Driving safety has been an issue of great concern in the United States throughout the years. According to the National Center for Statistics and Analysis (NCSA), in 2003 alone, there were 6,267,000 crashes in the U.S. from which 1,915,000 were injury crashes, including 38,764 fatal crashes and 43,220 human casualties. The U.S. Department of Transportation spends millions of dollars every year on research that aims to improve roadway safety and decrease the number of traffic collisions. In spring 2002, the Center for Advanced Traffic System Simulation (CATSS), at the University of Central Florida, acquired a sophisticated reconfigurable driving simulator. This simulator, which consists of a late model truck cab, or passenger vehicle cab, mounted on a motion base capable of operation with six degrees of freedom, is a great tool for traffic studies. Two applications of the simulator are to study the contribution of Light Truck Vehicles (LTVs) to potential rear-end collisions, the most common type of crashes, which account for about a third of the U.S. traffic crashes, and the involvement of Larger Size Vehicles (LSVs) in red light running. LTVs can obstruct horizontal visibility for the following car driver and has been a major issue, especially at unsignalized intersections. The sudden stop of an LTV, in the shadow of the blindness of the succeeding car driver, may deprive the following vehicle of a sufficient response time, leading to high probability of a rear-end collision. As for LSVs, they can obstruct the vertical visibility of the traffic light for the succeeding car driver on signalized intersection producing a potential red light running for the latter. Two sub-scenarios were developed in the UCF driving simulator for each the vertical and horizontal visibility blockage scenarios. The first sub-scenario is the base sub-scenario for both scenarios, where the simulator car follows a passenger car, and the second sub-scenario is the test sub-scenario, where the simulator car follows an LTV for the horizontal visibility blockage scenario and an LSV for the vertical visibility blockage scenario. A suggested solution for the vertical visibility blockage of the traffic light problem that consisted of adding a traffic signal pole on the right side of the road was also designed in the driving simulator. The results showed that LTVs produce more rear-end collisions at unsignalized intersections due to the horizontal visibility blockage and following car drivers' behavior. The results also showed that LSVs contribute significantly to red light running on signalized intersections and that the addition of a traffic signal pole on the right side of the road reduces the red light running probability.

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Every year, approximately 34,000 individuals are fatally injured in crashes on US roads [1]. These fatalities occur across many types of crash scenarios, each with its own causation factors. One way to prioritize research on a preventive technology is to compare the number of occupant fatalities relative to the total number of occupants involved in a crash scenario. Four crash modes are overrepresented among fatalities: single vehicle road departure crashes, control loss crashes, cross-centerline head-on crashes, and pedestrian/cyclist crashes [2]. Interestingly, three of these crash scenarios require the subject vehicle to depart from the initial lane of travel. Lane departure warning (LDW) systems track the vehicle lane position and can alert the driver through audible and haptic feedback before the vehicle crosses the lane line. Lane departure prevention (LDP) systems can perform an automatic steering maneuver to prevent the departure. Another method of prioritizing research is to determine factors common among the fatal crashes. In 2017, 30.4% of passenger vehicle crash fatalities involved a vehicle rollover [1]. Half of all fatal single vehicle road departure crashes resulted in a rollover yet only 12% of fatal multi-vehicle crashes involved a rollover [1]. These often occur after the driver has lost control of the vehicle and departed the road. Electronic stability control (ESC) can provide different braking to each wheel and allow the vehicle to maintain heading. While ESC is a promising technology, some rollover crashes still occur. Passive safety systems such as seat belts, side curtain airbags, and stronger roofs work to protect occupants during rollover crashes. Seat belts prevent occupants from moving inside the occupant compartment during the rollover and both seat belts and side curtain airbags can prevent occupants from being ejected from the vehicle. Stronger roofs ensure that the roof is not displaced during the rollover and the integrity of the occupant compartment is maintained to prevent occupant ejection. The focus of this dissertation is to evaluate the effectiveness of vehicle-based countermeasures, such as lane departure warning and electronic stability control, for preventing or mitigating single vehicle road departure crashes, cross-centerline head-on crashes, and single vehicle rollover crashes. This was accomplished by understanding how drivers respond to both road departure and cross-centerline events in real-world crashes. These driver models were used to simulate real crash scenarios with LDW/LDP systems to quantify their potential crash reduction. The residual crashes, which are not avoided with LDW/LDP systems or ESC, were analyzed to estimate the occupant injury outcome. For rollover crashes, a novel injury model was constructed that includes modern passive safety countermeasures such as seat belts, side curtain airbags, and stronger roofs. The results for road departure, head-on, and control loss rollover crashes were used to predict the number of crashes and injured occupants in the future. This work is important for identifying the residual crashes that require further research to reduce the number of injured crash occupants. / Doctor of Philosophy / Every year in the US, approximately 34,000 individuals are fatally injured in many different types of crashes. However, some crash types are more dangerous than other crash types. Drift-out-of-lane (DrOOL) road departure crashes, control loss road departure crashes, head-on crashes, and pedestrian crashes are more likely to result in an occupant fatality than other crash modes. In three of these more dangerous crash types, the vehicle departs from the lane before the crash occurs. Lane departure warning (LDW) systems can detect when the vehicle is about to cross the lane line and notify the driver with beeping or vibrating the steering wheel. A different system, called lane departure prevention (LDP), can provide automatic steering to prevent the vehicle from leaving the lane or return lane. In control loss crashes, the vehicle's motion is in a different direction than the vehicle's heading. During control loss, it is easier for the vehicle to roll over which is very dangerous. Electronic stability control (ESC) can prevent control loss by applying selective braking to each tire to keep the vehicle's motion in the same direction as the vehicle's heading. If a rollover still occurs, vehicles are equipped with passive safety systems and designs such as seat belts, side curtain airbags, and stronger roofs to protect the people inside. Seat belts can prevent occupants from striking the vehicle interior during the rollover and both seat belts and side curtain airbags can prevent occupants from being ejected from the vehicle. Stronger roofs ensure that the roof is not displaced during the rollover to prevent occupants from being ejected from the vehicle. The focus of this dissertation is to estimate how many crashes LDW, LDP, and ESC systems could prevent. This was accomplished by understanding how drivers respond after leaving their lane in real crashes. Then, these real crash scenarios were simulated with an LDW or LDP system to estimate how many crashes were prevented. The occupants of residual crashes, which were not prevented by the simulated systems, were analyzed to estimate the number of occupants with at least one moderate injury. Understanding which crashes and injuries that were not prevented with this technology can be used to decide where future research should occur to prevent more fatalities in road departure, head-on and control loss crashes.

The utilisation of navigation systems in cars has given rise to road safety concerns, and the design and functionality of such systems must therefore be adjusted to the users’ needs, since they have to divide their attention between driving and the operation of the navigation system. The study was aimed at finding the optimum system response time (SRT) which would enable a driver to focus as much as possible on the road while attaining an efficient task completion time using an electronic navigational system. The research project consists of two separate experiments and was completed by 10 subjects. Experiment 1 included a temporal reproduction task and a secondary memory task. The subjects had to memorise two symbols and then reproduce six time spans ranging from 1 to 30 s to provide a baseline measurement of their time estimation abilities. Experiment 2 consisted of a simulated automobile driving task. While driving in the simulator the subjects completed a memorising task displayed on a touch screen. The task was presented with seven different system response times (SRTs) ranging from 0 to 30 s. The effects of different SRTs on the eye movement from road to monitor, regarding the duration of fixation and the frequency of change were evaluated. The distribution of gazes to the secondary task was analysed to provide information about the time estimation performance in the driving simulator. Other dependent variables tested were the accuracy of selected items, memory game performance, drive performance and the subjective state of the test person. The results of this study can be employed to find the optimum duration of inter-task delays for in-vehicle technical devices. / Psychology / M.A. (Psychology)

De nombreux chercheurs et cliniciens sont sceptiques quant à la validité des questionnaires autoadministrés, lorsqu’utilisés auprès d’une population carcérale (Gendreau, Irvine et Knight, 1973), surtout si celle-ci est composée de délinquants sexuels (Marshall et Hall, 1995). La sensibilité des sujets investigués jumelés à la transparence des questions expose l’évaluateur à la possibilité que le participant dissimule et modifie ses réponses (Tierney et McCabe, 2001). L’objectif de ce projet est de comprendre les processus impliqués dans la performance des participants à une évaluation autoadministrée. Les données de 282 délinquants sexuels ayant complétés le Multidimensional Inventory of Development, Sex, and Agression (MIDSA) ont été analysées afin de mieux comprendre l’interaction entre les échelles de désirabilité sociale, les temps de latence et les coefficients d’ajustement du modèle de Rasch. La convergence des analyses de temps de latence et des échelles de désirabilité sociale semble indiquer que certains participants dissimuleraient consciemment leurs réponses. Notamment, les participants détectés par les échelles de désirabilité sociales sembleraient répondre de manière de plus lente aux échelles d’évaluations, et certains d’entre eux offriraient des patrons de réponses incohérents à la prescription du modèle de Rasch. Les hypothèses permettant d’expliquer les potentiels mécanismes liés à la dissimulation seront discutées. / Many researchers and clinicians are skeptical towards the validity of self-reported assessment used within a forensic population (Gendreau, Irvine, & Knight, 1973), especially when used within a sexual offender population (Marshall & Hall, 1995). The sensitivity of the topics addressed as well as the transparency of the questions expose the evaluator to possible dissimulations or distortions in the subject responses (Tierney & McCabe, 2001). Responses of 282 sexual offenders who completed the Multidimensional Inventory of Development, Sex, and Aggression (MIDSA) were analyzed in order to understand the interaction between response time, social desirability scales and Rasch person-fit scores in order to account for response distortion. The convergence of latency times and social desirability scales seems to indicate that certain participants consciously manipulate their responses. Notably, participants detected by social desirability scales seem to respond more slowly to particular items. Other participants may answer in ways that are incoherent with the predicted responses according to the Rasch model. Hypotheses as to potential mechanisms underlying this process will be discussed.

Les temps de réponse dans une tache de reconnaissance d’objets visuels diminuent de façon significative lorsque les cibles peuvent être distinguées à partir de deux attributs redondants. Le gain de redondance pour deux attributs est un résultat commun dans la littérature, mais un gain causé par trois attributs redondants n’a été observé que lorsque ces trois attributs venaient de trois modalités différentes (tactile, auditive et visuelle). La présente étude démontre que le gain de redondance pour trois attributs de la même modalité est effectivement possible. Elle inclut aussi une investigation plus détaillée des caractéristiques du gain de redondance. Celles-ci incluent, outre la diminution des temps de réponse, une diminution des temps de réponses minimaux particulièrement et une augmentation de la symétrie de la distribution des temps de réponse. Cette étude présente des indices que ni les modèles de course, ni les modèles de coactivation ne sont en mesure d’expliquer l’ensemble des caractéristiques du gain de redondance. Dans ce contexte, nous introduisons une nouvelle méthode pour évaluer le triple gain de redondance basée sur la performance des cibles doublement redondantes. Le modèle de cascade est présenté afin d’expliquer les résultats de cette étude. Ce modèle comporte plusieurs voies de traitement qui sont déclenchées par une cascade d’activations avant de satisfaire un seul critère de décision. Il offre une approche homogène aux recherches antérieures sur le gain de redondance. L’analyse des caractéristiques des distributions de temps de réponse, soit leur moyenne, leur symétrie, leur décalage ou leur étendue, est un outil essentiel pour cette étude. Il était important de trouver un test statistique capable de refléter les différences au niveau de toutes ces caractéristiques. Nous abordons la problématique d’analyser les temps de réponse sans perte d’information, ainsi que l’insuffisance des méthodes d’analyse communes dans ce contexte, comme grouper les temps de réponses de plusieurs participants (e. g. Vincentizing). Les tests de distributions, le plus connu étant le test de Kolmogorov- Smirnoff, constituent une meilleure alternative pour comparer des distributions, celles des temps de réponse en particulier. Un test encore inconnu en psychologie est introduit : le test d’Anderson-Darling à deux échantillons. Les deux tests sont comparés, et puis nous présentons des indices concluants démontrant la puissance du test d’Anderson-Darling : en comparant des distributions qui varient seulement au niveau de (1) leur décalage, (2) leur étendue, (3) leur symétrie, ou (4) leurs extrémités, nous pouvons affirmer que le test d’Anderson-Darling reconnait mieux les différences. De plus, le test d’Anderson-Darling a un taux d’erreur de type I qui correspond exactement à l’alpha tandis que le test de Kolmogorov-Smirnoff est trop conservateur. En conséquence, le test d’Anderson-Darling nécessite moins de données pour atteindre une puissance statistique suffisante. / Response times in a visual object recognition task decrease significantly if targets can be distinguished by two redundant attributes. Redundancy gain for two attributes is a common finding, but redundancy gain from three attributes has been found only for stimuli from three different modalities (tactile, auditory, and visual). This study extends those results by showing that redundancy gain from three attributes within the visual modality is possible. It also provides a more detailed investigation of the characteristics of redundancy gain. Apart from a decrease in response times for redundant targets, these include a decrease in minimal response times and an increase in symmetry of the response time distribution. This study further presents evidence that neither race models nor coactivation models can account for all characteristics of redundancy gain. In this context, we discuss the problem of calculating an upper limit for the performance of race models for triple redundant targets, and introduce a new method of evaluating triple redundancy gain based on performance for double redundant targets. In order to explain the results from this study, the cascade race model is introduced. The cascade race model consists of several input channels, which are triggered by a cascade of activations before satisfying a single decision criterion, and is able to provide a unifying approach to previous research on the causes of redundancy gain. The analysis of the characteristics of response time distributions, including their mean, symmetry, onset, and scale, is an essential tool in this study. It was therefore important to find an adequate statistical test capable of reflecting differences in all these characteristics. We discuss the problem and importance of analysing response times without data loss, as well as the inadequacy of common methods of analysis such as the pooling of response times across participants (e.g. Vincentizing) in the present context. We present tests of distributions as an alternative method for comparing distributions, response time distributions in particular, the most common of these being the Kolmogorov-Smirnoff test. We also introduce a test yet unknown in psychology: the two-sample Anderson-Darling test of goodness of fit. We compare both tests, presenting conclusive evidence that the Anderson-Darling test is more accurate and powerful: when comparing two distributions that vary (1) in onset only, (2) in scale only, (3) in symmetry only, or (4) that have the same mean and standard deviation but differ on the tail ends only, the Anderson-Darling test proves to detect differences better than the Kolmogorov-Smirnoff test. Finally, the Anderson-Darling test has a type I error rate corresponding to alpha whereas the Kolmogorov-Smirnoff test is overly conservative. Consequently, the Anderson- Darling test requires less data than the Kolmogorov-Smirnoff test to reach sufficient statistical power.

Este trabalho apresenta um estudo sobre sistemas operacionais de tempo real (RTOS) utilizados na implementação da infraestrutura de controle digital para sistemas mecatrônicos, mas serve também como referência para outros sistemas que possuam restrições de tempo. Além de ter um caráter experimental, onde foram medidos e analisados dados como o pior tempo de resposta dos sistemas e a latência para tratamento de interrupções, este trabalho de pesquisa ainda contempla a implementação e uso de RTOS em situações práticas, bem como contempla a construção de uma plataforma geral de pesquisa que servirá de base para futuros trabalhos no laboratório de mecatrônica. Os sistemas analisados neste trabalho foram o VxWorks, QNX, Linux, RTAI, Windows XP, Windows CE e \'mü\'C/OS-II. Outro produto gerado durante este trabalho foi um Live CD para auxiliar na implementação e ensino de conceitos e sistemas de tempo real. / This work presents a study about real time operating systems (RTOS) that are utilized as infrastructure to create digital control systems for mechatronics systems, and also for systems that have critical time constraints. Parameters like worst case response time and interrupt latency were measured for each operating system. This research project also covers the implementation and use of RTOS in practical situations. A general research platform for robotics and real time research was also developed and will be used for future works in the Mechatronics Laboratory. The tested systems were VxWorks, QNX, Linux, RTAI, Windows XP, Windows CE and \'mü\'C/OS-II. Another product released during this work was a Live CD to aid the implementation and teaching of real time systems and concepts.

The growing interest towards wireless communication services over the recent years has increased the demand for radio spectrum. Inefficient spectrum management together with the scarcity of the radio spectrum is a limiting factor for the development of modern wireless networks. As a solution, the idea of cognitive radio networks (CRNs) is introduced to use licensed spectrum for the benefit of the unlicensed secondary users. However, the preemptive priority of the licensed users results in random resource availabilities at the secondary networks, which makes the quality-of-service (QoS) support challenging. With the increasing demand for elastic/interactive data services (internet based services) and wireless multimedia services, QoS support becomes essential for CRNs. This research investigates the voice and elastic/interactive data service support over CRNs, in terms of their delay requirements. The packet level requirements of the voice service and session level delay requirements of the elastic/interactive data services are studied. In particular, constant-rate and on-off voice traffic capacities are analyzed over CRNs with centralized and distributed network coordination. Some generic channel access schemes are considered as the coordination mechanism, and call admission control algorithms are developed for non-fully-connected CRNs. Advantage of supporting voice traffic flows with different delay requirements in the same network is also discussed. The mean response time of the elastic data traffic over a centralized CRN is studied, considering the shortest processor time with and without preemption and shortest remaining processor time service disciplines, in comparison with the processor sharing service discipline. Effects of the traffic load at the base station and file length (service time requirement) distribution on the mean response time are discussed. Finally, the relationship between the mean response times of interactive and elastic data traffic is studied.

We consider a single-part, two-echelon supply chain problem for spare parts. The network consists of a single manufacturing plant, a set of service centers (SCs) and a set of customers. Both echelons keep spare parts using the base-stock replenishment policy. The plant behaves as an M/M/1 queueing system and has limited production and storage capacity. Demand faced by each SC follows an independent Poisson process. The problem is to determine optimal location-allocation and optimal base-stock levels at both echelons while satisfying the target service levels and customer preferences of SCs. We develop a mixed integer non-linear programming model and use cutting-plane method to optimize the inventory-location decisions. We present an exact solution procedure for the inventory stocking problem and demonstrate the limitations of using traditional inventory models like METRIC-like and Approximate in case of high utilization rates. We show the effectiveness of our proposed cutting-plane algorithm and provide important managerial insights for spare parts management.