bluuebunny/crossref_metadata_2025 huggingface dataset:
Verification of Voids in Coarse Aggregate Testing: Determining Stone-on-Stone Contact of Hot-Mix Asphalt Mixtures
Authors: Watson Donald E. , Masad Eyad , Ann Moore Kathryn , Williams Kevin , Cooley L. Allen
Published: April 2007

During NCHRP Project 9-8, Designing Stone Matrix Asphalt Mixtures, the voids in coarse aggregate (VCA) concept was selected as the preferred method to determine whether stone-on-stone contact existed in stone matrix mixtures. It is believed that stone-on-stone contact is important for open-graded friction course (OGFC) mixes to minimize the potential for rutting. Therefore, the same VCA requirements were adopted for OGFC mixes as had been developed for stone matrix asphalt mixtures. The objective of this study was to verify the VCA concept for defining stone-on-stone contact within OGFC mixtures by using digital imaging techniques such as analyzing particle contacts and the air voids size distribution. The effect of aggregate breakdown on stone-on-stone contact by the VCA method was also evaluated. The following conclusions are based on the information presented in this study. ( a) A general guideline for determining the critical breakpoint sieve would be to select the finest sieve for which there is at least 10% of the total aggregate retained. This sieve size also should differentiate between the aggregate skeleton and filler particles. ( b) Digital imaging provides a scientific method for identifying when stone-on-stone contact exists and supports the VCA. An advantage of digital imaging is that it can quantify the number of contacts between aggregate particles.
Ruggedness Evaluation of the Dynamic Angle Validation Kit for Superpave Gyratory Compactors
Authors: Hall Kevin D.
Published: April 2007

Superpaver hot-mix asphalt (HMA) specimens are compacted in the laboratory with the Superpave gyratory compactor (SGC). The SGC compacts specimens through application of pressure and an applied angle of gyration. The original compaction specification for the SGC requires the angle of gyration to be 22 ± 0.35 mrad (1.25° ± 0.02°), measured externally against the compaction mold. Questions about the ability of different compactors to produce HMA specimens of the same mix having the same density led to development of the dynamic angle validation (DAV) kit, which measured the angle of gyration internally (on the inside of the mold). Two task groups were formed independently to develop a standard specification for DAV usage; the groups combined efforts and produced AASHTO PP48, with a companion ASTM specification slated for consideration in the fall of 2003. The specifications did not include a statement of precision and bias. The task groups conducted a ruggedness study using the guidelines contained in ASTM C-1067 and E-1169. Factors considered in the ruggedness study included height of mix used in the mold with the DAV, number of gyrations used to determine the angle of gyration, operating temperature of the DAV, and the nominal maximum aggregate size of the mix used with the DAV. Six SGC models were included in the study. The ruggedness study showed no factor significantly affected the DAV-measured angle. The findings clear the way for a planned interlaboratory study to establish the precision of the angle of gyration measured with the DAV.
Determining Air Voids Content of Compacted Stone Matrix Asphalt Mixtures
Authors: Xie Hongbin , Watson Donald E.
Published: April 2007

This study compared the difference in air voids, optimum asphalt content, and voids in mineral aggregate (VMA) by using the saturated surface dry (SSD) and CoreLok methods for determining bulk specific gravity of the compacted specimen. The critical air voids level at which stone matrix asphalt (SMA) mixtures are considered to become permeable was also determined for the gradations used in this study. Some of the pertinent conclusions are as follows. (a) There is a significant difference between air voids content measured by the SSD method and the CoreLok method, (b) The CoreLok method resulted in a higher optimum asphalt content and VMA than designs based on the SSD method. (c) The CoreLok method may have a system error that overestimated the air voids content at zero to low air voids levels; therefore, a correction factor was suggested to apply to the CoreLok results if needed. (d) At a permeability threshold of 125 X 10-5 cm/s, the critical air voids contents are 4.5%, 5.7%, and 7.8% by the SSD method for 19-, 12.5-, and 9.5-mm nominal maximum aggregate size (NMAS) SMA mixtures, respectively, (e) Both the SSD and corrected CoreLok methods can be used for SMA 9.5-mm NMAS mixtures. For SMA 12.5-mm NMAS mixtures with 6.0% or more air voids and for SMA 19-mm NMAS mixtures with more than 4% air voids, there is a greater potential for error by the SSD method, and the corrected CoreLok method should be used.
Workability of Hot-Mix Asphalt
Authors: Gudimettla Jagan M. , Cooley L. Allen , Brown E. Ray
Published: April 2007

The term "workability" has been used to describe several properties related to the construction of hot-mix asphalt (HMA). For this study, workability was defined as a property describing the ease with which HMA can be placed, worked by hand, and compacted. This definition provides a term that is applicable to movement of HMA through equipment to the roadway, handwork of HMA, and compactibility on the roadway. The primary objective of this study was to evaluate a prototype device to measure the workability of HMA mixes that could identify the change in workability due to changes in mix characteristics. The findings of this study led to successful design of a device to measure the workability of HMA mixes. The workability of HMA was affected by aggregate type, nominal maximum aggregate size, binder type, and temperature. Gradation shape did not have a significant effect on workability. However, numerous two- and three-way interactions that included gradation shape were significant. Mixes modified to meet a PG76-22 were significantly less workable than mixes containing an unmodified PG64-22. There was a relationship between workability and temperature that showed increased workability at higher temperatures.
Bridge Aesthetics for Reconstruction of System Interchange at 1-25 and 1-40: New "Big I," Albuquerque, New Mexico
Authors: Whitney Alex , Chung Barry
Published: April 2007

The interchange reconstruction project at I-25 and I-40 will be used as a case study to show that aesthetic enhancements that are simple yet have significant visual impact can be developed and implemented for bridges. The history of the planning process is traced, and the vision and goals for the aesthetic enhancements are described. Attention is then turned to the way recommendations were developed into reality from the design and public consultation process through to the implementation of the design of aesthetic features. The New Mexico Department of Transportation and the city of Albuquerque had the foresight to plan the aesthetics for their Interstate reconstruction program in a corridorwide fashion well ahead of the actual design and construction. That planning allowed the stakeholders to agree on a vision of what the reconstructed Interstate should look like and provide to the surrounding community. This vision was continued in the final design of the new bridges. Designers chose bridge aesthetic treatments that blended into the surrounding landscape. Bold use of color, repetitive bridge elements, and repeating textures added to simple and fluid structure lines, producing economical bridges that made a visual statement. Fiscal responsibility was injected in the development of the aesthetic treatments by involving the owner and major stakeholders in the aesthetic task force. Estimated construction costs were continually monitored during the design with input from the contracting community. Finally, when money was tight, difficult decisions were made to delay certain aesthetic elements, such as public art, until alternative funding could be secured.
Behavior of Integral Abutments Supported by Steel H-Piles
Authors: Burdette Edwin G. , Ingram Earl E. , Tidwell J. Brandon , Goodpasture David W. , Deatherage J. Harold , Howard Samuel C.
Published: April 2007

A summary of already-reported results of earlier tests on integral abutments supported by steel H-piles is provided, and a detailed description of further testing is given. The additional tests were performed on an abutment that was consistent with what was still in use by the Tennessee Department of Transportation (TDOT) and was 20% wider than the abutments in the earlier tests. The tests consisted of pulling horizontally a simulated abutment supported by a steel H-pile and restrained against free rotation at the top. Test results clearly showed that the wider abutment was capable of withstanding larger horizontal displacements than the abutments in the earlier tests, although the former performed adequately to satisfy TDOT criteria. In the tests reported here with the currently used abutment width, the abutment-pile was capable of withstanding horizontal displacements at the ground surface well beyond the 1-in. (25.4-mm) maximum displacement permitted by TDOT criteria.
Fiber-Reinforced Polymer Shear Strengthening of Short-Span, Precast Channel Beams in Bridge Superstructures
Authors: Jones Jessie X. , Heymsfield Ernest , Durham Stephan A.
Published: April 2007

A national study concluded that at least 14 states use precast channel beams for their bridge superstructures. Before the mid-1970s short-span (19-ft) precast channel beam bridges were designed by the Arkansas State Highway and Transportation Department for H15 loading without any provision for shear reinforcement. A recent statewide survey has identified 389 of these bridges that remain in service. About 3% are load posted. Approximately one-third of the 389 bridges are exhibiting deterioration that may be serious. During a recent investigation by the University of Arkansas, 33 precast channel beams were evaluated for structural strength. It was determined that many of these units have inadequate shear capacity. A shear crack frequency distribution curve was developed through examination of the 33 tested beams. A simple shear strengthening technique is presented consisting of fiber-reinforced polymer (FRP) strips as external stirrups. The technique has been developed so that it can be easily implemented in the field. The FRP strips are spaced to prevent the full formation of a diagonal crack between two adjacent strips and designed to ensure a flexural failure rather than a sudden shear failure. Four beams retrofitted with the proposed retrofit technique and two control beams were load tested to failure to evaluate the effectiveness of the technique. Results from the experiment show that the retrofitted beams exhibited at least a 290% increase in deflection ductility and a 418% increase in energy ductility.
Simplified Live Load Distribution Factor Equation for Steel Girder Bridges
Authors: Phuvoravan Kitjapat , Chung Wonseok , Liu Judy , Sotelino Elisa D.
Published: April 2007

The "S-over" equation for load distribution factor (LDF) was first introduced in the 1930s in the AASHTO standard. Finite element studies, however, have shown it to be unsafe in some cases and too conservative in others. AASHTO LRFD 1994 introduced a new LDF equation as a result of the NCHRP12-26 project. The equation is based on parametric studies and finite element analyses. It is considered to be a good representation of bridge behavior. However, it involves a longitudinal stiffness parameter that is not initially known in design and thus requires an iterative procedure to correctly determine the LDF value. The need for an iterative design procedure is perceived by practicing engineers as the major impediment to wide acceptance of the AASHTO LRFD equation. A new, simplified equation that is based on the AASHTO LRFD formula but does not require an iterative procedure is developed. Fortythree Indiana bridges were selected and analyzed with a sophisticated finite element model. The new, simplified equation produces LDF values that are always conservative compared with those obtained from the finite element analyses and are generally greater than the LDF obtained using AASHTO LRFD specification. Therefore, the simplified equation provides a simple, yet safe specification for LDF calculation.
Feasibility of Steel Fiber Concrete in End Zones of Posttensioned Bridge Girders: Results of Special Anchorage-Device Acceptance Test
Authors: Haroon Saif A. , Yazdani Nur , Tawfiq Kamal
Published: April 2007

The secondary spiral and skin reinforcement in the anchorage zone of prestressed, posttensioned girders cause congestion and pose difficulty in the placement of concrete. Also, it is labor intensive to produce and place the secondary anchorage reinforcement. A study was conducted to determine the feasibility of reducing or eliminating the secondary reinforcement and replacing with steel fibers for posttensioned anchor zones because of the expected improvement in mechanical properties of fiberreinforced concrete over nonfibrous concrete. The AASHTO special anchorage device acceptance test was performed. Variations of spiral and skin reinforcement, with concrete strengths ranging from 24 to 34.5 MPa (3,500 to 5,000 psi), were used to investigate the performance of the two types and various amounts of steel fibers. Experimental results indicated that 1% hooked-end steel fiber could reduce a maximum of 79% of the secondary reinforcement for a minimum concrete strength of 32.5 MPa (4,710 psi). Lower volumes of steel fibers may also result in reduction of secondary reinforcements.
Survey of Current Practice for Design of High-Strength Concrete Prestressed Bridge Girders
Authors: Mary Beth D. Hueste , Cuadros Gladys G.
Published: April 2007

A survey was conducted to determine the current state of practice for the design of high-strength concrete (HSC) prestressed bridge girders among the 52 state departments of transportation (DOTs) in the United States. A total of 41 responses were received during a 6-month period spanning from June through November 2002. It was found that the AASHTO Standard Specifications for Highway Bridges, 16th edition, is the most popular code for bridge design in current practice. In most cases its implementation is partial; most states plan complete implementation between 2003 and 2007. State DOTs have a large variation in the number of new bridges constructed, ranging from 4 to 400 bridges per year. The percentage of bridges constructed with HSC prestressed girders ranges from 0% to 100%. HSC is widely used in current practice, with 85% of the responding DOTs using specified concrete compressive strengths at service in the range of 6,000 to 8,000 psi. In this study the definition of HSC is concrete with specified compressive strengths for design of 6,000 psi or greater, made without the use of exotic materials or techniques. In some cases concrete mixture designs are governed by the specified concrete compressive strength at release. This parameter tends to be critical when it is greater than 6,000 psi. Almost half of the DOTs have some concerns related to the use of HSC, and seven DOTs have made inhouse adjustments to the design specifications for HSC prestressed bridge girders.
Deflections of Polyvinyl Chloride Pipes in Clayey Backfill
Authors: Dhar Ashutosh Sutra , Siddiquee M. S. A. , Sinha Ahmad Niaz
Published: April 2007

Seven different rib profiled polyvinyl chloride (PVC) pipes were investigated in a test facility developed at the Bangladesh University of Engineering and Technology. The pipes were backfilled with native Dhaka clay. Use of native soil as backfill material saves the additional costs associated with importing materials and conserves resources such as granular soil. The test facility was designed to study the performance of buried pipes under a quasi-live load. The study revealed that the PVC pipes with diameters ranging from 203 to 790 mm, areas per unit lengths of 13 to 34 mm2/mm, and moment of inertia per unit length of 266 to 7,925 mm4/mm performed reasonably well in the backfill of native Dhaka clay. Pipes were tested in three different burial depths: 600, 900, and 1,200 mm. Deflections of the pipes corresponding to a maximum wheel load of 73.3 kN (16,500 Ibf) were between 0.17% and 0.64% of the pipe diameters. Deflections were calculated with the current design methods for live load and compared with the measurements. The comparison revealed that a method based on a load spreading rate of 1.15 times the depth calculated the effect of surface live load reasonably well. However, a method based on analysis of the soil-pipe interaction is required to account for live load over a wider range of installation conditions.
Fatigue Behavior of Prestressed Tubular Bridge Deck of Fiber-Reinforced Polymer
Authors: Wu Zhenhua , Mirmiran Amir , Swanson James
Published: April 2007

An experimental study was undertaken to assess the flexural fatigue performance of a new deck system of fiber-reinforced polymer (FRP) that has been installed on a bridge in Delaware County, Ohio. The deck consists of a series of 4-in. (102-mm) square pultruded FRP tubes with a thickness of 1/4 in. (6.4 mm), laid side by side on existing stringers, perpendicular to the direction of traffic. The tubes are posttensioned up to 20 kips (90 kN) with 0.6-in. (15-mm) diameter seven-wire strands at midpoints between the stringers in the direction of traffic. Four double-span FRP deck specimens with two different tube sizes and three different span lengths were tested in flexural fatigue under AASHTO-prescribed footprint of wheel loads for an HS20 truck. Panel action in the deck system was inadequate for the most part, as only the tubes that were directly under the load carried the majority of the load. Subsequent slippage between these tubes and their adjacent tubes can cause cracking in the asphalt overlay. However, no such crack has been observed on the actual bridge after 1 year in service. Panel action is generally improved at higher prestress levels. Prestressing also offers additional redundancy and reserve strength for the system. While longer span decks fail in bending, shorter span decks generally suffer from local shear failure as a result of stress concentrations at the corner of the tubes under the applied load or at the support. The fatigue problem is less critical for longer span decks and smaller tube sizes.
Evaluation of Premature Deterioration of Concrete Bridge Barriers by Petrographic Examination
Authors: Delem Laetitia , Van Dam Thomas , Peterson Karl R. , Sutter Larry
Published: April 2007

Many of the current-generation concrete bridge barriers used in Michigan have deteriorated at a rate greater than expected. For an assessment of the possible causes of this premature distress with the objective of alleviating future occurrences, sixteen core specimens from eight sites constructed between 1983 and 2001 were evaluated. The evaluation included visual inspection, stereo and petrographic optical microscopy, and scanning electron microscopy. The major observations revealed through this analysis were that poor consolidation, marginal air-void systems, alkali-silica reaction associated with chert and siltstone in the fine aggregate, corrosion of reinforcing steel, and possibly frost susceptibility of fine siltstone aggregates were responsible for the deterioration. These results provide the basis for improving the quality of such barriers in future construction.
Use of the Impact-Echo Method to Evaluate Damage due to Distributed Cracking in Concrete Plate Members: Theory and Field Trials
Authors: Kesner Keith , Sansalone Mary J. , Poston Randall W.
Published: April 2007

The research evaluated the feasibility of using transient stress waves to detect and quantify cracking caused by distributed damage mechanisms, specifically alkali-silica reactivity and delayed ettringite formation. It was found that distributed damage produced significant and quantifiable changes in the waveforms and spectra obtained from impact-echo results. Numerical (finite element) studies were used to determine how distributed damage in concrete plates affected propagation of impact generated stress waves. To quantify the damage, the rate of stress wave attenuation can be assessed and compared with values predicted by theory. To verify the results obtained in the numerical simulations and to develop correlation between changes in impact-echo signals and the actual amount of damage, impact-echo tests were performed on a specially prepared plate specimen made from concrete modified to produce distributed cracking over time. The actual amount of damage in the plate was determined periodically by using neutron radiography. A correlation between the amount of damage in the samples and changes in impact-echo signals was established. The correlation was verified in field and laboratory studies on concrete sections with distributed damage. The amount of cracking predicted from the analysis of impact-echo tests agreed with the actual amount of cracking obtained from neutron radiography of the core samples. This research demonstrates that the impact-echo method can be used to detect and quantify the amount of distributed damage in concrete plates. However, the mechanism responsible for the damage cannot be ascertained from either impact-echo test results or neutron radiographs.
Ettringite Deposits in Air Voids
Authors: Detwiler Rachel J. , Taylor Peter C. , Powers Laura J.
Published: April 2007

Investigations of pavements suffering from freeze-thaw damage in the presence of deicing salts have found significant deposits of ettringite in the air voids. Concern has been expressed that the deposition of ettringite in air voids reduces their effectiveness in protecting the concrete. A series of experiments intended to reproduce the process of deterioration in the laboratory allowed the authors to observe the sequence of events. A suite of cements was selected to provide a range of C3A contents, sulfate contents, and sources of sulfate within the cement (that is, either the clinker or the gypsum). Specimens were subjected to a modified version of ASTM C666 in which salt solutions with and without added gypsum were substituted for the water, and the specimens were allowed to dry periodically. Sacrificial companion specimens were examined petrographically, and the observations were correlated with mass loss, fundamental transverse frequency, and length change. The results demonstrate that the deposition of ettringite does not adversely affect the ability of the air voids to protect the concrete. The sequence of events (microcracks first, then ettringite deposits), the morphology of the ettringite (long, loosely packed needles), and the lack of association of air voids containing significant ettringite deposits with cracks all indicate that the deposition of ettringite is opportunistic. The observed large deposits of ettringite are a consequence of saturation and freeze-thaw damage, not a cause.
Merlin: Microsimulation System for Predicting Leisure Activity-Travel Patterns
Authors: van Middelkoop Manon , Borgers Aloys , Timmermans Harry
Published: April 2007

Development of a model of annual activity-travel patterns of leisure and vacation travel is reported. The simulation system, called Merlin, is a hybrid model system consisting of discrete choice models and rule-based models. It predicts the annual number of day trips and vacations, and the profile of such trips and vacations, including duration, travel party, timing, destination, type of accommodation, transport mode, day of departure, and expenditures. Separate models are derived for each of these facets. Microsimulation is used to predict aggregate patterns. The model's performance is satisfactory.
Daily Stop-Making Model for Workers
Authors: Chu You-Lian
Published: April 2007

A mathematical model was used to predict workers' stop-making propensity as well as to discern the potential interactions in stop making over different time periods in a worker's day. Five time periods were examined, including before the morning commute, morning commute, midday, evening commute, and after the evening commute. With the New York Metropolitan Transportation Council's household survey data, a multivariate probit model was developed to allow the joint determination of workers' stop-making choices (across different times of day). To establish the stop-making relationship, the model took into account factors relating to sociodemographics, land use density, transportation service, and work schedule. Extensive statistical tests were given to the model specifications and the assumptions underlying the model structure. The possible interdependence of stop-making decisions was analyzed by using the modeling results, including the sign and magnitude of the correlation coefficients. The empirical results provide useful insights into the substitution and complementarity effects in stop making among the five time periods. They also provide exploratory methodological evidence that could lead to an approach to determine whether to assume an independent or a simultaneous choice structure for characterizing the true choice process of workers' stop-making decisions.
Comprehensive Econometric Microsimulator for Daily Activity-Travel Patterns
Authors: Bhat Chandra R. , Guo Jessica Y. , Srinivasan Sivaramakrishnan , Sivakumar Aruna
Published: April 2007

The Comprehensive Econometric Microsimulator for Daily Activity-Travel Patterns (CEMDAP) is a microsimulation implementation of an activity-travel modeling system. Given as input various land use, sociodemographic, activity system, and transportation level-of-service attributes, the system provides as output the complete daily activity-travel patterns for each individual in each household of a population. The underlying econometric modeling framework and the software development experience associated with CEMDAP are described. The steps involved in applying CEMDAP to predict activity-travel patterns and to perform policy analysis are also presented. Empirical results obtained from applying the software to the Dallas-Fort Worth area demonstrate that CEMDAP provides a means of analyzing policy impacts in ways that are generally infeasible with the conventional four-stage approach.
Car-Rider Segmentation According to Riding Status and Investment in Car Mobility
Authors: Elgar Alon , Bekhor Shlomo
Published: April 2007

Population segmentations for mode choice models are investigated. Several researchers have shown that car and bus users differ substantially in their value of time, in both revealed-preference and stated-preference surveys. This line of research is followed, and a new methodology to segment the population is presented. The hypothesis that two further segmentation dimensions will produce meaningful results is verified. In the first segmentation, car drivers are distinguished from car passengers. In the second segmentation, the population is divided according to their investment in mobility by car. With data from a revealed-preference survey conducted in the Tel Aviv, Israel, metropolitan area, several multinomial logit models were estimated with respect to each population segment. The results show clearly that households with a high investment in car mobility have a much higher value of time than do those with a low investment in mobility. In addition, car drivers perceive higher transit penalties than do car passengers. An interesting result, which exceeded the expectations, was the strong increase of the waiting time penalty at high investment in car mobility. The cumulative effect of the value of time, bus transit penalties, and additional in-vehicle travel time by transit modes prevents most car drivers from potentially changing their travel mode to transit. The proposed procedure, if adopted in the estimation of transportation models, would reduce much of the evident gap between the expected and actual demand generated by changes in transit services.
Model for Allocation of Maintenance Activities to Household Members
Authors: Vovsha Peter , Petersen Eric , Donnelly Robert
Published: April 2007

Household maintenance activities and associated tours, even if individually implemented, should be thought of as satisfying the needs of the entire household rather than simply the needs of the person who implements the activity. These activities are characterized by a high degree of substitution between household members who could implement them. This characteristic suggests a modeling structure in which maintenance activities are generated by the entire household and then allocated to the household members for implementation. In this approach, the modeling of allocated activities is executed by a sequence of two linked discrete choice models. The first model relates to the entire household and returns total daily frequency of individual maintenance tours by purpose. The second model relates to the tour level and returns the allocation of each generated tour to a particular household member. Within the general framework of a regional demand modeling system, these models are applied after, and are conditional on, the mandatory and joint tour generation stage. The statistical analysis and model estimation for this implementation of allocated household maintenance activities allow for important insights into the intrahousehold decision-making mechanism and improved travel demand forecasts. Models of this type have been implemented as components of the regional travel demand modeling system recently developed for the Mid-Ohio Regional Planning Commission.
Bilevel Programming Approach to Optimizing a Logistic Distribution Network with Balancing Requirements
Authors: Huang Bo , Liu Nan
Published: April 2007

Traditional approaches to a location allocation problem have focused on the allocation of customers to a distribution center (DC) according to some arbitrary geographical boundaries (e.g., administrative zones and census districts), which usually incurs underuse or overcrowding of these centers. Location allocation with balancing requirements (e.g., balanced workload of service among DCs) has therefore been addressed. A distribution strategy with balanced-workload allocation aims to be cost-efficient and to improve customer service. A novel bilevel programming model is presented that minimizes the cost of the total distribution network and at the same time balances the workload of each DC for the delivery of products to its customers. A genetic algorithm-based approach was developed to cope with the bilevel model, and it was tested on a best realistic data set. In addition to the most cost-efficient design, the bilevel programming model presents a picture to decision makers that shows the trade-off between the objective of cost minimization and the balancing requirements. It is also shown that the bilevel model offers a flexible framework that allows the incorporation of more requirements and constraints if necessary.
Violations of Expected Utility Theory in Route-Choice Stated Preferences: Certainty Effect and Inflation of Small Probabilities
Authors: Avineri Erel , Prashker Joseph N.
Published: April 2007

Common travel-choice models are based on the maximum utility assumption. However, the use of expected utility theory in descriptive models of individual choice has been criticized by behavioral scientists and recently also by transportation researchers. The aim of this work is to examine whether violations of expected utility theory may be found in travelers' stated-preference behavior. In this work, a route-choice stated-preference experiment was conducted. A questionnaire, inspired by experiments of Kahneman and Tversky, presented simple route-choice problems. Evidence was found of two violations of expected utility theory. The first is known as the Allais paradox (certainty effect), which is demonstrated by a situation in which the extreme underweighting of high probabilities, which fall short of certainties, makes certain (low) travel time outcomes very attractive. Evidence of another violation of expected utility theory, inflation of small probabilities, is shown on the basis of a set of stated-preference route-choice problems. The experimental results may be explained by prospect theory, an alternative model of decision making under risk.
Modeling Interaction Between Internet Communication and Travel Activities: Evidence from Bay Area, California, Travel Survey 2000
Authors: Srinivasan Karthik K. , Reddy Athuru Sudhakar
Published: April 2007

Increasingly, advanced information technologies affect both activity and travel participation. Although several studies have focused on specific activities such as e-shopping or telecommuting, this study focuses on the relationship between physical and virtual activity participation in maintenance and discretionary activities (specifically using Internet technologies). In particular, three related dimensions are investigated using a series of statistical models: ( a) factors affecting information and communications technology (ICT) use and the propensity to perform virtual activities using the Internet, ( b) the relationship between physical and virtual activity participation and ICT use, and ( c) interactions among ICT use, activity attributes, and observed travel behavior. The models are estimated by using recent empirical activity-diary data from the San Francisco Bay Area (California). The results provide considerable evidence in support of substitution and generation of trips due to ICT use (particularly the Internet). The results highlight the influence of technological familiarity, work-related attributes, time constraints, timing of travel, mobility and connectivity needs, and sociodemographic factors on the interactions between ICT use and travel patterns of users. These results have important implications for travel demand estimation and forecasting given the growing adoption and use of ICT among various segments of the population.
Transportation Utility Fee: Oregon Experience
Authors: Springer Carl D. , Ghilarducci John
Published: April 2007

Ten Oregon agencies have adopted transportation utility fee (TUF) programs to augment shrinking roadway maintenance revenues. Four additional agencies are investigating the feasibility of TUF programs this year, which would generate about $6,000 per road mile annually through this new mechanism. Clackamas County (population 345,000), in the process of investigating a transportation maintenance fee (TMF) program, will become the largest agency in the state with this type of finance system if the fee is adopted. Initial annual revenue estimates were $20 million for eligible maintenance activities, but these were scaled back to $4.2 million through the public review process. If adopted, this funding shift could provide opportunities to transfer a portion of the gas tax funds to capital project investments, which are substantially underfunded. The TMF development process in Clackamas County included a convergence of traditional travel demand forecasting with near-term traffic impact techniques to create a road user nexus at a parcel level. To accomplish this, trip estimates were done with ITE methods with a cross-check of the regional travel demand model. A major challenge was to make a reasonable assessment of travel activity for every building in the county. Each of the 97,000 residential and 7,000 nonresidential tax lots was evaluated by using tax assessment and state employment records to estimate travel activity and proportionately allocate fees. Lessons learned in this project include the trade-offs between road user fee market value and technical and legal defensibility and justification for better interagency land use data organization.
Modeling Commercial Vehicle Travel
Authors: Allen William G. , Agnello Paul
Published: April 2007

A new commercial-vehicle trip forecasting model has been developed for the Baltimore Metropolitan Council (BMC). BMC includes trucks in its regional modeling but has previously excluded an important category of nonpersonal travel with passenger cars, light trucks, and other vehicles. These include light-duty delivery vehicles, taxis, government vehicles, service personnel vehicles, craftsmen vehicles, and similar vehicles. The challenge in estimating commercial vehicle trips is to define them and obtain data on observed trip patterns. Traditional surveys were judged unlikely to be useful, so an innovative way was devised to synthesize commercial vehicle counts at those locations where classification count data already existed. BMC staff conducted new counts at locations throughout the region. Commercial vehicles were defined as those bearing any text or logo or carrying equipment of an obviously commercial nature. A database was created and used to calibrate a count model, which was then applied to estimate commercial counts at more than 550 locations. These counts indicated that commercial traffic is almost 8% of the total traffic volume. The researchers synthesized a trip table from these count data and used that table to develop a commercial trip model that would estimate link volumes accurately. The resulting assignment error is -1.9% and the regional percent root-mean-square error is 12.5%. The result is a process that exhibits reasonable sensitivities to the key input variables and matches counts very well. A forecast was made and the results were found to be reasonable. The procedure was implemented within BMC's regional model set.
Integrated Modeling Approach to Total Incident Delay
Authors: Qi Yi (Grace) , Teng Hualiang (Harry)
Published: April 2007

In congestion management, total traffic delay is typically derived based on look-up tables for incident duration, capacity reduction, and frequency that are determinants of total incident delay. The studies that adopted this approach indicate that some factors, such as weather, may not be included in the look-up tables because of their limited size and the lack of rigorous identification of influencing factors to be included in the tables. In addition, the marginal effect of the influencing factors on total traffic delay cannot be analyzed. In this study, statistical models with identified influencing factors for incident duration, lane blockage, and frequency were developed and then integrated into the queuing-based delay equation. Through the development of advanced statistical models, the variables or factors that significantly influence incident duration, lane blockage, and frequency can be identified. When these statistical models are plugged into the queuing-based delay equation, the marginal effect of the identified factors on total delay can then be derived analytically. On the basis of incident data collected in New York City, the proposed approach was demonstrated to be successful.
The Trouble with Intercity Travel Demand Models
Authors: Miller Eric J.
Published: April 2007

The current state of operational practice in intercity travel demand modeling was critically reviewed. Conventional model structures and specifications as well as a range of theoretical and practical problems with current models were studied. These included problems with the total demand model specification, modeling intercity mode choice with nested logit models, modeling access and egress trips to and from common carrier line-haul modes, forecasting the demand for new modes of travel, dealing with highway congestion, aggregation issues in intercity models, and data collection issues. The study concluded with some suggestions about promising research and development directions for model improvement.
Understanding and Managing Conflict in Transportation Project Public Involvement
Authors: Barnes Gary , Langworthy Peter
Published: April 2007

The purpose of this project is to understand why public involvement in transportation project planning sometimes fails to reach a resolution that is acceptable to both the agency and the public and to determine how the process could be modified to reduce the likelihood of this outcome. A case study of a very complex and ultimately unsuccessful public involvement effort is described. This is used as the primary data source for development of a prototype of a general model of conflict management. It is concluded that there are a small number of independent dimensions around which conflict can arise and that some projects by their nature have a higher level of potential for conflict around one or more of these dimensions. The conclusion is that each of these dimensions needs to be analyzed and the likely level of conflict identified before the public involvement process begins and that the process should be explicitly structured to focus on addressing and resolving the high-conflict areas first. How public involvement efforts can be modified to better manage specific types of conflict and achieve mutually acceptable results is also described.
Gap Analysis of Public Transport Needs:Measuring Spatial Distribution of Public Transport Needs and Identifying Gaps in the Quality of Public Transport Provision
Authors: Currie Graham
Published: April 2007

A new approach to assessing the performance of public transport in meeting the needs of transport-disadvantaged people in the community is described. It reviews previous and current research in this area and describes how a new approach has been developed and applied with Hobart, Australia, as a study area. The approach aims to identify geographical gaps in public transport provision where travel needs are high but services are poor or nonexistent. It involves the use of readily available socioeconomic statistics to quantify the distribution of needs in the community with a single transport needs index. A public transport network model measures the public transport accessibility to these groups and a geographical information systems approach is used to display the distribution of the identified gaps between service and needs. The technique is highly relevant for smaller urban centers where the justification of public transport subsidies is largely social-needs-based—that is, where congestion and environmental benefits of transit are less critical. It is also relevant to recent work in transport accessibility audits and in the assessment of community impacts of alternative transit development strategies.
Forecasts of Future Vehicle Miles of Travel in the United States
Authors: Polzin Steven E. , Chu Xuehao , Toole-Holt Lavenia
Published: April 2007

Transportation infrastructure demand is driven by a need to replace existing infrastructure and to provide capacity to meet future travel demands. Thus, long-term transportation policy and financial planning benefit from an understanding of future investment needs. The hypothesis that the United States has reached a critical juncture in underlying sociodemographic conditions and travel behavior that will result in more moderate rates of future vehicle miles of travel (VMT) growth is explored. Two simple model formulations for predicting VMT are proposed, and historical trends for establishing inputs for scenario forecasts of future VMT are examined. An understanding of future VMT demand is critical for policy decision making and infrastructure investment planning. The VMT predicting formulas enable National Household Travel Survey information to be used to predict input components in forecasting future VMT. Two VMT predictions are provided and compared with a forecast reported in 2002 Status of the Nation's Highways, Bridges, and Transit: Conditions and Performance. While this study builds a case for slowing VMT growth, it hypothesizes that there may continue to be declining system performance despite slower VMT growth because more of the roadway system is at or near critical congestion levels and hence more susceptible to performance deterioration with modest increases in travel demand. It also suggests that land use pattern effects on travel behavior and person travel time budget growth are the least understood factors and possibly weak links in reaching conclusions about the ultimate pace of VMT growth.
Implementing a Program for Access Management in Texas: Lessons Learned
Authors: Frawley William E. , Eisele William L.
Published: April 2007

The Texas Department of Transportation recently sponsored research through the Texas Transportation Institute to provide recommendations for implementing a comprehensive access management program in the state. The research includes a provision to produce an access management guidebook for Texas for planners and engineers to use when planning, designing, and reviewing highway projects and access requests. This study describes some lessons learned in the research related to access classification, access spacing criteria, median alternatives, and overall implementation of the program. In terms of access classification, considerations include what type of access classification system is necessary to develop a successful program. For access spacing alternatives, lessons learned were related to what unsignalized access (driveway) spacing criteria guidelines are most applicable for adoption in Texas and why. In terms of lessons learned in overall implementation of the program, several questions were raised that have led to localized changes to the program that strengthened it overall. This study presents the results of these and other lessons learned, describes the background of access management, and outlines selected alternatives used in existing access management programs in other states. The status of the comprehensive access management program in Texas is presented. The research and experiences that emerged as a result of this project are expected to be useful to engineers and planners in Texas as well as other states that are developing or modifying comprehensive access management programs.
Delivering Best Value Highway Performance
Authors: Harding Nick , Godfrey Patrick , Benjamin Danny
Published: April 2007

Highway authorities in the United Kingdom and around the world are being challenged to deliver best value in highway maintenance and management. But what is best value, and how can it be delivered? This study explains the concept of best value and argues that, to be able to deliver, authorities must have a best value process in place that involves measuring their performance and then acting on the evidence they gain from their measurement. It introduces the use of a new approach to performance measurement that draws on the measurement of softer issues such as business culture and customer perceptions as well as the traditional hard measures; it is the actions that measurement stimulates that make the difference and not the measurement itself. The approach is based on work carried out at the University of Bristol, United Kingdom, and has been developed in work for U.K. highway authorities by Halcrow Group along with supply-chain partners. The need for a common language of measurement is explained. The common language creates understanding, providing a line of sight to the overall goals of the authority, and enables the authority to demonstrate continuous improvement—an essential element of best value delivery. The study demonstrates how this approach can be used for managing highway maintenance contracts and provides a practical example of how a performance measurement regime can be developed.