bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling Incremental Pavement Deterioration by Integrating Pavement and Intermodal Management System Data Bases
Authors: Andres Kevin M. , Tolliver Denver D.
Published: January 2019

The U.S. Congress mandated the development of six transportation management systems with the passage of the Intermodal Surface Transportation Efficiency Act of 1991. Each of these management systems provides transportation planners with an inventory of transportation facilities and associated performance data that can be used to relate the performance of the facility. Toward the end of achieving better transportation planning, the management systems can be further integrated to yield a powerful transportation planning tool that can be used to analyze and quantify the pavement needs of intermodal facilities. Pavement designers can use this tool for traffic forecasting to allow more representative pavement designs. Transportation planners can also use this tool to predict the results of changes in shipping practices before they occur. The described procedure greatly enhances the transportation planning process by allowing the process to be more proactive rather than reactive. Modal shifts in freight traffic can result in significantly increased highway maintenance costs. These shifts can be induced by changes in the regulatory or fiscal policies governing transportation or by physical changes in the transportation infrastructure. As an example, the abandonment of a set of branch lines is analyzed to determine the increased highway maintenance costs that would result if all shipments currently carried by rail along the branch lines were diverted to truck transportation. A background of the transportation management systems and their application to transportation planning is provided.
Artificial Neural Network for Selecting Pavement Rehabilitation Projects
Authors: Flintsch Gerardo W. , Zaniewski John P. , Delton James
Published: January 2019

The use of an artificial neural network simulator to develop and implement an automatic procedure for screening and recommending roadway sections for pavement preservation is described. This procedure is part of an automatic project recommendation procedure extension of the Arizona Department of Transportation's (ADOT's) pavement management system. The output of the recommendation procedure is a list of candidate projects for consideration in the 5-year pavement preservation program. The artificial neural network simulator was used to “learn” the knowledge from historical project selection. The neural network was trained with the pavement condition and characteristics and the sections selected for the ADOT's pavement preservation program for several years. The trained neural network predicted a correct output for 100 percent of the training facts and 76 percent of the testing examples. Further refinements of the artificial neural network architecture should result in better-performing networks. The artificial neural network analysis reduces the level of effort required to identify candidate sections for the pavement preservation program, reduces subjectivity, and minimizes the probability of missing sections that should be programmed.
Performance Trends for Portland Cement Concrète General Aviation Pavements in Illinois
Authors: Van Dam Thomas , Bildilli James
Published: January 2019

The deterioration and performance of portland cement concrete general aviation (GA) airport pavements in Illinois are discussed. Two popular design procedures are reviewed, and typical GA pavement sections are structurally evaluated by using the ILLI-SLAB finite-element model. Subjected to GA pavement loading conditions, 125- and 150-mm-thick slabs would be considered structurally adequate, whereas 100-mm-thick slabs would not be expected to perform well. It was determined that slab size, as determined by the ratio of the slab length over the radius of relative stiffness (L/ l) was strongly correlated to pavement distress and performance. As the slab size was increased higher incidences of distress at higher severity levels were observed. Performance trends were identified by using a deterioration rate approach that accounts for the performance of individual sections. It is believed that this procedure reflects actual performance trends by addressing the issues of long-lived pavement sections, the impact of maintenance, and the influence of inspection variability.
Reliability-Based Processing of Markov Chains for Modeling Pavement Network Deterioration
Authors: Li Ningyuan , Xie Wei-Chau , Haas Ralph
Published: January 2019

Accurate prediction of pavement deterioration is the most important factor in the determination of pavement repair years and optimization programming of highway network maintenance. The Nonhomogeneous Markov Probabilistic Modeling Program, developed to determine pavement deterioration rates in different stages, is described. In this program the transition probability matrices (TPMs) are considered as a time-related transition process. Each element of the TPMs is determined on the basis of a reliability analysis and a Monte Carlo simulation technique. This avoids the use of the existing conventional methods, which involve taking an average subjective opinion of pavement engineers or observing a large number of multiyear pavement performance data and conducting a number of statistical calculations. As a result a series of TPMs for an individual pavement section for different stages can be determined by running the program. Furthermore, the pavement condition state in terms of a probability vector at each stage (year) is calculated. In applying the models both the predicted actual traffic (in terms of equivalent single axle loads) at each stage and the maximum traffic that the pavement can withstand at each defined pavement condition state interval are considered to be random variables. In addition, the sensitivities of pavement deterioration rates to pavement design parameters, such as traffic growth rate, subgrade strength, and material properties, are studied. Finally, an example of calculating the TPMs for a pavement section located in southeastern Ontario, Canada, is demonstrated. It shows that the sensitivities of the TPMs to traffic growth rate, subgrade deflection, and pavement thickness are significant.
Methodology for Estimating Remaining Life of Continuously Reinforced Concrete Pavements
Authors: Dossey Terry , Easley Steve , Mccullough B. Frank
Published: January 2019

A methodology was developed for estimating the remaining life of a nonoverlaid continuously reinforced concrete pavement. The models presented use several key predictors: the early-age crack distribution pattern in the concrete caused by volumetric changes, the coarse aggregate type used, and the presence or absence of a swelling subgrade that will accelerate the rate of failure development in later life due to dynamic loadings. Considering these factors, the models can accurately estimate the additional 18-kip equivalent single axle loads (ESALs) that will take the pavement from its current condition in terms of failures per mile (FPM) to a user-defined “failure threshold,” such as 10 or 15 FPM. Using traffic models developed in another study, the number of additional ESALs to failure can be translated into time to failure for planning purposes. The overall objective of the analysis is to determine the optimum time to overlay—before failure and preferably before the onset of irreparable damage to the pavement.
A Different Perspective for Investigation of Portland Cement Concrete Pavement Deterioration
Authors: Marks Vernon J. , Dubberke Wendell G.
Published: January 2019

Many early Iowa portland cement concrete (PCC) pavements provided good performance without deterioration for more than 50 years. In the late 1950s, Iowa was faced with severe PCC pavement deterioration called D-cracking due to crushed limestone containing a bad pore system. Selective quarrying solved the problem. In 1990, cracking deterioration was identified on a 3-year-old US-20 pavement in central Iowa. The coarse aggregate was a crushed limestone with an excellent history of performance in PCC pavement. Examination of cores showed very few cracks through the coarse aggregate particles. The cracks were predominately confined to the matrix. A high-resolution, low-vacuum Hitachi scanning electron microscope with an energy dispersion detector was used to investigate the deterioration. Subsequent evaluation identified a very small concentration of silica gel (silicon) but substantial amounts of sulfur and aluminum (assumed to be ettringite) in the air voids. Some of these voids have cracks radiating from them leading to the conclusion that the ettringite-filled voids were centers of pressure causing the cracks. The ettringite in the voids, after being subjected to sodium chloride brine, initially swelled and then dissolved. The research has indicated that the premature deterioration may be due to ettringite and may have been mistakenly identified as alkali-silica reactivity.
Development of Jointed Concrete Pavement Database for State of Texas
Authors: Dossey Terry , Ruiz Mauricio , Mccullough B. Frank
Published: January 2019

A jointed concrete pavement database was developed as part of a pavement information management system for Texas. Topics discussed include the identification of variables, a statewide selection of pavement projects using an experimental factorial design, and the collection of performance information through a visual condition survey. A preliminary distress index for jointed pavements is also presented. In this analysis, the distress variables collected in the field are reduced to a single performance value and related statistically to the various design variables of the pavement projects investigated.
Analysis of Anchor Mooring Lines in Cohesive Seafloor
Authors: Bang S. , Taylor R. J. , Yu Jie , Kim H. T.
Published: January 2019

An analytical solution method capable of determining the geometric configuration and developed tensile forces of mooring lines associated with fixed plate/pile or drag anchors embedded in cohesive seafloor has been developed. The solution method is capable of analyzing multisegmented mooring lines embedded in layered cohesive seafloor soils, utilizing a systematic iterative solution search method based on specified boundary conditions. The results of the developed analytical solution method have been verified through comparisons with the centrifuge model tests and field tests and were found to be very effective.
Using Cone Penetration Test to Determine Drained Friction Angle of Sands
Authors: Huang X. H. Shen , Juang C. H.
Published: January 2019

Existing relations that are commonly used for determining the drained friction angle (Φ’) of sands using tip resistance (qc) from a cone penetration test are examined. Emphasis is placed on reducing the uncertainty associated with these qc-Φ’ relations. A methodology is developed by which the uncertainty in these relations, called model uncertainty, may be reduced through the use of an aggregation technique based on characterization of sand compressibility. Case studies are presented to illustrate the entire methodology. Results of the case studies show that the uncertainty associated with these qc-Φ’ relations may be reduced and the reliability of the estimated drained friction angle may be improved.
Reliability-Based Design of Reinforced Earth Retaining Walls
Authors: Basheer Imad A. , Najjar Yacoub M.
Published: January 2019

Reliability of an earth structure can be assessed from the knowledge of the governing probability distribution and its related statistical parameters, namely, the mean and variance. In this study, the mean and variance for the design parameters (width and length of the reinforcing ties) of reinforced earth retaining walls supporting sandy soils are determined using the first-order Taylor series approximation. Design diagrams that enable estimation of both mean and variance also are developed to avoid extensive computations that involve partial differentiation. Errors associated with truncating second-order terms are also evaluated. It is found that for soils with moderately variable physical parameters, the first-order approximation is adequate for estimating both the mean and variance.
Liquefaction Risk Assessment: Evaluation of Three Statistical Models
Authors: El Zahaby Khalid M. , Rahman M. S.
Published: January 2019

One approach to liquefaction risk assessment is based on a comparison of the earthquake and soil parameters for the site under study to those known to have either caused or not caused liquefaction at other sites during earlier earthquakes. In this study, three statistical models for liquefaction risk assessment are evaluated and compared. Both linear and nonlinear discriminant analyses are performed on the same set of historical data. It is found that the model with an energy-based formulation for the development of pore water pressure results in the least number of misclassified cases of liquefaction and nonliquefaction. The main conclusion derived from this study is that the use of an integral measure of seismic action, viz., dissipated energy, may result in a better assessment of liquefaction risk.
Development of Computer Vision Technique for in Situ Soil Characterization
Authors: Hryciw Roman D. , Raschke Scott A.
Published: January 2019

Construction and rehabilitation of highways, tunnels, and bridges require detailed information about subsurface stratigraphy. This study presents development of a new method for characterizing subsurface soil in situ using computer vision. Hardware and software systems are integrated to obtain the grain-size distribution (GSD) of subsurface soils continuously with depth and to identify small-scale subsurface anomalies. Research is being conducted in three phases. The first phase consists of measuring the GSD of detached cohesionless soil specimens in the laboratory from digital images obtained with a computer vision system (CVS). The second phase uses the CVS to develop image processing and analysis techniques to classify soil assemblies in the laboratory and identify subsurface anomalies by simulating the manner in which images will be acquired in situ. A texture analysis approach has been developed that can detect changes in stratigraphy. The technique has been successful in identifying different types of dry, uniformly graded soils. Finally, a subsurface vision probe is being designed and constructed that will capture video images at three different levels of magnification continuously with depth.
Determination of Internal Deformation Field in Asphalt Cores Using X-Ray Computer Tomography
Authors: Synolakis Costas Emmanuel , Zhou Zenyou , Leahy Richard M.
Published: January 2019

Although existing nondestructive evaluation methods and transducers provide useful quantitative information on composite materials, they measure only macroscopic deformations and, often, only after the strain has exceeded a certain predetermined threshold. It is well established, however, that maintenance intervention is more effective if applied early in the deformation process. A new method for computing the microscopic internal displacement fields associated with permanent deformations of three-dimensional asphalt-aggregate cores with complex internal structure and satisfying the small gradient approximation of continuum mechanics is presented. The displacement fields are computed from a sequence of three-dimensional X-ray computed tomography images, obtained using a new imaging protocol developed specifically for mass-fraction and mix-density estimates of composite cores. By assuming that the image intensity of the tomographic images represents a certain conserved property that is incompressible, a constrained nonlinear regression model for motion estimation is developed. Successive linear approximation is then employed and each linear subsidiary problem is solved using variational calculus. The resulting Euler-Lagrange equations are approximated and solved using finite differencing methods and a conjugate gradient algorithm in a multiresolution framework. The method is validated using pairs of synthetic images of plane shear flow. The three-dimensional displacement field in the interior of a cylindrical asphalt/aggregate core loaded to a state of permanent deformation is calculated using this method.
Development of Digital Image-Processing Algorithm to Compute Unified Crack Index for Salt Lake City
Authors: Jitprasithsiri Siriphan , Lee Hosin , Sorcic Robert G. , Johnston Richard
Published: January 2019

This paper presents the recent efforts in developing an image processing algorithm for computing a unified pavement crack index for Salt Lake City. The pavement surface images were collected using a digital camera mounted on a van. Each image covers a pavement area of 2.13 m (7 ft) × 1.52 m (5 ft), taken at every 30-m (100-ft) station. The digital images were then transferred onto a 1-gigabyte hard disk from a set of memory cards each of which can store 21 digital images. Approximately 1,500 images are then transferred from the hard disk to a compact disc. The image-processing algorithm, based on a variable thresholding technique, was developed on a personal computer to automatically process pavement images. The image is divided into 140 smaller tiles, each tile consisting of 40 × 40 pixels. To measure the amount of cracking, a variable threshold value is computed based on the average gray value of each tile. The program then automatically counts the number of cracked tiles and computes a unified crack index for each pavement image. The crack indexes computed from the image-processing algorithms are compared against the manual rating procedure in this paper. The image-processing algorithms were applied to process more than 450 surveyed miles of Salt Lake City street network.
Relating Failure Tests Performed in Hollow Cylinder Apparatus to Inherent Anisotropy
Authors: Richardson Ian Reginald , Chapman David Neil , Brown Stephen
Published: January 2019

Described are failure tests performed on a fine-grained Leighton Buzzard sand in the Nottingham hollow cylinder apparatus. These tests were conducted to characterize the inherent anisotropy of the material formed during the sample preparation procedure. An image analysis procedure for determining preferred particle orientation is introduced and its derivation discussed. An attempt is subsequently made to relate the statistically significant preferred orientation to the anisotropic shear strength properties of the Leighton Buzzard sand.
Simplified Rapid Assessment Approach to Road Network Management
Authors: Liautaud Gerard , Faiz Asif
Published: January 2019

A simplified approach, using limited network-specific data and the recently developed World Bank HDM Manager, was applied to the highway network of Peru to provide interim guidelines on appropriate standards and policies to be implemented, pending the results of a more elaborate study involving a full-scale road condition and traffic inventory. The design of the methodology is described, as is its application to define the best maintenance strategies for paved and unpaved road networks. The order of magnitude of the level of expenditures required is determined, and a tentative prioritization scheme for road activities is developed.
Experiments with Anti-Icing in Washington State
Authors: Dye David L. , Krug Harry O. , Keep Dale , Willard Raymond
Published: January 2019

Many transportation agencies are feeling pressure to become more efficient in delivering maintenance products and services, including winter operations. Nowhere is this pressure greater than in Washington State, where elected officials and the public are demanding increased levels of service despite service-delivery cost increases and a decreased maintenance budget. In an attempt to meet these demands, the Washington State Department of Transportation (WSDOT) is conducting research on the cost-effectiveness of anti-icing, or pretreatments. The results of the first year of a 2-year research project are documented. The objectives of the research are to (a) determine the effectiveness of pretreatment operations in a variety of winter conditions, (b) determine the cost of the pretreatment operations and compare it with the cost of traditional winter operations in the same geographical area, and (c) provide recommendations for widespread implementation of pretreatment procedures within WSDOT if feasible and cost-effective. Three case studies are documented; in all cases, pretreatment operations provided a level of service comparable to that of past traditional operations. In addition, traditional winter operation methods were estimated to cost 3 to 11 times as much as pretreatment methods. More case studies and an expanded pretreatment program in WSDOT are planned for 1995–1996.
Pitfalls of Using R2 to Evaluate Goodness of Fit of Accident Prediction Models
Authors: Miaou Shaw-Pin , Lu An , Lum Harry S.
Published: January 2019

In developing statistical models of traffic accidents, flow, and roadway design, the R2 goodness-of-fit measure has been used for many years to (a) determine the overall quality and usability of the model, (b) select covariates for inclusion in the model, (c) make decisions as to whether it would be worthwhile to collect additional covariates, and (d) compare the relative quality of models developed from different studies. The pitfalls of using R2 to make these decisions and comparisons are demonstrated through computer simulations of commonly used accident prediction models, including the Poisson and negative binomial regression models. Because accident prediction models are nonnormal and functional forms are typically nonlinear, it is shown that R2 is not an appropriate measure to make any of the decisions and comparisons mentioned. Also, three properties are identified as desirable for any alternative measure to appropriately evaluate these models: (a) it should be bounded between 0 and 1—a value of 0 if no covariate is included in the model and a value of 1 if all the necessary covariates are included; (b) it should increase proportionally as equally important, independent covariates are added to the model one at a time, regardless of their order of selection; and (c) it should be invariant with respect to the mean (i.e., the value of the measure should not change by simply increasing or decreasing the value of the intercept term). Finally, two recent research efforts aimed at developing alternative measures with such properties are briefly reported.
Bayesian Assignment of Coverage Count Locations to Factor Groups and Estimation of Mean Daily Traffic
Authors: Davis Gary A. , Guan Yuzhe
Published: January 2019

Mean daily traffic (MDT) is the expected traffic volume at some site on a typical day, and it is usually estimated from short-count data by computing average daily traffic (ADT) and then correcting this ADT for the season or day of week of the count. Although considerable guidance exists on how to construct seasonal factor groups from automatic traffic recorder counts, less guidance is available on how to select the appropriate factors for correcting a particular short count or for estimating MDT when the appropriate factors are uncertain. A data-driven approach to assigning highway sites to factor groups using arbitrary samples of daily traffic counts, a method for designing traffic count samples to minimize the likelihood of assigning the site to the wrong factor group, and a Bayes estimator of MDT are described. A likelihood function describing the sample count is combined with prior estimates of the probabilities that a site belongs to each factor group to produce posterior classification probabilities. The site is then assigned to that factor group showing the highest posterior classification probability. The classification method is evaluated by using actual traffic data and appears to perform reliably with 14-day samples. A Bayes estimator of MDT is then developed, which is applicable even when it is unclear to which factor group a short-count site ought to be assigned. This estimator is evaluated by using actual data, and it also performs creditably with 14-day samples.
Rate-Quality Control Method of Identifying Hazardous Road Locations
Authors: Stokes Robert W. , Mutabazi Madaniyo I.
Published: January 2019

A brief historical perspective on the development of the rate-quality control method and its use in the identification of hazardous roadway locations is presented. The evolution of the formulas used in the rate-quality control method from their origin in the late 1950s to their present form is traced. The derivation of the basic formulas used in the method is also presented and discussed. It is suggested that, contrary to assertions in the literature, the accuracy of the equations used in the rate-quality method is not improved by eliminating the normal approximation correction factor from the original equations. The need for the correction factor is particularly apparent at higher probability levels. Charts are provided for determining an appropriate correction factor for those who may wish to incorporate these factors into the equations.
Initial Improvement in Ride Quality of Jointed, Plain Concrete Pavement with Microsurfacing: Case Study
Authors: Moulthrop James S. , Day Larry , Ballou W. R.
Published: January 2019

Safety, cost, ride quality, and performance are characteristics of pavement systems that are considered high-priority customer demands by transportation agencies throughout the world. Ride quality is the characteristic most notable to the traveling public. Throughout the United States, numerous state and federal agencies have developed specifications that require that road contractors meet a minimum level of ride quality before a pavement is approved for payment. Studies have shown that initial (as constructed) ride quality is an important factor in determining overall serviceability and length of time to rehabilitation or reconstruction. A case study in Cowley County, Kansas, in which the ride quality of an existing jointed, plain concrete pavement was significantly improved by the placement of a thin, polymer-modified, asphaltemulsion microsurfacing system, is described. The existing pavement conditions, the construction techniques used by the contractor, and the smoothness measurements before and after construction are noted and discussed. It was found that a marked reduction in roughness can be accomplished with unique construction techniques and microsurfacing.
Evaluation and Implementation of Automated Profilogram Reduction System: APPARE
Authors: Zhu J. Jim , Zhu Wenli , Smailus Thomas , Martinez Mark
Published: January 2019

APPARE is a personal computer–based scanner and software system to aid in automated pavement profile analysis and roughness evaluation. The system was developed for the Louisiana Department of Transportation and Development (LDOTD) and the Louisiana Transportation Research Center (LTRC). It analyzes the statistical properties of road-pavement profiles and reports their roughness according to indexes such as the international roughness index and the profile index. APPARE can process profilograms and other digitized road profiles. Field evaluation results conducted by LTRC and Districts 03, 04, and 62 of LDOTD on a total of 126.8 km (79.1 mi) of newly constructed pavements are reported. On the basis of these extensive test data and comparison of APPARE with alternatives, LDOTD recently decided to adopt APPARE as its standard profilograph test procedure for quality control and acceptance of newly constructed pavement. Statewide implementation of APPARE is under way, and a new profilograph test procedure, DOTD TR 641, is being developed by the Materials and Testing Section of LDOTD. The implementation was complete by the end of 1995. In addition, LTRC has moved that the blanking-band profile index be abolished and that the international roughness index evaluated by APPARE be used instead as the standard roughness index reported by a profilograph.
Prediction of Low-Temperature Cracking of Asphalt Concrete Mixtures with Thermal Stress Restrained Specimen Test Results
Authors: Zubeck Hannele K. , Vinson Ted S.
Published: January 2019

A deterministic model and a probabilistic model were developed to predict low-temperature crack spacing as a function of time using thermal stress restrained specimen test results, pavement thickness and bulk density, pavement restraint conditions, and air temperature. The effect of aging on pavement properties was incorporated in the models by predicting the field aging with long-term oven aging treatment in the laboratory. The calculation of the crack spacing is based on the theory that the pavement slab cracks when the pavement temperature reaches the cracking temperature of the mixture and the slab is fully restrained. The deterministic model predicts crack spacing with time, whereas the probabilistic model predicts crack spacing and its variation with time and yields the reliability of the design with regard to a minimum acceptable crack spacing criterion defined by road authorities. The probabilistic model is recommended for use in predicting the low-temperature cracking of asphalt concrete mixtures.
Field Validation of Thermal Stress Restrained Specimen Test: Six Case Histories
Authors: Zubeck Hannele K. , Zeng Huayang , Vinson Ted S. , Janoo Vincent C.
Published: January 2019

Construction histories, cracking observations, and temperature data were collected for five test roads in Alaska, Pennsylvania, and Finland. A full-scale and fully controlled low-temperature cracking test program was conducted at the U.S. Army Cold Regions Research and Engineering Laboratory. Specimens were fabricated in the laboratory with original asphalt cements and aggregates from the test roads. The thermal stress restrained specimen test (TSRST) results obtained for these samples were correlated with the field observations. On the basis of a statistical analysis of the data, the TSRST fracture temperature is associated with the field cracking temperature and crack frequency for the test roads where mixture properties dominated low-temperature cracking. It was concluded that the TSRST can be used to simulate low-temperature cracking of asphalt concrete mixtures.
Superpave Models: Predicting Performance during Design and Construction
Authors: Huber Gerald A. , Zhang Xishun , Fontaine Robin
Published: January 2019

The Strategic Highway Research Program (SHRP) spent $50 million researching asphalt binders and asphalt mixtures and provided three main products: an asphalt binder specification, an asphalt mixture specification, and Superpave, an asphalt mixture design system that encompasses both the binder and mixture specification. SHRP researchers have provided tools that promise more robust asphalt mixtures with reduced risk of premature failure. Implementation of the specifications and mix design system will require overcoming several obstacles. Superpave must be demonstrated to be practical and easy to use. The impact of Superpave aggregate requirements on aggregate availability must be determined. The Superpave gyratory compaction procedure has been uniquely defined and then calibrated to traffic volume. The reasonableness of this approach must be tested in widespread application. Perhaps the largest implementation hurdle exists in the performance models. Expensive test equipment is necessary to do the performance-based tests. The performance predictions must be established as reasonable to justify the cost. A highway reconstruction project containing three Superpave Level 1 mix designs is documented including quality control done with the Superpave gyratory compactor. Superpave Level 2 performance-based tests were carried out to predict permanent deformation of the design and the mixture as constructed. The performance-based engineering properties obtained from the tests are evaluated, and the reasonableness of the performance prediction models is discussed.
Modified Cold In-Place Asphalt Recycling
Authors: Murphy Daniel T. , Emery John J.
Published: January 2019

Cold in-place asphalt recycling has been shown to be a technically sound, cost-effective, environmentally friendly method of strengthening and maintaining a wide range of deteriorating asphalt pavements. The overall process combines testing and mix design procedures, milling, processing and mixing units with microprocessor control of emulsion addition, compaction, placement of a wearing surface and quality assurance testing. In laboratory work and a number of Ontario projects during the past 3 years it has been shown that modification of the cold in-place process to incorporate new aggregate results in an improved recycled binder course with closer voids and stability control. These findings address observed conventional cold in-place asphalt recycling problems such as high residual asphalt cement content (flushing), fine mix (high percent passing 4.75 mm and 75 μm), rutting (low initial stability with emulsion system), and adequacy of in-place material thickness. Structural equivalency factors for cold in-place recycled asphalt compared with conventional binder course hot-mix asphalt have been developed. Resilient properties of laboratory and field samples have been determined with the Nottingham asphalt tester and used in standard mechanistic design programs such as BISAR. Future applications of modified cold in-place asphalt recycling to improve flexible pavements will undoubtedly include airports, which will require consideration of special features such as operational constraints.
Prediction of Asphalt Cement Content of Compacted Hot-Mix Asphalt Specimens Using Nuclear Gauges
Authors: Alattar Iyad A. , Al-Qadi Imad L.
Published: January 2019

Determining asphalt cement (AC) content of hot-mix asphalt (HMA) for quality control/quality assurance using extraction methods is a lengthy, time-consuming, and hazardous process. A demand for a faster and safer method led to the development of different nuclear gauges capable of predicting the AC content of HMA samples. Measuring the AC content of compacted specimens by nuclear gauges is a new technique whose feasibility was evaluated. A total of 216 Marshall compacted specimens were cast and tested in an attempt to develop correction models. The study program investigated the effect of various HMA parameters on the measured AC content, including aggregate gradation and type, air void content, moisture content, AC content, and specimen weight. Specimens were prepared at two different mix design formulas using AC-30 and compacted at two different compaction efforts to investigate the effect of air voids. Specimens (1200 g each) used for calibration were prepared at 3 to 7 percent AC content, whereas specimens prepared for measurements were prepared at 4 to 6 percent. Quartzite and diabase aggregate were used as open and dense graded in prepared mixes. Three levels of moisture content in HMA were evaluated. Different calibration models were developed for different asphaltic mixtures. The evaluated nuclear gauge for measuring AC content for compacted HMA specimens produced satisfactory results when the parameters of tested and calibration parameters were the same. The study found that specimen weight is the most significant factor. Other parameters have different degrees of influence on the measured AC content. Statistical models were developed to correct for the evaluated parameters.
Development of Peak-Hour and Peak Directional Factors for Congestion Management Systems
Authors: Gunawardena Nishantha R. , Sinha Kumares C. , Fricker Jon D.
Published: January 2019

A statewide congestion management system involves the application of large amounts of traffic data to a large number of roadway links at a detailed level. A procedure has been developed to identify congestion on roadway links at a macroscopic level using daily volume counts. Daily volume counts are used to determine a.m. and p.m. peak-hour ( K) and peak-directional (D) factors. These factors are then used with average daily traffic data to determine whether a link is congested at a preliminary level and in need of further analysis. Links identified as congested can then be subjected to a more detailed microscopic study using hourly volume counts to determine extent, duration, and severity of congestion. Development of a.m. and p.m. K and D factors for five different classes of roadways is discussed and values that can be used in congestion management systems are recommended.
Recommendations for Developing Customer Focus in Statewide Transportation Planning Process
Authors: Cunningham Lawrence F. , Christensen Keri , Dunn Diane , Gonzales Elvira , Hirsch Mary P.
Published: January 2019

The Intermodal Surface Transportation Efficiency Act of 1991 ushered in a new era in transportation planning, transforming the missions of transportation departments into more diverse agendas that include information management and long-range planning. Today's transportation officials face a complex task. Success in transportation planning is measured not just in terms of connectivity and operational efficiency, but in the ability to respond to a host of complicated concerns; the ability to achieve a variety of operational, managerial, and financial objectives; and in proficiency in involving the public in the entire transportation planning process. The Colorado Department of Transportation, in cooperation with the Graduate School of Business Administration at the University of Colorado at Denver, conducted a three-phase investigation on the development of customer focus in the statewide transportation planning process. From this systematic methodology, the research team established a series of recommendations for developing a customer focus in the statewide transportation planning process. These recommendations were developed in several areas including broadening the mission and process; strengthening public involvement in project orientation; improving organization flexibility; and implementing marketing orientation, market research process, and techniques and approaches for dealing with high priority public involvement issues.
Special Features of Florida's Mobility Management Process
Authors: McLeod Douglas S.
Published: January 2019

The purpose of the Florida Mobility Management Process (MMP) is to improve the mobility of residents and tourists. Although all states must develop congestion management systems (CMS), special features of the Florida CMS, which others may wish to consider, are presented. Florida's special MMP features include: development framework, applicability of MMP and CMS to all urbanized areas, MMP and CMS relationship with the transportation planning process, multimodal alternatives analyses of major investments, institutional arrangements, implementation techniques, performance measures, and MPO prototypes.
Partnerships for Multimodal Transportation Planning
Authors: Hauser Edd , Breese Amy R.
Published: January 2019

AASHTO, in cooperation with NCHRP, has initiated a series of research studies dealing with the issue of multimodal transportation planning. This paper comments on some of the findings from the one project in this series that focuses on the dynamics of partnerships formed to carry out the planning, design, and implementation of multimodal and intermodal projects. An intensive industry scan has been completed, resulting in an interactive data base of approximately 60 multimodal projects throughout the country. From these 60 candidate projects, 12 were selected for more intensive study through a case study approach. The results of the case studies revealed a number of common, underlying themes. Included among those themes is the finding that local governments and private sector partners must be included in earlier stages of multimodal transportation planning than is currently being practiced. One of the key hypotheses tested with the data available on these partnerships was the impact of the Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) as a catalyst to stimulate multimodal projects and to improve the multimodal planning process. In this regard, one finding of this study is that before the 1990s, it appears that a major emphasis of partnership formation was simply to secure funding from a variety of sources for such projects. Since ISTEA was passed, however, objectives more frequently cited by partners relate to meeting societal values and traveler needs.
Incremental Regionalism: Staged Approach to Development of Regional Transportation Organizations
Authors: Hartgen David T. , McCoy William J. , Walcott Wayne A.
Published: January 2019

Recent efforts to form a regional transportation organization for the greater Charlotte, North Carolina, region are discussed. The 13-county area, more than 126 km (75 mi) across, is uniformly low density and consists of 43 independent jurisdictions and cities, five state department of transportation districts, and five metropolitan planning organizations in two states. Regional travel patterns are just beginning to emerge along the highly radial road network. Since the late 1980s, at least four attempts to form consensus on regional transportation planning needs have been made but all have failed to galvanize. The history of these efforts is traced, and the causes of success and failure are reviewed. It is suggested that failure occurred primarily because the region is not yet truly integrated economically and the regional plans were politically too advanced. An incremental model of regional organization growth is then proposed. In this model organizational structure is related to the demography, commuter patterns, and physical, economic, and political regional integration over the next 30 years. Regions go through 17 definable steps as they emerge from separate cities and become part of large metropolises. The key roles of policy officials, businesses, staff, and others in facilitating regional planning in the absence of regional structure are explored.
Household Motor Vehicle Ownership and Use: How Much Does Residential Density Matter?
Authors: Schimek Paul
Published: January 2019

The question of whether population density affects the amount of household automobile travel in the United States is revisited. Controls for income and demographics are included in a multivariate regression model of vehicle travel that includes vehicle ownership as an intermediate factor and that treats a household's pick of neighborhood density and the amount of travel as a simultaneous relationship. The data come from the 1990 Nationwide Personal Transportation Survey. It is found that density matters, but not much. A 10 percent increase in density leads to only a 0.7 percent reduction in household automobile travel. By comparison, a 10 percent increase in household income leads to a 3 percent increase in automobile travel. The results are similar when vehicle trips are used as the dependent variable. The effect of density is so small that even a relatively large-scale shift to urban densities would have a negligible impact on total vehicle travel.
MUSSA: Land Use Model for Santiago City
Authors: Martinez Francisco
Published: January 2019

MUSSA is a land use model developed to interact with the Santiago four-stage transport model called ESTRAUS. It was developed as an application of the BID-CHOICE theory of the competitive urban land market, where land rents are endogenous and consistent with equilibrium conditions, including land availability and developers’ behavior. Interaction with transport occurs through economic access measures obtained from the ESTRAUS model; in turn, MUSSA provides the locations of activities (households and firms). Total activity volumes and population forecasts are exogenously provided by a region input-output model. The whole system interacts through a central data base with a graphic interface (geographic information system) under Windows. MUSSA is able to forecast location choices of 65 household clusters into 264 zones and six dwelling types plus five firm types allocated to lot sizes; residents and firms compete for the available land. It is a fully disaggregated behavioral location model that is applied in a static equilibrium approach. The package and the model are presented; its capacities and limitations, data requirements, software, and outputs are described; and some performance indexes are presented.
Urban Form and Pedestrian Choices: Study of Austin Neighborhoods
Authors: Handy Susan L.
Published: January 2019

Supporters of the New Urbanism suggest that the right design will encourage walking, thereby encouraging interaction and a greater sense of community and discouraging automobile dependence. Existing research provides insufficient evidence to support this belief, however, largely because of limitations in the data and methodologies that researchers have used. The research described moves beyond a simple test of correlations to an exploration of how urban form fits into a more comprehensive model of choices about pedestrian trips. First, a model for individual choices about pedestrian trips is proposed. Second, the results of a study of six neighborhoods in Austin, Texas, are presented. Data from a survey of residents in these neighborhoods support the proposed model and suggest that certain aspects of urban form can play an important role in encouraging walks to a destination but that the savings in travel from the substitution of walking for driving is likely to be small.
Consideration of 24-hr Volumes in Selection of Traffic Signal Control Strategies for Isolated Intersections
Authors: Lee Stephen C. , Lee Joe
Published: January 2019

Selection of the most appropriate traffic signal control strategy for isolated intersections is a difficult and complicated process. TRAF-NETSIM was used to evaluate the operational performance of an isolated intersection under pretimed, semiactuated, and actuated control for continuous 24-hr traffic volumes. Guidelines were developed for selecting the most effective control strategy. Findings include the following: either pretimed or actuated control is the most effective strategy for isolated intersections without flashing for the 24-hr and peak 8-hr traffic volumes. The conventional three-dial pretimed controller is still a valuable control strategy and should not be eliminated from consideration. The most effective strategy for the peak 8-hr operation of an isolated intersection is probably the most effective one for overall 24-hr operation, as well. The combined control strategy (which consists of one or more of the pretimed, actuated, and semiactuated controls dependent on the hourly volumes) without flashing is the most effective strategy for the 24-hr and peak 8-hr traffic volumes. The signal flashing mode is very effective during the night when the total intersection critical lane volume falls below 500 vehicles per hour. Advanced pretimed controllers are generally more effective than conventional three-dial pretimed controllers. There is no direct, universal method to determine the most effective combined traffic signal control strategy for isolated intersections.
Pedestrian Travel Times and Motor Vehicle Traffic Signals
Authors: Noland Robert B.
Published: January 2019

Traffic signals generally have been installed to maximize the flow of motor vehicle traffic by reducing the average travel delay time. Under free-flow conditions, motor vehicle travel delay is very sensitive to the amount of green phase and the total cycle of the traffic signal. Average pedestrian delay at traffic signals is not taken into account. Some simple examples are used to demonstrate that travel time delay costs to pedestrians caused by existing signalization cycles may often result in increased travel time costs to society. In areas with heavy pedestrian traffic (or during peak pedestrian hours), traffic signals should trade off the costs of motor vehicle delay with pedestrian delay. This may suggest that in some areas, motor vehicle traffic should be banned or severely restricted. Narrower street widths that can allow reduced total signal cycle times can also reduce pedestrian delay.