bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimum Design and Operation of Airport Passenger Terminal Buildings
Authors: Saffarzadeh Mahmoud , Braaksma John P.
Published: April 2007

The standard procedures for the design and operation of airport passenger terminal buildings (PTBs) often lead to either high operating and maintenance costs or passenger dissatisfaction. A new philosophy of planning, design, and operation that is based on optimum resource utilization and passenger flow management and control was initiated. An optimum resource utilization model was developed on the basis of important issues such as an early association of physical and operational plans, the stochastic nature of airport demand, the long-term costs of over- and undersupply of PTB facilities, performance measures, and utilization of scarce resources. Three submodels were developed as part of the optimum resource utilization model, that is, the simulation, optimization, and flow management and control models. An object-oriented simulation model, which consists of a set of simple submodels and nodes, was developed to perform as a real-world airport terminal. The optimization model will provide a list of optimum required resources for all predefined segments of the PTB. A real-time flow management and control model was developed, in which the PTB operator would be able to respond to preplanned or spontaneous events.
Use of Public Transportation by Airport Passengers
Authors: Mandle Peter B. , Mansel Douglas M. , Coogan Matthew A.
Published: April 2007

Transportation plans in some communities have focused on providing rail service to the local airport, whereas other communities have emphasized bus and van service. The opportunity for rail, bus, and van service at U.S. airports and the use of these services by airline passengers at the large airports in the United States and overseas are reviewed. On the basis of the airline passenger mode share data presented, there appears to be a “ceiling” on the market for public transportation (rail, bus, and shared-ride vans) at airports in the United States. The ceiling on public transportation use by airline passengers in most cities appears to be about 10 to 15 percent, even at airports with rail service. The primary potential market for rail service is passengers who have trip ends in downtown areas (or other areas well served by rail), who are traveling alone and who have little or no baggage, and who are familiar with the rail service and are able to walk from the rail station to their final destination. In many cities the objectives of transportation planners and airport operators (i.e., encouraging the use of efficient access modes) might best be served by transportation plans that focus on bus or van services.
Analysis of Pedestrian Gait and Perception-Reaction at Signal-Controlled Crosswalk Intersections
Authors: Fugger Thomas F. , Randles Bryan C. , Stein Anthony C. , Whiting William C. , Gallagher Brian
Published: April 2007

Pedestrian accident analysis and reconstruction remain the most difficult areas for the accident analyst. Although data relating to average pedestrian walking speeds, perception-reaction, and pedestrian accident reconstruction can be found in the literature, proper pedestrian study data pertaining to real-life situations are lacking. Pedestrians were observed at signal-controlled crosswalk intersections, and their perception-reaction to the crosswalk signal, acceleration rate to reach constant walking velocity, and average walking speed once steady state velocity is achieved were determined. Experimental test data collected regarding pedestrian gait analysis, initiation, and steady state walking speeds are presented. “Real world” pedestrian observations were gathered at a variety of intersections, ranging from busy downtown intersections to suburban intersections throughout the greater Los Angeles area. Kinematic data on pedestrian movements were obtained using high-speed digital video. A high-speed video motion analysis system was used to reduce the data and to obtain the mean acceleration and time to steady state walking velocity. Perception-reaction data collected on 288 subjects show a significant percentage of the pedestrians initiating movement within 1 s of Walk light illumination. Some differences were observed when the state of anticipation was being considered, and these results are presented. The mean acceleration (0.14 ± 0.09 g) and steady state velocity (1.36 ± 0.24 m/s) values did not demonstrate a significant difference between males and females. The width of the street or initial state of anticipation did not have an effect on either mean acceleration values or steady state velocities.
Locator Tones for Pedestrian Signals
Authors: Louise Bentzen Billie , Barlow Janet M. , Gubbé Douglas
Published: April 2007

The two primary problems experienced by visually impaired persons at pedestrian-actuated intersections are determining whether there is a pushbutton and locating the push button. Many countries use accessible pedestrian signals much more widely than has been done in the United States, and a number of these—including Australia, Hong Kong, Sweden, Denmark, Germany, Belgium, and Austria—routinely require the use of a locator tone. Typically emanating from the push-button housing, a pushbutton locator tone indicates to pedestrians that they are expected to push a button to request a pedestrian phase. It enables visually impaired pedestrians to locate the push button quickly and efficiently. Research was undertaken to determine the effect of locator tone repetition rate on efficiency of pedestrians’ location of the push-button pole. Repetition rates of 1.0 and 1.5 Hz resulted in equal pole location speed, faster than that for the 0.5 Hz repetition rate, and were preferred over the 0.5 Hz repetition rate. Locator tones 2 dB above ambient sound resulted in faster pole location than did tones 5 dB and 10 dB above ambient sound. Push-button locator tones should have a standardized repetition rate between 1.0 Hz and 1.2 Hz so that it may be ensured that visually impaired pedestrians can efficiently locate push buttons. Locator tones need be no more than 5 dB louder than ambient traffic sound.
Trip Length Distributions in Commodity-Based and Trip-Based Freight Demand Modeling: Investigation of Relationships
Authors: Holguín-Veras José , Thorson Ellen
Published: April 2007

Commodity-based and vehicle-trip-based freight demand modeling is discussed. The characteristics of the trip length distributions (TLDs) are examined, defined in terms of tons, as required in commodity-based modeling, and in vehicle trips, as required in trip-based modeling. With data used from a major transportation study in Guatemala, the TLDs are estimated for both tons and vehicle trips. The analysis revealed that ( a) the shape of the TLDs depends upon the type of movements being considered; ( b) TLDs defined in terms of tonnage differ significantly from those defined in terms of vehicle trips; ( c) TLDs for different types of vehicles, transporting similar commodities, reflect the range of use of each type of vehicle; ( d) though tons TLDs and vehicle TLDs are different, the relationship between them seems to follow a systematic pattern that, if successfully identified, would enable transportation planners to estimate one type of TLD given the other; and ( e) major freight generators affect the shape of the TLDs, so complementary models may be needed to provide meaningful depictions of freight movements.
Traffic Characteristics of Protected/Permitted Left-Turn Signal Displays
Authors: Noyce David A. , Fambro Daniel B. , Kacir Kent C.
Published: April 2007

At least four variations of the permitted indication in protected/permitted left-turn (PPLT) control have been developed in an attempt to improve the level of driver understanding and safety. These variations replace the green ball permitted indication with a flashing red ball, a flashing yellow ball, a flashing red arrow, or a flashing yellow arrow indication. In addition, the Manual on Uniform Traffic Control Devices allows several PPLT signal display arrangements. The variability in indication and arrangement has led to a myriad of PPLT displays throughout the United States. The level of driver understanding related to each PPLT display type, and the associated impact on traffic operations and safety, has not been quantified. A study was conducted to evaluate the operational characteristics associated with different PPLT signal displays. Specifically, the study quantified saturation flow rate, start-up lost time, response time, and follow-up headway associated with selected PPLT displays. No differences in saturation flow rate and start-up lost time were found due to the type of PPLT signal display. Saturation flow rates ranged from 1,770 to 2,400 vehicles per hour of green per lane and were related to differences in driver behavior between geographic locations. The variation in start-up lost time and response time between locations was primarily related to differences in phase sequence. The flashing red permitted indications were associated with the longest follow-up headway times, since drivers are required to stop before turning left with a flashing red permitted indication. The shortest follow-up headway was associated with the five-section cluster display using a green ball indication.
Gas-Kinetic Modeling and Simulation of Pedestrian Flows
Authors: Hoogendoorn Serge , Bovy Piet H. L.
Published: April 2007

Insight into pedestrian flow operations is important in both planning and geometric design of infrastructure facilities such as railway stations as well as in the management of pedestrian flows in such facilities. Lack of empirical knowledge regarding the characteristics of pedestrian flows under varying circumstances and designs motivates using a model-based approach. In this study, a new pedestrian flow model based on the gaskinetic modeling paradigm is established. The mesoscopic equations describe the dynamics of so-called pedestrian phase-space density, which can be considered as a two-dimensional generalization of the phase-space density used in gas-kinetic vehicular traffic flow. Convection, acceleration, and noncontinuum transition terms govern the dynamics. The latter terms reflect the dynamic influence of pedestrians decelerating and the changing angle of movement due to pedestrians interacting. Numerical solutions of the resulting gas-kinetic equations are established by using a novel particle discretization approach. Essentially, this approach upgrades the mesoscopic equations to a microscopic pedestrian flow simulation model. Using the particle discretization approach, the model’s behavior is tested for different test-case scenarios. The model is shown to produce plausible speed-density functions from which walking speeds and travel times can be derived for a variety of conditions.
Validation of High-Fidelity Traffic Simulation Models
Authors: Rao Lei , Owen Larry
Published: April 2007

A multistage validation framework that accounts for the realistic nature of traffic simulation output data is proposed. The framework consists of conceptual validation and operational validation. The operational validation comprises a qualitative approach, which involves static and animated Turing tests, and a quantitative approach, which involves three levels of statistical tests. Particularly in the third-level statistical test, the autocorrelation and nonstationary nature of traffic simulation output data is emphasized, its implications on validation methods are explored, and a univariate nonseasonal autoregressive-integrated-moving-average (ARIMA) modeling approach is proposed. Finally, numerical results for an actual freeway network are presented. The validation results illustrate that the proposed multistage validation procedure can account for the complexity of the validation task and its conclusions.
Observation-Based Lane-Vehicle Assignment Hierarchy: Microscopic Simulation on Urban Street Network
Authors: Wei Heng , Lee Joe , Li Qiang , Li Connie J.
Published: April 2007

A lane-assignment model in a vehicle-based microscopic simulation system describes a vehicle’s position during its journey on an urban street network. In other words, it is used to estimate an individual vehicle’s location, speed, routing plan, lane-choice plan, lane-changing plan, and car-following plan from its entrance to a street network until the end of the trip. From the authors’ observations and study of lanechoice and lane-changing behavior, it is concluded that a vehicle is assigned to a lane in a logical manner depending on the relationship between its route-planned motivation and traffic conditions in the current lane and other lanes. A lane-assignment model consists of three components: lane choice, car following, and lane changing. The lane-changing component is composed of three submodels—a decision model, a lane-changing condition model, and a lane-changing maneuver model. Rules are discussed for lane-choice and lane-changing modeling based on videotaped observations over four-lane urban streets. Then a heuristic structure of a lane-vehicle-assignment model is proposed, which exposes the inherent relationship between vehicle-based travel behavior and lane-vehicle assignment on an urban street network. With the addition of a lane-assignment model derived from observed data, a simulation may be developed to correctly represent travel behavior and dynamic traffic assignment at the lane level and provide a more effective tool for design and evaluation of the performance of strategies for traffic control, traveler information, and congestion alleviation.
Delay Variability at Signalized Intersections
Authors: Fu Liping , Hellinga Bruce
Published: April 2007

Delays that individual vehicles may experience at a signalized intersection are usually subject to large variation because of the randomness of traffic arrivals and interruption caused by traffic signal controls. Although such variation may have important implications for the planning, design, and analysis of signal controls, currently no analytical model is available to quantify it. The development of an analytical model for predicting the variance of overall delay is described. The model is constructed on the basis of the delay evolution patterns under two extreme traffic conditions: highly undersaturated and highly oversaturated conditions. A discrete cycle-by-cycle simulation model is used to generate data for calibrating and validating the proposed model. The practical implications of the model are demonstrated through its use in determining optimal cycle times with respect to delay variability and in assessing level of service according to the percentiles of overall delay.
Operating High-Occupancy Vehicle Lanes: Issues for Consideration
Authors: Obenberger Jon , Rupert Bob
Published: April 2007

A commitment to proactively manage, operate, and provide the necessary services for support of a high-occupancy vehicle (HOV) system is needed so that all HOV facilities can meet intended objectives and performance expectations. This operational focus should be integrated into all phases of an HOV system, from the strategic system planning through the ongoing performance monitoring and evaluation of specific facilities. The ongoing performance monitoring and evaluation of HOV facilities should be the basis for making continuous incremental changes in the way the system is managed, the way facilities are operated, and the way that support programs and services are utilized. HOV facilities are not appropriate in every location, and conditions change over time. Changes may warrant continuous adjustments or significant revisions in HOV facility operation. Before proposal of any significant changes in operation, all relevant factors, interests, alternatives, and associated impacts should be considered and analyzed in detail. These operational alternatives should include incremental revisions to improve the performance of the HOV system or specific facilities. Significant operational changes should be considered only after all possible incremental adjustments have been made to improve the performance of the existing HOV lane. In accepting federal aid, agencies have agreed to manage, operate, and maintain HOV facilities as they were originally planned, designed, constructed, and approved. Situations in which a federal review of operational changes to HOV facilities is required, the information needed to support such a review, and the existing federal requirements against which this review will be completed are identified. A review of the important issues and possible impacts resulting from any significant operational change is needed so as to determine whether federal approval is required and to assure consistency with the federal aid program provisions of 23 U.S.C. and 49 U.S.C.
Success Factors and Decision Issues for High-Occupancy Vehicle Facilities
Authors: Schofer Joseph L. , Czepiel Edward J.
Published: April 2007

Factors affecting success of high-occupancy vehicle (HOV) lanes are explored. An earlier study was conducted to support future HOV choices in Chicago, which has no such facilities, in part because of concerns about risks and possible negative outcomes. HOV facility performance characteristics were assembled and updated. Comparisons of closed and operating HOV lanes, as well as case studies, highlighted the importance of HOV lane utilization as a success factor and suggested 800 to 1,000 HOVs per lane-hour as typical of the success-failure boundary. A number of key factors in the HOV planning and decision process were explored. HOV lanes were found to be generally favorable for transit; flexibility of access restrictions (such as occupancy requirements and tolling options) makes it feasible to assure acceptable lane utilization levels; HOV2+ seems to be the access restriction most feasible in typical markets; evidence on formation of new carpools is mixed (this question warrants more study); lane addition rather than conversion is usually essential for feasibility; and organized opposition to HOV lanes demands careful planning and promotion of utilization. Criteria for identification of more promising HOV facility locations are provided.
Top-Down Cracking of Rigid Pavements Constructed with Fast-Setting Hydraulic Cement Concrete
Authors: Heath Andrew C. , Roesler Jeffery R.
Published: April 2007

Test sections of jointed plain concrete pavement were constructed with fast-setting hydraulic cement concrete (FSHCC) as part of the California Department of Transportation accelerated pavement-testing program. Many of the longer slabs cracked under environmental influences before any traffic load was applied to them. Data from field instrumentation were recorded and analyzed along with laboratory test data to determine the cause of the cracking. Cores drilled through the cracks indicated that cracking began at the top of the slabs and propagated downward. This was confirmed with the ILLI-SLAB (ILSL2) finite-element package in which high tensile stresses were predicted at the top of the slab as a result of the differential drying shrinkage between the top and base of the slab and the nonlinear nature of the negative temperature gradients through the slab. Laboratory free-shrinkage tests with the test section concrete indicated significantly higher levels of shrinkage compared with that achieved with ordinary Type II portland cement. Load plus environmental stress analysis with ILSL2 suggested that the critical failure location for the FSHCC pavements would be near the corner of the slab and not at the midslab edge.
Effect of Lime on Ignition Furnace Calibration
Authors: Prowell Brian D. , Youtcheff Jack
Published: April 2007

This study investigated mix components, other than aggregate source, that were perceived to affect the ignition furnace mixture calibration. Four sets of experiments with one aggregate were designed and run to evaluate the effects of the amounts of lime, sulfur, calcium carboxylates, and fines. Five asphalt binders with different chemistries were evaluated. Two binders had high and low sulfur contents, respectively; two other binders contained relatively high concentrations of carboxylates. Various concentrations of hydrated lime (0 to 3 percent by weight) were added to mixtures and were found to have a significant effect on the ignition furnace correction factor for all five binders. The magnitude of the effect was large enough to cause the quality control tests to fail the tolerances established by the Virginia Department of Transportation. The lime appears to react with the sulfur dioxide (SO2) formed from the combustion of organic sulfur to generate calcium sulfate. The amount of sulfur present in the asphalt can significantly affect the ignition furnace correction factor. Initial thoughts that calcium carboxylates are reacting with carbon dioxide (CO2) to produce some form of calcium carbonate were not substantiated. The influence of carboxylic acid groups, however, does come into effect in the presence of lime. This suggests that lime reacts with the combustion gases to produce some form of carbonate. Basalt fines and portland cement did not have a significant effect on the ignition furnace correction factor. Additional testing should be conducted to assess the effects of fines representing other aggregates, particularly carbonates.
Alternative Solvent for Reducing Health and Environmental Hazards in Extracting Asphalt: An Evaluation
Authors: Collins-Garcia Holly , Tia Mang , Roque Reynaldo , Choubane Bouzid
Published: April 2007

Trichloroethylene is a solvent currently used by the Florida Department of Transportation (FDOT) and many state highway agencies for separation of asphalt binders from asphalt paving mixtures in their quality control programs. However, it has been proved that trichloroethylene contributes to ozone depletion, and it is also known to be a carcinogen. The goal of the present study was to determine whether a more environmentally sound and less hazardous solvent could be used for this purpose. The solvent investigated is an n-propyl bromide with the trade name EnSolv. Preliminary studies show that it is safer than many other solvents available today. The study was performed to determine whether EnSolv could be a substitute for trichloroethylene without changing current testing methods. The tests performed included the asphalt solubility test, extraction and recovery of asphalt binders from mixtures, and penetration and viscosity tests with the recovered binders. The results of the study showed that EnSolv could be a suitable replacement for trichloroethylene. In addition, EnSolv could also be recycled and reused in the extraction and recovery procedures.
Measuring Smoothness of Virginia’s Asphalt Overlays
Authors: McGhee Kevin K.
Published: April 2007

In the summer of 1996 the Virginia Department of Transportation (VDOT) initiated the pilot of a new special provision regarding the smoothness of asphalt pavement surfaces. This special provision is based on the international roughness index (IRI) and is administered with a laser-equipped South Dakota–style inertial road profiler. A critical assessment of the nontraditional equipment and methods used to administer the special provision is provided. Issues addressed in the critique include provision exemptions, the ability to identify and contend with construction variability, and peculiarities of the equipment that affect the ability of VDOT to administer a modern acceptance provision.
Flexural Capacity of Compact and Noncompact High-Performance Steel Plate Girders
Authors: Azizinamini Atorod , Sause Richard
Published: April 2007

As a result of a cooperative research program between FHWA, the U.S. Navy, and the American Iron and Steel Institute, high-performance steels (HPSs) with yield strengths of 485 MPa [70 kips/in.2 (ksi)] (HPS-70W) and 690 MPa (100 ksi) (HPS-100W) were developed. During the past 2 years, several bridges in the United States have used these new grades of steel. Because of a lack of test data, AASHTO specifications placed several limitations that prevent bridge designers from taking full advantage of HPSs. In response to AASHTO limitations, which preclude full use of the advantages that the HPS-70W and HPS-100W steels have to offer, research investigations were initiated at the University of Nebraska–Lincoln, Lehigh University, and the Georgia Institute of Technology. Partial results of research activities under way at the University of Nebraska–Lincoln and Lehigh University to remove design limitations related to the use of HPSs are presented.
Quantified Checklists for Construction Inspection Examination
Authors: Samuels Allan F.
Published: April 2007

Quantified checklists provide a generalized measure of the workmanship of a constructed product and of processes. Checklists are developed by selecting important attributes from program standards such as specifications, drawings, or manufacturer’s information. Inspectors examine each attribute and mark it as either conforming (yes), nonconforming (no), or not applicable. The percentage of attributes that conform to the requirements is determined by dividing the number of conforming events by the total number of events inspected and converting the ratio to a percentage. Practical experience with the development and management of checklists is described, and theory about inspection by the method of attributes is provided. The Construction Operations Section of the Arizona Department of Transportation is using the results to analyze specification effectiveness and manage inspection and quality processes. There is also potential for the concept to be refined for use as a means of determining payment of incentives or disincentives and for engineering analysis.
Kentucky Contract Time Determination System
Authors: Werkmeister Raymond F. , Luscher Becky L. , Hancher Donn E.
Published: April 2007

The results of research funded by the Kentucky Transportation Cabinet (KyTC) to develop a new method for determining of construction contract time for its highway construction contracts are reported. The current system in Kentucky was analyzed to determine how a new system could provide better-estimated durations. Current methods of other departments of transportation were analyzed to provide insight for a new system. It was predetermined that a computer system was best suited; however, the development of the system needed input from KyTC engineers with construction experience. A task force of the study advisory committee worked with Kentucky Transportation Center research engineers to develop the basis for the new contract time determination system, called the Kentucky Contract Time Determination System (KY-CTDS). The KY-CTDS program was developed to provide a conceptual estimating tool for prediction of construction contract time for the Kentucky Department of Highways. It makes use of predetermined project classifications and lists major activities that are believed to control the project schedule. Production rates and activity relationships have also been determined and are embedded in the program. Experienced KyTC engineers can make final adjustments using the model. This program uses Microsoft Project 98 and Microsoft Excel, version 7.0, software and operates on a personal computer. It outputs a graphical bar chart schedule to be used only for estimation of contract time for bidding purposes. Program output should also help in resolving construction disputes. The program is not suitable for detailed scheduling of construction operations.
Estimation of Traffic Volume on Rural Local Roads
Authors: Seaver William L. , Chatterjee Arun , Seaver Mark L.
Published: April 2007

Traffic volumes on local roads have not received much attention from highway planners and researchers, although local roads constitute the majority of road mileage in a state. In recent years the need for reliable estimates of vehicle-miles of travel on local roads has been recognized for the analysis of air quality and highway safety issues. To provide a better understanding of traffic volumes on local roads and to explore alternative methods for estimation, data from Georgia were analyzed by using different statistical procedures. The findings of this analysis are presented, along with the results of an attempt to develop a mathematical model for estimation of local road traffic volumes.
Data Warehouse Strategy to Enable Performance Analysis
Authors: Papiernik Daniel K. , Nanda Dhruv , Cassada Robert O. , Morris William H.
Published: April 2007

The Virginia Department of Transportation (VDOT) has engaged to implement an enterprise data warehouse as part of a strategic investment in its information technology (IT) infrastructure. Data warehousing provides an information architecture that serves as the enterprisewide source of data for performance analysis and organizational reporting. To assist VDOT in achieving its strategic outcome area objectives, a programming and scheduling (P&S) data mart is being developed to track preconstruction project activities. This data mart and subsequent data marts function as departmental decision support platforms, enabling VDOT’s operating divisions to perform their own enhanced analytical processing, visualization, and data mining for more informed business decision capabilities. Presented is a case study based on the enterprise data warehouse and P&S data mart being developed and implemented for VDOT by TransCore. Explicitly described is how one VDOT division, Programming and Scheduling, will benefit by investing in IT to achieve its strategic goals. The design approach, methodology, and implementation procedure for the P&S decision support data mart are detailed. The methodology for capturing the performance measures that have been defined by the P&S division in the context of its strategic outcome areas is highlighted. Recommended future direction and the technologies that the agency should adopt to continue to maximize their IT investment are outlined.
Real-Time Indicators of Vehicle Kilometers of Travel and Congestion: One Year of Experience
Authors: Hwang Ho-Ling , Greene David L. , Chin Shih-Miao , Gibson Angela A.
Published: April 2007

Automated traffic data posted on the Internet by four cities have been continuously downloaded, processed, and archived for more than 1 year by an automated system developed by Oak Ridge National Laboratory and funded by the U.S. Bureau of Transportation Statistics. Although the experimental system is far from national in scale and scope, it has shown that automated collection and processing of local traffic data via the Internet for national purposes is feasible and practical. Strong seasonal patterns make it too early to estimate statistical models of traffic growth, but comparisons of the same months in 1998 and 1999 indicate changes ranging from 1 percent to 3 percent for the monitored systems. Direct measurements of delay on the monitored systems are lower than published estimates for previous years. Although some progress in the input of missing data has been made, missing data are still a major problem, and better methods are needed.
Integrating Genetic Algorithms and Geographic Information System to Optimize Highway Alignments
Authors: Jha Manoj K. , Schonfeld Paul
Published: April 2007

A comprehensive highway cost model can be used for optimizing highway alignments subject to a number of design constraints. Because a geographic information system (GIS) can spatially represent the locations of properties, floodplains, streams, and other geographical characteristics of significance in a highway cost model, it can provide valuable input to a highway design optimization model. Additionally, a GIS-based model can be developed to compute geographically sensitive costs to be used with an iterative optimization scheme. However, connecting a GIS to a highway optimization model requires full automation of an entire search process in which there is a continuous exchange of inputs and outputs until the optimized solution is obtained. An integrated model is developed by linking a GIS model with an optimization model employing genetic algorithms (GAs). The GIS model provides accurate geographical features, computes location-dependent costs, and transmits these costs to an external program. That program computes length-dependent costs and user costs and then, using GAs, optimizes the highway alignment to minimize the sum of all costs. An example study using real land use and environmental features is presented for a part of Talbot County, Maryland. The computational performance of the integrated model is assessed.
Complete Count of U.S. Transportation Workforce
Authors: Sen Basav , Rossetti Michael A.
Published: April 2007

Described are the development and application of an original methodology for a comprehensive and consistent count of transportation-related employment in the United States. In addition, the study represents a general example of how transportation analysts can effectively use and combine classification-based data to answer specific crosscutting questions. The method involved computing the union of two different sets of transportation employment data: transportation industry data, counting all workers in industries that provide or support transportation, and transportation occupational data, counting all workers performing transportation functions. A union, instead of a straightforward sum, was used to avoid double counting of workers employed in the defined transportation and transportation-related industries. A broad definition of transportation-related industries and occupations was used, allowing a complete accounting of employment generated by transportation in the economy. It was concluded that transportation industries account for 13 million workers, or about 10 percent of total nonfarm employment of 128.4 million, and transportation occupations outside of transportation industries accounted for another 3.5 million workers, or about an additional 3 percent of nonfarm employment. Thus, about 16.5 million workers either work directly in or support transportation activity in the U.S. economy; this constitutes about 13 percent—approximately 1 in 8 jobs—of the nonfarm workforce.
Evaluation of Moisture Susceptibility of Asphalt Mixtures: Conventional and New Methods
Authors: Khosla N. , Birdsall Brian G. , Kawaguchi Sachiyo
Published: April 2007

Evaluation of a mixture’s moisture sensitivity is currently the final step in the Superpave® volumetric process. This step is accomplished by using AASHTO T-283, which tolerates a range of values in the test variables of sample air voids and degree of saturation. The tensile strength ratios determined for the mixes in this study varied with the air void level and degree of saturation. Although the levels of conditioning were within the specifications for AASHTO T-283, test results both passed and failed the 80 percent criterion, depending on the severity of conditioning. An alternative to measuring indirect tensile strength is a test that evaluates a mixture’s fundamental material properties. A relatively simple test is proposed that measures the cohesion and friction angle for asphalt mixtures. In addition, the Superpave shear tester (SST) was incorporated as a tool in evaluating moisture sensitivity. The proposed axial test determined the cohesion and angle of friction of the mix. The friction angle remained constant for the conditioned and unconditioned samples. Hence, conditioning of the samples had practically no effect on the mixture’s internal friction. The cohesion of the mix decreased when the mix was subjected to conditioning. The reduction in cohesion was greater in the case of the Fountain aggregate, which is known to be highly moisture susceptible. The shear tests to failure performed on the SST confirmed the results of the new apparatus, which provides a simple method for determining a mixture’s cohesion. The loss of cohesion due to conditioning can be used to determine a mixture’s moisture susceptibility. The three antistrip additives used in this study were hydrated lime, a liquid amine, and a liquid phosphate ester.
Field Validation of New Superpave Low-Temperature Binder Specification Procedure: Performance Data from Pennsylvania Test Sections
Authors: Dongré Raj , Bouldin Mark G. , Maurer Dean A.
Published: April 2007

A new specification procedure was proposed recently to determine the low-temperature performance grade of asphalt binders. This new procedure uses bending beam rheometer (BBR) and direct tension test (DTT) data at two temperatures to determine the low-temperature grade of an asphalt binder. A study was conducted to validate this procedure by using asphalt binder retained samples from the widely published test road in Pennsylvania. This road was constructed in 1976 in Elk County, and performance—including low-temperature transverse cracking index—was monitored over 6 years. In this study, the retained binder samples from test sections T-1 to T-6 were tested with the BBR and the new Superpave® DTT. The data from these two tests were analyzed to obtain critical cracking temperatures and low-temperature performance grades. Results indicate that the new procedure correctly predicts the temperature at which cracking was observed in the field.
Calibration and Validation of a Dynamic Traffic Assignment Model
Authors: He Rachel R. , Ran Bin
Published: April 2007

A new approach is proposed to calibrate and validate the most critical components of a dynamic traffic assignment (DTA) model: dynamic route choice and flow propagation. By presenting approximate joint probability distribution functions of the temporal link traffic flows on a network, it is possible to derive the likelihood functions for estimating dynamic route choice and actual flow propagation. This approach also enables statistical tests to be performed for validation of DTA models. Both procedures are presented with a small numerical example and a larger network. These examples also indicate that it is possible to calibrate and validate a DTA model with detection errors and incomplete data, especially when real-time traffic counts are available on only a few links in the network.
Simulating a Regularly Sampled: Bus Location System
Authors: Khan Sarosh I. , Hoeschen Brian
Published: April 2007

Between 1967 and 1997, transit agencies in 20 cities installed automatic vehicle location (AVL) systems to improve safety, efficiency, and quality of service. The bus AVL system typically provides a means of tracking individual buses for fleet management. More recently, the AVL data have also been used to develop algorithms to predict bus arrival time, estimate link travel time, and detect incidents. Other traffic management and control applications are also being explored. Therefore, the availability of a simulation capable of mimicking a bus location system that reports vehicle location at regular, prespecified intervals is becoming increasingly important. CORSIM, an integrated freeway and surface street traffic simulation model, also simulates buses on prespecified routes and stations for given dwell time distributions and frequency of service. However, very little has been reported about CORSIM’s bus simulation module. CORSIM’s bus route simulation module and its drawbacks are examined, and the results of an effort to compare data collected from the Denver Regional Transportation District bus AVL system and the microsimulator for a test network are presented. Bus location data from the field and the simulation were collected at regular intervals under both recurring congestion and nonrecurring congestion conditions. Linear referencing in a geographic information system was used to extract bus location data for the test network from the AVL system, and external programs were written to collect the same data from the microsimulator. Based on the bus location data, space mean speeds were estimated and compared to evaluate the performance of the model. The results are encouraging. However, several obstacles remain and they are discussed in detail.
Development of Short-Term Operational Planning Model for Transit Service Analysis
Authors: Pendyala Ram M. , Ubaka Ike
Published: April 2007

The subject is an integrated model of transit demand and supply that accounts for the interrelationships between ridership and service. The model consists of a set of equations in which ridership is predicted as a function of service and then service is predicted as a function of demand. In addition, the model accounts for interroute relationships by considering the competing or complementary nature of various routes within a transit system. The model proceeds through a series of iterative demand-and-supply computations to determine the appropriate service parameters and corresponding ridership levels for individual transit routes. The input variables include socioeconomic, demographic, and transit system data. The model has been implemented within a userfriendly, menu-driven software environment and has been applied on a test-case basis in the Volusia County area of Florida. The case-study results are very encouraging—the model predicted ridership on individual routes with an average absolute percent error of 24 percent despite the lack of high-quality data. Further refinements and validation tests of the model are planned for the future.
Structural Equation Model of Customer Satisfaction for the New York City Subway System
Authors: Stuart Kenneth R. , Mednick Marc , Bockman Johanna
Published: April 2007

A more complex model in content and design than previously applied to the measurement of customer satisfaction within the transportation industry is used in this study. Drawing from the results of previous studies that had a narrower focus, a network of 10 potentially important factors that affect customer satisfaction within the New York City subway system was postulated and tested using data collected from a cross section of adult residents. Results indicate that several factors have a direct influence on satisfaction, whereas others have an effect through intermediary variables. Path coefficients for the posited model are statistically significant, although several factors have notably more impact than others. Using model diagnostics, minor revisions and improvements to the initial model have been made while adhering closely to the principles of the original theory. Future developments are discussed, as is the model’s application for planning and resource allocation.
Assessment of 100-Year-Old Foundation System to Meet Current Retrofit Load Demands
Authors: Martin McCabe W. , Felice Conrad W.
Published: April 2007

Results are presented of a geotechnical investigation and foundation analysis as a component of the seismic retrofit to the Amtrak King Street Station in Seattle, Washington. The purpose of this effort was to assess the condition of the existing pile foundation, to quantify the foundation response to revised seismic loads, and to provide recommendations for retrofitting of the foundation. King Street Station is a one- to three-story brick masonry structure with a 12-story clock tower. The building was constructed in 1906 in the area of a reclaimed tide flat. The foundation for the structure consists of timber piles; however, no information was available on the length of the piles or whether they were treated with a preservative. The approximate length of the piles was established at 9.7 m using ground-penetrating radar. A core sample obtained from one of the timber piles showed them to be untreated timber and in good condition. The subsurface investigation revealed a liquefiable granular fill soil in the upper 6 m underlain by medium-dense marine sands overlying dense glacial soils. An engineering analysis of the expected performance of the piles during the design seismic event showed that the piles could settle approximately 100 to 355 mm because of liquefaction of the marine sand layer and that the deflection of the piles under lateral loading was substantially in excess of the static loads. Steel pipe minipiles were recommended as a mitigation measure.
Assessment and Reuse of Old Foundations
Authors: Hertlein Bernard H. , Walton William H.
Published: April 2007

Little is known about the foundations beneath many historic buildings and bridges. For rehabilitation projects, it is important to know the nature of the foundation system and its condition. In replacement projects, cost savings and sometimes environmental benefits can be gained from the reuse of existing foundations in new structures. In large cities, almost any new construction involves the demolition of a previous structure, which poses the problem of what to do with the old foundations. Many are too deep to be removed economically, and some are almost certain to be in the way of proposed new foundations. It is therefore a great advantage if they can be incorporated into the new design, but to do this, the engineer must have accurate information about the foundation type and depth to estimate load-bearing capacity. The authors have worked on a number of projects in the last few years that have included increasing the load on or reusing existing foundations. Information about foundation type and depth has been gained from the use of specialized nondestructive tests. In many cases, the authors also had access to archive information that included soil borings in the vicinity to correlate with test data. The methods used to assess existing foundations and allow their inclusion in the design of new foundation systems are discussed, and case histories are given for concrete drilled shafts, timber piles, and steel sheet piles.
Transportation Routes in Soils Susceptible to Ground Failure: New Madrid Seismic Zone
Authors: Romero Salome , Rix Glenn J. , French Steven P.
Published: April 2007

Geologic deposits susceptible to ground motion amplification under seismic loading in the New Madrid Seismic Zone are delineated using multiple data sources including in situ measurements, geologic maps, and remote-sensing imagery. Soils are classified on the basis of the recommendations from the National Earthquake Hazards Reduction Program, which recommends a classification based on the average shear wave velocity of the geologic material in the upper 30 m. Measurements of shear wave velocity were obtained from Central United States Earthquake Consortium state geologists, the U.S. Geological Survey, and several researchers. However, since this is a predominantly rural area, limited field test data are available. Therefore, several other data sources are introduced including geologic maps and remote-sensing imagery to extrapolate dynamic properties in areas lacking extensive field measurements. Each data source was incorporated into a geographic information system for subsequent analysis. Bridges susceptible to failure from amplification of seismic waves and located on key transportation routes are identified for subsequent risk assessment or seismic retrofitting since the performance of these structures affects disaster planning and rescue efforts and may have severe consequences for the national economy.