. However, the plate and cup system cannot adequately replace the bending beam rheometer for low-temperature testing. In the case of CRM mixtures, a modified Hveem mix design procedure was developed and validated on an actual NDOT project. Temperature susceptibility, moisture sensitivity, rutting resistance, and low-temperature cracking of CRM mixtures also are presented.
Short-Term and Long-Term Aging Behavior of Rubber Modified Asphalt Paving Mixture
Authors: Liang Robert Y. , Lee Suckhong
Published: August 2018

Aging of asphalt has been an important subject area that has received extensive studies in recent years. Test results of short-term and long-term aging behavior of crumb rubber modifier (CRM) modified asphalt paving materials are presented. Eighteen combinations of CRM modified binders in terms of CRM size, CRM content, and base asphalt cement grade were studied by Brookfield viscometer test and dynamic shear rheometer test. The short-term aged binders were prepared using thin film oven test. Viscosity was measured at 350°F in the Brookfield thermosel after mixing at 375°F for 2 hr. The test results showed that the size and percentage of CRM affected the viscosity development in the modified binders: the smaller the CRM size and the higher the CRM content, the higher the viscosity measured after 2-hr reaction at 375°F. Short-term aging exerted more viscosity increase in the CRM modified binders than in the unmodified binders. Modified binders showed less weight loss than unmodified binders. The modified binders showed higher complex modulus G* than unmodified. Short-term aging increased G*, with modified binders exhibiting higher increase. The Marshall mix design yielded various CRM modified mixes. The result of indirect tensile strength tests showed that short-term and long-term aging increased the measured tensile strengths. The resilient modulus test results, in general, supported the general understanding that aging tended to increase resilient modulus.
Arkansas Experience with Crumb Rubber Modified Mixes Using Marshall and Strategic Highway Research Program Level I Design Methods
Authors: Gowda Gary V. , Hall Kevin D. , Elliott Robert P.
Published: August 2018

Unmodified and crumb rubber modified mixes conforming to the Arkansas State Highway and Transportation Department Type II surface course specifications were designed for heavy traffic conditions and environmental conditions typical to Arkansas by using the Marshall and Superpave Level I methods. Specimens prepared at appropriate design asphalt contents were evaluated for both volumetric and performance considerations. Three mix types, an unmodified hot-mix asphalt concrete, a dry process rubber modified asphalt, and a wet process asphalt rubber, were included in the investigation. For the asphalt cement, crumb rubber, aggregate type, and aggregate gradation used, the design asphalt content and the VMA were reduced for the SHRP Level I method relative to the Marshall method. Incorporation of crumb rubber into hot-mix asphalt concrete provided increased rutting resistance; however, the rubber modified mixes did not show enhanced resilient and tensile properties when tested at 25°C. Also, the performance-related properties of the SHRP Level I asphalt-rubber mixes (5, 10, and 15 percent A-R blends) evaluated did not differ significantly at 5 percent level of significance.
Babbitt, Minnesota: Case Study of Pretreated Crumb Rubber Modified Asphalt Concrete
Authors: Stroup-Gardiner Mary , Chadbourn Bruce , Newcomb David E.
Published: August 2018

A 2.38-mm (No. 10) mesh crumb rubber from waste passenger tires was pretreated with a low-viscosity petroleum-based product and used as an aggregate replacement in asphalt concrete mixtures. The preconstruction testing consisted of the development of an appropriate aggregate gradation, mix design information, and fundamental mixture properties such as temperature susceptibility, moisture sensitivity, low temperature behavior, and permanent deformation characteristics. Five crumb rubber modified (CRM) asphalt concrete plus two control test sections were placed in Babbitt, Minnesota, in the fall of 1993. Variables in the CRM sections include pretreated and untreated crumb rubber and CRM mixtures in just the wear course or throughout the 150-mm (6-in.) pavement section. Laboratory results indicated that there was little difference in the temperature susceptibility between the mix design and behind-the-paver mixtures. Although the mix design samples indicated some increase in the moisture sensitivity of the CRM mixtures, no difference was seen in the behind-the-paver materials. There was some indication that the CRM mixtures would exhibit a greater ability to dissipate thermal stresses through a better ability to strain at cold temperatures. Some slight to moderate improvements were seen in both moisture sensitivity and low temperature behavior when the crumb rubber was pretreated. Falling weight deflectometer results were used to backcalculate the layer moduli for all of the test sections. Results indicate no difference in any of the layer moduli; these results agree with the laboratory resilient moduli results. After two winters, all test sections are performing equally well. Anticipated damage by snowplows to the coarser gradation used with the CRM mixtures did not occur.