bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Incentive System and Cognitive Orientation on Teams' Performance
Authors: Naranjo-Gil David , Cuevas-Rodríguez Gloria , López-Cabrales Álvaro , Sánchez Jose M.
Published: January 2012

Organizations are adopting team-based structures to promote cooperation and coordination of actions and, thus, enhance performance (Libby and Thorne 2009; Chenhall 2008). However, team-based structures do not automatically improve performance. The economics literature suggests that working in teams may impair performance because of the potential conflict between individual and group incentives. In contrast, the organizational behavior literature argues that working in teams may enhance performance via members' collectivist cognitive orientation. This paper analyzes how both the economic incentive system and the team's predominant (individualist or collectivist) cognitive orientation affect team performance. We conduct an experiment with postgraduate students. Our results show that enhanced team performance is positively related to both individual economic incentives and predominately collectivist orientation in the team, and that the effectiveness of any incentive system design seems to be related to the team's predominant cognitive orientation.
Genetic algorithm using a modified backward pass heuristic for the dynamic facility layout problem *
Authors: Ripon Kazi Shah Nawaz , Glette Kyrre , Koch Dirk , Hovin Mats , Torresen Jim
Published: January 2012

Layout planning in a manufacturing company is an important economical consideration. In the past, research examining the facility layout problem (FLP) generally concerned static cases, where the material flows between facilities in the layout have been assumed to be invariant over time. However, in today’s real-world scenario, manufacturing system must operate in a dynamic and market-driven environment in which production rates and product mixes are continuously adapting. The dynamic facility layout problem (DFLP) addresses situations in which the flow among various facilities changes over time. Recently, there is an increasing trend towards implementation of industrial robot as a material handling device among the facilities. Reducing the robot energy usage for transporting materials among the facilities of an optimal layout for completing a product will result in an increased life for the robots and thus enhance the productivity of the manufacturing system. In this paper, we present a hybrid genetic algorithm incorporating jumping genes operations and a modified backward pass pair-wise exchange heuristic to determine its effectiveness in optimizing material handling cost while solving the DFLP. A computational study is performed with several existing heuristic algorithms. The experimental results show that the proposed algorithm is effective in dealing with the DFLP.
Building Support for New Transportation Funding and Financing Program
Authors: Lorenz Julie
Published: January 2012

The transportation community is well aware of the universal problem of (a) infrastructure investment needs, associated funding requirements, and the need for more flexible financing approaches and (b) public uncertainty over the efficacy of investing in transportation as opposed to other uses of their money. These are long-standing issues regardless of economic cycles, and they relate to the state of infrastructure needs and shifting economic and demographic patterns as well as public desires for public processes that are fair, equitable, efficient, and transparent. Recognizing these challenges, the Kansas Department of Transportation (DOT) embarked on a multiyear experiment to reinvent transportation planning and project selection processes in an effort to achieve greater support through stakeholder consultation, collaboration, and adoption of improved and expanded methods for ranking and selecting projects that appeal to broader issues of public concern (such as job creation) instead of merely engineering measures of need. Seven years of experimentation in consultation, collaboration, and revising processes provides many lessons for the transportation community that may be applicable in whole or in part for other state or regional transportation agencies. This paper critically examines the methods and tools used by the Kansas DOT, including surveys, road rallies, collaborative planning efforts, social media outreach, economic impact analysis, and expanded project selection processes. Taken together, this work has produced a positive outcome, including the recent funding by the Kansas legislature of a new 10-year transportation improvement program.
Innovative Traffic Demand Management Strategy
Authors: Kim Youngho , Kang Seong-Cheol
Published: January 2012

Various traffic demand management strategies have been implemented to alleviate traffic congestion, but they have often failed to effectively mitigate congestion in roads, especially when surging demand is concentrated in a short period of time. The proposed expressway reservation system is an innovative and bold strategy in traffic demand management: drivers would make reservations for traveling on expressways. This paper explores the viability of introducing the expressway reservation system during two major national holidays in South Korea. To that end, a survey on the expressway reservation system was conducted. More than 80% of the 1,000 survey respondents said that their perceived travel time during the national holidays was two to three times longer than usual. The percentage of respondents willing to change their departure time to reduce travel time during the national holidays also exceeded 80%. This tendency grew stronger as perceived travel time became longer. Of those who would change their departure time, almost 84% said that changing their departure time up to ±4 h from their initially intended time would be acceptable. Despite such a willingness and flexibility in changing the departure time, only 51.4% of the respondents thought that the expressway reservation system was necessary. Nonetheless, 73.4% of the respondents said that they would participate in the expressway reservation system if it were implemented. Statistical analysis showed that perceived travel time, age, and travel distance were the most influential factors for the public's acceptance of the expressway reservation system.
Evaluating the Impact of Transit Service on Parking Demand and Requirements
Authors: Rowe Daniel H. , Christine Bae C.-H. , Shen Qing
Published: January 2012

Many jurisdictions in the United States typically set minimum parking requirements for residential multifamily developments based on old data that were collected in suburban settings with little transit availability. Such parking requirements applied to urban settings with adequate transit service often result in an oversupply of parking, which in turn creates a barrier to smart growth. Not only does the oversupply of parking encourage automobile use and reduce housing affordability, but it also increases development costs, consumes land and natural resources, and increases associated air and water pollution. This research examines the relationship of parking demand and transit service in First Hill– Capitol Hill (FHCH) and Redmond, two urban centers in King County, Washington. An alternative method to collect parking demand data is explored. The results show a strong relationship between transit service and parking demand. The FHCH urban center, which abuts downtown Seattle, exhibited higher levels of transit service and lower parking demand. Parking demand in FHCH was observed to be 0.52 parking space per dwelling unit, which was about 50% less than parking demand observed in Redmond, a growing mixed-use suburban center, and 50% less than data reported by the Institute of Transportation Engineers. After a review of the parking policies of each urban center, opportunities to improve regulations—including adjusting minimum parking requirements and allowing for reductions in required parking when developers implement solutions to reduce demand for parking—were identified.
Transit-Oriented Development at the Urban Periphery
Authors: Pan Haixiao , Shen Qing , Liu Chang
Published: January 2012

Major cities in China are extending rail transit into the urban periphery to counter urban growth and suburbanization that are automobile-driven and automobile-dependent. In the meantime, transit-oriented development (TOD) has been adopted widely in Chinese cities. Given the adoption of the TOD concept by many rail transit station areas at the peripheries of metropolitan regions, it is imperative to explore how TOD can be applied appropriately there. In this study, two station areas were examined in Songjiang, a district located approximately 30 km from the city center of Shanghai, China. These station areas have developed according to some basic TOD principles, and, in many important ways, they are representative of newly developed rail transit station areas in Shanghai and in other major Chinese cities. The conduct of a questionnaire survey allowed for investigation of resident travel behavior, assessment of the effectiveness of the TOD application, and discussion of how TOD should be adapted to peripheral locations in a large and complex metropolitan region. The study concluded that planners must carefully substantiate the basic TOD concept in connection with this particular kind of application setting. Careful consideration should be paid to mixed land use, differentiated density, and to pedestrian and bicycle travel and their connection with rail transit. Planners also must pay close attention to each peripheral area's economic and social conditions, as well as its relationships with the central city and with other parts of the metropolitan region. This case study not only provided timely feedback on current planning practice in Shanghai and other Chinese cities but also contributed to the literature on the adaptation of TOD to local circumstances.
Development of Indicators of Opportunity-Based Accessibility
Authors: Chen Yali , Ravulaparthy Srinath , Deutsch Kathleen , Dalal Pamela , Yoon Seo Youn , Lei Ting , Goulias Konstadinos G. , Pendyala Ram M. , Bhat Chandra R. , Hu Hsi-Hwa
Published: January 2012

“Accessibility,” defined as the ease (or difficulty) with which opportunities for activity can be reached from a given location, can be measured with the cumulative amount of opportunities from an origin within a given amount of travel time. These indicators can be used in regional planning and modeling efforts to integrate land use and travel demand, and an attempt should be made to calculate these indicators for the smallest geographic area. The primary objective of this paper is to illustrate the creation of realistic space-sensitive and time-sensitive block-level accessibility indicators to track the availability of opportunities. These indicators support the development of an activity-based travel demand model by Southern California Association of Governments to provide second-by-second and parcel-by-parcel modeling and simulation. The indicators also provided the base information for mapping opportunities of access to 15 types of industries at different times during a day. The indicators and their maps were defined for the entire region of Southern California through largely available data that included the Census Transportation Planning Package, Dun & Brad-street postprocessed data, detailed highway networks and travel times from the four-step regional models, and arrival and departure times of workers by industry.
Simultaneous Modeling of Endogenous Influence of Urban Form and Public Transit Accessibility on Distance Traveled
Authors: Miranda-Moreno Luis F. , Bettex Laetitia , Zahabi Seyed Amir H. , Kreider Tyler M. , Barla Philippe
Published: January 2012

This paper describes an attempt to understand better the endogenous relationships between urban form, accessibility to public transit, and daily travel distance. A model of two simultaneous equations was implemented. The model took into account the interaction between the ownership of vehicles and the choice of household location as explanatory endogenous variables for total distance traveled by respondents. Choice of household location was defined on the basis of cluster analysis (neighborhood typology) driven by land use mix, population density, and accessibility to transit. With socioeconomic variables controlled for, the impacts of neighborhood typologies combined with car ownership levels as endogenous choices were estimated with the use of a model with simultaneous equations. This research used data from the Quebec City, Quebec, Canada, origin–destination survey conducted in 2001. The data set included responses from more than 50,000 individuals. Among other results, the presence of endogeneity was confirmed. When endogeneity was not taken into account, the joint effects of car ownership and household location choices were underestimated. According to the model with simultaneous equations, the total distance traveled by individuals was primarily influenced by employment status and household structure. In fact, the total distance per individual had an average rate of growth of 50% when the individual was working full-time. The distance also increased by 5.7% per child and decreased by 2.4% per person. Although the elasticities of urban form and transit supply variables introduced individually into the model were small, the elasticities of neighborhood type as endogenous variables were much more relevant.
What Happens When Government Workers Move to the Suburbs?
Authors: Burke Matthew I. , Li Terry , Dodson Jago
Published: January 2012

A resurgence of state-led decentralization activity is occurring in Australia, with governments promising to move 20% of all public servants in the city center to middle and outer suburban locations in two of the country's largest cities, Perth and Brisbane, within a decade. The effects of these policies on transport, however, have not been assessed or meaningfully considered by the government. Therefore, this study asked the following: What will be the effects on transport of government office decentralization policies in cities with strong monocentric structures? “Decentralization” may be defined as the process by which city regions increase the proportion of jobs located outside the central business district and its immediate frame. In this paper two key research activities are reported on to address this research gap. An extensive review of previous modeling and travel behavior studies on monocentric versus polycentric urban structures and workplace relocation programs is summarized. This review highlighted mixed results for the transport sector and suggested possible research paths to identify the impacts for cities where decentralization was proposed. The review led to a large modeling effort with the multimodal Brisbane Strategic Transport model to examine the likely impacts for greater Brisbane under specific decentralization scenarios. Results are provided for modal shares, vehicle kilometers traveled, travel times, levels of service on key links, and transit patronage. The type of decentralization policy selected was found to affect reverse commuting and transit use. The results suggested that only those policies directing employment to key rail and busway nodes would mitigate potentially adverse impacts.
Traffic Use of Rest Areas on Rural Highways
Authors: Al-Kaisy Ahmed , Kirkemo Zachary , Veneziano David , Dorrington Christopher
Published: January 2012

Rest areas provide the occupants of passenger vehicles and the operators of heavy vehicles an opportunity to use a restroom, walk around, stop for a meal, sleep for a while, or pause to use a cellular phone. These activities have a direct impact on several aspects of the design of rest areas, from parking to facility sizing, water needs, and wastewater generation and handling. All these components are directly influenced by one critical factor: entering traffic volumes. The study presented here used data from 44 study sites to examine the amount of traffic that used rest areas, expressed as the percentage of the main-line hourly volume that entered the rest area, as well as the effect of many underlying variables that were believed to affect the use of rest areas. The study found that the average rate of rest area use by main-line traffic for different highway categories (high- and low-volume Interstates and arterials) varied from 8.4% to 12.3%. For main-line traffic entering rest areas, the overall average rate of use was approximately 10% and the overall 85th percentile was about 15%. The study identified two peaks during the day for the percentage of main-line traffic using the rest area, but vehicular counts at rest areas showed only one peak at about midday. Given this peak demand, the midday period should be considered in the planning and design of rest area facilities. For the majority of rest areas examined, the average rate of use during the midday period varied roughly from 13% to 17% of main-line traffic.
Developing Capacity Models for Local Roundabouts
Authors: Wei Ting , Grenard Jeromy L. , Shah Hardik R.
Published: January 2012

Modern roundabouts are gaining popularity in many parts of the United States. However, because of a lack of well-established capacity models, many transportation professionals rely on international experience when analyzing the capacity of U.S. roundabouts. From a comprehensive evaluation of U.S. roundabouts, the authors of NCHRP Report 572 developed capacity models for single-lane and multilane roundabouts. NCHRP Report 572 suggests that these models can be calibrated for local conditions by adjustment of two key parameters: critical headway and follow-up headway. However, there is little direct connection between such calibrated models and the actual flow rates achieved in the field. For communities with congested roundabouts, this paper presents a streamlined process to develop capacity models. The process consists of video data collection, data processing and verification, and model development. The process was applied to a case study of three roundabouts in Carmel, Indiana. The single-lane roundabout capacity model developed in the case study is substantially different than the model in NCHRP Report 572. Overall, the streamlined process to develop capacity models for local roundabouts proved valuable, and it can be scalable according to available resources. The capacity models developed by this process are based on actual flow rates at local congested roundabouts and will provide an accurate capacity estimation for planning new roundabouts or capacity improvements. The difference between the case study's capacity model and the NCHRP Report 572's capacity model may be partially attributed to driver familiarity. The study underscores the importance of using capacity models that are applicable to local conditions.
Speed–Flow Curves for Freeways in Highway Capacity Manual 2010
Authors: Roess Roger P.
Published: January 2012

Since the 1965 edition of the Highway Capacity Manual (HCM), fundamental curves representing the relationship between speed and volume or flow rate have formed the basis of design and analysis methodologies for basic freeway segments and for uninterrupted flow segments of multilane highways. As the 2010 edition of the HCM was being developed, a new set of freeway speed–flow curves was recommended. Somewhat late in the development process, the recommended curves became controversial. This paper presents the recommended curves and the research behind them and the controversies that affected the outcome. A final set of curves for HCM 2010 was recommended on the basis of extensive comparative statistical analyses of a substantial database and on several conditions that the TRB Highway Capacity and Quality of Service Committee voted to impose on the curves characteristics. Recommendations for the future are made.
Right-Turn-on-Red Volume Estimation and Incremental Capacity Models for Shared Lanes at Signalized Intersections
Authors: Creasey F. Thomas , Stamatiadis Nikiforos , Viele Kert
Published: January 2012

The Highway Capacity Manual (HCM) is one of the most widely used transportation documents in the world. The signalized intersections methodology, one of the most frequently used portions of the manual, is used to estimate capacity and average control delay for individual lane groups and for intersections as a whole. The method does not estimate control delay for vehicles permitted to turn right on red, nor does it include these vehicles in the computation of capacity. It is recognized that vehicles making right turns on red (RTORs) increase intersection capacity. Thus, capacity, delay, and level of service may not be predicted accurately when RTORs occur. For the specific case in which a shared through and right-turn lane exists and RTORs are permitted, models were developed to estimate the number of RTORs that can be expected and the additional capacity that is realized. The models are deterministic and are consistent with the HCM methodology, are easily understood by analysts, produce reasonable results, and account for the probabilistic nature of RTORs occurring from shared lane approaches. The capacity model also demonstrates that, where RTORs are permitted and do occur, the HCM method results in an underestimation of capacity and an overestimation of delay for approaches containing shared lanes.
Decision Tree–Based Model for Estimation of Work Zone Capacity
Authors: Weng Jinxian , Meng Qiang
Published: January 2012

The ability to estimate work zone capacity accurately is imperative because accurate estimates are a key input to estimates of queue length and traffic delay in work zones. This paper aims to develop a decision tree–based model that considers 16 influencing factors to estimate freeway work zone capacity accurately. The F-test splitting criterion and the postpruning approach are employed to grow and prune the decision tree. Freeway work zone capacity data collected from 14 states and cities are used to train, check, and evaluate the decision tree–based capacity estimation model. Statistical comparison results demonstrate that the decision tree–based model outperforms existing short-term and long-term freeway work zone capacity estimation models, especially when the input values of influencing factors are only partially available for the existing models. A comparison with the Highway Capacity Manual (HCM) also indicates that the decision tree–based model can provide a more accurate estimate of freeway work zone capacity. From the decision tree–based model, traffic engineers can easily estimate work zone capacity for a given freeway work zone by tracing a path down the tree to a terminal node. Because of its accuracy and ease of use, the proposed decision tree–based capacity model is a good alternative for traffic engineers to use in estimating freeway work zone capacity. It is expected that the decision tree–based capacity model could be applied to the HCM chapter on freeway facilities.
Cycle-by-Cycle Queue Length Estimation for Signalized Intersections Using Sampled Trajectory Data
Authors: Cheng Yang , Qin Xiao , Jin Jing , Ran Bin , Anderson Jason
Published: January 2012

Queue length estimation is an important component of intersection performance measurement. Different approaches based on different data sources have been presented. With the latest developments in vehicle detection technologies, especially probe vehicle technologies, use of vehicle trajectory data has become possible. In this paper, an improved method for queue length estimation for signalized intersections is proposed. This method is able to provide cycle-by-cycle queue length estimation for signalized intersections with sampled vehicle trajectories as the only input. The keystone of the entire approach is the concept of the critical point (CP), which represents the changing vehicle dynamics. A CP extraction algorithm is introduced to identify CPs from raw trajectories. Using the CPs related to queue formation and dissipation, the authors propose an improved queue length estimation method based on shock waves. The performance of this approach is evaluated with several data sets under different flow and signal timing scenarios, including a recently collected data set from a Global Positioning System logger. The results indicate that this trajectory-based approach is promising.
Development of Managed-Lane Access Guidelines Based on Gap Acceptance Theory
Authors: Yang Chulsu , Mattingly Stephen P. , Williams James C. , Kim Hyunwoong
Published: January 2012

One strategy for improving freeway performance is implementation of managed lanes (MLs). Vehicles access an ML located in the freeway median by weaving across the general purpose lanes (GPLs) and entering the ML from the leftmost lane of the GPLs. Such intense lane-changing maneuvers cause traffic turbulence, which induces special operational problems with capacity, level of service, and safety. The principal objective of this research is to develop design guidelines for the ML access (or exit) spacing between the entrance (or exit) ramp and the ML access opening and for the ML access opening length. This research develops analytical weaving models based on gap acceptance theory; the models estimate the probability of successful weaves in these weaving distances. The research also develops design guidelines for these distances on the basis of the analytical weaving models.
Capacity of Multilane All-Way Stop-Controlled Intersections Based on the Conflict Technique
Authors: Li Haiyuan , Tian Zong , Deng Wei
Published: January 2012

This paper presents an improved model for assessing the capacities of vehicular movements at all-way stop-controlled (AWSC) intersections with multilane approaches. In contrast to the current approach-based model incorporated in the 2000 edition of the Highway Capacity Manual (HCM), the proposed model simplifies the process of estimating the capacities of AWSC intersections and could be applied at any multilane AWSC intersections. On the basis of the conflict technique, a model was developed for estimating the capacities of vehicular movements at multilane AWSC intersections under three traffic demand levels: under-saturated, partially saturated, and fully saturated. Model parameters were calibrated by field data collected from 41 AWSC intersections with various lane configurations throughout the United States. The effectiveness and reliability of the proposed model were verified in comparison with the methodology of HCM 2000 with various lane configurations and traffic demands. The proposed model addresses the major limitations of the current HCM 2000 methodology, which deals only with the conditions of two lanes on each approach at AWSC intersections.
Traffic Flow Forecasting and Spatial Data Aggregation
Authors: Kuhn Kenneth , Nicholson Alan
Published: January 2012

Research investigated ways to forecast traffic flow over an area covering multiple links of a roadway network. The question arose of whether to construct one large-scale model or to combine results from separate smaller-scale models. Intuition favors link-specific analyses, but econometric results show how using aggregate models can increase accuracy. It is shown how theory holds that correlations between traffic conditions on different roadway links and errors in link-specific observations of traffic conditions increase the relative accuracy of larger-scale models, whereas site-specific sensitivities suggest smaller-scale data. Empirical evidence is presented regarding the relative accuracy of various models of traffic flow rate. One form of a seasonal autoregressive integrated moving average time series model for general flow forecasting is chosen, along with methodologies for automatically selecting models based on input data. Studies based on data from the Tokyo Metropolitan Expressway show that increasing data aggregation consistently increases model accuracy. Sums of forecasts of link flows yield predictions of areawide flow roughly as accurate as predictions based on univariate analysis of areawide data. Areawide flows are easier to predict accurately than link flows. Modeling large-area traffic flow with a univariate model is considerably simpler but produces less subsequently useful results than use of separate, link-specific models.
Real-Time Solution of Velocity-Based First-Order Continuum Traffic Model with Finite Element Method
Authors: Sadabadi Kaveh F. , Haghani Ali
Published: January 2012

Two approximate solution methods are investigated for the velocity-based version of a first-order continuum traffic flow model commonly known as the Lighthill–Whitham–Richards model. The finite difference and finite element methods are commonly used to numerically solve partial differential equations. The finite difference method adopted uses a standard Godunov scheme to solve the continuum model. The finite element method uses one-dimensional simplex elements with first-order interpolation function along with a Galerkin scheme to derive the element characteristic matrices and vectors. A high-resolution, real-world data set from the Next Generation Simulation program is used to evaluate the two solution methods. Results show that both methods provide accurate approximations to the observed speeds. The accuracy and quality of solutions and future directions of work in this area are discussed.
Multiregime Sequential Risk-Taking Model of Car-Following Behavior
Authors: Talebpour Alireza , Mahmassani Hani S. , Hamdar Samer H.
Published: January 2012

Car-following models constitute the main component of operational microscopic simulation models and are intended to capture intervehicle interactions on highway sections. Most existing car-following models are deterministic and do not capture the effects of surrounding traffic conditions on the decision-making process of the driver. An extension to a previously introduced sequential risk-taking model is offered to capture the effects of surrounding conditions on driving behavior. The model extension recognizes two behavioral regimes that depend on the complexity of the decision situation associated with the prevailing congestion. With each regime is associated a value function capturing driver preferences for gains associated with a particular acceleration. A probabilistic regime selection mechanism relates the driver's choices to prevailing traffic conditions. The model is calibrated against actual trajectory data. Initial results show that the model provides realistic behavioral patterns previously identified in the literature.
Use of Skew-Normal and Skew-t Distributions for Mixture Modeling of Freeway Speed Data
Authors: Zou Yajie , Zhang Yunlong
Published: January 2012

Normal, lognormal, and other forms of distribution have been used to characterize speed data. Recently, several researchers have used the normal mixture model to fit the distribution of speed. To investigate the applicability of mixture models with other types of component density, a study was done that fits 24-h speed data collected on I-35 in Texas by using skew-normal and skew-t mixture models with an algorithm of expectation maximization type. The results show that a finite mixture of skew distributions can significantly improve the goodness of fit of speed data. Compared with normal distribution, skew-normal and skew-t distributions can accommodate skewness and excess kurtosis themselves; thus the skew mixture models require fewer components than normal mixture models to capture the asymmetry and bimodality present in speed data. The results of the study indicate that a two-component skew-t mixture model is the optimal model, and this model can better account for heterogeneity in the data. The study verifies that traffic flow condition is the main cause for heterogeneity in the 24-h speed data. The research methodology can be used to analyze freeway speed data characteristics. The findings can also be used in development and validation of microscopic simulation of freeway traffic.
Alternative Definitions of Passing Critical Gaps
Authors: Toledo Tomer , Farah Haneen
Published: January 2012

A substantial proportion of the road network in most countries consists of two-lane highways. Available gaps for passing are a fundamental element in the operation of such highways. Providing passing opportunities is important for reducing the formation of vehicle platoons in the traffic flow, increasing the level of service, and improving safety. Passing opportunities also affect fuel consumption and emissions. Despite the importance of passing on two-lane highways, few studies have focused on exploring passing gap definitions when modeling passing behavior. Research was done to investigate various definitions of passing gaps, and these definitions were used to develop passing gap acceptance models. Data on passing maneuvers collected with a driving simulator were used to develop and calibrate three models. The generic structure of these models was composed of the drivers’ desire to pass and their gap acceptance decisions. The impact of traffic characteristics, road geometry, and driver characteristics was included in these models. The results show that the passing gap definition has a significant impact on the models’ ability to explain passing behavior. Moreover, the estimation results show that modeling a driver's desire to pass the vehicle ahead has a statistically significant contribution in explaining passing behavior. Variables that capture the impact of the traffic conditions, geometric characteristics of the road section, driver characteristics, and the unobserved heterogeneity in the driver population were found to have a significant impact on drivers’ desire to pass and their gap acceptance decisions.
Variations in Parameters of Time Headway Models According to Macroscopic Variables, Fundamental Diagram, and Exogenous Effects
Authors: Ha Duy-Hung , Aron Maurice , Cohen Simon
Published: January 2012

Relationships between macroscopic traffic level and time headway distribution are discussed. Several authors have studied time headway distribution as a function of aggregate traffic volume and have used various probabilistic models. The gamma-generalized queuing model (gamma-GQM) has been shown to have very high performance and effectiveness in modeling real-life time headway data in most cases. Consequently, the parameters of the gamma-GQM are studied to investigate the links between macroscopic information and time headway variable. The systematic data collected in 2005 from the RN 118 national roadway in France allowed study of the effects not only of traffic volume but also of traffic occupancy and space mean speed on time headway distribution. These macroscopic variables were obtained on the basis of the calculation aggregated over 6 min of data. A study of time headway distribution following the empirical fundamental diagram was also implemented. Exogenous conditions such as weather and lane type were taken into account. As a result, the variations of the gamma-GQM parameters were established and interpreted according to the various contexts. Two exogenous factor types influencing time headway distribution in the standard condition are proposed: impeding and propulsive factors. These two factors are differentiated by the tendencies of the scale parameters of the gamma-GQM compared with the corresponding values in the standard condition.
Estimating Acceleration, Fuel Consumption, and Emissions from Macroscopic Traffic Flow Data
Authors: Wang Meng , Daamen Winnie , Hoogendoorn Serge , van Arem Bart
Published: January 2012

With increasing public concern about the environment, livability and sustainability have become important issues in dynamic traffic management (DTM). Microscopic fuel consumption and emission models use vehicle speed and acceleration as inputs and are suitable for investigating the environmental effects of DTM measures at the link level. However, the lack of microscopic traffic data limits the application of these models. A method is provided for acquiring microscopic information from macroscopic traffic data. The main approach is to reconstruct the traffic state and vehicle group trajectories with an adaptive smoothing method, derive acceleration from the reconstructed vehicle trajectories, and calculate fuel consumption and emissions with filtered speed and estimated acceleration as inputs. The derived acceleration is compared with vehicle trajectories from simulation. Validation of the method shows that the estimated acceleration reflects the congestion characteristics. A case study investigating the environmental benefits of a freeway control algorithm on a Dutch freeway was conducted to illustrate the application potential of the method.
Wiedemann Revisited
Authors: Hoogendoorn Serge , Hoogendoorn Raymond G. , Daamen Winnie
Published: January 2012

A new data-driven stochastic car-following model based on the principles of psychospacing or action-point modeling is presented. It uses empirical or experimental trajectory data and mimics the main microscopic behavioral characteristics present in the data. In the action-point model, regions are defined in the relative speed–distance headway plane, in which the follower is likely to perform an action (increase or decrease acceleration) or not. These regions can be established empirically from vehicle trajectory data and thereby yield a joint cumulative probability distribution function of the action points. Furthermore, the conditional distribution of the actions (the size of the acceleration or deceleration given the current distance headway and relative speed or given the acceleration before the action) can be determined from these data as well. To assess the data correctly, a new filtering technique is proposed. The main hypothesis behind this idea is that the speed profile is a continuous piecewise linear function: accelerations are piecewise constant changing values at nonequidistant discrete time instants. The durations of these constant acceleration periods are not fixed but depend on the state of the follower in relation to its leader. The data analysis illustrates that driving behavior shows nonequidistant constant acceleration periods. The distributions of the action points and the conditional accelerations form the core of the presented data-driven stochastic model. The mathematical formalization that describes how these distributions can be used to simulate car-following behavior is presented. Empirical data collected on a Dutch motorway are used to illustrate the workings of the approach and the simulation results.
Livestock Inheritance and Education: Attitudes and Decision Making among Samburu Pastoralists
Authors: Lesorogol Carolyn , Chowa Gina , Ansong David
Published: January 2012

This study investigates current practices and attitudes regarding livestock inheritance and education. There is evidence that investments in education may in some cases replace traditional forms of livestock inheritance, reflecting current perceptions of the relative values of pastoralism and forms of employment for which formal education is required. This trend suggests that a long-standing and critical mechanism for intergenerational transmission of wealth is changing.
RETRACTED: Steady State Analytical Equation of Motion of Linear Shaped Charges Jet Based on the Modification of Birkhoff Theory
Authors: Lim Seokbin
Published: January 2012

Birkhoff theory exhibits an analytical steady state liner collapse model of shaped charges followed by jetting process. It also provides the fundamental idea in study of shaped charges and has widened its application in many areas, including a configuration where the detonation front strikes the entire liner surface at the same time providing the α = β (liner apex angle α, and the liner collapse point angle β) condition in the literature. Upon consideration of the detonation front propagation along the lateral length of the core charge in LSCs (linear shaped charges), a further modification of the Birkhoff theory motivated by the unique geometrical condition of LSCs and the α = β condition is necessary to correctly describe the jetting behavior of LSCs which is different than that of CSCs (conical shaped charges). Based on such unique geometrical properties of LSCs, the original Birkhoff theory was modified and an analytical steady state LSCs model was built. The analytical model was then compared to the numerical simulation results created from Autodyn™ in terms of M/C ratio and apex angles in three different sized LSCs, and it exhibits favorable results in a limited range.
Elevated Peripheral Blood Plasma Concentrations of Tie-2 and Angiopoietin 2 in Patients with Neuroendocrine Tumors
Authors: Melen-Mucha Gabriela , Niedziela Agata , Mucha Slawomir , Motylewska Ewelina , Lawnicka Hanna , Komorowski Jan , Stepien Henryk
Published: January 2012

Background: Gastro-entero-pancreatic/neuroendocrine (NET) tumors are highly vascularized neoplasms. However, our knowledge concerning circulating levels of the angiogenic factors in NET patients still remains insufficient. Methods: The aim of this study was to measure plasma concentrations of VEGF, angiopoietin 1 (Ang-1), angiopoietin 2 (Ang-2), soluble Tie-2, endostatin, osteopontin (OPN) and chromogranin A (CgA) in 36 NET patients and 16 controls. Results: Only the plasma concentrations of Tie-2 and CgA were higher in NET patients as compared to controls. These levels were within the reference range in controls; however one control demonstrated slightly elevated Tie-2 and 4 elevated CgA. Similarly, in the subgroup of patients with carcinoid syndrome, only Tie-2 and CgA concentrations were higher than those in patients with non-functioning NETs. In turn, in the subgroup of metastatic patients, only Ang-2 levels were higher than in those with localized disease. A positive correlation was found between Ang-2 and Tie-2 levels in metastatic patients and between Ang-1 and Tie-2 in localized NETs. Conclusions: The plasma concentration of Tie-2 is proposed as an additional marker for NET patients and seems to be similarly effective as the currently used CgA level. Moreover, higher plasma levels of Ang-2 together with the positive correlation between Ang-2 and Tie-2 levels in metastatic subjects, implies that cases with a Tie-2 level above the upper limits, together with higher level of Ang-2 seem to be highly predictive of metastases.
Polydnaviruses of Parasitic Wasps: Domestication of Viruses To Act as Gene Delivery Vectors
Authors: Burke Gaelen R. , Strand Michael R.
Published: January 2012

Symbiosis is a common phenomenon in which associated organisms can cooperate in ways that increase their ability to survive, reproduce, or utilize hostile environments. Here, we discuss polydnavirus symbionts of parasitic wasps. These viruses are novel in two ways: (1) they have become non-autonomous domesticated entities that cannot replicate outside of wasps; and (2) they function as a delivery vector of genes that ensure successful parasitism of host insects that wasps parasitize. In this review we discuss how these novelties may have arisen, which genes are potentially involved, and what the consequences have been for genome evolution.
Chiroptical Switches: Applications in Sensing and Catalysis
Authors: Dai Zhaohua , Lee Jennifer , Zhang Wenyao
Published: January 2012

Chiroptical switches have found application in the detection of a multitude of different analytes with a high level of sensitivity and in asymmetric catalysis to offer switchable stereoselectivity. A wide range of scaffolds have been employed that respond to metals, small molecules, anions and other analytes. Not only have chiroptical systems been used to detect the presence of analytes, but also other properties such as oxidation state and other physical phenomena that influence helicity and conformation of molecules and materials. Moreover, the tunable responses of many such chiroptical switches enable them to be used in the controlled production of either enantiomer or diastereomer at will in many important organic reactions from a single chiral catalyst through selective use of a low-cost inducer: Co-catalysts (guests), metal ions, counter ions or anions, redox agents or electrochemical potential, solvents, mechanical forces, temperature or electromagnetic radiation.
Enhanced Responsivity of Photodetectors Realized via Impact Ionization
Authors: Yu Ji , Shan Chong-Xin , Qiao Qian , Xie Xiu-Hua , Wang Shuang-Peng , Zhang Zhen-Zhong , Shen De-Zhen
Published: January 2012

To increase the responsivity is one of the vital issues for a photodetector. By employing ZnO as a representative material of ultraviolet photodetectors and Si as a representative material of visible photodetectors, an impact ionization process, in which additional carriers can be generated in an insulating layer at a relatively large electric field, has been employed to increase the responsivity of a semiconductor photodetector. It is found that the responsivity of the photodetectors can be enhanced by tens of times via this impact ionization process. The results reported in this paper provide a general route to enhance the responsivity of a photodetector, thus may represent a step towards high-performance photodetectors.
Carbamate derivatives and sesquiterpenoids from the South China Sea gorgonian Melitodes squamata
Authors: Huang Li-Si , He Fei , Huang Hui , Zhang Xiao-Yong , Qi Shu-Hua
Published: January 2012

Five carbamate derivatives, obtucarbamates C and D (1, 2), dimethyl ((carbonylbis(azanediyl))bis(2-methyl-5,1-phenylene))dicarbamate (3), obtucarbamates A and B (4, 5), and four aromadendrane-type sesquiterpenoids, (+)-4β-N-methenetauryl-10β-methoxy-1β,5α,6β,7β-aromadendrane (6), (−)-4β-N-methenetauryl-10β-methoxy-1β,5β,6α,7α-aromadendrane (7), (−)-4α,10β-aromadendranediol (8), (+)-4β,10β-aromadendranediol (9) were obtained from the South China Sea gorgonian coral Melitodes squamata Nutting. Compounds 1, 2, 6, and 7 were new, and their structures were established by spectroscopic analyses. Compounds 6 and 7 contained a taurine group that was rarely found in marine natural compounds, and 7 showed moderate antibacterial activity. The possible biosynthesis routes of 1–5 were conjectured.
Atresia and Sudden Sensorineural Hearing Loss
Authors: Smith Steven P. , Milov Simon , Goebel Joel A.
Published: January 2012

This case study summarizes findings in an adult male, aged 57, who presented to the Adult Audiology Clinic with aural atresia in the right ear resulting in a conductive hearing loss and a sudden sensorineural hearing loss in the left ear. Treatment options included reconstruction surgery
in the right ear, bone anchored hearing aid in the right ear to overcome the conductive hearing loss, bone anchored hearing aid in the left ear for single sided deafness, and intratympanic steroid injections in the left ear to salvage hearing.This case study highlights that when a patient
is educated on all available options the patient is then able to make a decision comfortable to him and to help improve his hearing.
Auditory Brainstem Response Testing in Neurodiagnosis: Structure versus Function
Authors: Peterein Judy L. , Neely J. Gail
Published: January 2012

This case report describes a 44-yr-old female referred by an outside facility who presented with progressive hearing loss in her left ear. Magnetic resonance imaging (MRI) results were normal, but a battery of audiological tests suggested neural hearing loss in the left ear. Following
diagnosis of left neural hearing loss, the patient was successfully fit with a hearing aid on the left ear.This case report underlines the importance of using a battery of medical, radiologic, and audiological tests in the accurate determination of hearing loss site of lesion. Obvious retrocochlear
dysfunction was revealed via auditory brainstem response (ABR) testing. MRI did not reveal underlying structural abnormality. Without the addition of the ABR to the diagnostic test battery, a cochlear hearing loss site of lesion would most likely have been diagnosed. Accurate diagnosis of
hearing loss site of lesion is critical for patient counseling and treatment as well as for patient follow-up and monitoring.