bluuebunny/crossref_metadata_2025 huggingface dataset:
Computerized System for Efficient Scheduling of Highway Construction
Authors: Hegazy Tarek
Published: May 2018

A practical model for scheduling and cost optimization of highway construction is presented in this paper. The model's objective is to minimize total construction cost while respecting the time and resource constraints of a project. For flexibility, the model allows each activity to have three alternative construction methods, from cheap and slow to fast and expensive. At the core of the model is an innovative scheduling algorithm for crew assignments along the various highway sections so that work continuity is maintained. The model is designed to be flexible enough to allow nontypical sections as well as variable sequence of work among the sections. For cost optimization, the model uses a nontraditional optimization technique, genetic algorithms. Details of the model formulation are presented in this paper along with its implementation in a simple-to-use computer system. To demonstrate the capabilities of the system, a realistic example is given of a highway project that is fast-tracked by using two crews working simultaneously from opposite sides. The example shows the usefulness of the system for what-if analysis, schedule optimization, and legible presentation of detailed crew assignments and activities’ progress speeds. Extensions of the model to incorporate project control features are then highlighted.
Knowledge-Based Scheduling Analysis Software for Highway Rehabilitation and Reconstruction Projects
Authors: Lee Eul-Bum , Harvey John T. , Samadian Michael M.
Published: May 2018

Most of California's highway infrastructure was built between 1955 and 1970. These pavements had 20-year design lives, and many now require frequent maintenance. In 1998, the California Department of Transportation (Caltrans) launched the Long-Life Pavement Rehabilitation Strategies (LLPRS) program to rebuild approximately 2,800 lane kilometers of high-traffic-volume urban freeway in the 78,000-lane kilometer state highway network over a 10-year period. Priorities identified for the successful implementation of LLPRS projects are the selection of construction schedules and the development of traffic management plans that minimize road user and agency costs. This paper presents a construction simulation program called CA4PRS (Construction Analysis for Pavement Rehabilitation Strategies). The program was developed as a scheduling and production analysis tool for LLPRS projects for use during the planning and design stages. CA4PRS estimates the optimized distance and duration of highway rehabilitation projects. It takes into account the constraints of scheduling interfaces, pavement design, lane closure tactics, and contractor logistics. As a knowledge-based computer system on a Microsoft Access database, it uses Monte Carlo simulation, critical path method analysis, and linear scheduling. CA4PRS is designed to help highway agencies and paving contractors make construction schedule decisions that balance rehabilitation productivity, traffic inconvenience, and agency cost. Application of the CA4PRS model to urban freeway rehabilitation projects in California, including the I-10 Pomona, I-710 Long Beach, and I-15 Devore projects, has demonstrated its value in saving millions of dollars for both Caltrans and road users.
Forecasting Payments Made under Construction Contracts
Authors: Mills Peter , Tasaico H. A. (Burt)
Published: May 2018

Staff at the North Carolina Department of Transportation (NCDOT) have close control over each highway construction project until the construction contract is let; thereafter, the contractor manages the pace of work, which dictates the flow of payments. These payments make up about one-third of all NCDOT expenditures, so reliable forecasts are important in programming and in cash management. With no other means to predict the pace of construction through the duration of the contract, NCDOT must rely on statistical analyses of past payments to forecast future payments to contractors. Dye Management Group, Inc., which was retained by NCDOT to implement cash management strategies at the department, designed two statistical models of payments to contractors: the first to estimate payments on individual contracts, or the “payout curve,” and the second to estimate total payments made under all contracts in a month. The parameters in both models were initially estimated with data from 4,128 payments made under 336 highway construction contracts completed between August 2000 and June 2002. The first model achieved an adjusted R2 of .93. Although it was useful to engineers in managing individual projects, the model required awkward specifications of seasonal effects to forecast aggregate cash flows. Seasonality was simply accommodated in the second model, which achieved an adjusted R2 of .92. Dye Management Group and NCDOT have operated the second model for more than 2 years and, with a database that has grown to more than 11,000 monthly payments, have consistently achieved mean absolute percentages of error under 10%.
Risks with Multiple Pay Factor Acceptance Plans
Authors: Burati James L.
Published: May 2018

It is rare that a state highway agency (SHA) uses only a single quality characteristic to determine the pay factor for a lot. This paper deals with two specific types of risk associated with the use of multiple quality characteristics: remove and replace provisions and the effect on pay factor determination if the quality characteristics are correlated. First, computer simulation studies showed that typical acceptance plan provisions that call for lot removal and replacement at a given quality level, such as a percentage of material within specification limits of 60 or 50, can place much greater risk on the contractor when they apply to multiple characteristics. An approach to correct this problem was developed. Next, a total of 1,742 sets of asphalt content (AC), air voids (AV), and voids in the mineral aggregates (VMA) test results were analyzed for correlations. VMA values were positively correlated with both AV and AC values. Additional simulation studies showed that while this correlation does not affect the long-term average pay factor for a lot, it increases the variability in the individual lot composite pay factors. The positive correlation also increases the weighting of AV and AC in a composite pay equation. The use of multiple quality characteristics for determining the pay factor for a lot introduces sources of risk that are not present when only one characteristic is used. Any SHA that uses multiple pay factors should consider performing the types of remove and replace and correlation analyses presented in this paper.
Development of the Florida Department of Transportation's Percent within Limits Hot-Mix Asphalt Specification
Authors: Sholar Gregory A. , Page Gale C. , Musselman James A. , Upshaw Patrick B. , Moseley Howard L.
Published: May 2018

The Florida Department of Transportation adopted a percent within limits approach in July 2002 for the acceptance and payment of all hot-mix asphalt. Contractor test data, after being verified by the department, are used to calculate payment. Acceptance and payment for dense-graded Superpave® mixtures are based on the following five asphalt material properties: roadway density, percent air voids, asphalt binder content, percent passing the No. 8 sieve, and percent passing the No. 200 sieve. Acceptance and payment for open-graded friction course mixtures are based on the following four asphalt material properties: asphalt binder content, percent passing the 3/8-in. sieve, percent passing the No. 4 sieve, and percent passing the No. 8 sieve. Contractor test data from recently completed construction projects were used to develop representative standard deviations of the asphalt material properties used for payment and acceptance. These standard deviations were then used to develop tolerance values for the percent within limits system. A system has been developed to handle acceptance and payment of small quantity LOTs (two or fewer sublots) within the same specification. In lieu of the department sampling and testing numerous independent samples and performing F-and t-tests to validate the contractor's results, an alternative verification and resolution system has been developed.
Design and Construction of a Full-Width, Full-Depth Precast Concrete Deck Slab on Steel Girder Bridge
Authors: Harrison Alex , LeBlanc N. David
Published: May 2018

The West Sandusky Street Bridge over I-75 in Findlay, Ohio, consisted of a single 170-ft-span hybrid steel plate girder bridge with a concrete deck. To minimize closure times on West Sandusky Street and reduce traffic delays on I-75 during the bridge's replacement, full-width, full-depth precast concrete deck panels were proposed for the bridge deck construction. The precast deck panels are posttensioned both longitudinally and transversely to minimize cracking and improve durability and are constructed with shear stud pockets to allow for the installation of shear studs after erection and posttensioning. During detail design, a finite element analysis of the bridge deck was carried out to determine the required level of prestress in the deck. A time-dependent analysis was subsequently completed to determine the long-term creep effects and posttensioning losses, including the effects of restraint from the steel girders. A sensitivity analysis determined the optimum curing time required before stressing the longitudinal posttensioning tendons and grouting the shear pockets. The steel plate girders were designed for the long-term creep effects due to the posttensioning of the deck, which imposed additional axial loads and moments on the steel girders. The replacement deck panels were fabricated before bridge demolition and road closure. Bridge construction was completed in fall 2004.
Experimental Investigations of the Effects of Multiple Heat Straightening Repair on the Structural Properties of Bridge Steels
Authors: Kowalkowski Keith , Varma Amit H.
Published: May 2018

The effects of multiple damage-heat straightening repair cycles (i.e., multiple cycles of damage followed by heat straightening repair) on the fundamental structural properties of typical bridge steels ASTM A36, A588, and A7 were evaluated. The damage and repair parameters considered in the study are the damage strain (ed), the restraining stress (sr), and the number of multiple damage-repair cycles (Nr). The effects of these parameters on the following structural properties were evaluated: elastic modulus, yield stress, ultimate stress, percent elongation, surface hardness, and fracture toughness. Seventy-five laboratory-scale specimens made from A36, A588, or A7 steel were subjected to multiple damage-repair cycles, and their effects on the structural properties were evaluated. The results indicate that multiple damage-repair cycles have a small influence (±15%) on the elastic modulus, yield stress, and ultimate stress. However, the percent elongation and fracture toughness of the damaged-repaired steel are influenced significantly. On the basis of reductions in the percent elongation and fracture toughness, it is recommended that A7 and A36 steel be limited to three damage-heat straightening repair cycles. A588 steel can be subjected to five damage-heat straightening repair cycles.
Measuring Rebar Cover Depth in Rigid Pavements with Ground-Penetrating Radar
Authors: Al-Qadi Imad L. , Lahouar Samer
Published: May 2018

Ground-penetrating radar (GPR) is a nondestructive investigation tool that is usually used in flexible pavement evaluation to estimate the thicknesses of the various layers composing the pavement. GPR is also used in flexible pavements to detect subsurface distresses, such as moisture accumulation and air voids. For rigid pavements and bridge decks, GPR is used to measure the thickness of the concrete slab and detect the location of reinforcing bars (rebar). Rebar detection is typically achieved, in this case, when an experienced operator finds the rebar's classic parabolic signature in the GPR data. This paper presents image-processing techniques that can be used to detect the rebar parabolic signature automatically in GPR data collected from rigid pavements with a high-frequency ground-coupled antenna. After detection of the rebar, the reflected parabolic shape is fit to a theoretical reflection model to estimate the pavement's dielectric constant and the rebar depth. The algorithms were validated on GPR data collected from a known continuously reinforced concrete pavement section. The technique showed an average error of 2.6% on the estimated rebar cover depth.
Evaluation of Dowel Bars Installed in Airfield Concrete Pavement Construction Joints by Using Plastic Sleeves
Authors: Yu Thomas
Published: May 2018

This paper presents the results of an evaluation of the effectiveness of an innovative process for installing dowel bars in construction joints without drilling. The procedure involves inserting plastic sleeves with the same outside dimensions as the drilled holes into plastic concrete to create the holes for installation of the dowel bar, rather than drilling. The plastic sleeves are later removed, and the dowel bars are inserted in the holes left behind. To avoid any deleterious effects, the technique must produce dowel bar alignments that are comparable with those of the bars installed under the conventional method and must not cause any other problems. A field test was conducted to evaluate the viability of the new technique. The evaluation is based on the key factors that determine the engineering feasibility of the new procedure, which include dowel bar alignment, consolidation of concrete around the plastic sleeves, and the impact of the insertion techniques on pavement surface profile. The test results showed that the plastic sleeves can produce dowel bar alignments that are comparable with or better than those produced by the conventional drilling method, without any deleterious effects.
Changing the Shape and Location of Pavement Load Transfer Devices
Authors: Cable James K.
Published: May 2018

Load transfer is an important aspect of portland cement concrete joint design. To date, aggregate interlock and round steel dowels have been used to accomplish load transfer. Research was done to examine the use of steel dowels of alternative shapes to provide load transfer. A field research project in Iowa has used two elliptical bars of different sizes at three spacings and numbers of bars per joint. Test sections included bars across the entire joint and sections using bars only in the wheelpaths. The impact of cut, fill, and transition sections was also factored into the experimental design. This paper documents the construction of the project, testing that is being done, and the initial results of the work.
Initial Ride Quality of Hot-Mix Asphalt Pavements
Authors: Stroup-Gardiner M. , Carter Alan , Das Thomas , Bowman Brian
Published: May 2018

Ride quality assessed with an inertial profiler on flexible pavement was used to provide initial information on the following key issues: repeatability associated with international roughness index (IRI) values for a wide range of hot-mix asphalt (HMA) material variables, timing of acceptance testing for initial ride quality, IRI changes with type of roadway, influence of stops and starts in the paving operation on ride quality, identification of “bump,” and effect of grinding on IRI. IRI was calculated for 25-ft intervals instead of the standard 0.1 mi (528 ft) for all testing to highlight local anomalies such as bumps due to paving stoppages. Results indicate that the standard deviation of three replicate passes with an inertial profiler is 5 in./mi (includes 46 HMA mixes on the Auburn University National Center for Asphalt Technology test track). IRI measurements with time suggest that initial acceptance testing can be conducted within 7 days, which allows more flexibility in scheduling by the agency. Limited traffic also slightly reduces the IRI values, which is to the contractor's advantage. IRI values are suggested for two-lane county roads and medium- to high-traffic facilities. Separate IRI ranges are indicated for each of these categories on the basis of the type of HMA construction: new, repair and overlay, and mill and overlay. These ranges are set for best and good practices (continuous paving, no stoppages; consistent supply of trucks, very short stops). IRI values greater than 125 in./mi in any given 25-ft interval indicate a bump; bumps can be ground so that these areas have IRI values of less than 100 in./mi.
Performance Testing of Segregated Hot-Mix Asphalt Samples to Evaluate Segregation Models
Authors: Wu Junxia , Romero Pedro
Published: May 2018

Testing of asphalt concrete samples was conducted by using the asphalt pavement analyzer test, the Superpave® shear tester (SST) frequency sweep test, and the SST repeat shear at constant height test to determine the rutting susceptibility that might be expected from samples that have different levels of segregation. Previous research had divided segregation into four levels: none, light, medium, and high. Test results suggest that samples with different segregation levels might show similar rutting susceptibility. Therefore, performance-related models were established in which segregation was divided into three levels: good, fair, and unacceptable. The performance-related models were applied to field data, and examination indicates that the modified models are capable of assessing segregation in field projects. Examination also found that fine segregation was present. Fine segregation can be predicted by extrapolating the developed model from the coarse part to the fine part. However, more data should be investigated to develop acceptable criteria for fine segregation. A methodology was developed to improve pavement quality by controlling aggregate segregation and poor compaction in placed mats. With the models and the proposed methodology, realistic construction uniformity could be assessed by agencies and contractors, which is the first step in obtaining pavements with high performance and longer service life.
Refinement of the Hot-Mix Asphalt Ignition Method for High-Loss Aggregates
Authors: Hurley Graham C. , Prowell Brian D.
Published: May 2018

Four methodologies for determining the asphalt content of mixtures containing high-loss aggregates in the ignition furnace were evaluated: the standard method using the Thermolyne furnace (control), the Troxler NTO infrared furnace, the Ontario method, and a Tempyrox glass-cleaning oven. Six aggregate sources with high ignition furnace aggregate corrections were obtained from around the country: four dolomites, a basalt, and a serpentine/chlorite. Calibration factors were determined for each method at optimum asphalt content. Additional samples were then tested at optimum plus 0.5% asphalt content, and the measured asphalt content was calculated by using the correction factor determined for that method and aggregate source. The Tempyrox Pyro-Clean furnace, commonly used for cleaning laboratory glassware, produced the lowest aggregate correction factors. The standard method and the Ontario method, both using the Thermolyne ignition furnace, produced the smallest bias or error in measured asphalt content. The standard deviation of the corrected asphalt contents for these high-loss sources was higher than the within-laboratory standard deviation reported for AASHTO T308. The only exception was the Alabama source using the standard method. The Ontario method and Tempyrox oven generally reduced the variability of asphalt content measurements for high-loss aggregates. None of the methods evaluated statistically reduced aggregate breakdown on the nominal maximum aggregate size and 4.75-mm sieves. The Ontario method significantly reduced, but did not eliminate, aggregate breakdown on the 0.075-mm sieve. The Ontario method is the best method for immediate implementation for determining the asphalt content by the ignition method for high-loss aggregates.
Predicted 95th Percentile Speeds on Curved Alignments Approaching a Stop
Authors: Schurr Karen S. , Spargo Benjamin W. , Huff Ryan R. , Pesti Geza
Published: May 2018

The objective of this project was to develop a model that describes design speed profiles of vehicles traversing horizontal curves on approaches to stop-controlled intersections on two-lane two-way rural highways. Once speed prediction models were determined, a procedure for the design of horizontal curves that would accommodate vehicles transitioning from high speeds to a stop was developed. Speed profiles were developed with the use of data from 15 study sites in Nebraska. The multiplicative model was used to provide prediction equations for speed profiles. Separate profiles were created for passenger cars and heavy vehicles because speeds were significantly different. The heavy vehicle data were separated further for alignments with and without horizontal curvature. It was concluded that posted speed, median type, presence of rumble bars, roadway surface condition, and degree of rutting did not significantly affect the vehicle speed profiles at these sites at a 95% confidence level. During the comparison of speeds, it was found that the intercepts of the regression lines for approaches with and without horizontal curves were significantly different in the case of heavy vehicles. The speed of heavy vehicles on tangent approaches was generally about 8 mph higher than on sites that exhibited horizontal curvature. The rate of deceleration remained almost the same on all approaches to intersections, except near the stop. For passenger cars, there was no statistically significant difference between curved and tangent alignments. A guidebook for the geometric design of intersection realignment Methods A through D, referred to in the 2004 Green Book, is also included in the project's report.
Operational and Safety Effects of U-Turns at Signalized Intersections
Authors: Carter Daniel , Hummer Joseph E. , Foyle Robert S. , Phillips Stacie
Published: May 2018

In an effort to balance vehicular safety, mobility, and access, many transportation officials favor the use of raised median cross sections on highways. However, this decision leads to much controversy from those opposed to the resulting lack of direct driveway access. One of the issues in this controversy is the effect of increased U-turns at adjacent intersections. The purpose of this research was to determine the operational and safety effects of U-turns at signalized intersections. The operational analysis involved measurements of vehicle headways in exclusive left-turn lanes at 14 signalized intersections. Regression analysis of saturation flow data showed a 1.8% saturation flow rate loss in the left-turn lane for every 10% increase in U-turn percentage and an additional 1.5% loss for every 10% U-turns if the U-turning movement was opposed by protected right-turn overlap from the cross street. The safety analysis involved a set of 78 intersections. Fifty-four sites were chosen randomly, and 24 sites were selected on the basis of their reputation as U-turn problem sites. Although the group of study sites was biased toward sites with high U-turn percentages, the study found that 65 of the 78 sites did not have any collisions involving U-turns in the 3-year study period. U-turn collisions at the remaining 13 sites ranged from 0.33 to 3.0 collisions per year. Sites with double left-turn lanes, protected right-turn overlap, or high left-turn and conflicting right-turn traffic volumes were found to have a significantly greater number of U-turn collisions.
Actual Driving Data Analysis for Design Consistency Evaluation
Authors: Cafiso Salvatore , Di Graziano Alessandro , La Cava Grazia
Published: May 2018

In recent years, researchers have proved that a consistent highway design ensures that successive elements are coordinated to produce harmonious and homogeneous driver performances and does not provoke unexpected events. Knowledge and practice show that drivers make fewer errors near geometric features that conform to their expectations. On this basis, the importance of identifying inconsistencies on highways for its significant contribution to road safety is emerging as an important feature in highway design. Although several techniques and models for evaluating the consistency of a design in a quantitative way have been identified and some countries have implemented the design consistency concept in their road design guidelines mainly in a qualitative way, there have been only a few efforts to measure actual driving behavior. The aim of this paper was to determine design inconsistencies on existing two-lane rural roads with the use of actual driving behavior by means of field data measurements and to verify their agreement with a consistency evaluation model. Furthermore, suitable equipment and a procedure for surveying driving dynamics and driver workload have been developed. In particular, driving behavior was assessed through direct measurements and parameters taken from data collected on a selected sample of test drivers by using a purposely designed instrumented vehicle. The vehicle, named the driver instrumented vehicle acquisition system (DIVAS), was driven under real traffic conditions on a two-lane rural road. The design classes of consistency of the test courses also were evaluated with a well-known safety criteria model. Data collection and treatment procedures are presented, and data analysis and results from this first experiment are given.
Design and Operational Performance of Double Crossover Intersection and Diverging Diamond Interchange
Authors: Bared Joe G. , Edara Praveen K. , Jagannathan Ramanujan
Published: May 2018

Transportation planners and traffic engineers are facing the challenge of inventing ways to mitigate congestion during the peak hours. Alleviating delays and improving safety for passengers and pedestrians are the primary motives. One way of achieving these objectives is to search for alternative intersection and interchange designs. This paper presents the results of a study on two new alternate designs: double crossover intersection and diverging diamond interchange. These designs were studied for different traffic scenarios with the use of traffic simulation, and the results showed better performance during peak hours than that of similar corresponding conventional designs. Better performance includes better level of service, shorter delays, smaller queues, and higher throughput.
Models for Lane Utilization Prediction for Lane Drop Intersections
Authors: Lee Jae-Joon , Rouphail Nagui M. , Hummer Joseph E.
Published: May 2018

Lane drops downstream of signalized intersections can be found on many urban and suburban streets and highways. Because drivers tend to avoid using the short lane because of the potential for stressful merges downstream of the signal, the short lane is typically underused. Previous research indicates that the default lane utilization factors in the Highway Capacity Manual (HCM) appear to overestimate traffic in the short lane. The purpose of this research is to develop models to predict lane utilization factors for six intersection types and to assess how low lane utilization affects the observed intersection capacity and level of service. Traffic and signal data were collected at 47 sites in North Carolina. On the basis of 15 candidate factors, multiple regression models were developed for predicting the lane utilization factor. Field-measured delays were compared with delays estimated by the HCM with the use of regression models for lane utilization. It was found that even with the new models for lane utilization, the HCM consistently overestimated delay for all types of lane drop intersections with low lane utilization: a reassessment of the effect of lane utilization on capacity may be in order. This study also found that the downstream lane length and traffic intensity positively correlate with the lane utilization factor and that some geometric variables at the approach may also influence lane utilization.
Air Transportation Network Flows
Authors: Hsiao Chieh-Yu , Hansen Mark
Published: May 2018

Passenger flow is an important planning factor in an air transportation system. However, forecasting segment (link) and airport flows becomes more complicated in a hub-and-spoke system since segment flows are the aggregations of route flows, and the number of routes increases with hubbing activities. This research develops an equilibrium model considering certain important characteristics of an air transportation system such as distance, airport delay, airline competition, and networks to predict segment and airport passenger flows from the viewpoint of the whole system. The major features of the model include ( a) treatment of segment flows and airport delays as endogenous by considering the feedback of assigned segment flows and their impacts on airports; ( b) reflecting the flexibility of air networks, a start with all links between all airports as the potential network and determination of the predicted network according to the equilibrium flows on segments; and ( c) connection of key elements of the system so that it can evaluate the system impacts of some element changes. The model is demonstrated by applying it to the National Airspace System of the United States. Several characteristics of the model are also investigated. In addition, a policy experiment shows that improvement of an airport not only affects the airport itself but also changes the flows and performance of other airports–-the model can be a tool for evaluating systemwide effects. Finally, the model's limitations and possible remedies are discussed.
Taste Variations in Airport Choice Models
Authors: Pathomsiri Somchai , Haghani Ali
Published: May 2018

A mixed multinomial logit model for analyzing choice of departure airport in a multiple-airport system (MAS) is presented. The model aims to capture random taste variations across passengers in response to airport level of service through a set of random coefficients. A case study is carried out for the Baltimore, Maryland–Washington, D.C., MAS. The 1998 Air Passenger Survey database is used to estimate the model. The results indicate significant taste variations in response to flight frequency and airline fare even within smaller segments by both trip purpose and residency status. Analyses of the model provide several insightful results, such as distribution of perceived level of service and time value. In addition, the model is used to simulate the impact of interesting scenarios on market share. Substantial policy implications for airport management are also provided.
Accounting for Random Taste Heterogeneity in Airport Choice Modeling
Authors: Hess Stephane , Polak John W.
Published: May 2018

The findings from a disaggregate analysis of the choice of airport, airline, and access mode for business travelers living in the San Francisco Bay Area, California, are presented. Aside from formulation of the multidimensional choice process, the main objective is to explore random taste heterogeneity among decision makers in their evaluation of the attractiveness of the different alternatives. The results indicate that this heterogeneity is present in tastes relating to in-vehicle access time, access cost, and flight frequency. Accounting for this heterogeneity leads to gains in model fit but, more important, leads to important insights into the differences in behavior across decision makers and avoids the bias introduced into trade-offs when fixed coefficients are used in the presence of significant levels of heterogeneity. In terms of substantive results, the models also reveal a significant impact of changes in out-of-vehicle access time, indicate a preference for service on jet over turboprop flights, and show that experience plays an important role in air travel choice behavior.
Statistical Modeling and Analysis of Landing Time Intervals
Authors: Rakas Jasenka , Yin Huifang
Published: May 2018

Existing literature suggests that analyses of landing time intervals employ simple statistical models based on time-separation histograms, usually approximated by normal distributions. Although the literature focuses on important issues such as safety, capacity improvements, and separation rules, it does not take into account another important issue: the possible, unique behavior of airlines, pilots, and controllers. In this study such possible, unique behavior is taken into account and a statistical analysis on landing time intervals is performed to find the operational properties of Los Angeles International Airport (LAX), California. On the basis of the properties found, operations of a dominant airline at LAX are compared with those of other airlines by using the Performance Data Analysis and Reporting System (PDARS) database. The PDARS database allows the calculation of landing time intervals on a runway level. A new mathematical model is constructed to fit the probability distribution of landing time intervals, and it is found that the proposed model has the best maximum log likelihood estimations compared with those of existing models. The results also reveal that the behavior of the dominant airline differs from that of the other airlines. The proposed model better approximates the shape of the probability distribution, especially the left-hand side, which usually contains information of greater importance regarding airport operations and especially regarding safety, since all smaller landing time intervals and the landing intervals that fail the safety requirements are concentrated in this part of the probability distribution curve.
Going South?
Authors: Hansen Mark , Hsiao Chieh Yu
Published: May 2018

The recent increase in flight delays in the U.S. domestic system is analyzed by estimating an econometric model of average daily delay that incorporates the effects of arrival queuing, convective weather, terminal weather conditions, seasonal effects, and secular effects (trends in delays not accounted for by other variables). From the estimation results it was possible to quantify some sources of higher delays in late 2003 and early 2004 and track changes in delays that are not attributable to major causal factors. Results suggest that when these factors are controlled for, delays decreased steadily from 2000 through early 2003, but that the trend reversed thereafter. Of the total delay increase between early 2003 and early 2004, half to two-thirds can be attributed to specific sources.
Operational Consequences of Alternative Airport Demand Management Policies
Authors: Hansen Mark , Zhang Yu
Published: May 2018

The current demand management policy at LaGuardia Airport (LGA) New York, must be changed in 2007 under the provision of the Wendell H. Ford Aviation Investment and Reform Act for the 21st Century of April 2000 (AIR-21). As a preliminary step for developing a new policy, this study considered how past policies, along with other factors, have affected operational performance at LGA. The interaction between LGA and the rest of the aviation system was also investigated by estimating simultaneous equations of average delay for LGA and the National Airspace System (NAS) by using two-stage least squares. The results demonstrate that the arrival delay impact of AIR-21 on LGA was in the form of Increased Ground Delay Program holding and that although delay increased markedly under AIR-21, there were also observable improvements in the ability of LGA to handle traffic. Furthermore, on the basis of the simultaneous equations analysis, it was found that 1 min of arrival delay at LGA causes about 2 min of delay elsewhere in the NAS, suggesting that demand management at LGA is a national rather than a local issue.
Cost-Effective Reporting of Travel on Local Roads
Authors: Blume Kelly , Lombard Marais , Quayle Shaun , Worth Phill , Zegeer John
Published: May 2018

The purpose of the Highway Performance Monitoring System of the Rural and Local Roads Reporting Project was to develop a more accurate, yet cost-effective, methodology for estimating vehicle miles traveled (VMT) on urban local roads, rural local roads, and rural minor collectors throughout Florida. A review of Florida's existing methodology, methodologies of five “peer” states, and available research was completed to develop specific evaluation criteria that could then be applied to several conceptual methodologies developed from the synthesis of information. The project team selected a preferred VMT estimation methodology that used census data and random sampling. The preferred methodology makes use of available census data and an intuitive correlation between travel and population density, job density, and roadway density, while it eliminates the dependence on volume groups that is part of FHWA's methodology for higher-order roadways. The density factors are used to group similar zip code tabulation areas (ZCTAs) into subregions to allow random samples taken in one subregion to represent similar ZCTAs statewide on the basis of any or all the following: population, job, and roadway density. A minimum number of random samples is selected to retain statistical validity while minimizing costs to conduct traffic counts. The methodology is flexible enough to allow adjustments (e.g., restratification based on indicators such as coefficients of variation) that improve the quality of the results from year to year. Implementing a test case of the methodology to determine real-world applicability is the next logical step in the research process.
Customized Pretrip Prediction of Freeway Travel Times for Road Users
Authors: Wouters Jacorien A. A. , Chan Kin-Fai , Kolkman Joost , Kock Rutger W.
Published: May 2018

One objective of the Department of Transport (DoT) in the Netherlands is to provide better information to road users about the traffic situation on Dutch freeways. The idea was put forward to use existing historical freeway inductive loop data to predict a customized pretrip travel time for road users. To investigate the feasibility and usefulness of that idea, DoT launched the AIDA project. A prototype database was constructed; it contained almost 2 years of travel time data for all Dutch freeway road sections with inductive loops. A statistical algorithm was designed to compute the average travel time for any freeway journey on any future date and time. An Internet trial application was built to test the database and algorithm. Accuracy of the travel time predictions was evaluated with independent loop data. The usefulness for road users was investigated with an online survey. Results show a good match between the predicted and actual travel times. Only in 10% of analyzed cases did the actual travel time exceed the predicted travel time by more than 5 min. Of 161 respondents, 50% indicated that they found the information useful. Furthermore, 22% indicated that they would consider a different departure time on the basis of AIDA information. Thus the project has shown convincingly that the AIDA concept is not only feasible but also useful to road users. Presently DoT is looking into the uses of the concept for road users and possibly also for traffic operators.
Factors Affecting Minimum Number of Probes Required for Reliable Estimation of Travel Time
Authors: Cetin Mecit , List George F. , Zhou Yingjie
Published: May 2018

Using probe vehicles rather than other detection technologies has great value, especially when travel time information is sought in a transportation network. Even though probes enable direct measurement of travel times across links, the quality or reliability of a system state estimate based on such measurements depends heavily on the number of probe observations across time and space. Clearly, it is important to know what level of travel time reliability can be achieved from a given number of probes. It is equally important to find ways (other than increasing the sample size of probes) of improving the reliability in the travel time estimate. This paper provides two new perspectives on those topics. First, the probe estimation problem is formulated in the context of estimating travel times. Second, a method is introduced to create a virtual network by inserting dummy nodes in the midpoints of links to enhance the ability to estimate travel times further in a way that is more consistent with the processing that vehicles receive. Numerical experiments are presented to illustrate the value of those ideas.
Two Minutes per Person per Day Each Year
Authors: Toole-Holt Lavenia , Polzin Steven E. , Pendyala Ram M.
Published: May 2018

During the past several decades significant changes in travel behavior in the United States have occurred. Evidence from the Nationwide Personal Transportation Survey series and the 2001 National Household Travel Survey (NHTS) indicates that the average daily travel time per person has increased by 1.9 min per year between 1983 and 2001. The objective of this paper is to explore the growth of daily travel time expenditures. Changes in society, technology, incomes, attitudes, and sociodemographic and household structure have been hypothesized as having contributed to the travel time growth. This analysis explores those variables and their relationship to increases in travel time. Aggregate values are used to investigate the relationships between daily travel time expenditures and sociodemographic characteristics. This paper comments on the share of travel time growth that can be explained by the available variables and speculates on the implications of other factors on travel time expenditure growth. A review of the NHTS data set and an analysis of the relationships between the data set and travel time expenditures make clear that travel budget changes that appear to be related to the set of available variables do not explain the full reason for the significant increase in travel time spending. The increases are across all market segments: age, income, gender, ethnicity, household composition, and so on. Thus, shifts in demographic or other traveler conditions do not fully explain the increases in trip making. That has a significant implication for transportation planning–-traditional sociodemographic predictors for trip making do not appear to be sufficiently causal to be useful for understanding current and future factors influencing trip making and travel expenditure changes.
Developing Custom Tools for Deriving Complex Data from Travel Survey Databases
Authors: Venigalla Mohan , Chalumuri Soujanya , Mandapati Rajit
Published: May 2018

Data from large-scale travel survey databases, such as the Nationwide Personal Transportation Survey (NPTS) and the National Household Travel Survey (NHTS), are often used to derive complex parameters for transportation modeling applications not originally targeted by the surveys. When situations demand complex data manipulation tasks, publicly available tools for the purpose do not obviate the need for data users to sift through entire databases and develop custom solutions. This paper presents a flexible methodology for developing custom database tools for cost-effectively deriving application-specific information from travel survey data. The seven-step methodology accounts for assessment of needs, verification of validity of travel survey data to the application, establishment of scientific justification, development of functional requirements of the system, development of data model, definition of processes, and development and testing of tools. To demonstrate the methodology, a case study involving derivation of locality-specific parameters for emission factor models from the NPTS and NHTS databases is presented. With the use of this methodology, a custom database application called Travel-Related Inputs Model for MOBILE6.x (TRIMM) was developed for this case study. The working mechanisms of TRIMM are illustrated. The methodology outlined, though specific to travel survey databases, is sufficiently generic to be used for developing custom tools to derive various modeling parameters from large transportation databases.
Assessing Robustness of Imputation Models Based on Data from Different Jurisdictions
Authors: Zhong Ming , Sharma Satish , Liu Zhaobin
Published: May 2018

The literature indicates that many highway and transportation agencies in North America and Europe estimate missing values in their collected traffic data records. Estimating missing values is known as data imputation. Such a convention can be traced back to early traffic monitoring systems in the 1930s; however, no studies have been found to assess the accuracy of imputations carried out by transportation practitioners. The imputation methods used by highway agencies are varied and intuitive in nature. Some of them could result in large imputation errors in certain circumstances. Those errors can lead to significant deviations in the resulting operation plans and designed structures. Therefore, it is necessary to evaluate the accuracy of various imputation methods that highway agencies use. This study identifies and tests typical imputation methods on automatic traffic recorder data from Alberta and Saskatchewan in Canada. With assessment of imputation methods based on the data from different highway agencies, it is possible to evaluate their robustness and suitability for use across jurisdictions. The accuracy of individual imputation models was statistically analyzed, and comparisons and recommendations were made. Study results clearly indicate that models using additional observations as input and more sophisticated prediction techniques consistently produce better imputations. It is believed that this study would be helpful for traffic engineers in reviewing their imputation practices and, hence, in improving their data quality.
Evaluation of Microwave Radar Trailers for Nonintrusive Traffic Measurements
Authors: Zwahlen Helmut T. , Russ Andrew , Oner Erdinc , Parthasarathy Meghna
Published: May 2018

A trailer using two Wavetronix microwave radar units in side-fire mode was developed to measure traffic nonintrusively, including time-stamped arrival records, moving average speed ( N = 16), length, and classification (0 to 20 ft, 20 to 40 ft, more than 40 ft) of each vehicle. This paper reports on an initial validation of a prototype trailer on a four-lane section of US-50 east of Athens, Ohio. Traffic on the road was independently measured with video and radar, and the results were compared with records from the trailer to verify that the trailer was measuring the traffic with reasonable accuracy. The system records the arrival of more than 95% of all vehicles, with phantom and missed counts held to less than 5% in nearly all test cases. The overall average speed based on a 90-min time period is within 3 mph of the actual overall average values, although the observed standard deviation of the trailer moving average speed readings is about two to three times that of validation data, indicating that not all the variation is from traffic fluctuations. The vehicle classification is unreliable; the fraction of trucks in a lane can be severely overestimated or underestimated. The system needs further development to create a more reliable portable system for nonintrusive traffic measurements.