bluuebunny/crossref_metadata_2025 huggingface dataset:
Prácticas de estimulación y promoción del desarrollo infantil en la etnia Mayo
Authors: Vera Noriega José Ángel , Torres Ávila Miguel Ángel , Rodríguez Carvajal Claudia Karina , Siqueiros Aguilera José Pablo
Published: February 2014

En este estudio se identificaron las características de las prácticas de estimulación y promoción del desarrollo en una comunidad indígena Mayo del estado de Sonora y Sinaloa en el noroeste de México. Se evaluaron dos grupos de 50 madres cada uno: un primer grupo que llamaremos de resistencia étnica, hablaba la lengua mayo a sus hijos y participaba en un programa educativo no escolarizado cuyo objeto es estimular el desarrollo. Un segundo grupo de madres que llamaremos de asimilación étnica, no hablaba la lengua mayo y no pertenecía al programa educativo. Se realizó mediante la aplicación de entrevistas a las madres y con escalas de desarrollo psicológico para niños de 0 y 5 años de edad. Los resultados indican que la población no hablante y sin educación inicial (asimilación étnica) presenta baja frecuencia en el rango de problemas en el desarrollo y estimulación del niño en el hogar, comparado con la población hablante y con educación inicial (resistencia étnica). Se concluye en términos de un modelo intercultural de educación inicial para población indígena.
Análise do funcionamento diferencial dos itens do Exame Nacional do Estudante (ENADE) de psicologia de 2006
Authors: Primi Ricardo , Carvalho Lucas Francisco de , Miguel Fabiano Koich , Silva Marjorie Cristina Rocha da
Published: February 2014

Parte do Sistema Nacional de Avaliação das Instituições de Educação Superior considera o desempenho dos estudantes por meio do ENADE. Neste artigo efetuou-se uma análise dos itens da prova do ENADE de psicologia aplicada em 2006 tentando-se detectar itens com funcionamento diferencial (DIF), isto é, itens com problema de equivalência ao medir ingressantes e concluintes e estudantes de instituições públicas e privada. Analisou-se uma amostra de 26.613 estudantes ingressantes e concluintes representativa de todos os cursos do país. Empregou-se a análise de Rasch e regressão logística para se detectar o DIF. Onze itens dos 30 que compunham a prova apresentaram DIF. Dois tipos de DIF ocorreram, um tipo em itens com baixa discriminação e outro em itens com alta discriminação. O subgrupo mais relevante tende a favorecer alunos de instituições públicas. Discute-se também a questão da discriminação elevada como indicativo de DIF.
A more social science: barriers and incentives for scientists engaging in policy
Authors: Singh Gerald G , Tam Jordan , Sisk Thomas D , Klain Sarah C , Mach Megan E , Martone Rebecca G , Chan Kai MA
Published: February 2014

Scientists are increasingly called upon to engage in policy formulation, but the literature on engagement is strong on speculation and weak on evidence. Using a survey administered at several broadly “ecological” conferences, we investigated: (1) the extent to which respondents engage in policy‐related activities (including reporting scientific results, interpreting science for policy makers, integrating science into decision making, taking a position on a policy issue, and acting as a decision maker); (2) what factors best explain these types of engagement; and (3) whether respondents' activity levels match their stated beliefs on such activities. Different factors explain different forms of participation. Past negative experience was identified as a barrier to taking part in policy, while self‐perceived competence in navigating the science–policy interface was consistently important in explaining activity across all engagement types, highlighting the importance of training programs linking scientists to policy. Many respondents believed that scientists should interpret, integrate, and advocate, which contrasts with previous research and relatively low levels of self‐reported participation in policy.
Sensitivity and First‐Step Uncertainty Analyses for the Preferential Flow Model MACRO
Authors: Dubus Igor G. , Brown Colin D.
Published: February 2014

Sensitivity analyses for the preferential flow model MACRO were carried out using one‐at‐a‐time and Monte Carlo sampling approaches. Four different scenarios were generated by simulating leaching to depth of two hypothetical pesticides in a sandy loam and a more structured clay loam soil. Sensitivity of the model was assessed using the predictions for accumulated water percolated at a 1‐m depth and accumulated pesticide losses in percolation. Results for simulated percolation were similar for the two soils. Predictions of water volumes percolated were found to be only marginally affected by changes in input parameters and the most influential parameter was the water content defining the boundary between micropores and macropores in this dual‐porosity model. In contrast, predictions of pesticide losses were found to be dependent on the scenarios considered and to be significantly affected by variations in input parameters. In most scenarios, predictions for pesticide losses by MACRO were most influenced by parameters related to sorption and degradation. Under specific circumstances, pesticide losses can be largely affected by changes in hydrological properties of the soil. Since parameters were varied within ranges that approximated their uncertainty, a first‐step assessment of uncertainty for the predictions of pesticide losses was possible. Large uncertainties in the predictions were reported, although these are likely to have been overestimated by considering a large number of input parameters in the exercise. It appears desirable that a probabilistic framework accounting for uncertainty is integrated into the estimation of pesticide exposure for regulatory purposes.
Photochemistry and Photoinduced Toxicity of Acifluorfen, a Diphenyl‐Ether Herbicide
Authors: Scrano Laura , Bufo Sabino A. , D'Auria Maurizio , Meallier Pierre , Behechti Akbar , Shramm Karl Werner
Published: February 2014

Photochemistry studies can be helpful in assessing the environmental fate of chemicals. Photochemical reactions lead to the formation of by‐products that can exhibit different toxicological properties from the original compound. For this reason the photochemical behavior of the herbicide acifluorfen (5‐[2‐chloro‐4‐(trifluoromethyl)phenoxy]‐2‐nitrobenzoic acid) in the presence of different solvents was studied. Photochemical reactions were carried out using a high‐pressure mercury arc and a solar simulator. Kinetic parameters and quantum yields were determined. The identification of photoproducts was performed by mass spectrometry and [1H] nuclear magnetic resonance (NMR). Nitrofluorfen, hydroxy‐nitrofluorfen, 2‐chloro‐4‐(trifluoromethyl)phenol, 5‐trifluoromethyl‐5′‐nitrodibenzofuran, and other derivatives were identified. The photochemical reactions were also carried out in the presence of either a singlet or a triplet quencher, and in the presence of either a radical initiator or a radical inhibitor. Substances used as inhibitors of the excited levels T1 and S1 showed that photodegradation of acifluorfen begins from a singlet state S1 through a π,π* transition. The role of free radicals in the photodegradation of acifluorfen was determined and a radical mechanism was proposed. Toxicity tests against Daphnia magna Strauss showed that acifluorfen was not toxic at a concentration of 0.1 mM; however, photoproducts formed after 36 h of UV exposure of the herbicide induced a remarkable toxicity to the test organism.
Point‐ and Nonpoint‐Source Pesticide Contamination in the Zwester Ohm Catchment, Germany
Authors: Müller Karin , Bach Martin , Hartmann Holger , Spiteller Michael , Frede Hans‐Georg
Published: February 2014

Reducing pesticide loads in surface waters implies identifying the pathways responsible for the pollution. The current study documents the pesticide contamination of the river Zwester Ohm, a 4917‐ha catchment in Germany with 41% of the land used for crop production. Discharges and concentrations of 19 pesticides were measured continuously at three locations for 15 mo. The load detected at the outlet of the catchment amounted to 9048 g a.i. The losses represent 0.22% of the pesticides applied by the farmers. The contamination showed a seasonal pattern following the pesticide application times. The wastewater treatment plant system (WWTPS) in the catchment (two wastewater treatment plants [WWTP], 14 combined sewer overflows (CSO), four CSO tanks) emits during dry weather periods purified sewage and during storm events sewage mixed with stormwater runoff into the river. The contribution by the WWTPS to the pesticide load was defined as point‐source pollution (PSP). The load was dominated by PSP with at least 77% of the total pollution. No significant interdependencies between intrinsic properties of the pesticides, hydrometeorological factors, and the loads occurring in the stream could be found. Therefore, it is not possible to predict PSP for other catchments based on the results from this study. Whereas 65% of the total load entered the river via the WWTP, a portion of 12% was attributed to the CSO. The study points out that the influence of CSO on PSP should be taken into account in future catchment studies in areas with comparable agricultural structure.
Phosphorus Exchangeability and Leaching Losses from Two Grassland Soils
Authors: Sinaj S. , Stamm C. , Toor G. S. , Condron L. M. , Hendry T. , Di H. J. , Cameron K. C. , Frossard E.
Published: February 2014

Although phosphate phosphorus (P) is strongly sorbed in many soils, it may be quickly transported through the soil by preferential flow. Under flood irrigation, preferential flow is especially pronounced and associated solute losses may be important. Phosphorus losses induced by flood irrigation were investigated in a lysimeter study. Detailed soil chemical analyses revealed that P was very mobile in the topsoil, but the higher P‐fixing capacity of the subsoil appeared to restrict P mobility. Application of a dye tracer enabled preferential flow pathways to be identified. Soil sampling according to dye staining patterns revealed that exchangeable P was significantly greater in preferential flow areas as compared with the unstained soil matrix. This could be partly attributed to the accumulation of organic carbon and P, together with enhanced leaching of Al‐ and Fe‐oxides in the preferential flow areas, which resulted in reduced P sorption. The irrigation water caused a rapid hydrologic response by displacement of resident water from the subsoil. Despite the occurrence of preferential flow, most of the outflowing water was resident soil water and very low in P. In these soils the occurrence of preferential flow per se is not sufficient to cause large P losses even if the topsoil is rich in P. It appears that the P was retained in lower parts of the soil profile characterized by a very high P‐fixing capacity. This study demonstrates the risks associated with assessing potential P losses on the basis of P mobility in the topsoil alone.
Climatic and Agricultural Contributions to Changing Loads in Two Watersheds in Ohio
Authors: Moog Douglas B. , Whiting Peter J.
Published: February 2014

Trends in climatic variables, streamflow, agricultural practices, and loads of nutrients and suspended solids were estimated for 1976–1995 in the Maumee and Sandusky watersheds, two large agricultural basins draining to Lake Erie. To understand the contributions that various factors may have made to the trends in loads, earlier results of models linking loads to explanatory variables were combined with estimated trends in those variables. The study period was characterized by increases in temperature, wintertime precipitation and streamflow, conservation farming, and loads of nitrate and total suspended solids; decreases in snowfall and snow cover, fertilizer, manure from livestock, and loads of soluble reactive phosphorus; and relatively steady exports of total phosphorus. After removing the effects of trends in streamflow, nitrate loads increased much less while total suspended solids and total phosphorus loads declined. The analysis suggests that the nitrate increases were due largely to climatic factors, particularly increases in winter streamflow, decreases in snowfall and snow cover, and declining annual precipitation. Decreases in soluble reactive phosphorus were associated with changes in agricultural practices, particularly declines in fertilizer deliveries and head of livestock.
BER analysis of IM/DD FSO system with APD receiver over gamma-gamma turbulence
Authors: Petkovic Milica , Djordjevic Goran , Milic Dejan , Vasic Bata
Published: February 2014

In this paper, the bit-error rate (BER) performance of intensity modulated
with direct detection (IM/DD) free space optical (FSO) system using the
on-off keying (OOK) and avalanche photodiode (APD) receiver is analyzed. The
intensity fluctuations of the received optical signal are modeled by gamma
gamma distribution, while both zero and nonzero inner scale models are
observed. The total receiver noise includes APD shot noise and thermal noise.
The BER expression is theoretically derived and numerical results are
presented. The results illustrate the BER dependence on the turbulence
strength, propagation path length, APD gain and noise temperature.
The optimal dimensions of the domain for solving the single-band Schrödinger equation by the finite-difference and finite-element methods
Authors: Topalovic Dusan , Pavlovic Stefan , Cukaric Nemanja , Tadic Milan
Published: February 2014

The finite-difference and finite-element methods are employed to solve the
one-dimensional single-band Schr?dinger equation in the planar and
cylindrical geometries. The analyzed geometries correspond to semiconductor
quantum wells and cylindrical quantum wires. As a typical example, the
GaAs/AlGaAs system is considered. The approximation of the lowest order is
employed in the finite-difference method and linear shape functions are
employed in the finite-element calculations. Deviations of the computed
ground state electron energy in a rectangular quantum well of finite depth,
and for the linear harmonic oscillator are determined as function of the grid
size. For the planar geometry, the modified P?schl-Teller potential is also
considered. Even for small grids, having more than 20 points, the
finite-element method is found to offer better accuracy than the
finite-difference method. Furthermore, the energy levels are found to
converge faster towards the accurate value when the finite-element method is
employed for calculation. The optimal dimensions of the domain employed for
solving the Schr?dinger equation are determined as they vary with the grid
size and the ground-state energy.
Assessment of a Novel Method for Teaching Veterinary Parasitology
Authors: Pereira Mary Mauldin , Yvorchuk-St. Jean Kathleen E. , Wallace Charles E. , Krecek Rosina C.
Published: February 2014

A student-centered innovative method of teaching veterinary parasitology was launched and evaluated at the Ross University School of Veterinary Medicine (RUSVM) in St. Kitts, where Parasitology is a required course for second-semester veterinary students. A novel method, named Iron Parasitology, compared lecturer-centered teaching with student-centered teaching and assessed the retention of parasitology knowledge of students in their second semester and again when they reached their seventh semester. Members of five consecutive classes chose to participate in Iron Parasitology with the opportunity to earn an additional 10 points toward their final grade by demonstrating their knowledge, communication skills, clarity of message, and creativity in the Iron Parasitology exercise. The participants and nonparticipants were assessed using seven parameters. The initial short-term study parameters used to evaluate lecturer- versus student-centered teaching were age, gender, final Parasitology course grade without Iron Parasitology, RUSVM overall grade point average (GPA), RUSVM second-semester GPA, overall GPA before RUSVM, and prerequisite GPA before RUSVM. The long-term reassessment study assessed retention of parasitology knowledge in members of the seventh-semester class who had Iron Parasitology as a tool in their second semester. These students were invited to complete a parasitology final examination during their seventh semester. There were no statistically significant differences for the parameters measured in the initial study. In addition, Iron Parasitology did not have an effect on the retention scores in the reassessment study.
Effect of Cross-Anisotropy of Hot-Mix Asphalt Modulus on Falling Weight Deflections and Embedded Sensor Stress–Strain
Authors: Ahmed M. U. , Tarefder R. A. , Islam M. R.
Published: February 2014

In this study, the effects of cross-anisotropy on asphalt pavement responses are examined. A dynamic finite element model (FEM) was developed in ABAQUS to simulate pavement responses under falling weight deflectometer (FWD) and truck loads on a pavement section on I-40 at Mile Post 141 in New Mexico. This section was recently instrumented with strain gauges, moisture probes, and pressure cells. Pavement response (i.e., stress, strain, deflection) from the instrumented section is compared with the FEM-predicted values. Two combinations of cross-anisotropy are considered. The first combination considers cross-anisotropy of modulus in every layer of the pavement, and the second combination considers it only in the hot-mix asphalt layer. Time–deflection histories, stress, and strain are predicted from the FEM under FWD and truck loads. Results show that predicted deflections, stress, and strain are highly sensitive to cross-anisotropy. Predicted deflections, stress, and strain increase with a decrease in n-value, defined by the ratio of horizontal to vertical modulus of elasticity. Analyses are performed for two shapes of loading area: semicircle–rectangle and rectangle. Predicted stress and strain are shown to be larger for the rectangular shape of the loading area than for the semicircle–rectangle area. This study recommends including modulus anisotropy in FWD backcalculation and in pavement design.
Evaluation of the Benefits of Diamond Grinding of a Continuously Reinforced Concrete Pavement
Authors: Buddhavarapu Prasad , de Fortier Smit André , Banerjee Ambarish , Trevino Manuel , Prozzi Jorge A.
Published: February 2014

This paper discusses a study to evaluate the benefits on a continuously reinforced concrete pavement (CRCP) of diamond grinding used specifically for improving pavement functionality in surface macrotexture, skid resistance, roughness, and noise. The effectiveness of diamond grinding in improving those properties is calculated on the basis of in-field observations. The effect of three preexisting conditions (carpet drag, burlap drag, and transverse tining) on the effectiveness of diamond grinding is also evaluated. The results of the analysis indicate that diamond grinding improved the surface macrotexture by 0.6 mm and skid resistance by about 60%. The surface roughness of the diamond-ground sections was, on average, appreciably reduced, from 124 to 80 in./mi. An average overall reduction in noise level of 3.2 dB(A) was evident. A maximum reduction in the region of the noise frequencies (1,000 to 2,500 Hz) was observed, with a maximum noise reduction of 5.6 dB(A) at 1,600 Hz. The grinding operation produced a relatively uniform surface in relation to these properties despite the varying preexisting conditions across the CRCP.
Developing an Analysis Framework to Quantify and Compare Skid Resistance Performance on Porous and Nonporous Pavements
Authors: Zhang Lei , Ong Ghim Ping , Fwa Tien Fang
Published: February 2014

Porous pavement surfaces are widely used to improve wet-pavement skid resistance and to reduce skidding accidents. Numerous studies in the literature have examined the ability of porous pavements to provide better skid resistance than nonporous pavements; however, many of these studies were experimental and could not offer a mechanistic interpretation of the skid resistance behavior exhibited by porous pavements. This paper presents an analysis framework that can mechanistically quantify the skid resistance capabilities of porous and non-porous pavement surfaces and aid in understanding the key factors involved. The analysis framework consists of two key modules. The first determines the thickness of the water film accumulated on pavement surfaces for a given rainfall intensity, and the second computes wet-pavement skid resistance with consideration of structural mechanics, fluid dynamics, fluid–structure interaction, and flow within a porous medium. The developed framework is first validated against past experimental data and is found to predict skid resistance accurately. An illustrative case study is then presented to quantify and compare skid resistance performance between porous and nonporous pavements. This case study demonstrates that the developed framework not only effectively compares skid resistance performance between porous and nonporous pavements but also provides a fundamental understanding of the development of skid resistance on those surfaces.
Sound Absorption and Friction Responses of Nanoconcrete for Rigid Pavements
Authors: Gonzalez Marcelo , Safiuddin M. , Cao Jingwen , Tighe Susan L.
Published: February 2014

This paper reports the influence of nanosilica on friction and sound absorption responses of concrete for application in rigid pavements. The paper also discusses the feasibility of applying nano-lotus leaf as a coating for concrete material. Previous research on friction and sound absorption characteristics of concrete pavement primarily emphasized creating different surface textures through macrotexture modifications. The microstructure can also have a significant effect on surface texture, friction, and sound absorption characteristics of concrete. This research studied the friction and sound absorption properties of concrete on the basis of microtexture modification that used nanomaterials such as nano-silica and nano-lotus leaf. Several laboratory concretes were produced by using different proportions of nanosilica, which partially replaced cement by weight. The fresh concretes were tested for workability, wet density, and air content. The hardened concretes were tested for compressive strength, friction, and sound absorption. The British pendulum test was used to determine the friction number. An impedance tube was used to determine the sound absorption coefficient. Preliminary results indicate that nanosilica can increase friction and sound absorption of concrete pavements. In addition, the results show that nano-lotus leaf can be applied as a coating on concrete material for rigid pavements to improve retention of their friction properties during the wet season.
Development and Implementation of a Beam-Bridging Filter for Use in Airport Groove Identification
Authors: Wang Qiang , Hayhoe Gordon F.
Published: February 2014

Transverse grooves on runways prevent hydroplaning of aircraft at high speeds and are therefore a vital component of air safety. This paper proposes, for accurate identification of groove geometry, a new type of beam-bridging filter that uses a mechanical model to reduce the influence of short dips in pavement elevation profiles. This approach can adjust the effect of a tire's contact with the road surface by modeling the contact area as a beam element with a series of compressive springs. If small dips or grooves with a characteristic length significantly less than the length of the tire contact length are present in the pavement profile, the beam-bridging filter simulates a bridge over the dips or grooves as would be formed by the tire's contact with the ground. The beam-bridging filter is compared with other types of bridging filters: (a) the physical straightedge method, (b) simulation of a profilograph wheel, (c) the FHWA bridging (moving-average) filter, and (d) the University of Michigan Transportation Institute's bridging (improved moving-average) filter. Application of the bridging filter is demonstrated by its incorporation into a computer program for transverse groove identification for use on longitudinal profiles of airport runways. The example demonstrates that using the proposed beam-bridging filter leads to improved groove identification over implementation of current low-pass filters.
Assessment of the Reliability of Predicting Hydroplaning Risk Based on past Hydroplaning Accident Data on the Florida Interstate System
Authors: Yassin Menna , Jayasooriya Waruna , Gunaratne Manjriker
Published: February 2014

Computational tools that can predict hydroplaning risk are invaluable to departments of transportation for drainage designs associated with new pavements or lane expansions. PAVDRN is a computer software package developed under NCHRP sponsorship to determine threshold hydroplaning speeds on a given section of a highway during adverse weather conditions. This study evaluated the reliability of the PAVDRN software in predicting dynamic hydroplaning by using past statistics on dynamic hydroplaning accidents in the state of Florida. Two approaches, based on (a) estimated travel speed and (b) posted speed, were used to assess PAVDRN's effectiveness in accurately predicting hydroplaning accidents. Both approaches showed that this software had a reasonable degree of reliability. A third effort was also used to provide upgraded and realistic hydroplaning risk estimates when PAVDRN was used. This effort was facilitated by using additional information from the Florida Department of Transportation crash database to account for extraneous factors associated with hydroplaning that were not considered in PAVDRN's analytical models.
Influence of Temperature on Tire–Pavement Friction
Authors: Anupam K. , Srirangam S. K. , Scarpas A. , Kasbergen C.
Published: February 2014

Past experimental studies show that tire–pavement friction values are related to conditions surrounding the tire such as pavement temperature, ambient temperature, contained air temperature, and surface characteristics of the pavement. For measurements taken in different temperature conditions, road agencies generally apply correction factors. These correction factors are based primarily on experience and previous field test measurements that have very limited transferability under different conditions. This paper studies frictional behavior of test tires under different surrounding temperature conditions using finite element analysis. The scope of this research is to analyze the effect of pavement temperature, ambient temperature, and contained air temperature on frictional measurements. Finite element analysis of fully and partially skidding tires over different asphalt pavement surfaces, namely, porous asphalt, ultrathin surface, and stone mastic asphalt, is considered. Observation showed that a higher pavement temperature, ambient temperature, and contained air temperature resulted in a lower hysteretic friction for a given pavement surface and a given tire slip ratio. In contrast, a lower tire slip ratio and a pavement with higher macrotexture resulted in higher friction. This study highlights that a critical combination of these factors will decrease friction significantly.
Safety and Operational Benefits of Variable Speed Limits under Different Traffic Conditions and Driver Compliance Levels
Authors: Habtemichael Filmon G. , de Picado Santos Luis
Published: February 2014

Control of traffic by a variable speed limit (VSL) has been researched for a long time, but there is a lack of consensus on its safety and operational benefits and on the impact of driver compliance. This study provides quantitative evaluations of these benefits and shows the importance of driver compliance with VSLs. VISSIM and the technique of simulated vehicle conflicts (Surrogate Safety Assessment Model) were used in the study. To validate the safety analysis, an attempt was made to correlate the simulated vehicle conflicts with historic crashes. Three scenarios of traffic conditions were considered: heavily congested, lightly congested, and uncongested. Each scenario was further examined under four driver compliance levels: low, medium, high, and very high. The results con-firmed that the VSL had safety and operational benefits for motorway traffic. The system had the highest safety benefits during highly congested traffic conditions, followed by lightly congested conditions, and the least during uncongested conditions. Moreover, the system had the highest operational benefits during lightly congested traffic conditions, little benefit during uncongested conditions, and no benefit during heavily congested conditions. It was also found that the safety benefits of VSL were not at the expense of an increase in travel time. However, these benefits showed significant variations that depended on drivers' level of compliance with the system. The study concludes that the success of the VSL is highly dependent on the level of driver compliance.
Analysis of Crash Severity Based on Vehicle Damage and Occupant Injuries
Authors: Qin Xiao , Wang Kai , Cutler Chase E.
Published: February 2014

In recent years, the reduction of injury crashes has been heralded as a great success. Improvements in federally mandated safety standards and advancements made by automotive industries to enhance vehicle safety can be partially credited with the decline. Now the national strategy on highway safety is to move toward zero deaths. From this vision zero perspective, one of the appropriate strategies is to manage kinetic energy in crashes and collisions—that is, to minimize the energy transferred to the human body—because the kinetic energy is responsible for occupant injuries and fatalities. Vehicle damage conditions are an unbiased indicator of kinetic energy in collisions, and injury severity is the ultimate measure of occupant risk. In this study, vehicle damage and occupant injury models were developed for single-vehicle and multiple-vehicle crashes. The results of these models provide a complete view of crash severity determinants and how they affect occupant injuries and vehicle damage. Some factors have a consistent impact across both injury severity and vehicle damage; others are contradictory. Combining information from both occupants and vehicles is valuable for an impartial evaluation of specific components in highway design; this combining also provides an accurate assessment of the impacts of occupant characteristics, driver behavior, and error on the resulting bodily injuries.
Evolutionary Game Theoretic Approach to Rear-End Events on Congested Freeway
Authors: Chatterjee Indrajit , Davis Gary A.
Published: February 2014

Rear-end crashes on freeways contribute significantly to nonrecurring congestion. Reducing these events would significantly improve freeway capacity, particularly during peak hours. Although promising countermeasures, such as variable speed limits, changeable message signs, and vehicle-based improvements, are under consideration, currently there is a shortage of demonstrably proven countermeasures targeted at freeway rear-end crashes. Liability rules, in which the direct cost associated with a crash is divided between the drivers, their insurance companies, or both, are a primary mechanism for influencing the occurrence of freeway rear-end crashes. An exploratory effort uses concepts from evolutionary game theory to predict the effects of liability rules on rear-end crashes. In a typical two-vehicle car-following scenario, driving behavior can be associated with a utility that each driver expects to achieve depending on his or her and the opponent's actions. Such interactions between leader and follower are modeled as the outcome of an evolutionary process in which drivers with different driving behaviors are randomly and repeatedly matched against each other to play a two-player game. The outcome of these games determines the fraction of drivers pursuing a particular driving strategy for the next phase of the game. The stable long-run distribution of driving strategies is then used to predict the proportion of drivers who are more likely to be involved in a rear-end accident. It turns out that when direct crash costs are allocated evenly to the involved drivers, a population in which all drivers act to avoid crashes is not evolutionarily stable.
Computer Vision Techniques for the Automated Collection of Cyclist Data
Authors: Zaki Mohamed H. , Sayed Tarek , Cheung Andrew
Published: February 2014

One of the main challenges in the conduct of detailed analysis of cyclist behavior is the lack of reliable data. Collection of data through manual methods is a labor-intensive and time-consuming process. Two of the important areas of cyclist data collection are volume counts and average speed measurements. A volume count provides the basis for necessary exposure measures and conveys essential information about traffic patterns. Cyclist speed data are used for traffic control and safety studies. The application of computer vision (CV) techniques enables the collection of precise spatial and temporal measurements of road users in a resource-efficient way. This paper presents the use of a set of CV techniques for the automated collection of cyclist data. Cyclist tracks obtained from video analysis were used to perform screen line counts as well as cyclist speed measurements. The applications were demonstrated with the use of a real-world data set from a roundabout in Vancouver, British Columbia, Canada. Further analysis was conducted on the mean speed of cyclists with regard to several factors (e.g., travel path, helmet use, group size). The motivation for this research was to understand better cyclist behavior and how it varied under different conditions. Several conclusions could be drawn from the analysis of cyclist speed behavior. Group size, travel path, lane position, and helmet use were all found to affect the cyclist mean speed. Single cyclists had a slightly, but significantly, higher mean cycling speed than did group cyclists. The mean cycling speed was highest for those cyclists who used the road rather than the sidewalk. The mean cycling speed decreased for cyclists without helmets.
Is Evidence in Practice?
Authors: Winters Meghan , Weddell Angie , Teschke Kay
Published: February 2014

Countries with high cycling rates have national, school-based, mandatory cycling education programs; however, in North America, cycling education is diverse and disparate. The aim of this project was to understand what cycling safety content was delivered in Canadian jurisdictions and how training materials aligned with scientific evidence. Cycling safety literature was reviewed, and cycling education materials were compiled from drivers' licensing and cyclist education programs. The education materials were compared with the scientific evidence found in cycling safety literature to determine agreements, disagreements, or gaps. Fifty-six scientific articles focused on crash or injury risk, injury severity, or other safety outcomes and met the project's inclusion criteria. The evidence in these articles covered bicycling operations, visibility and safety gear, road characteristics, route types, and bicycle–motor vehicle interactions. Forty-eight training materials for cyclists, drivers, or both were gathered from 12 provincial and territorial driver's licensing jurisdictions, five municipalities, and seven advocacy organizations. Materials covered bicycle fit and maintenance, rules of the road, bicycle operations, visibility and safety gear, bicycle–motor vehicle interactions, route characteristics, and route types. Most education topics were supported by scientific evidence, except topics related to legislation or common sense. Evidence on motor vehicle passing distances conflicted with some educational material guidance about where to cycle on the road. A gap in the educational materials was the relative safety of different route infrastructure, important for route planning. This research illustrated the diversity of cycling education in Canada and revealed areas in which education materials could be modified to align with scientific evidence on safe cycling.
Commuter Cyclist Travel Behavior
Authors: Ahmed Farhana , Rose Geoffrey , Jakob Christian
Published: February 2014

The study reported in this paper examined commuter cyclist travel behavior specifically in response to changes in weather. An investigation into how bicyclists made their day-to-day riding decisions provided insights into the factors that guided their behavior in adverse weather. Disaggregate travel data collected from an in-depth survey were analyzed. Examination of general commuter cyclist travel behavior led to the identification of differences on the basis of riding frequency. Weather conditions were found to be a paramount factor in a commuter's riding decisions. Further survey results were analyzed to gain insight into the influence of end-of-trip facilities and to quantify whether riders who had access to such facilities were less sensitive to changes in weather. More than half of the respondents indicated that these facilities were important, in that they encouraged the respondents to ride to work when the weather was not favorable. Given the variability in day-to-day ridership, commuter riders were expected to alternate modes when faced with adverse weather. The modal shift of commuter riders was analyzed with a logistic regression model. When the model was used to predict the probability of a shift to private transport (e.g., drive alone, get a lift from someone else, use a motorcycle or motor scooter), it correctly predicted nearly 80% of the cases. The implications of the results for government policies and strategies that seek to increase commuter cycling in urban areas are discussed.
North America's First E-Bikeshare
Authors: Langford Brian Casey , Cherry Christopher , Yoon Taekwan , Worley Stacy , Smith David
Published: February 2014

The integration of electric bicycles (e-bikes) with bikesharing could increase the utility of bikesharing through a reduction of some barriers to bicycling and an increase in the number of prospective users. North America's first e-bikesharing system (cycleUshare) at the University of Tennessee, Knoxville, offers a new, sustainable transportation option for students, faculty, and staff. The cycleUshare system with two stations was launched as a small pilot project to study the technology and its users' experiences. This paper presents an overview of the cycleUshare system and reports experiences from the first year of operation. With 93 enrolled users, cycleUshare provided a unique opportunity to study not only the system's use but how individual users made trips with both regular bicycles and e-bikes and the factors that influenced those trips. The study reported here found that only 22% of users accounted for 81% of the trips. Factors of speed and convenience played major roles in participants' decisions to use the system, and speed and comfort were the most influential factors in the selection of an e-bike rather than a regular bicycle. Most of the reported trips were class related, although e-bikes were used for a wide variety of trip purposes. Walking was the mode most displaced by the system; this result indicated that e-bikesharing expanded user mobility. User perceptions about bicycle types were explored also. This model of e-bikeshare was effective in its capability to attract users to both regular bicycles and e-bikes and to expand user mobility.
Effect of Burnout on Accident Involvement in Occupational Drivers
Authors: Chung Yi-Shih , Wu Hui-Ling
Published: February 2014

Managing the health and wellness of occupational drivers requires the recognition of burnout as an occupational hazard. However, the literature is dominated by studies of stress rather than burnout. The manner in which burnout may affect accident involvement is investigated in occupational drivers. The proposed causal structure is based on the stressor–strain model, in which burnout mediates between occupational stress and accident involvement. The study recruited 915 public transport drivers. The Copenhagen Burnout Inventory and an effort–reward imbalance scale were adopted to measure burnout and occupational stress, respectively. Results of the analysis indicated that burnout exerted a direct effect on accident involvement beyond the effect of occupational stress. Enhancing the perception of a safety culture does not significantly reduce the effect of occupational stress on burnout; however, it does significantly reduce the effect of burnout on accident involvement and thus indirectly alleviates the effect of occupational stress on accident involvement. In summary, as a comprehensive measure of the adverse effect of various types of chronic stressors, burnout provides a strong indicator for the identification of drivers who pose a risk to the organization and to road safety. Burnout management should be incorporated into overall stress management. Occupational drivers normally experience a low level of empowerment and long work hours; thus, a safety culture is crucial to this occupational category to reduce burnout and ensure workplace safety.
Spatial and Temporal Analysis of Driver Gap Acceptance Behavior at Modern Roundabouts
Authors: Fitzpatrick Cole D. , Abrams Daniel S. , Tang Yue , Knodler Michael A.
Published: February 2014

Despite an increasing acceptance of modern roundabouts in the United States, unfamiliarity with this type of intersection is still widespread. This unfamiliarity results in drivers making unpredictable decisions about gap acceptance, thus increasing the difficulty of design decisions. The relationship between the spatial and temporal critical gaps accepted by drivers in modern roundabouts is explored with gap acceptance data from more than 1,500 vehicle interactions at the roundabout on the University of Massachusetts, Amherst, campus. The critical gap was determined to be 42 ft spatially and 2.2 s temporally, which correlated directly with the average speed of the circulating flow. A longer critical gap time was observed for heavy vehicles in the traffic stream. Even though the unidirectional flow of the circulating traffic creates a potentially unpredictable environment for the driver, careful and precise analysis to obtain an accurate and reliable value of the critical gap will allow for improved roundabout design.
Modeling Injury Outcomes of Crashes Involving Heavy Vehicles on Texas Highways
Authors: Islam Mouyid Bin , Hernandez Salvador
Published: February 2014

Concern related to crashes that involve large trucks has increased in Texas recently because of the potential economic impacts and level of injury severity that can be sustained. However, detailed studies on large truck crashes that highlight the contributing factors leading to injury severity have not been conducted in Texas, especially for its Interstate system. The contributing factors related to injury severity were analyzed with Texas crash data based on a discrete outcome-based model that accounts for possible unobserved heterogeneity related to human, vehicle, and road–environment factors. A random parameter logit (i.e., mixed logit) model was estimated to predict the likelihood of five standard injury severity scales commonly used in the Crash Records Information System in Texas: fatal, incapacitating, nonincapacitating, possible, and none (i.e., property damage only). Estimation results indicated that the level of injury severity outcomes was highly influenced by several complex interactions between factors and that the effects of some factors could vary across observations. The contributing factors include driver demographics, traffic flow, roadway geometric features, land use, time characteristics, weather, and lighting conditions.
Motorcycle and Motor Scooter Use in Victoria, Australia
Authors: Jordehi Babak Amani , Rose Geoffrey , Thompson Russell G.
Published: February 2014

Given that powered two-wheelers (PTWs) are overrepresented in crash statistics around the world, it is perhaps not surprising that much of the research and government policy attention on PTWs is focused on road safety issues. An understanding of the potential role that these vehicles can play as an urban travel option in the context of sustainable transport is limited. The need for better knowledge about the utilitarian use of this vehicle class is addressed by examining the usage patterns and demographics of riders in Victoria, Australia. The analysis draws on a special survey of PTW users that was conducted in conjunction with a major household travel survey. Because respondents indicated whether their PTWs were motor scooters or motorcycles, the analysis was segmented by PTW type as well as trip purpose and rider demographics (particularly age and gender). Cross-tabulations and hypothesis testing provided insight into important differences across subgroups, and logistic regression models examined the factors that correlated with whether a motor scooter or motorcycle was the most likely PTW to have been used for a particular journey. Rider gender, age, and distance to be ridden were significant explanatory variables. The results provide insight into the use of PTWs for utilitarian travel and the factors that help explain differences in the use patterns of motor scooters and motorcycles.
Comparison of Sichel and Negative Binomial Models in Estimating Empirical Bayes Estimates
Authors: Zou Yajie , Lord Dominique , Zhang Yunlong , Peng Yichuan
Published: February 2014

Traditionally, transportation safety analysts have used the empirical Bayes (EB) method to improve the estimate of the long-term mean of individual sites and to identify hotspot locations. The EB method combines two sources of information: (a) the expected number of crashes estimated by crash prediction models and (b) the observed number of crashes at individual sites. Because of the overdispersion commonly found in crash data, a negative binomial (NB) modeling framework has been used extensively in crash prediction estimation models. Recent studies have shown that the Sichel (SI) distribution provides a promising avenue for developing crash prediction models. The objective of this study was to examine the application of the SI model in calculating EB estimates. The study used crash data collected at four-lane undivided rural highways in Texas to develop SI models with fixed and varying dispersion terms. The results led to the following main conclusions: (a) the selection of the crash prediction model (i.e., the SI or the NB model) affected the value of the weight factor used for estimating the EB output and (b) the identification of hazardous sites, based on the EB method, could be different when the SI model was used. Finally, a simulation study that is designed to examine which crash prediction model can identify hotspots better is recommended for future research.