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1 SUMMARY Improved Models for Risk Assessment of Runway Safety Areas The objective of this research project was to develop and validate a user-friendly software analysis tool that can be used by airport and industry stakeholders to quantify risk and sup- port planning and engineering decisions when determining runway safety area (RSA) requirements to meet an acceptable level of safety for various types and sizes of airports. The underlying basis was the approach presented in ACRP Report 3: Analysis of Aircraft Overruns and Undershoots for Runway Safety Areas. The improved models and methodol- ogy provided by this research effort provide the capability to evaluate declared distances and the use of engineered material arresting system (EMAS), as well as the ability to consider the effects of obstacles inside or in the vicinity of the RSA. The RSA is intended to prevent the following five types of events from becoming an acci- dent: landing overruns, landing undershoots, landing veer-offs, takeoff overruns and takeoff veer-offs. The risk analysis for each type of event is threefold and considers probability (aka frequency), location, and consequence. The models for probability and location are specific for the event type, while the model for consequences is applicable to all five event types. The models are based on evidence from worldwide accidents and incidents that occurred during the past 27 years. The analysis utilizes historical data from the specific airport and allows the user to take into consideration specific operational conditions to which move- ments are subject, as well as the actual or planned RSA conditions in terms of dimensions, configuration, type of terrain, and boundaries defined by existing obstacles. The combined estimates for the probability model and location model provide an esti- mate that the event will take place and that the aircraft will stop or touch down beyond a certain distance from the runway area or strike an existing obstacle at a given speed. Using these estimates for the distances defined by the RSA bounds or by existing obstacles, it is pos- sible to estimate the risk of accidents. User-friendly software was developed and tested to help with the analysis. Input data to the analysis includes historical information on operations and weather and the definition of the RSA conditions and obstacles. The computer program runs a simulation to assess the risk for each historical operation and outputs average risk levels and probability distribu- tions for each type of incident and each RSA section challenged by the operations. Results help the user identify areas of higher risk as well as compare different RSA alternatives. Finally, the models developed in this research were validated using actual data for a sam- ple of eight airports. The analysis results using actual data for these airports were compared to actual accident and incident rates over the past 25 years for each of these airports. The objective of this validation effort was to gain industry confidence on using the new method- ology and software tool. The outcome of this project is an RSA analysis tool that may benefit airport planners and engineers and that can be used to support safety risk assessments and actions. The approach
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2 used and the software developed can be applied to evaluate any type of RSA improvement, including extending the RSA, using declared distances, and using EMAS, In addition, it is possible to analyze irregular RSA shapes and to consider the type of terrain and the presence of obstacles inside or in the vicinity of the RSA. The RSA analysis tool should be used only for planning purposes rather than to evaluate risk for real-time conditions or individual operations. In addition, the data used to develop the risk models included only multi-engine aircraft with maximum takeoff weight (MTOW) higher than 5,600 lb. The approach for consequences incorporated in the analysis was based solely on engineering judgment, rather than crashworthiness data. ACRP makes no warranties, expressed or implied, concerning the accuracy, completeness, reliability, usability, or suitability of any particular purpose of the information or the data contained in the program. The software tool should be used by airport professionals who are familiar with and qualified to perform RSA analysis.