bluuebunny/crossref_metadata_2025 huggingface dataset:
New Field System for Measuring Degree of Consolidation of Concrete During Vibration
Authors: Alexander A. Michel , Haskins Richard W.
Published: April 2007

Significant progress has been made in the development of a field prototype device for slipform pavers to measure the degree of consolidation of concrete during vibration. The device operates on the principle that since air is an insulator and fresh concrete is a conductor, electrical impedance measurements can indicate the release of air during the consolidation of fresh concrete. When the air is released from the fresh concrete through the process of vibration, the electrical impedance of the concrete drops in value. The device, which is based on the impedance bridge, is portable, battery-powered, noise resistant, and easy to operate. Fresh concrete has been found to be equivalent to an RC (resistor and capacitor in parallel) circuit in terms of its electrical response. Limited tests indicate that the entrapped air is released at a faster rate than entrained air, creating two distinct parts to the AC-resistance curve against time of vibration. The intersection of these two curves represents the point at which consolidation is complete. The system has a 0- to 15-V analog meter to indicate that point of completion. Project constraints did not permit the research to be completed by testing its performance on a slipform paver. However, the likelihood of commercialization has been augmented since a prototype and specifications now exist for a portable field meter.
Traffic Densification of Asphalt Concrete Pavements
Authors: Stroup-Gardiner Mary , Newcomb David E. , Olson Roger , Teig Jerry
Published: April 2007

A 5-year study of newly constructed pavements showed that a reduction in in situ air voids occurred both within and between wheelpaths for highways with an average daily traffic (ADT) load of less than 10,000 vehicles. Regardless of the level of voids immediately after construction, mixtures in the upper 65 mm (2.5 in.) within the wheelpath indicated a reduction in voids by 3 to 5 percent (e.g., from 10 to 6 percent voids), and by between 2 to 4 percent between the wheelpaths. Because only limited densification occurred below this depth for lower–traffic-volume facilities, reducing the mix design level of air voids from 4 percent to 2 percent for the lower lifts was suggested so that lower initial voids could be obtained during construction. An evaluation of older pavements indicated that moisture damage to the lower pavement layers was typical; thus, a change in mix design procedures might also help improve durability by increasing the film thickness. Pavements with high traffic volumes (>50,000 ADT) consistently indicated an increase in voids over time in the upper lift [40 mm (1.5 in.)], little change in the middle 65 mm (2.5 in.), and a decrease in the bottom 65 mm (2.5 in.). The hypothesis suggested to explain these findings was that a loss of material in the upper lifts was occurring, most probably due to moisture damage as the upper, more permeable wear course, commonly used in Minnesota, allowed water trapping at the wear and binder course (i.e., less permeable) interface. A further investigation of in situ void changes on an interstate indicated that for a pavement constructed with the same fine gradation in all lifts, traffic compacted the mixtures in a manner similar to that in low-volume roads. When the initial in situ voids increased from around 7 percent to nearly 10 percent, the influence of traffic on the densification was substantially increased.
Improving Asphalt Paving Productivity
Authors: Schmitt Robert L. , Hanna Awad S. , Russell Jeffrey S.
Published: April 2007

The asphalt paving industry has an opportunity to improve the productivity of labor, equipment, and material resources with existing technologies. A systems approach is provided for measuring and improving the use of asphalt paving resources with established productivity methods. Production data from an asphalt paving project are evaluated using crew balance charts and computer simulation to understand equipment interaction and minimize paving production costs. Implementation of productivity evaluation methods and construction process planning can reduce costs and increase profits on asphalt paving projects through more efficient use of resources. Owner agencies must be aware of contractor cost elements so that cost-effective project contract documents can be prepared. A review of current practices in asphalt paving productivity, analyses of traditional productivity measurement methods, and an application of improving productivity using collected data are provided. A productivity management system is proposed that uses existing global positioning system technology to process asphalt paving productivity data through real-time data acquisition, productivity analysis, and information feedback.
RoboCrane Construction of Bridges
Authors: Goodwin Ken
Published: April 2007

The National Institute of Standards and Technology (NIST) has developed conceptual designs, laboratory scale models, and computer simulations/animation of several configurations of remotely operated cranes to assemble highway bridges. NIST’s designs have been patented and trademarked as “RoboCrane.” Major opportunities exist to develop fullscale cranes and demonstrate construction of temporary bridges, causeways across wetlands, and overpasses for traffic management over repair sites. Remotely operated, mobile, lightweight cranes can put modular bridge sections in place and provide better control of loads. This could result in faster assembly and less environmental disturbance. RoboCrane configurations that are well suited for bridge assembly and their potential savings in time and cost are discussed.
Laboratory Testing of Stress-Laminated Wood Decks on Steel Beams
Authors: Dickson Barry , GangaRao Hota , Vijayachandran Vijith
Published: April 2007

Four different stress-laminated wood decks were laboratory-tested to measure composite action between deck and steel beams, transverse load distribution, performance of connectors, and deck construction cost. The models were subjected to cyclic loading varying from 9 to 89 kN. Static load tests were conducted after every 100,000 cycles. During static testing, strains and deflections in the beams were measured at 22, 44, 67, and 89 kN. The loss of tension in the connectors was also monitored after every 100,000 cycles. The readings were used to compare the composite action, load distribution, and tension loss in connectors. Load distribution values were verified with theoretical calculations.
Investigation of Critical Quality Assurance Parameter Variations for Concrete
Authors: Smutzer Richard K. , Gulen Sedat , Belew Youlanda K. , Anderson Virgil L.
Published: April 2007

The Indiana Department of Transportation is involved in preparing statistically sound specifications for strong and durable concrete used in quality assurance programs. Previous laboratory studies relating concrete strength to air content and concrete mix designs dealt with variation in compressive strength. This study searched for a statistically sound relationship between air content, concrete mix designs, and flexural strength. This study also developed a high-pressure method of hardened concrete air content determination. Sixty-four independent batches (combinations) of concrete were produced, each batch was subjected to a total of 24 tests—4 plastic and 20 hardened. The design factors were aggregate type and gradation, plastic air content, cement, and pozzolanic content and testing operator. After plastic testing, three flexural strength beams were cast from each batch of concrete. The experimental design response variables consisted of flexural, compressive, and split tensile strength along with pulse velocity. Analysis of variances, indicated that the optimum flexural strength could be obtained using as-received stone course aggregate and an air content of between 6 percent and 7.9 percent, with no fly ash. A high-pressure air meter, similar to the meter developed by the Army Corps of Engineers, was used. A strong statistical correlation of determination, r2 = 0.94, was obtained between plastic and the hardened concrete air content using this meter.
Geographic Information Systems as a Support Tool in Construction Cost Estimating in State DOTs
Authors: Ashur Suleiman A. , Crockett Barry
Published: April 2007

Geographic Information Systems (GIS) have been successfully implemented in various fields. Transportation agencies, however, have not yet recognized the full capabilities of GIS. The purpose of the GIS cost estimation project is to research the possibilities of analyzing data through the power of geographic management. The enhanced data management would assist in improving project cost estimation. Typically, state highway departments rely heavily on historical bid data to estimate construction projects. A systematic information collection, organization, and storage process must be used so that relevant historical cost data can be retrieved. Data collection and storage have been done for years but their usefulness at times appears worthless, primarily because of the amount of time required to page through and assimilate reams of compiled data. Analysis would be greatly simplified if one could visualize the data graphically. Using such technology should assist in easing the ever-increasing demand to analyze information to support more effective decision making.
Performance Measures for Construction Administration
Authors: Jahren Charles T. , Chase Gerald W. , McCollough Laura A. , Carlson Eric L.
Published: April 2007

A performance measuring system was developed for the Iowa Department of Transportation Offices of Construction. Measures were developed for eight key processes: inspection of work, resolution of technical issues, documentation of work progress and pay quantities, employee training and development, continuous feedback for improved contract documents, provision of safe traffic control, external/public communication, and provision of preletting information. The results indicate that the Iowa Offices of Construction are very cost-effective, are prompt in closing construction contracts, and have good relations with contractors and law enforcement officers. Improvements could be made by streamlining the procedures, reducing the time to resolve technical issues quickly, and improving traffic control. Researchers recommend refining the performance measuring system and continued performance monitoring.
PART 1: Finance: Transport Strategy for Polish Cities
Authors: Mitric Slobodan
Published: April 2007

A recent study requested by a group of mayors representing the largest Polish cities is summarized. The study was to be used as input into local and national debates about future directions of urban transport development in the country. The wider context is that of a major political and economic reform, begun in the late 1980s, involving no less than a rapidpaced transition from socialism to capitalism, featuring large-scale downsizing of the public sector, privatization, and a redistribution of political and resource powers from the state to local governments. Among the downstream effects of these changes has been an increase in private car ownership and use and a reduction in the market share of urban mass transit modes from between 80 and 90 percent of nonwalk daily trips to 70 percent or less. For transit operators, now owned by local governments, this has meant an added financial pressure coming after a decade of underinvestment in infrastructure, rolling stock, and other equipment. Large numbers of unemployed, retired, or otherwise low-income travelers, another consequence of restructuring the economy, have made it difficult to improve cost recovery by increasing fares. Traffic growth has generated congestion, since the structure and size of urban road networks were predicated on low car use. An urban transport strategy is proposed to respond to these problems. Its main short-term objective is to have an affordable and socially and environmentally acceptable modal split. In the longer term, the objective is to use the demand response to a much-reformed price system as the principal guide to how infrastructure and services should evolve. The key features of the strategy are as follows: ( a) evolution toward market-supplied services by a mixed-ownership mass transport industry; ( b) treatment of urban road networks as public utilities, focusing on cost recovery through pricing; ( c) linkage of pricing policies for mass transport and individual transport modes, in line with second-best thinking, aiming to reduce and even eliminate subsidies for both modes; and ( d) reliance on internally generated revenue leveraged by long-term borrowing to finance sectoral investments. It is therefore a counterpoint to a strategy wherein mass transport is a state-owned monopoly, the use of urban roads is subsidized as is mass transport, infrastructure investment is the instrument of preference as opposed to pricing, and sectoral investments and operating subsidies are financed from tax-generated budgets.
Review and Update of Virginia Department of Transportation's Cash Flow Forecasting Model
Authors: Gillespie James S. , Kyte Cherie A.
Published: April 2007

Accurate predictions of cash balances are essential to the month-to-month operations of transportation departments. The Virginia Department of Transportation (VDOT) relies on a general cash flow forecasting model to predict monthly outflows and inflows of cash to various activities. VDOT’s model was developed in the mid-1980s and reflects the realities of that time. Much has changed in the operational aspects of VDOT since then. The cash flow model was updated. The research focused on two components (or submodels) of the general cash flow model: the monthly factors submodel, which is used to forecast monthly expenditures on construction contracts, and the maintenance expenditures submodel, which is used to forecast monthly outlays on maintenance activities. The result was an update of the basic elements of the monthly factors submodel while, for the most part, retaining the original underlying methodology. The research yielded a new methodology for the prediction of monthly expenditures on maintenance. The new forecasting method is based on a regression equation.
Federal Allocation Formulas: Evaluation of Options for Intermodal Surface Transportation Efficiency Act Reauthorization
Authors: Raimi Matthew
Published: April 2007

In 1997, the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) will be reauthorized, and the formula for distributing federal highway funds to states is likely to be a key issue in the reauthorization process. One reason for the upcoming formula debate is that the current allocation process is not reflective of current federal objectives in transportation. Alternative proposals for distributing federal highway funds have already been introduced to Congress. ISTEA reauthorization will provide Congress with an opportunity to review the federal objectives in transportation and to reflect these objectives in the distribution of federal highway funds to states. In preparation for this debate, alternative scenarios for distributing federal highway funds are explored, and the scenarios are evaluated on the basis of the present overarching federal objectives in transportation. Included in this process is an evaluation of formula factors, such as lane miles and vehicle miles traveled, that make up individual scenarios. The goal is to encourage debate on and add to the discussion of how federal highway funds are or should be distributed to states.
Passenger Car Equivalents for Highway Cost Allocation
Authors: Torbic Darren , Elefteriadou Lily , Ho Tien-Jung , Wang Ying
Published: April 2007

Existing passenger car equivalent (PCE) values do not necessarily serve the purposes of highway cost allocation well, since their derivation has followed from a need to determine equivalency for traffic operations purposes. Highway cost allocation demands better knowledge of equivalencies among vehicle classes, for a wide range of vehicle types, and under the full range of traffic conditions. There are several possible methods for PCE development and various suggested PCE values, but there is currently no information on the suitability of these methods and estimates for cost allocation purposes. A framework for the development of PCEs is set forth, and some final PCE values for the 20 vehicle types and 30 weight groups that could be used in the current Federal Highway Cost Allocation Study are provided. Using traffic simulation models, PCE values were calculated for each of the 12 facility types for various roadway segments (i.e., grades, length of grade, number of lanes). PCEs were also calculated for high and low traffic volumes for additional flexibility in assigning congestion-related costs. The PCEs obtained for each roadway and traffic condition were combined into a weighted-average PCE value for each vehicle type and highway facility type, reflective of the actual geometric conditions of the entire highway. Weighted-average PCEs were separately calculated for congested and uncongested conditions for two different vehicle percentages.
Innovative Financing Approach for President George Bush Turnpike
Authors: Smith Frank J.
Published: April 2007

An innovative financing program for a toll project in Texas that has been financed and will be constructed by a joint-venture team composed of the Texas Department of Transportation (TxDOT) and the Texas Turnpike Authority (TTA) is described. The President George Bush Turnpike (State Highway 190) will connect 42.5 km (26.4 mi) of suburbs north of the city of Dallas. The project has been in various stages of planning and design since the late 1960s. Each agency working alone could not complete SH-190 in a timely and cost-effective fashion. Exploiting changes made to the state constitution in 1991 and maximizing the use of the innovative financing provision of the Intermodal Surface Transportation Efficiency Act, TxDOT, TTA, and FHWA in partnership developed a financing structure to accelerate the construction of this project.
Evaluation of Congestion Pricing Alternatives in the Twin Cities
Authors: Lari Adeel Z. , Buckeye Kenneth R.
Published: April 2007

A congestion pricing study for the Twin Cities metropolitan area was conducted in 1995–1996 by the Minnesota Department of Transportation and the Metropolitan Council of Minneapolis and St. Paul (Twin Cities), with sponsorship by FHWA. The effort was designated a congestion pricing preproject study by FHWA. After an initial screening, 11 pricing options for the Twin Cities were considered. Five regionwide pricing options were ultimately evaluated in detail. Because of the need to understand the relationships and effects of various pricing options, it was necessary to develop and apply adequate evaluation criteria to those options. An evaluation matrix was created to help planners and decision makers make recommendations concerning implementation of congestion pricing options and pricing features within those options that best meet identified objectives.
Modeling the Internalization of External Costs of Transport
Authors: O’Mahony Margaret M. , Kirwan Kieran J. , McGrath Sean
Published: April 2007

Increases in traffic congestion and pollution levels in urban areas in Europe have resulted in the need to develop reliable and transferable methods of assessing the environmental and social effects of transport pricing and other regulatory policies. To achieve this, it is necessary to quantify the marginal social costs of transport as a function of travel demand and then to obtain the optimum marginal social cost by maximization of utility subject to budget constraints. The work conducted by Trinity College, Dublin, on a project (TRENEN) funded by the European Union JOULE II Non-Nuclear Energy Program is described. The project involved the development and calibration of an optimization model, the TRENEN model, based on welfare economics to address fundamental issues relating to the external costs of transport. The determination of the optimum function type used to represent the transport demand–delay relationship (which was obtained using an existing four-stage network model) for input to the TRENEN model is described. The TRENEN model is quite different from network modeling in that it is fundamentally macrolevel in its approach and works in an economic framework rather than at a traffic network level. Also discussed is a calibration of the TRENEN model for Dublin, the capital city of Ireland. Dublin currently experiences high levels of traffic congestion, particularly in the morning peak period, resulting from a heavy demand for car travel and the poor level of service associated with public transport. The possibility of using the TRENEN model, which addresses the issue of “social equilibrium” at a macrolevel, in conjunction with the more traditional “network equilibrium” approach used by traditional four-stage microsimulation modeling techniques, is discussed.
Measuring the Contribution of Transportation to the U.S. Economy: U.S. Transportation Satellite Account
Authors: Fang Bingsong , Han Xiaoli
Published: April 2007

The importance of transportation to the U.S. economy is widely recognized. However, the current statistics within the U.S. national accounts and transportation statistics underestimate the true contribution of transportation to the U.S. economy. The U.S. Transportation Satellite Account (TSA), a multistage joint project between the Bureau of Transportation Statistics and the Bureau of Economic Analysis, attempts to provide a set of measures of the interdependence between transportation and the U.S. economy at the most detailed level. On the basis of these measures, determinations can be made of how much transportation contributes to the U.S. economy as a whole, which industries use how much transportation services, the extent to which transportation uses up social resources, and so on. The theoretical framework established for the core account of the TSA is presented. The structure of the account and estimation procedures for its construction are discussed. How the account can be combined with the U.S. Input-Output accounts to develop complete accounts with a more detailed representation of transportation for different purposes is illustrated.
PART 3: Society: Social Benefits of Transit: Case Study of Metropolitan Atlanta Rapid Transit Authority
Authors: Nelson Arthur C.
Published: April 2007

Advocates of transit suggest that there are several important social benefits of transit systems—savings in pollution, congestion, and general social costs. Estimates of such savings have been limited to general comparisons with the personal occupancy vehicle (POV) mode usually on a vehicle-miles-traveled basis. Those savings are simulated in the context of the Metropolitan Atlanta Rapid Transit Authority (MARTA). It is estimated that between 1980 and 1994, MARTA generated about $2.2 billion in total social cost savings by diverting POV riders to transit. Compared with the POV alternative, MARTA generates an average of about $107 million annually in savings to society even after considering society’s subsidies to transit. Shortcomings of the analysis and policy implications are discussed.
Measuring the Neighborhood Benefits of Rail Transit Accessibility
Authors: Lewis-Workman Steven , Brod Daniel
Published: April 2007

For many Americans, living near high-quality rail transit stations provides an array of benefits. The benefits arise from lower transportation expenses, changing development patterns, and other nonuse factors. Automobile-centered development patterns increase congestion, sprawl, and pollution. The benefits of transit-oriented neighborhoods are explored. A hedonic price function is used to estimate property values and the effect of proximity to rail transit stations. Geographical information system databases were used to calculate actual walking distances to transit, providing a much more accurate measure of the “proximity” variable than the usual measure of straight-line distance. The results indicate that proximity to rail transit stations can be a significant source of benefit to residents within walking distance. Whereas light rail transit stations in Portland, Oregon, indicate minimal effects, the magnitude of the benefits for the Bay Area Rapid Transit and New York City Metropolitan Transportation Authority stations, when compared with standard measures of transit benefits, indicate that benefits from transit exceed those attributable to transit use.
Behavior of Some Pavement Foundation Materials Under Repeated Loading
Authors: Nunes Manuel C. M. , Dawson Andrew R.
Published: April 2007

A wide range of alternative materials for pavement construction were studied, and assessment techniques to enable and increase their use were developed. Five secondary materials and a conventional crushed granite were considered for use in an unbound form or lightly treated with various binders (including primary and secondary binders) in a total of 11 road pavement subbase materials. The secondary materials studied were minestone, china clay sand, slate waste, fly ash, and furnace bottom ash. The laboratory program set up for this research essentially was based on repeated-load triaxial tests, and the techniques used for specimen preparation, conditioning, and testing for resilient behavior are described. In particular, the modifications of the procedures recommended by the European Committee for Standardization necessary for testing secondary materials are identified and described. The analysis of the resilient behavior of the materials studied led to the identification of two groups with identical characteristics: unbound type of behavior (which included lightly treated mixtures), and treated type of behavior. A definition of boundaries for those groups was attempted. The mechanical properties of these materials necessary for use in analytical methods of pavement design are also presented, and the implications of treatment in terms of triaxial strength and resilient modulus are discussed.
Chemical Approach to Formation of Calcite Precipitate from Recycled Concrete Aggregate Base Layers
Authors: Bruinsma James E. , Peterson Karl R. , Snyder Mark B.
Published: April 2007

The use of recycled portland cement concrete aggregate in pavement base layers has been associated with the reduction of filter fabric permittivity and the accumulation of calcite precipitate and other materials in pavement subdrainage systems. A mechanism of portlandite dissolution within base-layer pore waters, followed by exposure to atmospheric carbon dioxide via subdrainage systems, and subsequent calcite precipitation is explored using chemical thermodynamic techniques. Ion activities and pH levels are estimated for the equilibrium states of rainwater entering the pavement, base-layer pore water isolated from the atmosphere, and subdrainage water exposed to the atmosphere. Results derived agree with field and laboratory observations of pH levels.
Anisotropic Modeling of Granular Bases in Flexible Pavements
Authors: Tutumluer Erol , Thompson Marshall R.
Published: April 2007

A new cross-anisotropic model is proposed to predict the performance of granular bases in flexible pavements. A cross-anisotropic representation has different material properties (i.e., elastic modulus and Poisson’s ratio) assigned in the horizontal and vertical directions. Repeated-load triaxial tests with vertical and lateral deformation measurements can be used to establish these anisotropic properties. Simple stress-dependent granular material models, obtained from analysis of the laboratory test data, are used in a nonlinear finite element program, named GT-PAVE, to predict pavement responses. The horizontal and shear stiffnesses are typically found to be less than the vertical. The nonlinear anisotropic approach is shown to account effectively for the dilative behavior observed under the wheel load and the effects of compaction-induced residual stresses. The main advantage of using a cross-anisotropic model in the base is the drastic reduction or elimination of significant tensile stresses generally predicted by isotropic linear elastic layered programs.
Triaxial Characterization of Minnesota Road Research Project Granular Materials
Authors: Garg Navneet , Thompson Marshall R.
Published: April 2007

Six granular materials were used as base and subbase materials in the flexible pavement test sections for the Minnesota Road Research (Mn/ROAD) project. Crushed/fractured particles are not allowed in aggregate classes CL-1Fsp, CL-1Csp, CL-3sp, and CL-4sp. Ten to 15 percent crushed/fractured particles are required for CL-5sp. One hundred percent crushed/ fractured particles are required for CL-6sp. A comprehensive laboratory testing program was established to determine pertinent engineering properties of the granular materials. Rapid shear tests and repeated-load tests were conducted to determine the shear strength parameters (friction angle and cohesion), resilient modulus, rutting potential, stress history effects on shear strength, and moisture susceptibility. The results from the rapid shear tests and permanent deformation tests show that the rutting potential of a granular material can be characterized from rapid shear test at a confining pressure of 15 psi (103.35 kPa). The rutting parameter A was a function of the shear strength of the granular materials. The shear strength results obtained from rapid shear tests performed at a confining pressure of 15 psi reflect the rutting trends observed in the low-volume road test sections at the Mn/ROAD project. Results from repeated-load tests were used to develop the parameters for K-θ, UT-Austin, and Uzan’s models for evaluating the resilient modulus of granular materials. The axial strain values calculated from the resilient modulus models appear to be in good agreement with the measured axial strain values, except for the very low shear strength material CL-1Csp.
Using Suction and Dielectric Measurements as Performance Indicators for Aggregate Base Materials
Authors: Scullion Tom , Saarenketo Timo
Published: April 2007

A simple laboratory test for evaluating unstabilized granular base material is introduced. The test consists of monitoring the capillary rise of moisture within a 300-mm-high cylinder of compacted aggregate. The moisture conditions at the aggregate surface are monitored with a dielectric probe. A graph of surface dielectric versus time is used as the basis for performance classification. The poorest-performing materials are those that rapidly reach saturation and exhibit high surface dielectric values. The dielectric is a measure of the “free” or unbound water within the aggregate sample. It is not a simple measure of the moisture content of the material but an assessment of the state of bonding of the water within the fine aggregates. It is this unbound water that is thought to be directly related to the strength of the material and to its ability to withstand repeated freeze-thaw cycling. This test was developed by the Finnish National Road Administration and successfully used to investigate a major flexible base failure. The test is now under evaluation in Texas, where several Panhandle districts have reported cold-weather pavement cracking problems that they have attributed to the flexible bases. The test setup and equipment used are described, and test results from several base materials are presented. Also discussed are laboratory results from a recently completed project comparing eight Texas and four Finnish aggregates. One of the Finnish aggregates was classified as a poor performer; the remaining three were good performers. All of the Texas aggregates were rated as inferior to the high-quality Finnish aggregates. If this test is found to be successful in discriminating good- from bad-performing materials, it could be used to flag potentially poor performers and to evaluate the effectiveness of different base improvement techniques such as chemical stabilization or fines replacement.
Seasonal Variation of Backcalculated Subgrade Moduli
Authors: Long Bing , Hossain Mustaque , Gisi Andrew J.
Published: April 2007

Seasonal variations in pavement material properties and behavior due to variations in temperature and moisture conditions are known to affect the structural performance of pavement. Temperature, subgrade moisture content, and falling weight deflectometer (FWD) deflection data were collected monthly on four asphalt pavement test sections for a year. Subgrade moduli were backcalculated using the elastic layer theory with two calculation schemes and pavement models. Backcalculation of subgrade moduli by subdividing the subgrade into a compacted subgrade layer and a natural soil subgrade layer resulted in compacted subgrade moduli that are more sensitive to the seasonal variation for all sites. It was found that for almost all sites, the patterns of subgrade response, in terms of subgrade moduli versus subgrade moisture content, simulated sine-shaped forms signifying a temperature effect. The temperature effect was confirmed by the strong correlation between backcalculated subgrade moduli and pavement surface temperature during FWD tests. The lowest backcalculated subgrade moduli were obtained for two sections during months when asphalt surface temperatures were excessively high (greater than 40°C). Both backcalculation schemes showed similar trends in variation of subgrade moduli over seasons. When the AASHTO relative damage concept was used to compute the effective roadbed soil resilient modulus for design, similar values were found for both schemes for most of the sites. The minimum frequency of FWD testing to capture the seasonal variation of subgrade was found to be three tests per year, or testing every fourth month, assuming that unusually high temperature regimes could be avoided.
Field Performance and Mitigation of Shredded Tire Embankment
Authors: Gacke Steve , Lee Melany , Boyd Nancy
Published: April 2007

The design, construction, and mitigation of a shredded tire embankment that underwent pyrolysis and full combustion are discussed. The embankment was constructed to repair a 45-m-long section of SR-100 near Ilwaco, Washington, after a landslide occurred in native weathered siltstone. Because of foundation soil characteristics and the proximity of environmentally sensitive areas, the roadway was rebuilt using shredded tires as a lightweight embankment material. Construction of the 8-m (maximum depth of shredded tire chips) embankment went smoothly. Less than 2 months after completion, however, unusual asphalt cracking, odors, and steam were observed in the embankment. The steam and elevated surface temperature readings suggested pyrolysis or combustion of shredded tire chips. Weekly monitoring and sampling were conducted while mitigation options were evaluated. Less than 4 months following construction, an oily substance was observed in the water seeping from the drainage blanket underlying the embankment. The oil was immediately contained using booms, sumps, and a containment berm. Because exposure to oxygen could cause a flare-up, several in situ cooling methods were evaluated to minimize oxygenation of the material. Because of environmental and logistical concerns, excavation and water immersion of shredded tire chips was deemed the preferred mitigation measure. If using shredded tire chips as an embankment material is to be continued, it will be necessary to identify factors contributing to the pyrolysis/combustion so that preventive design criteria can be developed, and methods for remediating pyrolysis and combustion problems should they arise.
Perspectives on Liability for Constructive Reuse of High-Volume Waste Streams
Authors: Partridge Barry K. , Alleman James E. , Huber Brent W.
Published: April 2007

Large quantities of high-volume waste streams (HVWS), such as coal combustion by-products (CCBPs) and waste foundry sands (WFS), are landfilled in the United States annually. Waste generators facing increased landfill costs, reduced landfill space, and stringent permitting requirements are pursuing reuse options. Departments of transportation (DOTs) face growing pressure from waste generators, national associations, state legislatures, and the general public to find acceptable reuse applications for HVWS in roadway applications. Research results generally have been favorable toward the geotechnical and construction properties of CCBP and WFS. Furthermore, generators have been willing to provide the waste material to the job site at no cost, in lieu of incurring landfill tipping fees. Many DOTs, including the Indiana DOT (INDOT), have developed special provisions, specifications, and protocols for reusing HVWS. State and federal regulatory agencies typically have classified WFS as a solid waste under the Resource Conservation and Recovery Act (RCRA), while CCBP is excluded from RCRA regulation as a hazardous waste. WFS and CCBP can be excluded from Indiana RCRA solid waste regulation when used as a roadbase material. Despite these promising efforts, DOTs remain reluctant to reuse HVWS because of potential liability, primarily resulting from Superfund. Efforts by the 104th Congress to revise Superfund liability failed to address HVWS. Consequently, INDOT is developing a testing protocol to minimize liability and is considering indemnification clauses, which represent an added cost. Primarily liability issues are discussed here.
Safety Benefits of Traffic Calming
Authors: Zein Sany R. , Geddes Erica , Hemsing Suzanne , Johnson Mavis
Published: April 2007

This study was conducted to determine whether there are quantifiable collision-reduction benefits that result from traffic calming. Traffic calming is typically implemented to address speeding and external traffic concerns. It is intuitively recognized that successful traffic calming would therefore result in safety benefits. This research attempted to determine whether these safety benefits are measurable and significant. Four local traffic-calming projects in the Greater Vancouver area were reviewed as part of the research. All four of the projects achieved reductions in collision frequency, severity, and the annual collision claim costs. The magnitude of these benefits varied among the projects, with an average 40 percent reduction in collision frequency and 38 percent reduction in the annual claims costs. A total of 85 case studies from Europe, Australia, and North America were reviewed to determine the safety benefits of traffic calming as measured by other jurisdictions. The international case studies in which more than five precalming collisions per year occurred were analyzed separately. In this group of 15 studies, the decrease in collision frequency ranged from 8 percent to 95 percent. The implementation of traffic calming involves participation on the part of the general public, local municipalities, and emergency response organizations. The planning, engineering, and public consultation process are all a necessary part of the process to improving neighborhood livability. The results of this research provide evidence that the safety benefits of traffic calming are both quantifiable and significant.
Renewed Commitment to Traffic Calming for Pedestrian Safety
Authors: Sarkar Sheila , Jan Nederveen A. A. , Pols Albert
Published: April 2007

Success of road design depends to a large extent on how safe it is for different users. Unfortunately, in most instances the definition of road users in the United States has precluded pedestrians and bicyclists. Safety of pedestrians and bicyclists is most often relegated to a marginal status in many parts of the urban areas. The roads in the past few decades, with a few exceptions, were built for speed, ensuring maximum convenience to drivers, but, intimidating the green modes (pedestrians and bicyclists). Traffic calming is one way of reclaiming the roads for a more equitable use by different users. Many European countries have been successful in giving back the road to the pedestrians and bicyclists by implementing areawide traffic management and speed-reduction measures. The United States, however, is far behind these countries in actual implementation of such concepts, although thinking on these lines had started as early as the 1960s. There is a strong argument in favor of traffic calming in the United States based on facts and figures on accidents, road conditions, and driver behavior. In addition, field research in some European countries reveals the positive attributes of these planning principles and designs.
Pedestrian Impedance of Turning-Movement Saturation Flow Rates: Comparison of Simulation, Analytical, and Field Observations
Authors: Rouphail Nagui M. , Eads Brian S.
Published: April 2007

TRAF-NETSIM and its successor CORSIM are comprehensive micro-simulation environments that have been widely used to model the urban traffic environment in the United States and abroad. CORSIM is employed in this study to simulate and evaluate the effects of pedestrian flows on right-turn saturation flow rates at signalized intersections. The saturation flow rates returned by CORSIM were compared with field data collected throughout the United States and with three existing analytical models in the United States, Australia, and Canada. These comparisons indicated that CORSIM models pedestrian interference with the turning vehicles more severely than the three analytical methods, but with a smaller effect than the empirical data indicate. Further, the empirical data exhibit a logarithmic relationship between saturation flow rate and opposing pedestrian volume, compared with the linear relationship used in the simulation and analytical models. Implications for the design and analysis of signalized intersections are presented.
If You Build Them, Commuters Will Use Them: Association Between Bicycle Facilities and Bicycle Commuting
Authors: Nelson Arthur C. , Allen David
Published: April 2007

Conventional wisdom suggests that if bicycle pathways are provided, people will use them. This assertion is based on a combination of anecdotes, a few case studies, and mostly wishful thinking. Until now, there have been no cross-sectional studies of the association between bicycle pathway supply and commuting by bicycle that control for a variety of factors. Cross-sectional analysis, controlling for a variety of extraneous factors, can help to attribute differences in bicycle commuting to the overall supply of pathways. Cross-sectional data are applied here to 18 U. S. cities to help fill this gap in research. After considering such factors as weather, terrain, and number of college students, a positive association was found between miles of bicycle pathways per 100,000 residents and the percentage of commuters using bicycles. It is speculated that one problem with shifting the mode of commuting away from automobiles may simply be an inadequate supply of bicycle facilities. Although this work is the first of its kind, more systematic research is needed to confirm its findings.
Bicycle Journey-to-Work: Travel Behavior Characteristics and Spatial Attributes
Authors: Shafizadeh Kevan , Niemeier Debbie
Published: April 2007

The relationship between the demographic attributes and spatial clustering of individuals making a weekday bicycle journey-to-work commute and their commuting travel time is explored. The study uses data from a 1993 bicycle-intercept survey distributed in Seattle, Washington, in which individual bicycle-travel behavior characteristics were collected. The data include socioeconomic information, such as age, gender and income. The results indicate that these three factors may play unexpected roles in the length of bicycle commuting travel times for the journey-to-work trips. This study also suggests that separated bicycle paths play an integral part in the overall bicycle transportation network. Statistical analysis also indicated that cyclists traveling primarily on separated paths tend to make significantly longer trips.
Bicyclist Performance on a Multiuse Trail
Authors: Pein Wayne
Published: April 2007

Bicyclist crossing time from a full stop was measured using video recording equipment at 16 diverse trail-roadway intersections (two to six lanes, stop or signal controlled, divided or undivided) of the Pinellas Trail in Pinellas County, Florida. A total of 442 bicyclists (single individuals or randomly selected individuals from a group) were timed. The cruising speed of 65 bicyclists was also determined. A linear regression model was fit to the time and crossing-distance data. A linear regression was also fit to eight 85th percentile crossing-time points that were calculated from grouped raw data. Using kinematic physics, in which bicycle acceleration and intersection crossing velocity are variables, a theoretical equation was derived to predict bicyclist crossing time for any distance. This derived equation is a linear function of distance, so the regression coefficients could then be used to estimate bicyclist crossing velocity and acceleration on the Pinellas Trail. These estimated values for bicyclist acceleration and intersection crossing velocity compare favorably with the scant available data from foreign and domestic sources. Thus, the crossing-time prediction equation can be a useful tool when designing intersections for bicyclists, with application in signal timing and crossing-sight distance calculations.
State-of-the-Art Design of Roundabouts
Authors: Bared Joe G. , Prosser William , Esse Carol Tan
Published: April 2007

In the United States roundabouts are becoming more popular. European improvements in design, operations, and traffic regulations have led to safer performance in roundabouts than in conventional intersections. Consequently, capacity and delay have also improved. More uniform practices have emerged, particularly the yield-at-entry traffic rule and vehicle path deflection through the roundabout. For the benefit of U.S. planners and designers, a synthesis and recommendations based on up-to-date international and domestic practices are provided. Those practical design issues are concisely discussed: justification; safety and accident prediction; capacity; delays; location; design considerations (design vehicle, design speed, sight distance, deflection, central island, circulating roadway, entries and exits, splitter islands, signing, and landscaping); bicycle considerations; pedestrian considerations.
Operational Aspects of Michigan Design for Divided Highways
Authors: Dorothy Paul W. , Maleck Thomas L. , Nolf Sarah E.
Published: April 2007

Multilane trunk-line (state routes other than freeways) highways in the state of Michigan typically have one of two cross sections: five-lane or boulevard. The cross section of a five-lane facility consists of four through lanes and a continuous two-way center left-turn lane. The alternative to the center left-turn lane design is a divided highway with a median. The median widths may vary from as little as 1.2 m (4 ft) to more than 30 m (100 ft). Since left turns at intersections have a major effect on limiting the capacity of the intersection, Michigan uses directional U-turn crossovers to provide for an “indirect left-turn” maneuver at signalized intersections. The alternative to this boulevard strategy is to provide for direct left turns with a left-turn phase at the intersection. It was impossible to find appropriate locations in the field to evaluate the sensitivities of these designs and operations with various traffic volumes and left-turn volumes. Thus, computer modeling, via TRAF-NETSIM, was used to evaluate these designs operationally. The boulevard designs that used indirect left-turning strategies and signalized crossovers were superior, in most cases, to all other designs considered. The boulevard designs that used direct left-turning strategies had proportionally higher amounts of delay than all other designs considered, and their operation tended to fail as the percentage of left turns and traffic volume increased. In addition, with low percentages of left turns, the operation of a boulevard with an indirect left-turn strategy was similar for both signalized and stop-controlled crossovers.