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Crashes on wet pavements are responsible for 25% of all crashes and 13.5% of fatal crashes in the US (Harwood et al. 1988). This number represents a significant portion of all crashes. Current methods used by the Department of Transportations (DOTs) are based on wet over dry ratios and simplified approaches to estimate hydroplaning speeds. A fraction of all wet crashes is hydroplaning; although they are related, the difference between a "wet crash" and "hydroplaning" is a wet-crash hydrodynamic-based severity scale is less compared to hydroplaning where the driver loses control. This dissertation presents a new conceptual framework design to reduce wet- and hydroplaning-related crashes by identifying locations with a high risk of crashes using systemic, data-driven, risk-based approaches and available data. The first method is a robust systemic approach to identify areas with a high risk of wet crashes using a negative binomial regression to quantify the relationship between wet to dry ratio (WDR), traffic, and road characteristics. Results indicate that the estimates are more reliable than current methods of WDR used by DOTs. Two significant parameters are grade difference and its absolute value. The second method is a simplified approach to identify areas with a high risk of wet crashes with only crash counts by applying a spatial multiresolution analysis (SMA). Results indicate that SMA performs better than current hazardous-road segments identification (HRSI) methods based on crash counts by consistently identifying sites during several years for selected 0.1 km sections. A third method is a novel systemic approach to identify locations with a high risk of hydroplaning through a new risk-measuring parameter named performance margin, which considers road geometry, environmental condition, vehicle characteristics, and operational conditions. The performance margin can replace the traditional parameter of interest of hydroplaning speed. The hydroplaning risk depends on more factors than those identified in previous research that focuses solely on tire inflation pressure, tire footprint area, or wheel load. The braking and tire-tread parameters significantly affected the performance margin. Highway engineers now incorporate an enhanced tool for hydroplaning risk estimation that allows systemic analysis. Finally, a critical review was conducted to identify existing solutions to reduce the high potential of skidding or hydroplaning on wet pavement. The recommended strategies to help mitigate skidding and hydroplaning are presented to help in the decision process and resource allocation. Geometric design optimization provides a permanent impact on pavement runoff characteristics that reduces the water accumulation and water thickness on the lanes. Road surface modification provides a temporary impact on practical performance and non-engineering measures. / Doctor of Philosophy / Crashes on wet pavements are responsible for 25% of all crashes and 13.5% of fatal crashes in the US (Harwood et al. 1988). This number represents a significant portion of all crashes. Current procedures used by DOTs to identify locations with a high number of wet crashes and hydroplaning are too simple and might not represent actual risk. A fraction of all wet crashes is hydroplaning, although they are related to the difference between a "wet crash" and "hydroplaning" is a wet crash water-vehicle interaction is less compared to hydroplaning where the driver loses control. This dissertation presents a new procedure to evaluate the road network to identify locations with a high risk of wet crashes and hydroplaning. The risk estimation process uses data collected in the field to determine the risk at a particular location and, depending on the available data a transportation agency uses, will be the approach to apply. The first statistical method estimates the frequency of wet crashes at a location. This estimate is developed by using a statistical model, negative binomial regression. This model measures the frequency of dry crashes, wet crashes, traffic, and road characteristics to determine the total number of wet crashes at a location. Results indicate that this option is more reliable than the current methods used by DOTs. They divide the number of wet crashes by the number of dry crashes. Two elements identified to influence the results are the difference in road grade and its absolute value. The second statistical method to estimate wet crashes considers crash counts by applying a statistical process, spatial multiresolution analysis (SMA). Results indicate that SMA performs better than current processes based only on the crash counts. This option can identify the high-risk location for different years, called consistency. The more consistent the method is, the more accurate is the results. A third statistical method is a novel way to estimate hydroplaning risk. Hydroplaning risk is currently based on finding the maximum speed before hydroplaning occurs. A vehicle's performance related to the water-film thickness provides an estimation method developed by (Gallaway et al. 1971), which includes rainfall intensities, road characteristics, vehicle characteristics, and operating conditions. The hydroplaning risk depends on more aspects than tire inflation pressure, tire footprint area, or vehicle load on the wheel. The braking and tire tread affect the performance margin. Highway engineers can use this improved hydroplaning risk-estimation tool to analyze the road network. Finally, a critical review showed the available solutions to reduce the probability of having a wet crash or hydroplaning on wet pavement. The recommended strategies to mitigate wet crashes and hydroplaning provide information to allocate resources based on proven, practical strategies. Road geometry design can be optimized to remove water from the road. This geometry is a permanent modification of pavement characteristics to reduce water accumulation and water thickness on the road. Road surface treatments and non-engineering measures provide temporary measures to improve vehicle performance or driver operation.

Crash prediction models are used to estimate the number of crashes using a set of explanatory variables. The highway safety community has used modeling techniques to predict vehicle-to-vehicle crashes for decades. Specifically, generalized linear models (GLMs) are commonly used because they can model non-linear count data such as motor vehicle crashes. Regression models such as the Poisson, Zero-inflated Poisson (ZIP), and the Negative Binomial are commonly used to model crashes. Until recently very little research has been conducted on crash prediction modeling for pedestrian-motor vehicle crashes. This thesis considers several candidate crash prediction models using a variety of explanatory variables and regression functions. The goal of this thesis is to develop a pedestrian crash prediction model to contribute to the field of pedestrian safety prediction research. Additionally, the thesis contributes to the work done by the Federal Highway Administration to estimate pedestrian exposure in urban areas. The results of the crash prediction analyses indicate the pedestrian-vehicle crash model is similar to models from previous work. An analysis of two pedestrian volume estimation methods indicates that using a scaling technique will produce volume estimates highly correlated to observed volumes. The ratio of crash and exposure estimates gives a crash rate estimation that is useful for traffic engineers and transportation policy makers to evaluate pedestrian safety at signalized intersections in an urban environment. / Master of Science

This study is the first examination on the association between seven types of sleep disorder and driving risk using large-scale naturalistic driving study data involving more than 3,400 participants. Regression analyses revealed that females with restless leg syndrome or sleep apnea and drivers with insomnia, shift work sleep disorder, or periodic limb movement disorder are associated with significantly higher driving risk than other drivers without those conditons. Furthermore, despite a small number of observations, there is a strong indication of increased risk for narcoleptic drivers. The findings confirmed results from simulator and epidemiological studies that the driving risk increases amongst people with certain types of sleep disorders. However, this study did not yield evidence in naturalistic driving settings to confirm significantly increased driving risk associated with migraine in prior research. The inconsistency may be an indication that the significant decline in cognitive performance among drivers with sleep disorders observed in laboratory settings may not nessarily translate to an increase in actual driving risk. Further research is necessary to define how to incentivize drivers with specific sleep disorders to balance road safety and personal mobility. / Master of Science / This study is the first examination on the association between seven types of sleep disorder and driving risk using large-scale naturalistic driving study data involving more than 3,400 participants. The study identified seven sleep disorders - narcolepsy, sleep apnea, insomnia, shift work sleep disorder, restless legs syndrome, periodic limb movement disorder, and migraine among the participants and revealed that that females with restless leg syndrome or sleep apnea and drivers with insomnia, shift work sleep disorder, or periodic limb movement disorder are associated with significantly higher driving risk than other drivers without those conditons. Furthermore, despite a small number of observations, there is a strong indication of increased risk for narcoleptic drivers. The findings confirmed most results from previous simulator and epidemiological studies that the driving risk increased amongst people with certain types of sleep disorders except for those with migraines – there is no evidence showing increased driving risk associated with drivers with migraine. The inconsistency may be an indication that the significant decline in cognitive performance among drivers with sleep disorders observed in laboratory settings may not nessarily translate to an increase in actual driving risk. The public and private sectors can use the results to target their investments in supporting high risk individuals. And physicians now have more representative data on the level of risk in real world driving and thus more able to practice evidence-based medicine in consulting their patients with sleep disorders regarding driving safety and personal mobility.

Roundabout installations are becoming common practice among DOTs and other local governments due to their superior safety attributes compared to other conventional at-grade intersections, especially stop-control and uncontrolled intersections. Current U.S. national guidelines for roundabout illumination recommend systematic illumination for all roundabouts. This recommendation might become a potential hindrance to desired widespread installations due to implied financial costs, especially in rural areas because the competing stop-control and uncontrolled intersections can be kept unlit. Interestingly rural roundabouts in most countries around the world are not illuminated as indicated by a recent survey of international roundabout illumination policies and standards from 45 countries. Also, review of intersection safety literature does not identify any publication that supports a systematic illumination policy of U.S. roundabouts. In fact, despite this recommendation there is no quantitative research on influence of illumination levels on nighttime safety at roundabouts and little on conventional intersections. Conversely, the literature shows a significant number of published studies which have indicated that currently recommended illumination levels on roadways can be reduced without compromising nighttime safety. This dissertation evaluates the link between roundabout crashes and different illumination levels. At the beginning of this dissertation research, there was no available repository of quantitative intersection illumination levels which could be used in highway safety research. Also, existing protocols for measurement require expensive light meters and are extremely time consuming to follow, making them impractical to use to study a large number of intersections. Consequently, this dissertation first evaluates the relationship with the best available data. The best available intersection illumination data was obtained from the Minnesota data contained in the Highway Safety Information System (HSIS). Minnesota crash and illumination data from 2003 to 2010 were analyzed. This illumination data was a qualitative description of intersection illuminating schemes and/or luminaire arrangement. Therefore, this dissertation also developed a cost-effective, accurate, and rapid method for measurement of quantitative intersection illumination data, and applied the developed protocol to a case study in Georgia. The measured intersection illumination was analyzed together with crash data obtained from GDOT for 2009 to 2014. The results of a naive analysis on the best available data indicated among other findings that the presence of lighting can provide approximately 61 percent lower total nighttime crash rate compared to the unlit condition. Also, providing illumination to the roundabout circle alone can yield about 80 percent of the benefits (55 percent reduction from unlit condition) of illuminating both the roundabout circle and approaches (66 percent reduction from unlit condition). Field test results for the camera calibration indicate that the average intersection illuminance derived from the protocol is within 4 percent difference of the actual average intersection illumination estimated from following the existing protocols. Next, despite limited roundabout data and potential issues of selection bias which could not be addressed in this dissertation, a cautious roundabout illumination specific crash modification factor was estimated with a negative binomial regression model. The model results showed that an increase of 1 lux in average roundabout illuminance will result in a 4.72 percent reduction in expected number nighttime crashes. The results of this work are useful in creating a sound framework for DOTs and other transportation agencies to determine the most appropriate level of illumination for roundabouts. This study also makes a number of significant contributions to highway safety research. First, this work is the first quantitative study on the impact of illumination on safety at roundabouts. The status-quo for highway safety research regarding the impacts of illumination had been to treat road lighting as a binary (Lit/Unlit) variable. However, even in most places without purposely-built road lighting there is usually ambient lighting from abutting facilities such as a gas stations or a store. Second, this dissertation is the first documented application of the photographic method to roundabouts. It is also the first documented application of the photographic method’s camera specific constant calibration approach to transportation field measurements. Previous documented application of the photographic method to transportation field measurements used an exposure specific calibration approach. Unlike the camera specific constant calibration approach, the exposure specific approach is rigid and field measurements must always be done at the exposure settings used in calibrating the camera. Thirdly, this work demonstrates the first developed procedure to developing uniformity (contour) plots from the photographic method. Next, this work can serve as the basis for initial efforts to create an illumination specific quantitative crash modification factor. Currently, the Highway Safety Manual is lacking in this important safety parameter. Last, but not the least this work offers procedures for collecting luminance data from the field and also documents a database of intersection illumination levels and intersection characteristics which can be used by future research.

This research assessed the criminological significance of motor vehicle crash data within the criminal justice context. The study was conducted at the southern region Accident Bureau of the Ekurhuleni Metropolitan Police Department (EMPD). The objectives of this research are to: a. Explore and describe the extent and criminological impact of road traffic crashes on a macro level. b. Explore and describe the impact of road traffic crashes on a micro level. c. Explain the criminological significance of road traffic crash data in relation to effective road safety management. d. Evaluate and describe the attendance and recording procedure of road crashes. e. Evaluate and describe the supervisor’s responsibility in relation to the quality of crash data recorded. f. Evaluate and describe the effectiveness of crash statistics accessed by management and/or officials. g. Evaluate and explain the current prosecution procedure as part of the CJS. h. Evaluate existing policy about the crash-recording process applicable to operational law enforcement practitioners of the EMPD. i. Explore and describe the current state of motor vehicle insurance and its necessity from a criminological perspective. The researcher followed a mixed-methods approach, collecting quantitative data from recorded Accident Report Forms and qualitative data from interviews with participants active in their fields of expertise. Road crashes are characterised by injury and damage; victims suffer trauma and economic consequences, and the society and the economy as a whole are affected. The research suggests that accurate road crash data form a crucial component in the investigation, prosecution and development of road safety strategies in the quest towards improved road safety efforts. It also indicates that existing crash data are of such a sub-standard that traffic professionals will not be able to develop effective and efficient road safety strategies in pursuit of road safety / Criminology and Security Science / M.A. (Criminology)

The project focus has been development of guidelines and methods for upper extremity injury reduction in car crashes. The safety of the central body parts improves which indicates the need to develop methods for avoiding non-life threatening injuries such as fracture of the arms. The purpose of the project was to study the injury mechanisms for the upper extremity in car crashes, and the aim has been to propose methods to reduce the injuries. The project focuses on adult occupants inside the vehicles front seat, and frontal and side impacts. The procedure began with understanding and identifying the injury mechanisms. Studies show that most fractures occur on the forearm (radius and ulna) and on the wrists and hands. To determine which injury mechanisms that were most frequent, data were collected from 29 computer simulations with 29 different crash scenarios. The most common kind of impact was the medial part of the wrist in the central part of the instrument panel, combined with the impact of the elbow in the center consol. The results of the simulations created a basis for the method of the component test, with focus on the injury mechanism i.e. the forward movement of the arms into the instrument panel. The component test consisted of a test rig, on which was mounted with a measuring arm of a 50th percentile male dummy. The arm dropped into a block of expanded polypropylene (EPP-block) for observation and study, and with following variable parameters: the impact angle of the surface, velocity and position of the wrist. Then also an instrumented measuring arm from a 5th percentile female dummy was released into an instrument panel. The project contributes to knowledge about the injury mechanism of the upper extremity in car crashes. The most frequent injury mechanism is a forward movement of the arms resulting in an impact with the interior structure of the car. The most frequent injured region is the distal part of the upper extremity. The project has developed and suggested the first step to a test method for the specific injury mechanism. There is a need of more research on how impact angles and velocity affect the violence on the arm.

published_or_final_version / Pathology / Master / Master of Philosophy

The change of a vehicle’s velocity due to an impact, DeltaV (v) is often calculated and used in the scientific investigation of road traffic collisions. Two types of model are in common use to achieve this purpose, those based on the conservation of linear and angular momentum and the CRASH model which also considers the conservation of energy. It is shown that CRASH and major implementations of the momentum models are equivalent provided certain conditions are satisfied. Explicit conversions between the main variants of the models are presented. A method is also presented which describes a new formula for determining the total work performed in causing crush to a particular vehicle. This has the advantage of incorporating restitution effects and yields identical results to the momentum only models. Although the CRASH model has received adverse criticism due to perceived inaccuracies in the results, little work has been performed to determine the theoretical limitations on accuracy. This thesis rectifies that shortcoming. A Monte Carlo simulation and analytical model are developed here to provide two independent methods for determining the overall accuracy of the CRASH method. The principal direction of force was found to be the most likely to introduce error based on the CRASH assessment. It is shown how this and other sources of error in the CRASH model can be quantified for a particular collision suggesting priorities for minimising the overall uncertainty. The data from a series of well known crash tests are used with each of the models to provide comparison and validation data. It is recognised that without additional data velocity change is of limited use for forensic investigation. However DeltaV can be used as a proxy for acceleration and is particularly useful in studies involving injury causation. A method is also presented here which uses the change in velocity sustained by a vehicle in a planar collision to estimate the velocities of a vehicle before and after a collision. This method relies solely on conservation laws and is also applicable to situations where the coefficient of restitution is non-zero. An extension to the method is also described which allows an initial estimate to be modified to generate more realistic directions of force. This extension has the desirable effect of reducing uncertainty in the estimation of the direction of force which significantly improves the overall accuracy.

A chassis is known as the carrying unit of an automobile, like the engine, transmission shaft and other parts are mounted on it. Ladder chassis has longitudinal rails which are connected along the length with crossmembers through welding or mechanical fasteners. Rectangular box section is chosen for the longitudinal rails of ladder chassis. Design modifications are done in HyperMesh to improve torsional and bending stiffness of the chassis designed in steel and CFRP. Adding of the X- bracing cross-member and ribs are few of the techniques used to provide strength to chassis. This thesis aims to produce a light-weight chassis. A combination chassis of both steel and CFRP components is created by replacing heavy steel cross-members with CFRP cross-members, which resulted in the reduction of weight by 14.6%. Crash analysis is performed to all the chassis using Radioss. Depending on the result obtained from crash analysis and values of torsional and bending stiffness, the combination chassis is selected. Thickness optimization is performed to the combination chassis. It is observed that 7.91% of weight is further reduced in the combination chassis.