bluuebunny/crossref_metadata_2025 huggingface dataset:
Effectiveness and Efficiency of Policies to Promote Alternative Fuel Vehicles
Authors: Leiby Paul , Rubin Jonathan
Published: May 2007

Alternative motor fuels have been advocated in the name of energy security, regional air quality, greenhouse gas emission reduction, and even economic savings. The Energy Policy Act of 1992 (EPACT) sets a goal of replacing 30 percent of conventional fuel use with alternative fuels by 2010. Earlier analysis using a single-period equilibrium model demonstrated the feasibility of EPACT’s replacement goals. This earlier analysis, however, assumed mature markets with large-scale vehicle production and the widespread availability of alternative fuels at retail stations. These conditions are not currently attained. To better assess what may be necessary to achieve mature, large-scale alternative fuel and vehicle markets, the authors use the transitional alternative fuels and vehicles model and simulate market outcomes for the use and cost of alternative fuels and vehicles over the time period of 1996 to 2010, considering possible transitional barriers related to infrastructural needs and production scale. Prices and choices for fuels and vehicles are endogenous. The model accounts for dynamic linkages between investments and vehicle and fuel production capacity, tracks vehicle stock evolution, and represents the effects of increasing scale and expanding retail fuel availability on the effective costs to consumers. Various policy alternatives are evaluated, including fleet vehicle purchase mandates, fuel subsidies, and tax incentives for low-greenhouse-gas-emitting fuels.
Methodology for Assessing High-Occupancy Toll-Lane Usage and Network Performance
Authors: Murray Pamela M. , Mahmassani Hani S. , Abdelghany Khaled F.
Published: May 2007

A modeling framework for the evaluation of high-occupancy toll (HOT) facilities is discussed. It is based on a traffic simulation-assignment model interfaced with an unordered multinomial logit mode-choice model. The model allows for the prediction of high-occupancy, transit, and single-occupancy vehicle modal shares, based on prevailing traffic conditions and tolls. Also presented is an illustrative investigation of the sensitivity to various elements of the modal-choice function using the methodology and of the effect of different HOT facility features on HOT lane usage and associated system performance. These features include HOT lane configurations, pricing levels, carpooling attractiveness, changing departure times, and sensitivity to generalized cost. A representation of the south-central part of I-35W and the supporting roadways in the Fort Worth, Texas, area was used in the study. The results of the simulations were analyzed under each of the operating and behavior characteristics to evaluate the potential success of an HOT facility. Improving the carpooling attractiveness decreases the number of vehicles on the roadway but may not necessarily improve the average travel time for the system as a whole. The larger the departure-time window, the easier it is for travelers to carpool; however, the relatively small number of people choosing the HOV mode may inhibit the average travel time for the system from reflecting the impacts of the reduced vehicle trips. Increasing the sensitivity to time, or generalized cost, raises the HOV mode share when there is an HOT facility available.
Development of a New Toll Mode-Choice Modeling System for Florida’s Turnpike Enterprise
Authors: Dehghani Youssef , Adler Thomas , Doherty Michael W. , Fox Randy
Published: May 2007

The Florida Department of Transportation Turnpike Enterprise’s recent toll mode-choice model development activities are described. Because the simple toll travel forecasting analysis methods used were not adequate for reliably addressing contemporary toll study issues, there was a need for toll modeling innovations that address trip makers’ toll route decisions as a mode-choice step sensitive to changes in service levels by time of day, trip purpose, and socioeconomic attributes. Innovations developed for Florida’s turnpike began with data-collection efforts and toll model development for the Central Florida (Orlando) region. This represents the next generation of modeling system. Similar efforts are under way for the Miami–Fort Lauderdale area. The Orlando region toll mode-choice model, which is in its final validation phase, includes a statistically estimated nested mode-choice modeling system with a discrete choice for toll travel. The models were developed for a combination of four periods and four trip purposes, including visitor trips. Other key features are ( a) a pre-mode-choice time-of-day process; ( b) a generalized cost-assignment procedure that uses travel time and costs by time of day (rather than travel time alone); ( c) production of zone-to-zone travel time and costs consistent with travel paths; and ( d) a feedback loop process that uses an iterative successive averaging procedure to estimate travel times.
Planning-Level Areawide Multimodal Level-of-Service Analysis: Performance Measures for Congestion Management
Authors: Guttenplan Martin , Davis Beverly , Steiner Ruth , Miller Demian
Published: May 2007

The state of Florida has been experiencing an explosion of growth, and it is one of the fastest growing states in the country. While the state has been in the forefront of growth management initiatives, the results have been less than satisfactory. The state recognized the need to integrate land use planning efforts with transportation planning efforts. Legislation was passed that allows the formation of multimodal transportation districts, which focus on appropriate land use mixes and densities that would enhance the use of transportation modes other than the automobile. There are several key elements in the evaluation of these districts, using both land use analysis and the recently adopted multimodal level-of-service performance measures. To validate these evaluation techniques, especially focusing on the level-of-service performance measures, several case studies were undertaken. The guidelines for the formation of a multimodal transportation district provide local governments with a template for enhancing existing and new development. These guidelines also provide a blueprint for sustainable growth and the promotion and development of livable communities through the integration of transportation, land use, and urban design.
Intermodal and Multimodal Freight Policy, Planning, and Programming at State Departments of Transportation: Review of the Decade Since the Intermodal Surface Transportation Efficiency Act
Authors: Kale Steven R.
Published: May 2007

Intermodal and multimodal freight policy, planning, and programming in state agencies in the decade since passage of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) are summarized, providing a snapshot of state freight activities in the early 21st century and supplementing previous reports. Freight policy, planning, and programming requirements in ISTEA and the Transportation Equity Act for the 21st Century are reviewed. Freight efforts recently completed or under way in state agencies, primarily state transportation agencies, are summarized. The summary focuses on freight studies and plans, freight offices or programs, and selected information obtained from responses to a survey of state transportation agencies. The report may be useful to groups advocating freight agendas, developing freight outreach programs and future research ideas, or preparing recommendations for federal or state legislation.
Structured Public Involvement: Problems and Prospects for Improvement
Authors: Grossardt Ted , Bailey Keiron , Brumm Joel
Published: May 2007

Public involvement in transportation planning and design has a problematic history. Professionals lack access to a coherent, organized method for communicating with the public, and some important principles of public involvement known to community design professionals are still being discovered by transportation professionals. A protocol, structured public involvement (SPI), is proposed. SPI was designed to ensure that public involvement is meaningful to the professional and the public. Principles of SPI are presented, and a series of steps useful for engaging the general public in a complex design or planning problem is given. SPI is intended to be transparent, accountable, democratic, and efficient. SPI places the use of technology within a public involvement framework built on community design experience. While technology can be useful, it must be placed in a social context. That is, various technologies are used because they can address such problems as lack of access to information, inconvenient and time-consuming meetings, confusing terms and graphics, and one-way communication. Highlights and examples are drawn from practical experience, where SPI protocols have been designed and used to solve problems of route planning, highway design, and transit-oriented development. While each problem set called for a different mix of technical tools, the protocol within which those tools were used was the same, with similar encouraging results. With SPI, public participation is less contentious and more informed, and the professional has information of high quality with which to begin the design process.
Comparative Study of EMME/2 and QRS II for Modeling a Small Community
Authors: Yu Lei , Yue Peng , Teng Hualiang
Published: May 2007

The availability of so many computer-based travel-demand forecasting models provides transportation planners with powerful and flexible tools in the modeling phase of their planning or traffic-impact studies, but it has confused users in the selection of an appropriate model for a particular study. It is commonly recognized that none of the existing travel-demand models is perfectly suited for all network scenarios and traffic conditions. A particular model that is strong in one application scenario may be weak in a different application scenario. A comparative study is presented of two widely used travel-demand forecasting models, EMME/2 and QRS II, for applications to a small community. A structural comparison is performed, and a real-world small network is modeled by EMME/2 and QRS II to identify specific features and limitations of each model. Areas for comparison include model structure, drawing of the network, data input, network modification, parameter calibration, and modeling output. The study does not recommend either model to transportation planners for a practical application to a small community. Instead, the study identifies the major differences and common features of two models, which can help planners understand what they can expect from a certain model when they choose to use it.
Dynamic Trip Generation for a Medium-Sized Urban Community
Authors: Anderson Michael D. , Malave Dilip N.
Published: May 2007

Traditional transportation modeling activities in medium-sized urban communities follow the four-step planning process: trip generation, trip distribution, mode split, and traffic assignment. These models forecast daily traffic volumes on major roadways of the communities to support infrastructure investment decisions. Recently, researchers have focused on dynamic traffic-assignment models, which provide time as a measure in the trip-modeling process, to support incident management and intelligent transportation system–based decisions. As a methodology to support the dynamic traffic-assignment models, development of a dynamic trip-generation model for a medium-sized urban community is considered. An overview of the need for dynamic trip-generation data is presented, and a methodology and a data-collection effort to develop a dynamic trip-generation model are discussed. Results are included of a validation study performed on the model. It is concluded that the models developed in the effort can provide dynamic trip-generation data and represent a first step toward making the dynamic transportation model a viable resource.
Access Management at a High-Volume Interchange
Authors: Gluck Jerome , King Peter
Published: May 2007

Alternatives for improving operations and safety at the complex urban Highbridge Interchange of the Cross Bronx Expressway (Interstate 95) and the Major Deegan Expressway (Interstate 87) in New York City are presented. These alternatives were developed as part of the Bronx Arterial Needs Major Investment Study (BAN MIS) that is being performed for the New York State Department of Transportation. The unusually high levels of congestion on Interstate 95 and Interstate 87 required a high level of analysis and alternatives development for this location. This interchange experiences high levels of delay and accident frequency for several reasons. The interchange incorporates two of the most heavily used Interstate highways in the city, and both of these have a high volume of trucks. It includes or is adjacent to other heavily used facilities, including park-ways, other expressways, and high-volume local arterials and the George Washington Bridge (a 14-lane facility). Finally, it is sited in a part of the western Bronx and northern Manhattan of New York City that is severely constrained by adjacent land uses, severe grades, and elevation changes. The BAN MIS is exploring a wide range of strategies in the vicinity of Highbridge Interchange to improve traffic operations and safety. Strategies applied basic principles of access management to reduce conflicts and eliminate weaving, to separate through from local movements, and to maintain a hierarchy of roads by function. These principles are applicable to other interchange projects to help in developing alternatives for improving traffic operations and safety.
Evaluating Indirect Land Use and Environmental Effects of a Toll Discount Proposal
Authors: Racciatti Albert , Berge Paul
Published: May 2007

Physical improvements to a transportation network or policy actions such as toll decrease can have an impact on the environment by reducing the time and monetary costs of travel, which can work to enhance the attractiveness of surrounding land to developers, residents, and businesses. A proposed toll discount on the Chesapeake Bay Bridge-Tunnel connecting the Hampton Roads metro area with the rural Eastern Shore of Virginia was analyzed for its potential to influence land use and affect the environment. How practitioners can couple well-established technical assessment methods in various disciplines with public involvement and strategic planning to promote a comprehensive vision of the future for a rural area on the fringe of a growing metropolitan region was illustrated. Current conditions, assets, needs, goals and potential impacts were assessed in several key areas of interest to Eastern Shore residents: transportation, tourism, economic development, agriculture and aquaculture, natural resources, and quality of life (livable communities). The impact assessment examined the potential for effects attributable to toll reduction scenarios in each of these six topic areas. The assessment techniques included interviews, comparative case research, analysis of present and potential future regional development and commuting patterns through the application of a gravity model, and extensive public involvement in the form of public meetings and topic workshops. As a complement to the impact assessment, the study team formulated strategies and actions to manage future growth and development that could be anticipated with or without a reduction in the toll.
Measuring the Role of Transportation in Facilitating Welfare-to-Work Transition: Evidence from Three California Counties
Authors: Blumenberg Evelyn , Hess Daniel Hess
Published: May 2007

Welfare-to-Work transportation programs are premised on a conceptualization of the spatial mismatch hypothesis that focuses on the physical separation between the central city locations of welfare participants, rapidly expanding job opportunities in the suburbs, and the long commutes needed to connect them. Using data from three diverse California counties, welfare recipients’ spatial access to employment was examined. The results indicate that the traditional notion of the spatial mismatch is less relevant to welfare recipients, many of whom live in counties in which the urban structure does not fit the simple model of poor, central-city neighborhoods and distant, job-rich suburbs. Many welfare recipients live in job-rich areas; others live in neighborhoods that are spatially isolated from employment. Therefore, to be effective, transportation policies must be tailored to the diverse characteristics of the neighborhoods in which welfare recipients live.
Modeling and Laboratory Assessment of Capillary Rise in Stabilized Pavement Materials
Authors: Lee Kok Yun , Kodikara Jayantha , Bouazza Abdelmalek
Published: May 2007

Capillary rise tests were carried out on marginal material (scoria) stabilized with two cementitious additives, general purpose cement, and general blended cement up to 5.5% by dry weight. The test results indicated that capillary rise occurred along the entire specimen height of 345 mm (100%) for both specimens. The rate of rise and the water absorption reduced as the binder content was increased, and a similar trend was found for specimens cured at 7 to 28 days. The saturated hydraulic conductivity and porosity were found to be approximately 10-8 m/s and 0.3, respectively. The theoretical basis for the capillary rise is explained by using the simple capillary tube model and water retention characteristics. A simplified model was developed to analyze the capillary rise tests. The model appeared to present the capillary characteristics reasonably well. On the basis of the theoretical approach presented, the test appears to be directly relevant to the field scenario when free water is available at the base of the pavement; however, other scenarios may be simulated approximately.
Hydrated Lime Stabilization of Sulfate-Bearing Vertisols in Texas
Authors: Harris J. Patrick , Sebesta Stephen , Scullion Tom
Published: May 2007

Sulfate-bearing subgrade soils treated with calcium-based stabilizers often experience heaving problems (three-dimensional swell) caused by chemical reactions with the sulfate or sulfide minerals. Two research questions were addressed: ( a) what sulfate content results in deleterious chemical reactions using traditional (no mellowing) lime stabilization and ( b) how effective mellowing, double lime application and increased moisture content are at reducing swell in high-sulfate soils. To determine what concentrations of sulfate are too high for stabilization with lime in Texas, a soil from the Vertisol order was selected for three-dimensional swell measurements. This soil did not contain any detectable sulfates. Two different compounds were added to the soil: sodium sulfate (Na2SO4) and gypsum (CaSO4.2H2O). The sulfates were added to individual samples at concentrations of 0; 1,000; 2,000; 3,000; 5,000; 7,000; and 12,000 parts per million (ppm). The samples were then subjected to a three-dimensional swell test for a minimum of 45 days. Results of systematic swell experiments revealed that sulfate contents up to 3,000 ppm could safely be treated with traditional lime stabilization. Coarse-grained sulfates take longer to swell, but still swell and form deleterious reaction products. Mellowing is effective at treating sulfate concentrations up to at least 7,000 ppm, higher molding moisture contents (2% above optimum moisture) reduce swell better than optimum moisture, and single application of lime reduces swell better than double application. With systematic laboratory experiments, empirical field observations of sulfate limits presented by other investigators were confirmed.
Combined Measurement of Unknown Foundation Depths and Soil Properties with Nondestructive Evaluation Methods
Authors: Sack Dennis A. , Slaughter Scott H. , Olson Larry D.
Published: May 2007

Simultaneously determining both the depth of unknown bridge foundations and the measurement of soil properties along the length of the unknown foundation allows for a more complete and accurate analysis of foundation capacity and scour susceptibility. Foundation depths are measured by the parallel seismic testing method, whereas soil properties are measured with a seismic cone penetrometer. The new combined technique has a great advantage over previous foundation-testing systems in that no borehole is required for either test. Instead, the transducers used to collect all of the required data are mounted together into the same cone probe and pushed into the ground hydraulically from a track-mounted mobile rig. Field testing of the new technique has been carried out and shown that the system is capable of quickly and accurately measuring foundation depths and soil properties on a variety of soil types.
Design of Short Aggregate Piers to Support Highway Embankments
Authors: White David J. , Suleiman Muhannad T.
Published: May 2007

When new embankments are constructed over soft soils and existing roadways and embankments are widened rapidly, stability and differential settlement problems often result. Past approaches to mitigate these problems include overexcavation and replacement, preloading, lightweight fill, piles and concrete caps, geosynthetic-reinforced soil and pile-supported embankment systems, stone columns, lime-cement columns, and deep soil mixing. The advantages and limitations of these approaches are well documented in the literature. An alternative approach to support highway embankments that is less well documented, but that has seen increased use in recent years, is short aggregate piers. Although the technique has been used to support shallow spread footings, design approaches and parameter values have not been widely available for embankment support applications and are not well known in the field. The engineering properties and an approach used to design short aggregate piers for the support of highway embankments are summarized, and the mechanisms of load-settlement behavior are described. Techniques for evaluating overall stability, control and time rate of settlement, and bearing capacity are summarized. Performance measurements are referenced for embankment support projects recently constructed in Iowa.
Focusing Landslide Investigation Efforts with Geographic Information System Screening Techniques
Authors: Liao Quanyan , Dennis Norman D.
Published: May 2007

Conventional approaches to solve slope failure problems involve deterministic and probabilistic models to calculate the factor of safety for slopes. These models usually require a large amount of field and laboratory data on soil properties and slope geometry. This requirement makes the determination of conventional factors of safety highly unrealistic if required over large areas, unless some techniques are used to direct investigative efforts to those areas with higher potential for failure. An efficient screening methodology involves creating a hazard zonation map in which regions are classified according to varying instability potential. A database of slope failure details and the power of a geographic information system (GIS) were used to analyze digital data for various causative factors of slope instability to assess the reliability of current landslide prediction methods in northwest Arkansas. A hazard zonation model was created through statistical weighting techniques from remotely sensed imagery, publicly available spatial data, and slope failure data. All of this information was visualized and analyzed by using a GIS. The model's general applicability was tested on another area with similar geoenvironmental conditions with good results.
Effect of Positive Drainage on Flexible Pavement Life-Cycle Cost
Authors: Zaghloul Sameh , Ayed Amr , Ahmed Zubair , Henderson Brandt , Springer Jack , Vitillo Nick
Published: May 2007

Drainage characteristics have a significant effect on pavement performance. Pavements with poor subsurface drainage properties prematurely exhibit distress and have higher life-cycle cost. Shorter service life and higher maintenance cost are some of the reasons for the higher lifecycle cost. It has been proved in the last 20 years that subsurface drainage increases the pavement service life and reduces its life-cycle cost. A case study demonstrates and quantifies the benefits of providing subsurface drainage through reduction of moisture in daylighted base layers of flexible pavements. The effect of higher base course moisture content on the pavement in situ structural capacity was assessed through the analysis of deflection tests performed with the falling weight deflectometer. In this analysis, a structural adequacy index was used to assess the pavement structural service life. This information was then fed into a life-cycle analysis module to determine the effect of the higher moisture content on the pavement life-cycle cost. An increase in base course moisture content from 16% to 45% resulted in the reduction of pavement service life from 13 to 7 years. For a 40-year period, this translates to a three-fold increase in life-cycle cost for a 250-ft-long pavement section. Reducing moisture retention through various means, thereby improving the subsurface drainage quality of flexible pavement systems, can achieve substantial long-term savings.
Biaxial Testing to Investigate Soil-Pipe Interaction of Buried Fiber-Reinforced Cement Pipe
Authors: Moore Ian D. , Lapos Brian , Mills Cameron
Published: May 2007

Three tests were performed to develop baseline information on the behavior of fiber-reinforced cement (FRC) pipe under biaxial loading. Pipes were instrumented to measure circumferential strains at various locations around the circumference and to capture changes in vertical and horizontal pipe diameter. The first two tests examined the response of wet and dry pipes under conditions simulating steadily increasing overburden pressure in an embankment loading condition, reaching earth pressures equivalent to more than 15 m. The third test examined the time-dependent response of a second, wet pipe under sustained pressure of 180 kPa. Elastic soil-pipe interaction theory shows that increases in pipe deformation lead to a redistribution of loads to the surrounding ground and reductions in bending moments. Preliminary calculations for the three pipe tests indicated that, even in the low modulus backfill, the pipe deformations were sufficient to reduce applied earth pressures on the pipes and the bending moments within them. These pipes exhibited semirigid behavior, in which bending moments were reduced below levels experienced by a rigid pipe. Bending moment decreases were greater for the wet pipe than for the dry pipe because the wet specimens had lower manufactured wall thickness and wet FRC has a lower modulus. Reductions in the modulus of the FRC material were estimated to decrease moments by approximately 30% by the end of the 50-h time period of the third test and by approximately 36% at the peak overburden pressure (300 kPa) reached during the second test.
Lateral Load Behavior of Cast-in-Drilled-Hole Piles in Weakly Cemented Sand
Authors: Juirnarongrit Teerawut , Ashford Scott A.
Published: May 2007

Naturally occurring, weakly cemented sand is common along the southern California coast, as is the practice of using cast-in-drilled-hole (CIDH) piles in this type of soil. However, information on the lateral load behavior of piles for this soil type is limited. In current design practice, the standard p-y curves for sand are frequently used to analyze the lateral pile responses in cemented sand by neglecting the resistance from the soil cohesion. However, the accuracy of using these p-y curves for weakly cemented sand has not been evaluated, particularly for a wide range of pile diameters. Therefore, instrumented CIDH piles with diameters ranging from 0.4 to 1.2 m were installed in dense, weakly cemented sand and tested under lateral loading. On the basis of a comparison of backcalculated p-y curves for different pile diameters, the effect of pile diameter on the p-y curves was insignificant at load levels below the ultimate lateral soil capacity. Furthermore, the standard p-y curves currently available in the literature were implemented to compute the pile responses and were compared with the measurements. Using the standard p-y curves underestimated the soil resistance in weakly cemented sand for small diameter piles but tended to overestimate the soil resistance to large diameter piles. Therefore, the use of these standard p-y curves for large-diameter piles in weakly cemented sand should be used with caution.
Mobilization of Passive Earth Pressures Behind Abutments of Jointless Bridges
Authors: Arsoy Sami
Published: May 2007

Bridges without expansion joints are referred to as integral bridges. The abutment and the superstructure of integral bridges act as a single structural unit. As the temperature of an integral bridge changes, the length of the bridge increases and decreases. The changes push the abutment against the approach fill and pull it away and thus cause lateral deflections. The movement of the abutment into the approach fill develops passive earth pressure that is displacement dependent. Although earth pressures are detrimental for the substructure of a bridge, they are beneficial for the superstructure because they reduce the bending moments caused by the dead loads and the live loads in the bridge girders. Therefore, relying on the beneficial effects of the full passive earth pressures, regardless of the displacement, is not conservative. Charts are proposed to estimate the magnitude of the resultant force and the point of application of the resultant force as a function of the wall displacement. Medium-dense and dense granular backfill materials were considered in developing the charts. The need for estimating the maximum mobilized passive earth pressures for jointless bridges with cohesionless backfill may be fulfilled with the proposed charts.
Long-Term Performance of Broken and Seated Pavements
Authors: Rajagopal Arudi , Minkarah Issam , Green Roger , Morse Aric
Published: May 2007

A study was developed to evaluate the effectiveness of breaking and seating (B/S) as a rehabilitation strategy for retarding reflective cracking in asphalt concrete (AC) overlays on jointed reinforced concrete pavements (JRCP). Several test sections were constructed by milling the original AC layer, breaking and seating the concrete slabs, and constructing new AC overlays. Control sections were constructed adjacent to the B/S sections in the same way, but without breaking the underlying concrete slabs. Two types of pavement breakers were used in this study: guillotine and pile hammer. The majority of the concrete slabs were broken into 0.46-m (18-in.) segments. Performance of the test sections was monitored for a total period of 9 years. Breaking the concrete slabs into smaller pieces resulted in a reduction in the flexural strength, an increase in the surface deflection (50% to 100%), and a decrease in area and spreadability (20% to 30%). Within 2 to 4 years, reflection cracks developed over more than 80% of the joints in all the control sections. The B/S sections were relatively free of cracks after 9 years. This result clearly indicates that breaking and seating has been extremely effective in minimizing and delaying reflection cracking. Based on the results of this study, it was concluded that breaking and seating is an effective technique for the rehabilitation of composite pavements (AC over JRCP). It provides an effective solution for the maintenance and rehabilitation of in-service composite pavements.
Field Performance Evaluation of Class C Fly Ash in Full-Depth Reclamation: Case History Study
Authors: Wen Haifang , Tharaniyil Mathew P. , Ramme Bruce , Krebs Steve
Published: May 2007

Class C fly ash is a coal combustion product from lignite or subbituminous coal obtained as a result of the power generation process. In recent years, efforts were taken to incorporate self-cementing fly ash into fulldepth reclaimed (FDR) material to improve the structural capacity of asphalt pavement base layers. In this study, existing asphalt pavement in County Trunk Highway (CTH) "JK" in Waukesha County, Wisconsin, was pulverized in place and mixed with fly ash and water to function as a base course. To evaluate the contribution of fly ash to the structural performance of the pavement, nondestructive deflection tests were performed with a KUAB 2m falling weight deflectometer on the outer wheelpath 4 days and 1 year after construction. The modulus of fly ash- stabilized FDR base course increased by 49% 1 year after construction. The structural capacity of the fly ash-stabilized FDR base course in CTH JK also has increased significantly as it ages, because of the pozzolanic reaction. The results of this study indicate that the FDR mixes with selfcementing fly ash may provide an economical method of recycling flexible pavements and reduce the need for expensive new granular base courses for road reconstruction.
Experience with Cold In-Place Recycling as a Reflective Crack Control Technique: Twenty Years Later
Authors: Morian Dennis A. , Oswalt Jeffrey , Deodhar Akshay
Published: May 2007

Cold in-place recycling (CIR) of existing hot-mix asphalt materials has been an available treatment for more than 20 years. A study evaluated the performance of CIR projects and materials over that period. Contractors in northwestern Pennsylvania have constructed a total of 44 pavement sections. Ninety additional sections have been recycled as part of maintenance activities. (The latter are not included among the study sections.) A subset of these projects has been evaluated to determine performance characteristics and cost-effectiveness of the treatment and the material. The treatment is used typically on rehabilitation projects of roadways with 8,000 average daily traffic (ADT) or less but has been used on projects with up to 13,000 ADT. The performance of CIR in resisting reflective cracking from underlying concrete pavements and material properties over time is discussed. Material layer stiffness was evaluated using backcalculation of deflection measurement methods. Additionally, the cost of constructing these rehabilitation projects and their average cost-effectiveness are discussed.
Novel Method for Backcalculation of Asphalt Pavement Moduli
Authors: Zhang Xiaoning , Sun Lijun
Published: May 2007

There are many methods available for backcalculating pavement layer moduli. Because most use basin matching, they share similar drawbacks: the procedure may not converge, and the solution is probably not unique. Extensive calculations have revealed the existence of a point on the surface deflection basin, termed the "inertial point," whose deflection does not vary with the modulus of the upper layer. The relationship between the inertial point parameters and the structure information is established mathematically. The inertial point can be found directly from that relationship, and the subgrade modulus can be predicted as a by-product. Another important observation is that the surface course stiffness has a significant influence on the shape of the deflection basin near the loading center. From this observation, an iterative algorithm is developed to estimate the moduli of both the surface and base courses. The backcalculation method proposed will always obtain a unique solution because of the novel solution procedure used.
Enhancing Backcalculation Procedures Through Consideration of Thickness Variability
Authors: Zaghloul Sameh , Hoover Tom , Swan D. J. , Vitillo Nick , Sauber Robert , Jumikis Andris A.
Published: May 2007

Pavement structural performance and in situ structural capacity are evaluated by performing deflection testing and backcalculation analysis. Layer thickness information obtained from as-built data and core-bore logs is an essential input for this analysis and has significant impact on the backcalculated layer moduli. However, as-built records are not always available, and they provide general layer thickness information. Also, the number of cores and bores is limited because of their destructive nature. The current practice of backcalculation uses the common assumption that a pavement section has constant layer thickness, with allowable tolerance ignored, and that all variability in the measured deflection is related to variability in material stiffness. A pavement section is not expected to have identical thickness along its length. Also, pavement materials are undeniably nonhomogeneous and have variable stiffness along section length. However, this variability is expected to be within reasonable limits, especially for relatively new pavements constructed in accordance with stringent construction specifications and material properties and which exhibit similar distresses and deflections. A procedure was developed to account for the normal variability in layer thickness (allowable tolerance). This procedure is outlined and an implementation example is provided. The impact of ignoring the allowed variability in layer thickness on the backcalculation results, as well as on the design pavement moduli that are used in the rehabilitation analysis and design, is discussed.
Linear and Nonlinear Backcalculation for Site 1 in Hanover, New Hampshire
Authors: Uzan Jacob
Published: May 2007

Site 1 in Hanover, New Hampshire, is a test section with surface deflection, stress, and strain measurements. The data are used to perform linear and nonlinear backcalculation of pavement layer moduli and material parameters from the deflection bowls. The data show clearly that the pavement response is nonlinear and the following trends are observed: ( a) the base material stiffens relative to the subgrade as the load increases and ( b) the upper subgrade becomes softer as the load increases. The procedures and material characterization for linear and nonlinear analyses are presented. The nonlinear one uses an axisymmetric finite element program to compute displacements, stresses, and strains. The results of the backcalculation (using deflection bowls only) show better fit of the surface deflections with the nonlinear than with the linear approach. The linear procedure seems to introduce a systematic error in the fit. The nonlinear approach predicts a distribution of moduli in the structure that is acceptable from an engineering point of view. With the parameters obtained from backcalculation, displacements and stresses are computed and compared with the measured ones. It seems that the computed response differs from the measured one by a factor of about 1.5. The prediction of stresses and strains is slightly better with the nonlinear than with the linear procedure.
Impact of Overlays on Pavement Rutting and Their Interactions with Design and Material Quality
Authors: Mishalani Rabi G. , Kumar Ashutosh
Published: May 2007

Pavement performance over its life cycle is influenced by initial quality provisions and the factors that affect its condition during its operation. A study was conducted to assess the interaction between these types of variables, namely, initial design and material quality on the one hand and maintenance actions on the other. An earlier study was not able to capture separately the influence of initial design and material quality on pavement condition when maintenance actions were applied because of limitations in the deterioration model employed. In the present study a recently developed pavement rutting model was used to capture the effects these two initial quality variables, in conjunction with overlay maintenance applications, had on the life-cycle performance of roadways. The results indicate that the nature of the interactions between maintenance and design and between maintenance and material quality differs. When overlays are applied, rut depths under different design levels converge to a single constant value over the long run. However, under different material quality levels, rut depths converge to different constant values. Moreover, in absolute terms the sensitivity of the cumulative deterioration to design decreases to a small value as overlay frequency increases. However, the sensitivity with respect to material quality increases in absolute terms as the overlay frequency increases. Therefore, on the one hand, design and maintenance can substitute for one another with regard to rut progression; on the other hand, high maintenance frequency is necessary for reaping the value of high material quality.
Dynamic Time Domain Backcalculation of Layer Moduli, Damping, and Thicknesses in Flexible Pavements
Authors: Chatti Karim , Ji Yigong , Harichandran Ronald
Published: May 2007

A dynamic time domain method was developed to backcalculate the layer moduli, damping ratios, and thicknesses of asphalt pavements from dynamic falling weight deflectometer test data. The method uses the SAPSI program as a forward routine and a Newton-Raphson method for the backcalculation. The advantage of the time domain approach is that SAPSI can match selected features of the measured time histories directly, and inaccurate measurements at the ends of histories can be ignored. The peak deflections and the time lag between the peak of the load and the peak of the deflections at different sensors are matched. The Newton algorithm in MICHBACK is adopted to perform the backcalculation. The new algorithm is capable of backcalculating the moduli, damping ratios, and thicknesses of three-layer flexible pavements reasonably well. Backcalculations based on synthetic time histories generated using SAPSI show excellent stability and accuracy. Backcalculation using measured time histories yields less accurate results. Possible sources for the discrepancies when using field data are addressed.
Assessment of Overlay Roughness in Long-Term Pavement Performance Test Sites: Canadian Case Study
Authors: Smith James T. , Tighe Susan L.
Published: May 2007

A study was conducted on asphalt pavement overlay performance in the Canadian environment. It investigated the impact of asphalt overlay thickness, climatic zone, and subgrade type on the progression of roughness as described by the international roughness index (IRI). Data from the Canadian Long-Term Pavement Performance (LTPP) test sites were analyzed. As a result of the investigation, pavement factors that significantly impact overlay performance in the Canadian environment were identified. Data collected over the first 13 years of study were used to show national and provincial roughness trends from 53 test sites. The IRI data were statistically summarized (mean, standard deviation) for each category by the age of the overlay section. With the summarized data, regression analysis was used to determine an equation that best describes the progression of roughness. Two-factor analysis of variance was used to determine if there were any significant differences within specific categories. The results of the regression analysis were compared with the Canadian Strategic Highway Research Project LTPP to confirm the validity of the roughness progression equations. Results show that overlay thickness and climatic zones significantly impact the roughness, while subgrade type has little influence on the IRI values. The roughness progression equations achieved squared correlation coefficients ( R2) between 0.93 and 0.39, demonstrating the accuracy of the model equations.
Precision of Locked-Wheel Testers for Measurement of Roadway Surface Friction Characteristics
Authors: Choubane Bouzid , Holzschuher Charles R. , Gokhale Salil
Published: May 2007

The present state-of-the-art locked-wheel testers for roadway surface friction evaluation are fully automated. As with any testing using subjectdriven instrumented devices, the major concerns of the end usefulness of the resulting data are accuracy and precision. Although a level of uncertainty is always inherent in any measurement process, it must also be appropriately quantified or assessed. Therefore, the Florida Department of Transportation (FDOT) initiated a field study to assess the level of precision of its own locked-wheel testers for field measurements. Friction measurements were acquired by using four friction locked-wheel testers concurrently on a number of asphalt section sites. These test sections were randomly selected to include both open- and dense-graded surface mixtures. The collected friction data were first analyzed to determine the friction characteristics at each test location, in terms of a friction number at 40 mph with a standard ribbed test tire (FN40R). The results were then used as a basis for an evaluation of the repeatability and reproducibility of the friction units. In addition, the effects of pavement surface texture on friction measurements were assessed. A description of the testing program, the data collection effort, and the subsequent analyses and findings is presented.
Characterizing Road Roughness by Wavelet Transform
Authors: Wei Liu , Fwa T. F.
Published: May 2007

Summary roughness statistics are commonly used by highway agencies to characterize road roughness profiles to provide convenient numerical indices for pavement performance monitoring and management planning. Many different roughness indices have been used by different highway agencies worldwide. Unfortunately, since different indices are computed with different considerations and mathematical procedures, they often do not correlate with one another well. This presents a practical problem for exchange of information and experience among practitioners or highway agencies. A proposal is presented for the use of wavelet transform to overcome this problem. Wavelet transform can represent detailed pavement roughness features of different wavelengths quantitatively in terms of wavelet energy. The usefulness of wavelet transform representation of pavement roughness profiles was studied by analyzing the roughness data of 200 flexible pavement and 200 rigid pavement sections. Comparisons were made with four common roughness indices, namely, the international roughness index (IRI), rootmean-square vertical acceleration (RMSVA), mean absolute vertical acceleration (MAVA), and slope variance (SV). It was found that IRI, RMSVA, MAVA, and SV had pairwise coefficients of multiple determination ( R2) ranging from 0.18 to 0.75. But wavelet energy statistics had an R2 of at least 0.857 with each of the roughness indices. Therefore, wavelet energy statistics can be a useful common basis to relate different forms of pavement roughness measures.
Bay Area Rapid Transit's Comprehensive Station Plans: Integrating Capacity, Access, and Land Use Planning at Rail Transit Stations
Authors: Connolly Kevin , Payne Marianne
Published: May 2007

Planning at transit stations often involves an uneven field of stake-holders with varying degrees of interest in a station and its immediate area. Because a controlling influence among these stakeholders is usually absent, rail transit agencies often divide station area planning into its component parts and work with appropriate partners to develop plans and strategies for future investment. Although this approach is practical and expedient, it often ignores the integrated nature of a transit station, its surrounding land uses, and the larger transportation network. The San Francisco Bay Area Rapid Transit (BART) district—a heavy rail mass transit system serving the Bay Area—has recently completed a series of planning studies meant to integrate station capacity, access, and land use development. The overriding goal of a comprehensive station plan (CSP) is to create a consensus for future investment by partner agencies, the private sector, and BART alike. This new approach has been undertaken in direct support of BART's strategic plan, adopted in 1999, which has advanced a range of new policies and programs that ultimately have led to the CSP process. An overview of the CSP process is based on BART's initial experience at its Pleasant Hill Station along with examples from Balboa Park and Union City. How the CSP process integrates the components of station capacity, access, and area development to create a well-balanced investment strategy is also considered. Finally, the guidance in BART's strategic plan and achieving the plan's goals are particularly emphasized.