Many beneficial civilian applications of commercial and public small unmanned aircraft systems (sUAS) in low-altitude uncontrolled airspace have been proposed and are being developed. Associated with the proliferation of civil applications for sUAS is a paradigm shift from single-UAS visual operations in restricted airspace to multi-UAS beyond visual line of sight operations with increasing use of autonomous systems and operations under increasing levels of urban development and airspace usage. Ensuring the safety of sUAS operations requires an understanding of associated current and future hazards. This is challenging for sUAS operations due to insufficient mishap (accident and incident) reporting for sUAS and the rapid growth of new sUAS applications (or use cases) that have not yet been implemented. These applications include imaging, construction, photography and video, precision agriculture, security, public safety, mapping and surveying, inspections, environmental conservation, communications, parcel delivery, and humanitarian efforts such as delivery of medical supplies in developing nations. This paper will summarize research results in the identification of: 1.) Current hazards through the analysis of sUAS mishaps; and 2.) Future hazards through the analysis of a collection of sUAS use cases. The mishaps analysis will include the identification of mishap precursors and an analysis of their individual contributions to the mishaps as well as an analysis of worst-case hazards combinations and sequences. The future hazards are identified through an assessment and categorization of use cases for sUAS, the identification of associated paradigm shifts in terms of operations and new vehicle systems (both cross-cutting and for specific use case categories), the determination of future potential hazards (relative to the vehicle, ground control station, operations, and UTM system) arising from these paradigm shifts, and future potential impacts and outcomes (relative to the vehicle, other vehicles, people, ground infrastructure, and the environment). Key findings from these analyses are also summarized. The analysis results are then used to develop a set of combined (current and future) hazards for assessing risk.

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The theory o f induced growth in vehicle travel hypothesizes that highway improvements which add capacity to a specific corridor or regional transportation network will attract increased levels of vehicle traffic. This relationship of highway capacity to travel demand is an important consideration when evaluating how effective highway expansion alternatives will be in solving transportation problems. Two different but complementary empirical studies were conducted to quantify the effect of highway system improvements on travel behavior. In the first study, I apply ordinary least squares regression models to estimate travel demand elasticities with respect to travel time using travel survey data from the 1995 Nationwide Personal Transportation Survey. This is one of a very few research studies to use disaggregate household-level travel data. Travel time elasticities of-0.3 to-0.5 were found, after accounting for the effects o f household size, income, population density, and household employment. These results suggest that capacity additions that reduce travel time by 10 percent will increase vehicle-miles of travel by 3 to 5 percent. My second study investigates geographic differences in travel behavior before and after highway capacity was expanded in the Dallas-Fort Worth metropolitan area. Calibrated travel model data from 1984 and 1995 were used. This ix Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission. analysis is unique in that it applies three statistical research designs to quantify the effect of capacity expansion on induced demand for travel using a before-and-after case study approach. The three techniques, namely analysis of covariance, difference-indifferences, and OLS regression on travel changes from 1984 to 1995, produce similar results. After controlling for changes in number o f households, income, and population density, total weekday vehicle-miles of travel and daily trip productions were found to increase by approximately 20 percent and 7 percent, respectively, in survey zones that had undergone significant capacity additions versus zones that remained largely unchanged over the 11-year period. Overall, the results of this research provide evidence that highway capacity improvements generate additional demand for travel. These induced demand effects should not be ignored by transportation planners and policy makers when evaluating highway system investment alternatives.

The results of a study to characterize episodes of driver fatigue and drowsiness and to assess the impact of driver fatigue on driving performance are documented. This data-mining effort performed additional analyses on data collected in an earlier study by the Federal Motor Carrier Safety Administration of the effects of fatigue on drivers in local and short-haul operations. The primary objectives of the study were to investigate fatigue as a naturally occurring phenomenon by identifying and characterizing episodes of drowsiness during all periods of driving and to determine the operational or driving environment factors associated with drowsy driving. A total of 2,745 drowsy events were identified in approximately 900 total hours of naturalistic driving video data. Higher levels of fatigue were associated with younger and less experienced drivers. In addition, a strong and consistent relationship was found between drowsiness and time of day. Drowsiness was twice as likely to occur between 6:00 a.m. and 9:00 a.m., and approximately 30% of all observed incidences of drowsiness occurred within the first hour of the work shift. Insights about the relationship between driver fatigue and driver distraction and inattention are provided. This study presents an analytical framework for quantitatively assessing driver fatigue and drowsiness as a function of driver characteristics and the driving environment. It is hoped that the results will help to identify effective countermeasures for drowsy driving that will reduce the number of commercial-vehicle-related fatalities and injuries.

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