bluuebunny/crossref_metadata_2025 huggingface dataset:
Motor Vehicle Crashes and Land Use: Empirical Analysis from Hawaii
Authors: Kim Karl , Yamashita Eric
Published: April 2007

At first glance, the relationship between crashes and land use appears obvious. Various types of land uses tend to generate and attract different types of trips, and trip-making behavior affects the nature and volume of traffic. As the use of land intensifies, it does not seem unreasonable to expect that the potential exposure to crashes would also increase. Yet upon closer inspection, it is evident that crashes are more a function of the characteristics of drivers and travelers than the underlying uses of land. Using comprehensive police crash data linked to a land use database, the relationships between land use and automobile crashes in Hawaii are investigated. Recent developments in geographic information system technology and the availability of spatial databases provide a rich source of information with which to investigate the relationships between crashes and the environments in which they occur. Although the patterns in terms of crashes and the underlying use of land are difficult to describe, the implications of these findings for planners, developers, and those interested in traffic safety are apparent.
Evaluation of Lane Reduction “Road Diet” Measures on Crashes and Injuries
Authors: Huang Herman F. , Stewart J. Richard , Zegeer Charles V.
Published: April 2007

“Road diets” are often conversions of four-lane undivided roads into three lanes (two through lanes plus a center turn lane). The fourth lane may be converted to bicycle lanes, sidewalks, or on-street parking. Road diets are sometimes implemented with the objective of reducing vehicle speeds as well as the number of motor vehicle crashes and injuries. A study was conducted to investigate the actual effects of road diets on motor vehicle crashes and injuries. Twelve road diets and 25 comparison sites in California and Washington cities were analyzed. Crash data were obtained for these road diet (2,068 crashes) and comparison sites (8,556 crashes). A “before” and “after” analysis using a “yoked comparison” study design found that the percent of road diet crashes occurring during the “after” period was about 6% lower than that of the matched comparison sites. However, a separate analysis in which a negative binomial model was used to control for possible differential changes in average daily traffic, study period, and other factors indicated no significant treatment effect. Crash severity was virtually the same at road diets and comparison sites. There were some differences in crash type distributions between road diets and comparison sites, but not between the “before” and “after” periods. Conversion to a road diet should be made on a case-by-case basis in which traffic flow, vehicle capacity, and safety are all considered. It is also recommended that the effects of road diets be further evaluated under a variety of traffic and roadway conditions.
Whose Railroad Is This, Anyway?: Opportunities and Challenges in Regionalizing the Northeast Corridor
Authors: Roth Daniel L. , Aggarwala Rohit T.
Published: April 2007

The Northeast Corridor (NEC) is a regional asset that is planned, funded, and operated by a national institution—the National Railroad Passenger Corporation (Amtrak). This asymmetry may prevent the NEC from realizing its potential. Despite completion of the Northeast High-Speed Rail Improvement Project, the NEC will require massive investments in coming years. The historical funding pattern—via annual appropriations from the U.S. Congress—is unlikely to meet these needs. Regional funding sources may be able to provide sustained funding; this approach is closer to the state or local funding plus federal match regime that prevails in other modes and is expected to be used for new passenger rail corridors. A regional partnership might allow better planning for the Northeast’s long-term rail infrastructure needs and for NEC services; it might also provide a channel through which the region could assist Amtrak in funding additional frequency or lowering fares. Amtrak’s successful state partnerships, particularly with California, provide models for a regional partnership. The key problem is that in the Northeast no single government can address transportation at a regional level. As a result, an integrated partnership for Amtrak would likely require the creation of a regional entity for the corridor. Through its funding abilities, this entity could resolve the dilemma that exists today: Amtrak must preserve its national constituency and support, and the states fear losing access to federal funding. Significantly, resolving this dilemma does not necessitate any change in Amtrak’s current largely unified operation of the railroad.
Buying into Amtrak: One Way to Fit American Railroads into Government’s Transportation Spending
Authors: Perl Anthony
Published: April 2007

The nearly certain failure of the National Railroad Passenger Corporation (Amtrak) to meet a legislated mandate of attaining commercial self-sufficiency in 2002 and the major reassessment of transportation policies precipitated by America’s war on terrorism have opened a window of opportunity to improve the terms by which passenger trains fit into U.S. transportation policy. The future success of intercity passenger rail depends on going back to the drawing board of transportation policy to revisit railroads’ access to public finance. A major change from the public policy status quo on the rail mode’s financing recommends restructuring Amtrak to become a joint venture between government and privately owned railroads, as was envisioned by the original Rail Passenger Service Act of 1970. This change in corporate ownership would occur parallel with, and facilitate the implementation of, a new account in the transportation trust fund devoted to improvements in intercity rail infrastructure. This account would receive the tax revenues collected from some combination of federal excise taxes levied on railroad diesel fuel, other transportation expenditure by railroads (e.g., parts and equipment), passenger tickets, and express freight shipments. A share of railroads’ income taxes (or other sources of public revenue) could supplement the public revenues flowing into such a fund. Expenditures would be made on upgrading rail infrastructure capacity to handle increasing volumes of freight and passenger traffic and, where appropriate, to develop dedicated high-speed passenger rail infrastructure alongside existing rail rights-of-way.
Financially Internalizing Passenger Rail-Generated Nonuser Benefits
Authors: Schwartz Peter
Published: April 2007

One of the primary challenges facing passenger rail developers today is to bridge the gap between the distinct economic and financial forms of evaluation through which proposals for new or redeveloped rail systems are judged. Of particular importance is the difference in the two methods’ treatment of nonuser benefits, which are generally included in economic analysis but excluded from financial evaluation. The use of established tools, such as emissions credits and economic incentive programs (currently used to control industrial air pollution), are proposed as a means of capturing and monetizing nonuser benefits through passenger rail-generated emissions reductions. If this approach is adopted, then passenger rail developers will gain access to a funding source that will offset the costs associated with generating these benefits, thus automatically internalizing the costs within the process of financial evaluation.
Diesel Locomotive Retrofit: Conceptual Design with Twin Turbines Reduces Overall Emissions
Authors: Pier Jerome R.
Published: April 2007

The fine particulate matter component of diesel engine exhaust has been declared by the state of California to be a human carcinogen at any concentration and is therefore subject to measures for its reduction or total elimination. The diesel locomotive contribution to this problem is projected to be 46% of the total particulate tonnage from diesel engines in California in 2010. A conceptual design substitutes gas turbines for the main traction engine and head-end power (HEP) engine of a typical diesel electric commuter locomotive. Retaining the existing HEP engine while replacing the traction engine also is evaluated. Relying on burning conventional diesel No. 2 fuel oil, the conceptual design is projected to significantly reduce or eliminate measurable particulate matter and significantly reduce other exhaust pollutants. Because the gas turbine readily adapts to natural gas as a fuel without any loss in performance, the economics and additional emissions benefits also will be developed for the use of liquefied natural gas.
Improved Spiral Geometry for High-Speed Rail and Predicted Vehicle Response
Authors: Klauder Louis T. , Chrismer Steven M. , Elkins John
Published: April 2007

Two railroad curve transition spiral shapes are compared with respect to their dynamic performance: the traditional linear shape and an improved shape intended to provide optimal dynamic performance. The improved shape is attractive because it gives much better dynamic performance and flows from an improved way of thinking about spirals. The improved spiral design method and spiral shape to be evaluated are discussed, then results from simulating the operation of a rail vehicle over an improved spiral and over the corresponding traditional spiral are compared. The simulations were done using the NUCARS simulation program and a model of the Amtrak Acela passenger car. The simulated motion of the vehicle over the traditional spiral exhibits undesirable fluctuations of two types with different strengths and distinct causes. The weaker fluctuations are the result of impacts of wheel flanges against the outside rail partway through the spiral. These impacts might be softened or eliminated by use of a truck design that could steer more effectively than the design that was simulated (or by making spirals much longer). They are not much affected by the kind of spiral geometry used. The stronger fluctuations are caused by the shape of the traditional spiral and particularly by the abruptness with which superelevation ramp angle changes at each end. The improved spiral geometry eliminates these fluctuations almost completely and thereby will improve ride comfort and may reduce the cost of maintaining spiral track alignment.
Microscopic Modeling of Gage Widening
Authors: Zhang Yu-Jiang , Carr Gary , Fateh Mahmood
Published: April 2007

Many track-related derailments are caused by gage widening, a track safety factor that develops primarily as a result of degradation of the ties and fastenings. Gage degradation of a wooden-tie track is examined from a mechanistic point of view. A finite element model is used to simulate the lateral rail deflection under load and to investigate the growth mechanism of bad tie clusters. The ties are assumed to be in new condition at the beginning. Because the degradation of individual ties is not uniform, one tie is assumed to degrade first, which leads to load redistribution to the adjacent ties. Several different configurations and degradation patterns of tie clusters are examined, and rail deflections at each degrading stage are simulated for several scenarios. Results of the analysis indicate that rail deflection with different tie lateral-strength levels is not linear but follows a third-order polynomial trend. Rail deflection increases much more quickly when the lateral strength of a tie degrades below 50% of its capacity. The gage-restraint capacity of a track is determined not solely by the absolute number of defective ties in the track but mainly by bad tie clusters and the configuration of those clusters.
Quality Management of Base and Subgrade Materials with Seismic Methods
Authors: Nazarian S. , Yuan D. , Arellano Miguel
Published: April 2007

The acceptance criteria for compacted geomaterials (such as base and subgrade) are typically based on adequate in-place density. Unfortunately, the design of a given project is based on engineering parameters, such as strength and stiffness. A procedure based on seismic techniques to measure the modulus layer by layer shortly after placement is presented. The major advantage of seismic methods is that similar results are anticipated from the field and laboratory tests as long as the material is tested under comparable conditions. This unique feature of seismic methods in material characterization is particularly significant in quality control and quality assurance for ground treatment before, during, and after construction. Simplified field and laboratory tests are suggested that can be performed and interpreted rapidly and nondestructively so that problem materials can be identified before construction and any problems during the construction process can be adjusted. The field and laboratory methods are incorporated so the results can be readily reconciled without any scaling or simplifying assumptions. The simplified laboratory tests can be used to develop the ranges of acceptable properties for a given material. Nondestructive field tests can be performed to determine whether the contractor has achieved the minimum specified stiffness. A concept that uses seismic nondestructive testing technology to evaluate compacted materials and describes the equipment and setups developed for implementing the technology in both field and laboratory tests is presented. The methods have shown promise as practical tools for use by the highway and construction industries. Currently, the procedure is being implemented on a trial basis by the Texas Department of Transportation.
Resilient Modulus of Minnesota Road Research Project Subgrade Soil
Authors: Dai Shongtao , Zollars John
Published: April 2007

Laboratory remolded subgrade soil samples have been widely used to study subgrade resilient modulus ( M r). But physical conditions, such as moisture content and density, of such specimens may not represent in situ conditions very well. Therefore, AASHTO and the Long-Term Pavement Performance program have recommended that undisturbed, thin-walled tube samples be used to study subgrade resilient behavior. The Minnesota Department of Transportation (MnDOT) is developing mechanistic-empirical pavement design approaches through the Minnesota Road Research project and has realized the importance of M r in the design approaches. Currently, MnDOT is making an effort to study the M r of unbound pavement materials through laboratory experiments. Under a research project at MnDOT, several thin-walled tube samples of sub-grade soil were obtained from six different pavement sections at the Minnesota Road Research project. Repeated loading triaxial tests were conducted on the soil specimens to determine the M r at the MnDOT laboratory. Also, some soil properties, such as resistance, R-value, and plasticity index, were obtained. R-value is an indicative value of performance when soil is placed in the subgrade of a road subjected to traffic. Two constitutive models (the Uzan-Witczak universal model and the devia-tor stress model) were applied to describe the M r. The objectives of the research were to compare these two well-known constitutive models in describing subgrade soil resilient behavior and to study the effects of material properties on the M r. From the specimens tested, the experimental results showed that the universal model described the subgrade M r slightly better than the deviator stress model, and the coefficients in these two constitutive models were found to have correlation to material properties. Also, no well-defined relationships between the R-value and the coefficients in the constitutive models were observed from the results of the tested specimens.
Characteristics of Geogrid-Reinforced Aggregate Under Cyclic Load
Authors: Leng Jianjun , Gabr Mohammed A.
Published: April 2007

The characteristics of geogrid-reinforced aggregates over soft subgrade soil were investigated through a laboratory-testing program. Nine cyclic plate load tests were conducted with varying base layer thickness and reinforcement type. Results indicated that aggregate base course (ABC) degraded under cyclic loading as manifested by an increase in stresses at the interface between the ABC and the subgrade with increasing number of cycles. The improvement in stress distribution due to geosynthetic inclusion at the interface of ABC and subgrade soil is indicated by a decrease in the measured maximum stress (under the center of the loaded area) and the measurement of a more uniform stress distribution on the subgrade soil layer. The higher modulus geogrid provided a better load-spreading effect compared with a lower modulus geogrid used in the testing. The improvement in plastic surface deformation was related to two aspects: ( a) decrease in vertical deformation of the subgrade and ( b) decrease in lateral spread of the ABC. A model that incorporates the mechanics of reinforcement contributions to deformation and stresses and the effect of ABC degradation as a function of number of load cycles needs to be developed for the transportation community to fully realize the benefits of reinforcement in such an application.
New York State Department of Transportation Rock Slope Rating Procedure and Rockfall Assessment
Authors: Hadjin Douglas J.
Published: April 2007

The New York State Department of Transportation’s (DOT’s) Geotechnical Engineering Bureau has significant responsibilities in the field of rock and soil mechanics. Not the least of these is minimizing rockfalls and landslides and quickly responding when they occur. The Geotechnical Engineering Bureau has a long history of gathering and managing information about rock and soil slopes to anticipate needs and allocate resources. In 1988, the New York State DOT began to maintain rock slope, earth slope, and rockfall databases. Potential rockfall sites were identified and evaluated according to procedures presented by FHWA. In 1992, the New York State DOT devised its own rock slope rating system. To date, more than 2,800 rock slopes have been evaluated using the New York State DOT rating procedures. In addition, more than 475 rockfall incidents have been cataloged and incorporated into the New York State DOT databases. These databases have been integrated into a geographic information system environment.
Slope Stability of Loess Revisited
Authors: Lohnes Robert A. , Kjartanson Bruce H.
Published: April 2007

Guidelines to estimate the potential for slope instability and to give new insight into the slope evolution process in regions of deep to moderately deep loess were developed. Laboratory test data indicated a general trend of decreasing cohesion with increasing moisture content for each loess type. Curves for maximum stable slope height to slope angle were produced from the Culmann analysis using average shear strength parameters and unit weight values. Comparison of the theoretical curve for friable loess with empirical data showed good agreement for estimating maximum height at slope angles greater than 50°. Stability of slopes with slope angles ranging from 80° to 20° and corresponding heights calculated from an empirical relationship were assessed using Spencer’s method. Slopes with angles between 80° and 40° had safety factors close to 1.0. For gentler slopes, the safety factors range from about 1.4 to about 2.0 as the slope angle decreases. Empirical data may be a more reliable indicator of potential slope instability than the Culmann analysis over a wide range of slope angles. Analysis of slope failures after one intense rainstorm indicated that friable loess on steep slopes does not become saturated; however, the cohesion is reduced to a level that causes landslides. On gentle slopes, the soil became saturated above the liquid limit, thereby causing mudflows. Although natural events such as this are rare, anthropogenic activity may create slope instability. Analysis of another landslide below a roadway on a friable loess slope indicated a stable to marginally stable condition without surcharge loads, but safety factors dropped below 1.0 when a truckload surcharge was applied. These analyses suggest that natural and cut slopes in friable loess are at safety factors only slightly greater than 1.0. Any construction activity can upset this delicate equilibrium and result in a landslide.
Condition Assessment of Buried Metal-Tensioned Elements
Authors: Fishman K. L. , Gaus M. P. , Withiam J. L. , Bontea M.
Published: April 2007

Application of nondestructive test (NDT) methods to assess the condition of metal-tensioned elements in geotechnical engineering applications, including rock bolts, ground anchors, and soil nails, is described. Electrochemical tests, such as measurements of half-cell potential and polarization, were used to detect the presence of corrosion and to evaluate the integrity of corrosion protection systems. Mechanical wave propagation techniques, such as impact and ultrasonic tests, were used to locate features along the length of an element including loss of cross section from corrosion. Interpretation of test results requires knowledge of the electrical continuity between elements being tested and of the details of the installation of the system being evaluated. The utility of the NDTs was evaluated under controlled conditions on bench scale specimens in the laboratory and on buried specimens at a specially developed in situ test facility. However, given the numerous variables inherent to field installations that may have an effect on the measurements, the performance of the NDT technologies needed to be studied in the field. Results from condition assessment employing NDT technologies of tiebacks for a quay wall in Buffalo, New York, and rock bolts along a highway cut in Dresden, New York, are described. Background information is given for each site, including a description of the aggressiveness of the environment relative to corrosion in terms of results from chemical analysis of native soil samples. Results from NDT correlated well with features of the tieback and rock bolt installations. Electrochemical test results indicated that corrosion was occurring, but the wave propagation tests did not indicate any significant loss of cross section. NDT measurements should be archived to serve as a baseline against which future NDT results may be compared.
Cold In-Place Recycling and Full-Depth Strengthening of Clay-Till Subgrade Soils Results with Cementitious Waste Products in Northern Climates
Authors: Berthelot Curtis , Gerbrandt Ron
Published: April 2007

Saskatchewan is experiencing significant increases in commercial truck traffic due to grain transportation rationalization, consolidation of the rural grain elevator system, rural economic diversification, and expansion of resource industries. Although increasing truck traffic has longterm implications for the primary pavement system, significant increases hold immediate implications for thin paved roads; many were not originally designed to accommodate heavily loaded commercial trucks. There is a clear need to strengthen many Saskatchewan thin pavements. However, conventional structural strengthening typically involves regrading and granular subbase-base overlay systems, often too expensive because of the cost associated with aggregate hauls and regrading. As a result, the Saskatchewan Department of Highways and Transportation is investigating the use of cold in-place recycling and full-depth cementitious stabilization to strengthen Saskatchewan thin pavements. To this end, industrial waste coproducts such as coal fly ash, bottom ash, and kiln dusts are being investigated as structural cementitious soil stabilizers. The results are presented from preconstruction site investigation methods, laboratory materials characterization, and in situ quality assurance test results. Field performance after 2 years shows cold in-place recycling and cementitious stabilization to be a technically and economically feasible solution for strengthening Saskatchewan thin paved roads built on clay-till subgrades.
Effect of Wet-Dry Cycles on Resilient Modulus of Class C Coal Fly Ash-Stabilized Aggregate Base
Authors: Khoury Naji N. , Zaman Musharraf M.
Published: April 2007

A laboratory study was undertaken to investigate the effect of wet-dry (W-D) cycles on low-quality aggregates stabilized with Class C coal fly ash (CFA). Resilient modulus ( M r), unconfined compressive strength, and elastic modulus were used to evaluate this effect. Cylindrical specimens stabilized with 10% CFA, cured for 3 and 28 days, and subjected to different W-D cycles were tested. The M r values of 28-day-cured specimens increased as W-D cycles increased up to 12, beyond which a reduction was observed. For 3-day-cured specimens, M r increased with the number of W-D cycles. W-D action produced a greater detrimental effect on 28-day-cured specimens than on 3-day-cured specimens. The M r values of 28-day-cured specimens subjected to 30 cycles were approximately 5% lower than the corresponding M r values of specimens without any W-D cycles. The M r values of 3-day-cured specimens subjected to 30 W-D cycles, however, increased approximately 55% compared with the corresponding M r values of specimens with no W-D cycles. Also, it was found that 12 to 30 W-D cycles could be considered adequate to have a noticeable negative effect on 28-day-cured specimens; however, more than 30 cycles are needed for 3-day-cured specimens. Additionally, the positive effect of curing time was more dominant on 3-day-cured specimens, and the detrimental effect of W-D cycles was more influential on 28-day-cured specimens.
Precracking of Soil-Cement Bases to Reduce Reflection Cracking: Field Investigation
Authors: Scullion Tom
Published: April 2007

A new approach to minimize the amount of shrinkage cracking in newly constructed soil-cement (S-C) bases is described. The approach, microcracking, is demonstrated on three city streets constructed in October 2000 in a new subdivision of College Station, Texas. The bases on these streets were designed to meet the Texas Department of Transportation’s (DOT’s) specification 272 requiring an unconfined compressive strength of 500 psi after 7 days moist cure. The base aggregate available in this area is a sandy gravel. Meeting the Texas DOT strength requirement requires a high cement content, typically 6% to 8%. However, with this cement content, the city has experienced substantial shrinkage cracking. To mitigate this problem, the microcracking approach was evaluated. Based on research from Austria, this requires a maximum of five passes of a steel wheel vibratory roller applied a few days after finishing. This application introduces a network of hairline cracks into the base early in its life with the idea that these microcracks will minimize the major shrinkage cracks associated with S-C bases. Furthermore, because this is performed only a few days after placement, the microcracking will not affect the pavement’s overall structural capacity; the cracks will reheal and the base will continue to gain strength with time. During this study, the base stiffness was monitored with both the Humboldt Stiffness Gauge and a falling weight deflectometer (FWD). Large reductions in stiffness were monitored immediately after microcracking, but after 2 days of recovery, the base regained most of its initial stiffness. After 6 months, a visual inspection was made and the base stiffness was calculated from FWD data. The base was found to be very stiff, and only minor amounts of cracking were found in each of the three monitored sections. Consequently, draft specifications have been developed for incorporating microcracking in future projects.
Laboratory Testing of Suction and Deformation Properties of Base Course Aggregates
Authors: Kolisoja Pauli , Saarenketo Timo , Peltoniemi Hannu , Vuorimies Nuutti
Published: April 2007

The most significant problem related to base course aggregates in Finland and in many other countries affected by seasonal frost is the development of permanent deformations, especially during the frost-thawing period. From 1996 to 2000, a series of research projects was carried out to examine the mechanical, thermodynamic, electrical, and chemical factors that affect the seasonal variation of strength and deformation behavior of base course aggregates. The test series included frost heave tests and normal as well as long-lasting cyclic-loading triaxial tests performed in situations simulating seasonal conditions of dryness, moisture, and the period following a freeze—thaw cycle. Also, chemical and suction properties of the selected aggregates were examined. Results show clearly that even though the aggregates were reflecting significantly different permanent deformation behavior, the resilient deformation properties of all tested aggregates were relatively good, and their resilient modulus values were not significantly lowered even during the thawing phase. Meanwhile, the suction properties of aggregates appeared to have a significant effect on the deformation behavior. Suction properties, in turn, result foremost from the fines content but also from chemical properties of the aggregate. A fairly simple tube suction test proved to function well in identifying the problematic aggregates and in defining appropriate binder types and their required amounts. Further, the results suggest that the properties of aggregates bound with emulsified bitumen are not necessarily improved when binder content is increased.
Investigation of Recycled Concrete Made with Limestone Aggregate for a Base Course in Flexible Pavement
Authors: Kuo Shiou-San , Mahgoub Hesham S. , Nazef Abdenour
Published: April 2007

The research objectives were to investigate the feasibility of using recycled concrete aggregate (RCA) as a base course material in asphalt pavement, to evaluate the physical properties of RCA, and to develop practical and reliable guidelines and specifications. The tasks included literature review, sample collection, laboratory testing, accelerated performance testing and pavement distresses monitoring, falling weight deflectometer (FWD) test, theoretical analysis of pavement, and development of guidelines and specifications for the use of Florida RCA. Three test sections of asphalt pavement were constructed at the University of Central Florida’s circular accelerated test track. Two sections of different thicknesses were constructed with RCA base and one section with limerock (LR) base. A total of 362,198 load repetitions were applied to the test sections. This is equal to 811,324 repetitions of the 18-kip (80-kN) equivalent single-axle load. The pavement distresses of rutting, cracking, and settlement were monitored during the course of the performance testing. The FWD test was performed on the pavement test sections to backcalculate the in situ resilient moduli of RCA and LR for theoretical analysis of life expectancy. The findings support the hypothesis that RCA can be used effectively as a base course when appropriate quality control techniques are used. On the basis of the information obtained, a set of specifications for the use of RCA as a base course in flexible pavements was developed.
Geographical Variation in Cost of Air Travel: Analysis of the Domestic Airline Fares Consumer Report
Authors: Anderson William P. , Gong Gang , Lakshmanan T. R.
Published: April 2007

There is significant geographical variability in the cost of American domestic air travel. This variability may be attributable to a number of factors, including scale economies, the average length of trips, airport congestion, and other factors that vary by region. Also, in the post-deregulation environment the cost of air travel may depend on the level of competition in specific spatial markets. Data from Domestic Airline Fares Consumer Report are used to conduct descriptive and statistical analyses of the spatial variability of air travel cost. The ratio of average fare to distance (fare per mile) is used as a general measure of relative cost, which is observed to vary significantly across cities. Two regression analyses seek to identify the factors that drive this variation. The first takes weighted average fares in the 50 largest cities as its dependent variable, whereas the second takes average fares in more than 6,500 origin-destination pairs as its dependent variable. Results of both analyses indicate that fare per mile declines with the length of trip. They both also indicate a large and statistically significant competitive effect, whereby single-carrier market share has a positive effect on the fare. Regional variations are indicated in the results of the first regression, with higher fares in the Northeast and Midwest than in the West and South. The second set of regression results also indicates that, other things being equal, fares with origins or destinations in large cities tend to be higher.
Parking Capacity Requirements for Relocated Airports: The New Athens International Airport
Authors: Psaraki V. , Stathopoulos A. , Abakoumkin C.
Published: April 2007

The development of a parking plan for a relocated airport requires detailed documentation of parking demand forecasts, capacity assessment, revenues, and capital expenditures. These tasks are heavily dependent on characteristics of the access trip to the airport. Parking capacity requirements are estimated via passenger classification and discrete choice modeling at the existing airport. Both are conducted via passenger and parking survey studies specifically designed for this purpose. The resulting models are then used to forecast the short-term and long-term parking supply for the relocated airport by proper adjustment of the attribute values. The method is applied to the new Athens International Airport.
User-Perceived Level-of-Service Evaluation Model for Airport Baggage-Handling Systems
Authors: Pagani Joanne , Abd El Halim A. O. , Hassan Yasser , Easa Said
Published: April 2007

Background research shows that the design standards for baggage-handling systems (BHSs) do not consider the level of service (LOS) as perceived by the passengers. Moreover, it is evident that a national strategy for defining the LOS of BHSs and the means to improve it are lacking. An LOS model that can ascertain the LOS being achieved by the BHS would be beneficial to airlines, passengers, and airport designers. Such a model would enable airport authorities and airlines to determine when improvements are required and to develop a strategy for implementing the needed changes. In a study performed at six Canadian airports, more than 800 passengers rated the LOS provided by the overall BHS and its components. The results confirm that traditional time and space standards currently used by aviation agencies, airports, airlines, and baggage handlers are not adequate. Subsequently, a user-perceived LOS model was developed and should be useful in evaluating BHSs nationwide.
Time-Dependent Network Assignment Strategy for Taxiway Routing at Airports
Authors: Baik Hojong , Sherali Hanif D. , Trani Antonio A.
Published: April 2007

A time-dependent network assignment strategy is proposed for efficiently handling aircraft taxiway operations at airports. The suggested strategy is based on the incremental assignment technique that is frequently adopted in many urban transportation studies. The method assumes that the current aircraft route is influenced by previous recent aircraft assignments in the network. This simplified assumption obviates the need for iterative rerouting procedures for attaining some pure equilibrium state, which in any case might not be achievable in practical airport taxiway operations. The main benefit of applying the time-dependent network assignment approach to taxiway operations is the reduction and avoidance of possible conflicts that produce delays. Also proposed is a prototype of a fully time-dependent network assignment scheme that dispatches aircraft based also on future anticipated assignment. The suggested methodology could be adopted in the deployment of automated taxiway guidance systems that are planned for future implementation at congested airports.
Integrated Simulation Method to Evaluate the Impact of New Large Aircraft on Passenger Flows at Airport Terminals
Authors: Chiu Chiung-Yu , Walton C.
Published: April 2007

The development of new large aircraft (NLA) has been a topic of considerable interest and speculation. The first generation of the NLA with 555-seat capacity will presumably enter into commercial service by 2006. Due to the greater dimensions of the NLA and more simultaneous arrival passengers, there will be substantial impact on existing airports after its launch. Terminal operations, particularly individual passenger processing facilities, will be one of the most significantly affected components in the entire airport system. An integrated simulation method is proposed to evaluate the potential effects on the operation performance of primary processing facilities. The method uses scenario analysis in a before-and-after context and attempts to analyze the impact under current uncertainty of the operating characteristics of the NLA and its market share. The arrival passenger flow is modeled as a queuing network system, composed of a series of passenger processing facilities. The derivation of arrival and service probability distributions in the model is based on a survey of international airports and on observational data collected at selected international terminals. The integrated method may assist airport operators in examining the potential bottlenecks in the arriving-passenger flow and in evaluating operations. The simulation results indicate that the introduction of the NLA will have the largest effect on the baggage claim system.
New Aircraft Overrun Database, 1980-1998
Authors: Kirkland I. D. L. , Caves R. E.
Published: April 2007

A database for overruns of runways by aircraft is described. It contains 185 fields of data on 180 accidents and incidents that occurred in the English-speaking world between 1980 and 1998 to jet and turboprop aircraft used for transporting passengers or freight on civil operations. The data have been normalized to account for differences in airfield characteristics and aircraft performance. A first-cut analysis shows about two overruns per 10 million movements, three-quarters being after landing and one-quarter after an aborted takeoff. The majority of takeoff overruns occurred after a late decision to abort. A high proportion of overruns involves aircraft operating near or over their legal operating weight. Wet runways, contaminated runways, and tailwinds were factors in many overruns, particularly after landing fast or long. There is no statistical evidence that a precision approach improves the quality of approaches that subsequently become overruns. A large number of overruns have terminated beyond the previous international recommendations for the length of protection off the end of runways, and some 10% exceed the new recommendations.
How Airport Context and Service Are Related to General Aviation Aircraft Operations
Authors: Jolicoeur Peter A. , Khattak Asad J.
Published: April 2007

Nationwide, there is an effort to improve small airport facilities for reducing demand and congestion at primary commercial airports. Identifying the factors that are associated with operations can help decision makers select new airport sites, choose between airport improvement alternatives, and anticipate future service needs. There are many local benefits to attracting aircraft traffic, as operations are often associated with positive economic impacts. This research seeks to identify airport service and contextual variables that have strong associations with general aviation aircraft operations, in which an operation is defined as one aircraft landing or departing. It builds on the existing literature by incorporating aspects of land use, ground access, economic productivity, and regional transportation factors into a robust operations model. Data from multiple sources were combined using a geographic information system to create a unique longitudinal data set providing a comprehensive view of 41 North Carolina airports over a 12-year period, from 1988 to 1999. Fixed- and random-effects regression models were estimated, and many of the hypothesized factors associated with operations, including local population, surrounding commercial development, and available aviation services, were found to be statistically significant. Understanding these factors is useful for airport system planning, from anticipating future demand to attracting general aviation operations away from congested, primary airports.
Round-Robin Study for Field Permeability Test
Authors: Cooley L. , Maghsoodloo Saeed
Published: April 2007

Recently, a field permeability device and test procedure have been developed and tested by the National Center for Asphalt Technology (NCAT) that have shown the ability to identify pavement areas with high permeability to water. This device works by measuring the amount of water that flows into a pavement over a given time period by using a falling-head approach. Based on work conducted by NCAT, the use of this field permeability device has many potential benefits to the hot-mix asphalt industry. The field permeability device can be used as an almost real-time estimate of mat density and may be a good indicator of longitudinal joint quality. Because of the success NCAT has had with the device to date, a study was needed to evaluate the repeatability and reproducibility of the test method. Results of the round-robin study indicated that an estimate of permeameter–operator reproducibility was 10.0 × 10−5 cm/s. An overall standard deviation on permeability measurements was found to be 24.4 × 10−5 cm/s. Additionally, criteria were developed based on the variability of test results to specify field permeability testing for quality control type testing to ensure impermeable pavements.
Time-Temperature Superposition for Asphalt Concrete at Large Compressive Strains
Authors: Schwartz Charles W. , Gibson Nelson , Schapery Richard A.
Published: April 2007

A study was performed to evaluate whether time-temperature superposition principles would continue to apply to the behavior of asphalt concrete beyond the commonly assumed small strain (<100 με) limits. A series of unconfined uniaxial compression constant crosshead displacement rate tests were performed to large-strain values. The measured axial stress versus axial strain data were cross-plotted to produce stress versus reduced time master curves and corresponding temperature shift functions at various strain levels to determine the maximum strain level at which time-temperature superposition remains valid. The results suggest that asphalt concrete remains a thermorheologically simple material well into the postpeak region (i.e., that time-temperature superposition is valid throughout the useful stress-strain response). The results further suggest that the temperature shift function aT may be only a weak function of strain level. For many practical engineering purposes, however, the differences between the small-strain and large-strain temperature shift relations may be of negligible importance.
Toward a Micromechanics-Based Procedure to Characterize Fatigue Performance of Asphalt Concrete
Authors: Guddati Murthy N. , Feng Zhen , Kim Y.
Published: April 2007

A lattice-based micromechanics approach is proposed to characterize the cracking performance of asphalt concrete. A random truss lattice model was introduced and investigated for simulating the following: ( a) linear elastic and viscoelastic deformation of homogeneous materials in axial compression and shear loading experiments, ( b) linear elastic deformation and the stress field in heterogeneous materials in an axial compression loading experiment, and ( c) damage evolution in elastic solids under an indirect tensile test. The simulation results match well with the theoretical solutions and show excellent promise in predicting cracking patterns in the indirect tensile test. A brief discussion about ongoing work is also presented.
Predicting Viscoelastic Response and Crack Growth in Asphalt Mixtures with the Boundary Element Method
Authors: Birgisson Bjorn , Sangpetngam Boonchai , Roque Reynaldo
Published: April 2007

It has long been accepted that cracking of hot-mix asphalt pavements is a major mode of premature failure. Many state agencies have verified that pavement cracking occurred not only in fatigue cracking, in which a crack initiates from the bottom of the asphalt layer, but also in other modes such as low-temperature cracking and the more recently identified top-down cracking. To improve current pavement designs and the cracking resistance of mixtures, it is necessary to understand the mechanisms associated with crack initiation and crack growth in hot-mix asphalt mixtures. However, the complexity of the problem and the lack of simple-to-use analysis tools have been obstacles to a better understanding of hot-mix asphalt fracture mechanics and the development of better hot-mix asphalt fracture models. Until today, the well-known finite element method has been the primary tool used for modeling cracks and their effects in mixtures and pavements. Unfortunately, it is both complex and numerically intensive for fracture mechanics applications. The displacement discontinuity boundary element method is presented, which is a numerical method that has been very successful in many other engineering fields, as a potential method for modeling cracking in hot-mix asphalt mixtures and pavements. A series of examples are provided to illustrate the effectiveness of the method in dealing with cracks, crack propagation, and visco-elasticity in hot-mix asphalt. It was concluded that the method was easy to use, resulted in accurate solutions, required minimal computation time, and significantly simplified the modeling of crack-related problems.
Determining the Low-Temperature Fracture Toughness of Asphalt Mixtures
Authors: Marasteanu Mihai O. , Dai Shongtao , Labuz Joseph F. , Li Xue
Published: April 2007

There has been a sustained effort in applying fracture mechanics concepts to crack formation and propagation in bituminous pavement materials. Adequate fracture resistance is an essential requirement for asphalt pavements built in the northern part of the United States and Canada, for which the prevailing failure mode is cracking due to low-temperature shrinkage stresses. The current Superpave® specifications address this issue mainly through the use of strength tests on unnotched (smooth boundary) specimens. However, recent studies have shown the limitations of this approach and have suggested that fracture mechanics concepts, based on tests performed on notched samples, should be used instead. Research in progress at the University of Minnesota investigates the use of fracture mechanics principles to determine the low-temperature fracture properties of asphalt mixtures. A testing protocol is presented that makes it possible to obtain multiple measurements of fracture toughness as a function of crack propagation based on the compliance method to measure crack length. An increase in fracture toughness with crack length is observed, which is consistent with the behavior displayed by other brittle materials. The plateau of the curves may be representative of the asphalt concrete resistance to fracture, because the initial values can be significantly influenced by the presence of the inelastic zone at the crack tip.