bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Chronic Otitis Externa-Media on Brainstem Auditory Evoked Potentials in Dogs
Authors: Besalti O. , Sirin Y. S. , Pekcan Z.
Published: January 2009

The objective of the study was to present normative Brainstem Auditory Evoked potentials (BAEP) data elicited by both air-conducted clicks (30–100 dBHL) and bone-conducted clicks (100–130 dBHL) for healthy dogs, and dogs with chronic otitis externa-media (COEM). The data were analyzed to acquire reference values in 55 normal dogs and to estimate the degree of hearing impairment associated with the disease. Fifty-four dogs with COEM were divided into two degrees of severity. The first one included dogs with severe (n = 16), and the second with moderate COEM (n = 38). The recognisability wave V was found higher than the others at every stimulation level. Wave VII was not seen by the bone-conducted click at all stimulation levels, and also in cases with severe COEM by the air-conducted click. Recognisability of wave V was seen more than 50% at 60 dBHL in severe COEM. This ratio was seen at 30 dBHL in moderate COEM. In healthy dogs, the latencies of waves (I–VII) were compared between the left and the right side, and there were no significant differences between each side except for a shorter latency of wave VI. In conclusion, COEM caused increasing latency rather than total deafness, and BAEP can be suggested as an ancillary diagnostic tool in ear disorders.
Immunomodulating Effect of Methisoprinol on the Pronephros Macrophage and Lymphocyte Activity after Suppression Induced by Infectious Haematopoietic Necrosis Virus (IHNV) in Rainbow Trout (Oncorhynchus mykiss)
Authors: Siwicki A. K. , Małaczewska J. , Kazun B. , Wójcik R.
Published: January 2009

The purpose of this in vitro study was to determine the influence of methisoprinol on the activity of pronephros macrophages and lymphocytes after suppression induced by infectious haematopoietic necrosis virus (IHNV). For this study IHNV-free rainbow trout were used. Pronephros from 20 fish were removed and single leukocyte suspensions were separated. The IHNV significantly (P < 0.05) decreased the respiratory burst activity and potential killing activity of pronephros macrophages and proliferative response of lymphocytes stimulated by mitogens ConA and LPS. The results of our in vitro study showed that methisoprinol at a concentration of 50 mg/ml modulated (restored) the metabolic and potential killing activity of macrophages and proliferative response of lymphocytes suppressed by IHNV.
Entry of Heavy Metals into Food Chains: a 20-year Comparison Study in Northern Moravia (Czech Republic)
Authors: Čelechovská O. , Malota L. , Zima S.
Published: January 2009

The aim of the study presented here was to assess cadmium, lead and mercury contamination of wild-living animals and cattle in Northern Moravia (Czech Republic). Samples were collected in 2005–2007 at the same locations as in 1986–1989, in the same season of the year, and they were analyzed using the same methods (AAS ). In 2005–2007, a significant decrease (P < 0.01) in cadmium concentrations in plant fodders was found, while changes in lead and mercury concentrations were less marked, and they depended on the type of commodity. In the 2005–2007 period, a marked decrease (P < 0.01) in cadmium concentrations in the muscle and kidneys of the cattle, fallow deer, roe deer and pheasants (muscle 0.002–0.009 mg kg-1, kidneys 0.11–0.69 mg kg-1) was found. In the same period, mercury concentrations in the muscle, liver and kidneys were significantly lower (P < 0.01) in cattle, roe deer and hare tissues (muscle: 0.6–3.5 μg kg-1, liver 3.3–41.0 μg kg-1, kidney 16.3–43.2 μg kg-1). Lower lead concentrations in the 2005–2007 period were only found in cows (0.04 mg kg-1, 0.1 mg kg-1 and 0.6 mg kg-1 in muscle, liver and kidney samples, respectively). No significant differences in lead concentrations were found in the tissues of other animals. The study demonstrated a reduction in the amounts of heavy metals entering food chains in the study area in recent years.
Evaluating Impact of Pavement Condition Sampling Advances on Life-Cycle Management
Authors: Mishalani Rabi G. , Gong Liying
Published: January 2009

Over the past two decades, several new nondestructive technologies have been developed and applied in collecting raw condition data and processing them to produce useful condition input to infrastructure inspection, maintenance, and rehabilitation (IM&R) decision making aimed at minimizing expected total life-cycle cost. Such advances initially motivated the quantification of condition measurement uncertainty and the incorporation of this uncertainty in decision making. Following this development, the spatial variation of condition has been quantified and has led to the recent extension of decision-making methods to take into account sampling uncertainty and determine the optimal sample size, along with the other IM&R activities. In this paper, the evaluation of the contributions of the condition sampling–related advances to improved decision making is presented. An evaluation methodology is developed and subsequently applied to a realistic example facility. The methodology is based on comparing decision-making frameworks that reflect the advances of interest with those that do not. The basic idea behind comparing any two frameworks is to use each to produce optimal IM&R policies that are based on the specific assumptions they reflect and then to simulate these optimal policies within the framework reflecting the truth with regard to capturing the most realistic assumptions. The results of the application of this evaluation methodology indicate that the magnitudes of the value of the condition-sampling advances of interest are found to be appreciable in both expected total life-cycle cost and IM&R agency cost.
SA-CrackPro
Authors: Hu Sheng , Hu Xiaodi , Zhou Fujie , Walubita Lubinda F.
Published: January 2009

Crack propagation is a critical process in both reflective- and fatigue-cracking distress mechanisms. Computation of the stress intensity factor (SIF) at the crack tip provides the basis for crack propagation analysis. Because of the three-dimensional (3-D) nature of a cracked pavement and traffic loading, the best choice for calculating the SIF is 3-D finite element (FE) programs. However, the 3-D FE solutions are often expensive because of a large number for equations and a matrix with comparatively large bandwidth. Sometimes 3-D analyses may overload the available computer capability when the pavement structure is complex. To address these problems, a new FE analysis tool named SA-CrackPro was developed and is discussed in this paper. SA-CrackPro is essentially a two-dimensional SIF calculation program that incorporates a semian-alytical (SA) method. SA-CrackPro can provide the same satisfactory computations and results as a 3-D FE program at a much faster speed and with much fewer computer resource requirements. To simulate the pavement layer interface and load-transfer conditions at the joints (or cracks), thin-layer elements were introduced. To model crack propagation sufficiently and accurately, FE automeshing and remeshing techniques were proposed and implemented in the program. The accuracy of the program was verified through comparisons with a commercial 3-D FE package, ANSYS. Finally, the application of the program is demonstrated to conclude the paper.
Innovative Techniques with a Multipurpose Survey Vehicle for Automated Analysis of Cross-Slope Data
Authors: Mraz Alexander , Nazef Abdenour
Published: January 2009

Manual surveying methods have long been used in the field of highway engineering to determine the cross slope and the longitudinal grade of an existing roadway. However, these methods are slow, tedious, and labor intensive. Moreover, manual survey methods almost always require partial or full lane closure, which results in traffic delays, increases in costs, and inconvenience to the traveling public. In 2003, the Florida Department of Transportation acquired a state-of-the-art multipurpose survey vehicle (MPSV) that combines the advantage of an inertial profiler with the additional ability of simultaneously collecting images, cross slope, longitudinal grade, curvature, rutting, and roughness at highway speed. To complement the MPSV system, an automated analysis tool has been developed to process pavement geometry data for identifying areas with deficiencies in cross slope and longitudinal grade in a fast, efficient manner. In addition, this analytical tool computes a drainage path along the pavement surface. The program also displays the analysis results in two- and three-dimensional graphical formats, allowing for an easier interpretation of the data. The MPSV technology coupled with the developed cross-slope analysis tool provides an effective, practical, and cost-effective method to identify quickly potential problem-prone areas along a highway. This paper presents an innovative technique for the analysis of data on cross slope and longitudinal profile that helps identify areas with deficiencies in cross slope and surface drainage. Highway agencies can successfully implement similar systems and analysis methodology to complement and enhance their existing safety and pavement management programs.
First Findings from the Kansas Perpetual Pavements Experiment
Authors: Romanoschi Stefan A. , Gisi Andrew J. , Portillo Miguel , Dumitru Cristian
Published: January 2009

To investigate the suitability of the perpetual pavements concept for Kansas highway pavements, the Kansas Department of Transportation (KDOT) constructed four thick, flexible pavement structures on a new alignment on US-75 near Sabetha, Kansas. They were designed to have a perpetual life and have layer thicknesses close to those recommended by KDOT's structural design method for flexible pavements, which is based on the 1993 AASHTO Design Guide. To verify the approach of designing perpetual pavements on the basis of an endurance strain limit, the four pavements were instrumented with gauges for measuring the strains at the bottom of the asphalt base layers. Seven sessions of pavement response measurements under known vehicle load were performed between July 2005 and October 2007, before and after the pavement sections were opened to traffic. The analysis of the strain data indicated that, even during hot summer days, the strains of all four test sections were smaller than the endurance limit of asphalt–concrete. As expected, the strains were affected by the temperature in the asphalt layers and the speed of the loading vehicle. The analysis of the strain signals revealed that the transverse strain under the front axle did not recover completely before the arrival of the rear axles, a situation causing the accumulation of dynamic transverse strain to values higher than those of the corresponding longitudinal strains. A comparison between the measured response and that predicted by a linear-elastic model indicated that the predicted transverse strains were close to half the corresponding measured dynamic transverse strains, while the predicted longitudinal strains were close to twice the measured dynamic longitudinal strains. Furthermore, the predicted vertical stresses at the top of the subgrade layer were close to five times the measured stresses.
Multiple Wheel–Load Interaction in Flexible Pavements
Authors: Kim Minkwan , Tutumluer Erol
Published: January 2009

Various highway vehicle axle–wheel arrangements and aircraft gear–wheel configurations adopted currently to accommodate increasing load levels affect, according to different multiple wheel-loading scenarios, flexible pavement response and performance. The traditional approach of single wheel–load response superposition, especially in the case of nonlinear analysis, may not be adequate to analyze pavements subjected to such multiple wheel-load cases. These complex loading conditions require advanced pavement layered solutions for realistic consideration of nonlinear behavior of pavement foundation geomaterials (e.g., fine-grained subgrade soils and unbound aggregates used in untreated base–subbase layers), and at the same time use three-dimensional (3-D) finite element (FE) analyses to apply multiple wheel loading. In this study, stress-dependent resilient modulus models successfully incorporated into the 3-D FE-based mechanistic pavement analysis through a programmed user material subroutine in ABAQUS were used to predict pavement resilient responses at observed critical-load locations. The results indicated that proper characterizations of the nonlinear, stress-dependent pavement foundation geomaterials significantly affected predictions of critical pavement responses. Most important, pavement responses under multiple wheel loads were somewhat different from those obtained from the single wheel–load response superposition approach, which suggested the need for 3-D nonlinear FE analyses for improved response predictions.
Trends in Deflection with Application of Repeated Loads
Authors: Schmalzer Peter N. , Thompson Travis R. , Simpson Amy L.
Published: January 2009

Falling weight deflectometer (FWD) testing is now considered routine for the evaluation of pavement structures. Averaging of FWD load and deflection data collected at the same location and similar drop loads is common before further analysis. The stated reason for this averaging is to decrease the effect of the random error inherent in FWD deflection sensors. Implicit in this methodology is the assumption that there is no significant trend in deflection results with successive load applications. FWD data from the Long-Term Pavement Performance program were analyzed to determine whether a significant trend exists between deflection and drop number. In a majority of data sets, a statistically significant trend does exist for at least one deflection sensor. The trends are most common for the highest load level and the center deflection sensor. These trends are less often practically significant but are common enough that averaging deflection data can be expected to increase total error in a large minority of cases.
Rut Accumulation and Power Law Models for Low-Volume Pavements under Mixed Traffic
Authors: Dawson Andrew R.
Published: January 2009

The fourth-power law has been used for more than 40 years to assist the modeling of the damage that accumulates in pavements due to different traffic load levels and differing numbers of load applications. This paper studies the applicability and the limits of applicability of this law to typical low-volume road pavements with no or only thin seals that obtain their structural performance primarily from the aggregate base (or equivalent) layer and for which pavements’ deterioration is overwhelmingly due to rutting. After behavior of unbound granular pavement materials has been reviewed, data from four sources is used to show that it is sometimes impossible to model real pavement response by any power relationship. Furthermore, power values, even when usable, are highly variable and can vary widely with construction material and with distress criteria. It is shown that, even when a power law is a reasonable way of interpreting data, a value for the law of 4 is not. Some suggestions are given for alternative approaches and adaptations.
Use of Slab Curvature and ProVAL to Identify the Cause of Premature Distresses
Authors: Ruiz J. Mauricio , Miron Alberto G. , Chang George K. , Rasmussen Robert O. , Xu Qinwu
Published: January 2009

It has been argued that dynamic traffic loading due to the presence of a nonflat pavement shape may result in accelerated deterioration of the pavement because of higher stresses in the slab from restrained curling–warping movement. Slab curvature, though imperceptible to the naked eye, usually develops on the riding surfaces of the individual slab segments after construction. Select case studies on high- and low-altitude Bolivian concrete highways illustrate the magnitude of curvatures that are generated. The Butterworth high-pass and spectral density analysis tools in the ProVAL software are used to identify the pavement slab curvature in these projects. A mechanistic analysis is used to ascertain the causes of the observed longitudinal cracking. By resorting to a newly developed curvature index, the second-generation curvature index, the equivalent temperature gradient that corresponds to the fitted curvature was included in a finite element method analysis to determine stresses in the slabs. It is concluded that the curved shape of the slabs resulting from permanent curling–warping coupled with traffic loading is inducing excessive stresses and causing the observed cracking distress in one of the evaluated highways.
Modeling and Analysis of Truck Hydroplaning on Highways
Authors: Ong G. P. , Fwa T. F.
Published: January 2009

The widely adopted NASA hydroplaning equation has been able to predict closely the hydroplaning speed of passenger cars on a wet pavement. However, field observations and experimental studies have found that the equation cannot explain the hydroplaning behaviors of trucks. According to the NASA equation, trucks hydroplane only at a speed much higher than the normal range of travel speeds on highways. However, this conclusion is not supported by real-world experience and field tests. In addition, field observations and experimental studies have found that lightly loaded trucks are more prone to hydroplaning than heavily loaded ones. This phenomenon cannot be explained by the NASA equation, which states that, regardless of the magnitude of wheel load, hydroplaning speed is the same if tire inflation pressure remains unchanged. To the authors’ knowledge, no studies have demonstrated theoretically or analytically why trucks behave differently from passenger cars in their hydroplaning behaviors. Using the technique of three-dimensional finite element modeling, this paper analyzes the problem of truck hydroplaning with an analytical simulation model based on hydrodynamics theory. The formulation of the model is described, and the computed results are validated against past experimental studies. The effects of tire inflation pressure, footprint aspect ratio, and truck wheel load on truck hydroplaning speed are also examined to help explain the different hydroplaning behaviors of trucks and passenger cars.
Analytical Modeling of Effects of Rib Tires on Hydroplaning
Authors: Fwa T. F. , Kumar Santosh S. , Ong G. P. , Huang C. J. H.
Published: January 2009

Hydroplaning is known to be a major cause of wet-weather road accidents. The risk of hydroplaning in wet-weather driving is a function of the depth of surface water, pavement texture properties, and tire characteristics. With the aim to improve and ensure wet-weather driving safety, extensive experimental studies have been conducted by researchers to understand how tire characteristics (in particular, tire tread depth), would affect vehicle hydroplaning risk. Rib tires have been commonly used for such experiments. Relationships derived experimentally by past researchers are available to estimate the effect of rib-tire tread depth on hydroplaning risk. However, such statistical relationships have limitations in their application range and transferability. They also do not provide detailed insights into the mechanism of hydroplaning. These limitations can be overcome through development of a theoretically derived analytical model. This paper presents an analytical simulation study that is based on the theory of hydrodynamics. The method of modeling using finite element techniques is described. Measured data from past experimental studies are used to validate the simulation model. The simulation model is applied to analyze the effect of tire tread depth on hydroplaning for different surface water depths. The effect of tire inflation pressure on the hydroplaning risk of rib tires is also examined. In addition, the effect of different rib tire designs in relation to the number of grooves is studied. This study demonstrates that the proposed model can be a useful analytical tool for evaluating the hydroplaning risk of wet-weather driving.
Effect of Rubber Deposits on Runway Pavement Friction Characteristics
Authors: Chen Jian-Shiuh , Huang Chien-Chung , Chen Chih-Hsing , Su Kung-Yao
Published: January 2009

This purpose of this paper is to evaluate the effect of rubber deposits on pavement friction characteristics on the basis of macroscopic and microscopic measurements. Runway pavement sections at the Kaohsiung (Taiwan) International Airport were chosen for field and laboratory testing over a 16-month period. In the first step of the field testing, the monthly variation in friction was established by using the Saab surface friction tester (SFT) and British pendulum testing. In the second step, macro-texture measurements were made by the grease patch method. The last step of field testing was to take samples of rubber deposits for laboratory analyses by optical microscope and scanning electron microscopy. Results showed that rubber deposits had strong effects on runway surface friction. An aircraft landing appeared to result in an increase in the thickness of rubber deposits by approximately 0.05 μm. The microstructure of rubber deposits was shown to be accumulated by the directional distribution of multiple layers of polymer scale. The friction value measured in the backward direction was higher than that measured in the forward direction. The rate of decrease in the SFT friction value was found to be about 0.05 for an increase in rubber thickness of 0.1 mm.
Image Requirements for Three-Dimensional Measurements of Pavement Macrotexture
Authors: Gendy Amin El , Shalaby Ahmed
Published: January 2009

This paper examines the effect of wavelength range on the estimation of pavement macrotexture quality from a three-dimensional (3-D) surface model. Macrotexture indicators computed from two-dimensional (2-D) profiles are compared with power spectrum energy computed from 3-D surface heights in the frequency domain. Pavement samples with different types of surface conditions were evaluated by means of a noncontact photometric stereo system. For each pavement sample, surface heights were recovered and a 3-D surface model was constructed. Surface profiles were also measured manually with a dial gauge. The surface heights in frequency domain were divided into 10 wavelength ranges. Power spectrum energy was computed for each wavelength range. The correlation between the 2-D indicators (mean profile depth and root mean square roughness) and the power spectrum energy was examined. It was found that the texture indicators computed from the 3-D recovered surface could represent the 2-D indicators adequately. Moreover, the power spectrum energy provided a good estimation of the 2-D indicators when it was computed from wavelength ranges of approximately 13 times the expected range of the 2-D indicators.
Safety Effects of Targeted Program to Improve Skid Resistance
Authors: Lyon Craig , Persaud Bhagwant
Published: January 2009

The safety impacts of improving pavement skid resistance were examined in this study by using data from New York State. The New York Department of Transportation runs a skid-accident reduction program that identifies sections of pavement with a high proportion of wet-road accidents, friction-tests these locations, and treats those with both a high proportion of wet-road accidents and low friction numbers. An empirical Bayes before–after study was conducted of locations that were treated under this program. The results indicate that this can be a highly cost-effective safety treatment for both intersections and road segments that warrant skid resistance improvement because of a high frequency of wet road accidents and low friction numbers.
Multimodal Level of Service for Urban Streets
Authors: Dowling Richard , Flannery Aimee , Landis Bruce , Petritsch Theo , Rouphail Nagui , Ryus Paul
Published: January 2009

This paper presents the results of research to develop a national method for the multimodal assessment of the quality of service provided by an urban street. The method considers the level of service from the point of view of four types of travelers typically using the urban street: auto driver, transit passenger, bicycle rider, and pedestrian. Video laboratories and transit onboard surveys were used to develop data sets of the quality of service perceived by the general public for each of the modes of travel on the urban street. The laboratories were conducted in several different metropolitan areas of the United States. Four level-of-service (LOS) models were developed, one for each mode. The four LOS models share a common measure, user satisfaction. The models assign a letter grade LOS (A–F) based on the street cross section, intersection controls, and traffic characteristics (auto, transit, bicycle, and pedestrian volumes on the street). The models can be used in combination to compare the trade-offs of different street cross sections from the unique perspectives of each mode. The models are particularly useful for testing the impacts of converting auto through lanes to bicycle lanes, wider sidewalks, and wider planter strips.
Capacity Reduction at Incidents
Authors: Knoop Victor L. , Hoogendoorn Serge P. , van Zuylen Henk J.
Published: January 2009

Incidents on freeways cause large delays for road users. These delays depend largely on the capacity at the incident location, which is determined by the drivers’ behavior at the accident location. Few empirical facts are available on traffic operations during an incident. This paper presents high-quality videos of the traffic flow around two accidents recorded from a helicopter. From the collected images, traffic counts have been performed at the exact location of the incident. This has two advantages. First, the capacity at the bottleneck per lane could be estimated. Second, truck counts could be converted to passenger car units at the location of the bottleneck. Counts show that the (outflow) capacity of the remaining lanes is about 50% lower than the (free-flow) capacity of the same number of lanes. This means that the road capacity in the opposite direction is reduced by half by the rubbernecking effect. The capacity of the road in the direction of the accident is reduced by more than half because not all lanes are in use. The images provide information on the causes for the capacity reduction. A leader accelerates and the follower accelerates a short time later. The average time between these two accelerations is estimated at about 3 s, but the video also shows a large spread of these times. The results can be used to assess consequences of incidents, in an analytical way and in macroscopic or microscopic traffic simulators.
Analysis and Modeling of Automobile Users’ Perceptions of Quality of Service on Urban Streets
Authors: Flannery Aimee , Rouphail Nagui , Reinke David
Published: January 2009

Modeling travelers’ perception of service quality is an emerging research area in surface transportation. The first national effort to study automobile drivers’ perceptions is NCHRP Project 3-70. The study was developed in response to agencies’ needs to understand which factors enter into users’ perception of quality of service and the interaction between modes on urban streets. This paper describes the research efforts taken to analyze and model automobile level of service (LOS) from the driver's perspective. A data collection approach using video laboratories and a modeling approach suitable for the discrete and ordered nature of the response variable were selected. The approach enabled the estimation of the distribution of LOS responses, given a set of explanatory variables that describe the geometry and operational effectiveness of the urban street facility. Analysis indicated that participants’ responses tended to be highly variable and that models that characterize the distribution would be preferable to point estimates. A model that uses the number of stops per mile experienced on the facility and the presence of exclusive left-turn lanes at intersections gave the best fit to the data and matched the mean video clip LOS rating 71% of the time. Although direct links between various modes to the automobile users’ perceptions of service quality were not identified, the variable “number of stops” incorporates interruptions experienced by automobile drivers when interacting with buses, bicycles, or pedestrians on urban streets and when encountering traffic signal stops. Although the proposed model was found to improve LOS prediction as compared with the current Highway Capacity Manual method, there are implementation issues that have yet to be addressed.
Default Values for Highway Capacity and Level-of-Service Analyses
Authors: Zegeer John D. , Blogg Miranda , Nguyen Khang , Vandehey Mark
Published: January 2009

The Highway Capacity Manual (HCM) is the authoritative source providing state-of-the-art methodologies for evaluating highway, transit, bicycle, and pedestrian facilities. Default values are used to represent input parameters when the input parameters are difficult to measure or estimate. A default value is a representative value that may be appropriate for estimating an input parameter in the absence of local data. Before this study was done, no nationwide research effort had been conducted to assemble field measurements to determine whether the default values in the HCM represent typical field conditions. A sensitivity analysis was conducted for the input parameters in HCM 2000 that influence the service measures calculated in the HCM methodologies. Nineteen of these input parameters were determined to have a high degree of sensitivity in influencing the service measure results. These sensitive input parameters influence the service measures for the following HCM chapters: Urban Streets, Signalized Intersections, Pedestrians, Bicycle Paths, Multilane Highways, and Basic Freeway Segments. Based on the assembly of a nationwide database, specific default values were recommended for heavy vehicle percentages and peak-hour factors for uninterrupted flow facilities (freeways, multilane highways, and rural two-lane highways). It is recommended that default values for some input parameters continue to be developed based on existing HCM guidance. Other input parameters should be based on field measurements obtained from design plans. Additional guidance is provided to aid in the selection of default values based on the review of recent research documents.
Estimating Capacity of U-Turns at Unsignalized Intersections
Authors: Liu Pan , Pan Tao , Lu Jian John , Cao Bing
Published: January 2009

The study presented in this paper is a continuous effort following the authors’ previous studies to estimate the capacity of U-turn movements at unsignalized intersections. The objective of this study is to estimate the capacity of U-turn movements at unsignalized intersections on four-lane divided roads. The study focuses on several issues that have not been addressed in the previous studies. These issues include (a) the impedance effects of minor movements, (b) conflicting traffic volume, and (c) shared-lane capacity of the major street exclusive left-turn lane. To achieve the research objective, traffic data were collected at six median openings in the Tampa Bay area of Florida. The Highway Capacity Manual (HCM) capacity estimation method was tested against capacity measured in the field using Kyte's method. It was found that the HCM method provides reasonable capacity estimates for U-turn movements at unsignalized intersections. It was also found that the HCM shared-lane capacity model overestimates the capacity of the exclusive left-turn lane, which major street left-turning vehicles share with U-turning vehicles. A linear regression model was developed to estimate the capacity of the shared left-turn lane and to quantify the effects of U-turning vehicles on the capacity of an exclusive left-turn lane. It was found that the capacity of the exclusive left-turn lane decreases with an increase in the major street traffic volume, the major street right-turn volume, and the percentage of U-turning vehicles at the exclusive left-turn lane. Assuming that the major street right-turn traffic volume is 85 vehicles per hour (veh/h) and the conflicting major street through traffic volume is 1,000 veh/h, increasing the percentage of U-turning vehicles from 10% to 50% will reduce the capacity of the exclusive left-turn lane from 290 veh/h to 250 veh/h, which accounts for about a 14% capacity reduction.
Microscopic and Macroscopic Approaches to Delay Estimation with Oversaturated Conditions
Authors: Buckholz Jeffrey W. , Courage Kenneth G.
Published: January 2009

Chapter 16 of the 2000 Highway Capacity Manual (HCM) contains a widely recognized and well-accepted procedure for calculating per-vehicle control delay at signalized intersections. Appendix F of that chapter discusses the relationship between various components of control delay using cumulative arrival and departure curves. The delay obtained from these curves has certain limitations that need to be recognized if proper conclusions are to be drawn. To illustrate these limitations, a comparison is made between the delay obtained from cumulative curves and the delay obtained through a detailed analysis of vehicle trajectories. A comparison of the control delay obtained from trajectory analysis and that obtained from cumulative arrival–departure curves shows that the cumulative curves omit certain valid portions of the control delay, while including other portions of time that are not delay at all. Taking a macroscopic approach to oversaturated delay estimation, the HCM procedures for dealing with oversaturated conditions are described and their shortcomings are explored using an example of a multiperiod analysis of an oversaturated approach to a signal. It is demonstrated that the current HCM equations can overestimate multiperiod delay and that the assumption of a capacity that is constant from cycle to cycle can underestimate delay at high values of the volume-to-capacity ratio.
Testing Incremental Queue Accumulation Method Using Lankershim Boulevard NGSIM Data Set
Authors: Kyte Michael , Dixon Michael , Nayak Vidyut , Abdel-Rahim Ahmed , Strong Dennis
Published: January 2009

This paper presents a first validation of the proposed incremental queue accumulation method (IQA) to estimate delay using the new high-resolution data sets generated as part of FHWA's Next Generation Simulation Model (NGSIM) project. The paper provides examples of the queuing process using vehicle trajectories from the NGSIM data set collected along Lankershim Boulevard in Los Angeles, California. The paper compares field measurements of delay with estimates produced by the IQA method and the existing Highway Capacity Manual method. Results indicate that the IQA method provides more realistic results than the existing method by directly tracking the vehicle arrival and departure process. The paper also notes that consideration must be given to actual queue lengths when validating a model that makes an assumption of a stacked vertical queue.
Modeling Left-Turn Blockage and Capacity at Signalized Intersection with Short Left-Turn Bay
Authors: Zhang Yunlong , Tong Jiaxin
Published: January 2009

A left-turn bay that does not have a sufficient length would be blocked by the adjacent through traffic. Left-turn vehicles can also spill back to block the through traffic when the left-turn demand is high. These two types of left-turn-related blockages have adverse effects on the operation of a signalized intersection. Left-turn bay blockage by through traffic will reduce the left-turn capacity, and left-turn bay spillback will affect the adjacent through capacity. Both problems are uncharted in the Highway Capacity Manual (HCM). This research studies these two blockage scenarios associated with left-turn bays under different left-turn signal operations. The capacity of the left-turn and through movements is modeled as a function of the length of the left-turn bay by using a probabilistic approach, taking into account potential blockage due to a short left-turn bay length. The developed capacity model will be validated on the basis of CORSIM simulations of a real-world signalized intersection. The research is aimed at estimating the left-turn and adjacent through capacity when left-turn bay blockage or spillback occurs, to complement the HCM method and highlighting the effect of the length of the left-turn bay and the left-turn signal strategy.
Calibration Potential of Common Analytical and Microsimulation Roundabout Models
Authors: Gagnon Conrad , Sadek Adel W. , Touchette Andrew , Smith Mark
Published: January 2009

Recent interest in using modern roundabouts as an effective and safe method for intersection control in the United States stresses the need for accurate modeling tools. The objective of this paper is to assess the calibration potential of common analytical and microsimulation roundabout models to replicate operations at modern roundabouts. The models considered were aaSIDRA and RODEL (on the analytical side) and PARAMICS, SimTraffic, and VISSIM (on the microsimulation side). For this study, two modern roundabouts from New Hampshire were selected and videotaped during peak-hour conditions. The models’ approach delay outputs were compared with the measured field delay from the videotapes. Model calibration parameters were systematically changed to assess their impact on the results with respect to field observations. Among the conclusions of the study are that current roundabout analysis models vary in regard to the calibration options, that calibration can have a significant impact on improving the models’ results, and that calibration might be site specific.
Indicators of Performance on Two-Lane Rural Highways
Authors: Al-Kaisy Ahmed , Karjala Sarah
Published: January 2009

This paper presents an empirical investigation into performance indicators on two-lane rural highways. Field data from four study sites in the state of Montana were used in this investigation. Six performance indicators were investigated: average travel speed, average travel speed of passenger cars, average travel speed as a percent of free-flow speed, average travel speed of passenger cars as a percent of free-flow speed of passenger cars, percent followers, and follower density. The study examined the level of association between the selected performance indicators and major platooning variables, namely, traffic flow in the direction of travel, opposing traffic flow, percent heavy vehicles, standard deviation of free-flow speeds, and percent no-passing zones. Among all platooning variables investigated, traffic flow in the direction of travel was found to have the highest correlation with performance indicators. Other platooning variables exhibited only weak correlations with performance indicators. Also, follower density followed by percent followers exhibited the highest correlations with platooning variables.
Delay at Unsignalized Intersections
Authors: Brilon Werner
Published: January 2009

The estimation of average delay for vehicles at an intersection by analytic methods is based on queuing theory. Because of the variability of traffic demand over time, the estimation of delays for time-dependent flow and capacity—also with a temporary overload—is of primary interest. For the solution different approximate approaches are currently used in practice. They are based on the approximation of the priority system by an M/M/1 queue and on the so-called coordinate transformation technique developed by Kimber and Hollis. The original approach can be split into nine different cases. The paper investigates the background of these possible solutions and their quality of approximation. The kind of definition for the sum of all delays plays an especially important role. For each of the nine cases, average delay formulas are derived. The complete set of results offers new solutions, especially for the more realistic cases. Thus, initial queues at the beginning of the observed peak period as well as different conditions in the postpeak period can be described. As methods for validating these formulas, numerically exact results could be calculated by Markov chains. Also stochastic simulations and empirical data are used to check the approximate solutions against reality. As a result, a set of equations is recommended that can be applied to estimate average delays at unsignalized intersections for well-defined traffic conditions. These appear to be better fitted to the modeled priority type of intersections than are current approaches.
Control-Type Selection at Isolated Intersections Based on Control Delay under Various Demand Levels
Authors: Han Lee D. , Li Jan-Mou (James) , Urbanik Thomas
Published: January 2009

The Highway Capacity Manual (HCM 2000) displayed the figure Exhibit 10-15 for the purpose of forecasting the likely intersection control types for future facilities. Because this figure is from a source external to HCM, to verify it, this paper employs HCM methodologies for the estimation and comparison of control delay, the choice measure of effectiveness at intersections controlled by signal, all-way stop signs, and two-way stop signs. After detailed analyses of more than 5,000 cases using Highway Capacity Software, results of control delay with various control types under a wide range of demand conditions were charted for comparison with Exhibit 10-15. It is found that Exhibit 10-15 is inconsistent with the results from HCM methodologies and, perhaps, should be replaced with the figures developed in this paper. On the basis of the criterion of minimizing delay alone, it is found that if demand is unbalanced between major and minor streets and if the traffic is low on minor streets, two-way-stop control should be used; if demand is somewhat balanced and minor streets see low to medium traffic, all-way-stop control is preferred; otherwise, signal control should be favored. The paper also demonstrates that the percentage of left-turning traffic has a significant effect on decisions involving intersection control types.
Driver Behavior and Gap-Acceptance Characteristics at Roundabouts in California
Authors: Xu Feng , Tian Zong Z.
Published: January 2009

Critical headway and follow-up headway are two important parameters to perform design and operational analyses at a roundabout. This paper addresses drivers’ gap-acceptance behavior characteristics at roundabouts and presents the results of critical headway and follow-up headway measurements at seven single-lane and three multilane roundabouts in California. Results indicate that the mean critical headway is consistent with the values recommended by the newly completed research NCHRP 3-65; however, the follow-up headway is significantly lower than that recommended by NCHRP 3-65. This paper also reveals that circulating flow rate and speed are two major factors affecting critical headway and follow-up headway. Results from this study enhance the existing database related to drivers’ gap-acceptance behavior at U.S. roundabouts.
Implementing Actuated Signal-Controlled Intersection Capacity Analysis with Pedestrians
Authors: Cheng DingXin , Tian Zong Z. , Liu Hongchao
Published: January 2009

For an actuated signalized intersection, pedestrian calls are likely to affect the effective greens serving the vehicle movements, which affect the capacity and delay of the intersection. However, the current procedure in the Highway Capacity Manual 2000 (HCM) for analyzing actuated signalized intersections treats pedestrian crossing and timing statically, with either pedestrian calls at all signal cycles or no pedestrians at all. In reality, pedestrian arrivals are random events with some cycles having more pedestrians than others and other cycles having no pedestrian call at all. This paper demonstrates that the current procedure can lead to erroneous results in capacity and delay estimations. A model is introduced to overcome the shortcomings in the current procedure. The model takes into account the stochastic nature of pedestrian crossings and their effects. The model computes the probability of having pedestrian calls in a cycle and the corresponding capacities and delays for traffic movements. An implementation framework was developed to help practitioners conduct capacity analyses using the model. The model's results on a semiactuated signal-controlled intersection were comparable with the results from the SimTraffic microsimulation model. The effects of pedestrians on intersection capacity and delay were analyzed using the proposed model. Depending on the pedestrian volume and traffic conditions, the current HCM procedure could produce significant error, especially when the pedestrian volume is low, because it does not consider the stochastic nature of pedestrian arrivals.
A Finite Element Flux-Corrected Transport Method for Wave Propagation in Heterogeneous Solids
Authors: Mariani Stefano , Martini Roberto , Ghisi Aldo
Published: January 2009

When moving discontinuities in solids need to be simulated, standard finite element (FE) procedures usually attain low accuracy because of spurious oscillations appearing behind the discontinuity fronts. To assure an accurate tracking of traveling stress waves in heterogeneous media, we propose here a flux-corrected transport (FCT) technique for structured as well as unstructured space discretizations. The FCT technique consists of post-processing the FE velocity field via diffusive/antidiffusive fluxes, which rely upon an algorithmic length-scale parameter. To study the behavior of heterogeneous bodies featuring compliant interphases of any shape, a general scheme for computing diffusive/antidiffusive fluxes close to phase boundaries is proposed too. The performance of the new FE-FCT method is assessed through one-dimensional and two-dimensional simulations of dilatational stress waves propagating along homogeneous and composite rods.
Smoke-Free Medical Facility Campus Legislation: Support, Resistance, Difficulties and Cost
Authors: Sheffer Christine , Stitzer Maxine , Wheeler J. Gary
Published: January 2009

Although medical facilities restrict smoking inside, many people continue to smoke outside, creating problems with second-hand smoke, litter, fire risks, and negative role modeling. In 2005, Arkansas passed legislation prohibiting smoking on medical facility campuses. Hospital administrators (N=113) were surveyed pre- and post-implementation. Administrators reported more support and less difficulty than anticipated. Actual cost was 10-50% of anticipated cost. Few negative effects and numerous positive effects on employee performance and retention were reported. The results may be of interest to hospital administrators and demonstrate that state legislation can play a positive role in facilitating broad health-related policy change.
Tobacco Cessation Quitline Spending in 2005 and 2006: What State-Level Factors Matter?
Authors: Keller Paula A. , Beyer Eric  J. , Baker Timothy  B. , Bailey Linda  A. , Fiore Michael  C.
Published: January 2009

Tobacco cessation telephone quitlines are an effective population-wide strategy for smoking cessation, but funding for this service varies widely. State-level factors may explain this difference. Data from the 2005 and 2006 North American Quitline Consortium surveys and from publicly available sources were analyzed to identify factors that predict higher levels of per capita quitline funding. The best-fitting multivariate model comprised higher per capita tobacco control funding (2005 p = 0.004, 2006 p=0.000), not securitizing Master Settlement Agreement payments (2005 p = 0.008, 2006 p=0.01), and liberal political ideology (2005 p = 0.002, 2006 p=0.002). Select state-level factors appear to have influenced per capita quitline services funding. These findings can help inform advocates and policymakers as they advocate for quitlines and tobacco control funding.