Thesis (M. Eng.)(Aeronautical)--University of Pretoria, 2004. / Title from opening screen (viewed March 18, 2005). Summaries in English and Afrikaans. Includes bibliographical references.

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: finite element analysis; guardrail system; splice connection; post-rail connection. Includes bibliographical references (p. 127-130).

My diploma thesis deals with measuring the center of gravity (CG) the motorcycle. The first part is outlined with legislation and the types of motorcycle division. I mention the theoretical types of measuring the CG the motocycle there too. These methods are applied to the issue of motor vehicles. The chosen one way of measuring the center of gravity which is used for practical measurements of gravity the motocycle. The practical part included the weighing of the different types of motorcycles with a different occupancy. These values are then processed and the resulting CG are calculated for each motorcycle. The values of CG were compared by experiment with the program for the analysis of road accidents and reconnoitred the measured results with this program results. In the last chapter is the evaluation of individual CG motorcycle and the influence of changes in occupancy due to a motorcycle.

Les constructeurs automobiles sont tenus de respecter des minima sécuritaires vérifiés lors de crash-tests normalisés, d'où un nombre de scénarios de tests limité ne tenant pas compte des particularités individuelles. Ce mémoire propose d'évaluer le comportement humain réel en phase de pré-crash sur simulateur de conduite. L'expérimentation, intégrant un scénario d'accident difficilement évitable, a permis d'étudier le comportement de 76 conducteurs dont 40 sur simulateur dynamique. Pour ce groupe, 43 voies de mesures centrées sur le conducteur ont été intégrées au protocole. Parmi les résultats obtenus, on retiendra la possible détection précoce de l'accident, pour la moitié des conducteurs, sur la base de leur interaction avec le véhicule. Les manœuvres d’évitement amènent 25% des sujets à positionner l'avant-bras devant le volant au moment de l’impact. Cette situation peut compromettre l'efficacité des airbags, ce qui est vérifié sur banc statique, par le déploiement d'airbags face à un mannequin de type Hybrid III-50%. La projection du bras entraine un impact de 120g à la tête. De plus, l'intégration de membres supérieurs issus de SHPM montre que la situation provoque des fractures de l'avant-bras. Un modèle numérique a été conçu pour estimer les effets de la position atypique lors d'un crash frontal à 50km/h. L'accélération de la tête atteint 270g, synonyme de risques lésionnels élevés. Enfin, une modification technologique des airbags est proposée, basée sur l'hypothèse que la détection à distance peut permettre un déclenchement anticipé et plus lent des airbags. Testée expérimentalement et numériquement, cette évolution permet de respecter les critères lésionnels. / Automakers are lawfully required to achieve a minimum level of security which is checked during standardized crash tests. This results in a limited number of scenarios, which do not take individual specificities into account. This dissertation evaluates real human behaviour during the pre-crash phase, by means of a driving simulator. The experiment, integrating an unavoidable accident, studied the behaviour of 76 drivers, of which 40 drivers on a dynamic simulator. Concerning this group, 43 acquisition channels dedicated to drivers were added. From the results, one can retain that the crash can be predicted for half of the drivers through the observation of their behaviour and their interaction with the car. Due to swerving manoeuvres, 25% of the drivers have their forearm just in front of the steering wheel at the time of crash. This situation may compromise the efficiency of the airbags, that is verified experimentally on a static bench, by the deployment of airbags in front of a Hybrid III-50% dummy. The throwing of the arm causes an impact of 120 g to the head. In a second stage, the integration of left upper limbs from PMHS reveals that the situation is likely to generate fractures in the forearm. A numerical model has been designed to estimate the consequences of the atypical position during a frontal crash at 50km/h. The head acceleration reaches 270 g, synonymous with high lesion risks. Finally, a technological modification of the airbags is proposed to reduce this risk. The assumption is made that the use of remote sensors technologies can allow an early detection of the crash and therefore slower triggering of airbags. Tested experimentally and then numerically, this technical evolution reduces the violence of the impact to respect the injury criteria.

Crash response planning is a vital component of emergency management and highway emergency response planning. Evaluation of coverage of medical facilities is required to determine adequate access from crash sites to medical facilities. This study proposes a proof of concept for a planning tool that evaluates fatal and serious injury crash response coverage from crash sites to medical facilities in the Commonwealth of Virginia. Calculated travel times from fatal crash sites to medical facilities are compared with reported travel times to better estimate travel time modification factors. The modified travel times are used to determine coverage areas and evaluate serious injury crash response coverage of medical facilities in Virginia. A geo grid approach is used to demonstrate the proof of concept for a crash response planning tool. A risk grid is developed based on the aggregate number of fatal and serious injury crashes. This study includes serious injury crash response coverage because the number of serious injuries and serious injury rate are now included as reportable safety performance measures for state highway safety agencies. A mitigation grid is developed based on the travel time to the closest facility. Finally, a planning grid that combines risk and mitigation factors based on a decision matrix is presented. The resulting tool serves as a proof of concept for developing a crash response planning tool which enables planners to identify areas that do not have timely access from crash sites to medical facilities. / Master of Science / An objective of emergency responders is to safely transport crash victims from crash sites to medical facilities. Ensuring adequate access is an important goal of highway safety professionals. This study proposes a proof of concept for a planning tool that evaluates this access in the Commonwealth of Virginia. This study focuses on serious injury crash sites because the number of serious injuries and serious injury rate are now included as reportable safety performance measures for state highway safety agencies. Travel times from serious injury crash sites to medical facilities are used to identify areas that do not have timely access. Risk and mitigation assessments are performed by dividing the study area into equal sized cells. Risk and mitigation assessments are based on number of crashes and response travel times to the closest medical facility, respectively. These assessments are used to generate a proof of concept for a crash response planning tool which enables planners to identify areas that do not have timely access from crash sites to medical facilities.

One of the most important data elements recorded in the National Automotive Sampling System / Crashworthiness Data System (NASS/CDS) is the vehicle change in velocity, or ?V. ?V is the vector change in velocity experienced by a vehicle during a collision, and is widely used as a measure of collision severity in crash safety research. The ?V information in NASS/CDS is used by the U.S. National Highway Traffic Safety Administration (NHTSA) to determine research needs, regulatory priorities, design crash test procedures (e.g., test speed), and to determine countermeasure effectiveness. The WinSMASH crash reconstruction code is used to compute the ?V estimates in the NASS/CDS. However, the reconstruction accuracy of the current WinSMASH version has not previously been examined for side impacts. Given the importance of side impact crash modes and the widespread use of NASS/CDS data, an assessment of the program's reconstruction accuracy is warranted. The goal of this thesis is to quantify the accuracy of WinSMASH ?V estimations for side impact crashes, and to suggest possible means of improving side impact reconstruction accuracy. Crash tests provide a wealth of controlled crash response data against which to evaluate WinSMASH. Knowing the accuracy of WinSMASH in reconstructing crash tests, we can infer WinSMASH accuracy in reconstructing real-world side crashes. In this study, WinSMASH was compared to 70 NHTSA Moving Deformable Barrier (MDB) - to - vehicle side crash tests. Tested vehicles were primarily cars (as opposed to Light Trucks and Vans, or LTVs) from model years 1997 - 2001. For each test, the actual ?V was determined from test instrumentation and this ?V was compared to the WinSMASH-reconstructed ?V of the same test. WinSMASH was found to systemically over-predict struck vehicle resultant ?V by 12% at time of vehicle separation, and by 22% at time of maximum crush. A similar pattern was observed for the MDB ?V; WinSMASH over-predicted resultant MDB ?V by 6.6% at separation, and by 23% at maximum crush. Error in user-estimated reconstruction parameters, namely Principal Direction Of Force (PDOF) error and damage offset, was controlled for in this analysis. Analysis of the results indicates that this over-prediction of ?V is caused by over-estimation of the energy absorbed by struck vehicle damage. In turn, this ultimately stems from the vehicle stiffness parameters used by WinSMASH for this purpose. When WinSMASH was forced to use the correct amount of absorbed energy to reconstruct the crash tests, systemic over-prediction of ?V disappeared. WinSMASH accuracy when reconstructing side crash tests may be improved in two ways. First, providing WinSMASH with side stiffness parameters that are correlated to the correct amount of absorbed energy will correct the systemic over-prediction of absorbed energy when reconstructing NHTSA side crash tests. Second, providing some treatment of restitution in the reconstruction process will correct the under-prediction of ?V due to WinSMASH's assumption of zero restitution. At present, this under-prediction partially masks the over-prediction of ?V caused by over-prediction of absorbed energy. If the over-prediction of absorbed energy is corrected, proper treatment of restitution will correct much of the remaining error observed in WinSMASH reconstructions of NHTSA side crash tests. / Master of Science

No-passing zone crashes constitute a sizable percentage of the total crashes on two-lane rural roads. A detection and warning system has been devised and implemented at a no-passing zone site on route 114 of Southwest Virginia to address this problem. The warning system aims at deterring drivers from illegally conducting a passing maneuver within the no-passing zone area. The violating driver is warned in real time to stop the illegal act. This system is currently operational and its main function is to warn the no-passing zone violator. The aim of this research is to extend the warning system to the opposing vehicle in the same lane of the persistent violator in order to avoid crashes caused by the illegal maneuver that is taking place at a crest vertical curve of the two-lane rural road. In order to test the new system prior to its physical installation, a computer simulation has been developed to represent the real world violation conditions so that a better understanding of the problem and its varying scenarios would be achieved. The new simulation, which is the focus of this thesis, takes advantage of an existing simulation developed earlier to replicate only the illegal maneuver without giving any warnings to the opposing vehicle. The new program simulates the outcome of deploying a warning sign to the opposing driver for crash avoidance purposes assuming that all violators persist to pass the vehicle ahead. More than 712,000 computer runs were conducted to simulate the various possible outcomes including the sensitivity analysis. A critical comparison was made between the previous system that warned only the violating vehicle and the current program that warns both the violator as well as the opposing vehicle. The results indicate that warning the opposing driver would reduce the rate of unavoidable crashes by approximately 11% in the east direction and 13.25% in the west direction. / Master of Science

Modern SSDs are getting faster and smarter with near-data computing capabilities. Due to their design choices, traditional key-value stores do not fully leverage these new storage devices. These key-value stores become CPU-bound even before fully utilizing the IO bandwidth. LSM or B+ tree-based key-value stores involve complex garbage collection and store sorted keys and complicated synchronization mechanisms. In this work, we propose a cross-layered key-value store named Retina that decouples the design to delegate control path manipulations to host CPU and data path manipulations to computational SSD to maximize performance and reduce compute bottlenecks. We employ many design choices not explored in other persistent key-value stores to achieve this goal. In addition to the cross-layered design paradigm, Retina introduces a new caching mechanism called Mirror cache, support for variable key-value pairs, and a novel version-based crash consistency model. By enabling all the design features, we equip Retina to reduce compute hotspots on the host CPU, take advantage of the on-storage accelerators to leverage the data locality on the computational storage, improve overall bandwidth and reduce the bandwidth net- work latencies. Thus when evaluated using YCSB, we observe the CPU utilization reduced by 4x and throughput performance improvement of 20.5% against the state-of-the-art for read-intensive workloads. / Master of Science / Modern secondary storage systems are providing an exponential increase in memory access speeds. In addition, new generation storage systems attach compute resources near data to offload computation to storage. Traditional datastore systems are lacking in performance when used with the new generation SSDs (Solid State Drive). The key reason is the SSDs are underutilized due to CPU bottlenecks. Due to design choices, conventional datastores incur expensive CPU tasks that cause the CPU to bottleneck even before the storage speeds are fully utilized. Thus, when attached to a modern SSD, conventional datastores will underutilize the storage resources. In this work, we propose a cross-layered key-value store named Retina that decouples the design to delegate control path manipulations to host CPU and data path manipulations to computational SSD to maximize performance and reduce compute bottlenecks. In addition to the cross-layered design paradigm, Retina introduces a new caching mechanism called Mirror cache and a novel version-based crash consistency model. By enabling all the design features, we equip Retina to reduce compute hotspots on the host CPU, take advantage of the on-storage accelerators to leverage the data locality on the computational storage and improve overall access speed. To evaluate Retina, we use throughput and CPU utilization as the comparison metric. We test our implementation with Yahoo Cloud Serving Benchmark, a popular datastore benchmark. We evaluate against RocksDB(the most widely adopted datastore) to enable fair performance comparison. In conclusion, we show that Retina key-value store improves the throughput performance by offloading logic to computational storage to reduce the CPU bottlenecks.

Road safety is a serious societal concern in Riyadh city, Kingdom of Saudi Arabia. Because of the negative impact of traffic crashes which cause losses in the form of deaths, injuries and property damage, in addition to the pain and social tragedy affecting families of the victims, it is important for transport policy makers to reduce their impact and increase safety standards by reducing the severity and frequency of crashes in the city of Riyadh. It is therefore important to fully understand the relationship between traffic crash severity and frequency and their contributing factors so to establish effective safety policies which can be implemented to enhance road safety in Riyadh city. Data used in previous research have only consisted of basic information as there was unavailability of suitable and accurate data in Riyadh and there are very few studies that have undertaken as small area-wide crash analysis in Riyadh using appropriate statistical models. Therefore safety policies are not based on rigorous analyses to identify factors affecting both the severity and the frequency of traffic crashes. This research aims to explore the relationship between traffic crash severity and frequency and their contributing factors by using statistical models and a GIS approach. The analysis is based on the data obtained over a period of five years, namely AH 1425, 1426, 1427, 1428, and 1429 (roughly equivalent to 2004, 2005, 2006, 2007, and 2008). Injury crash severity data were classified into three categories: fatal, serious injury and slight injury. A series of statistical models were employed to investigate the factors that affect both crash severity (i.e. ordered logit and mixed logit models) and area-wide crash frequency (i.e. classical Poisson and negative binomial models). Because of a severe underreporting problem on the slight injury crashes, binary and mixed binary logistic regression models were also estimated for two categories of severity: fatal and serious crashes. The mixed binary logit model and the negative binomial model are found to be the best models for crash severity and crash frequency analyses respectively. The model estimation results suggest that the statistically significant factors in crash severity are the age and nationality of the driver who is at fault, the time period from 16.00 to 19.59, excessive speed, road surface and lighting conditions, number of vehicles involved and number of casualties. Older drivers are associated with a higher probability of having a fatal crash, and, as expected, excessive speeds were consistently associated with fatal crashes in all models. In the area-level crash frequency models, population, percentage of illiterate people, income per capita and income per adult were found to be positively associated with the frequency of both fatal and serious injury crashes whereas all types of land use such as percentages of residential use, transport utilities, and educational use in all models were found to be negatively associated with the frequency of occurrence of crashes. Results suggest that safety strategies aimed at reducing the severity and frequency of traffic crashes in Riyadh city should take into account the structure of the resident population and greater emphasis should be put on native residents and older age groups. Tougher enforcement should be introduced to tackle the issue of excessive speed. This thesis contributes to knowledge in terms of examining and identifying a range of factors affecting traffic crash severity and frequency in Riyadh city.

Traffic safety is one of the most essential aspects of transportation engineering. However, most crash prediction models are statistically-based prediction methods, which require significant efforts in crash data collection and may not be applied in particular traffic environments due to the limitation of data sources. Traditional traffic conflict studies are mostly field-based studies depending on manual counting, which is also labor-intensive and oftentimes inaccurate. Nowadays, simulation tools are widely utilized in traffic conflict studies. However, there is not a surrogate indicator that is widely accepted in conflict studies. The primary objective of this research is to develop such a reliable surrogate measure for simulation-based conflict studies. An indicator named Aggregated Crash Propensity Index (ACPI) is proposed to address this void. A Probabilistic model named Crash Propensity Model (CPM) is developed to determine the crash probability of simulated conflicts by introducing probability density functions of reaction time and maximum braking rates. The CPM is able to generate the ACPI for three different conflict types: crossing, rear-end and lane change. A series of comparative and field-based analysis efforts are undertaken to evaluate the accuracy of the proposed metric. Intersections are simulated with the VISSIM micro simulation and the output is processed through SSAM to extract useful conflict data to be used as the entry into CPM model. In the comparative analysis, three studies are conducted to evaluate the safety effect of specific changes in intersection geometry and operations. The comparisons utilize the existing Highway Safety Manual (HSM) processes to determine whether ACPI can identify the same trends as those observed in the HSM. The ACPI outperforms time-to-collision-based indicators and tracks the values suggested by the HSM in terms of identifying the relative safety among various scenarios. In field-based analysis, the Spearman’s rank tests indicate that ACPI is able to identify the relative safety among traffic facilities/treatments. Moreover, ACPI-based prediction models are well fitted, suggesting its potential to be directly link to real crash. All efforts indicate that ACPI is a promising surrogate measure of safety for simulation-based studies.