Near midair collisions are precursor events to actual collisions and may be an indicator of risk. While previous studies have used reports of near midair collisions to relate factors such as airspace saturation to near midair collisions, the reports relied upon were generally subjective in nature. With the adoption of automatic dependent surveillance-broadcast (ADS-B), the approximate position of every equipped aircraft can be recorded. A six-month case study was performed at the Purdue University airport to relate the number of 1000-foot proximity events to airspace saturation, and whether the Class D airspace affected this relationship. Through a logistic regression analysis, it was found that the risk of a proximity event increases exponentially as a function of airspace saturation. While the Class D airspace had a higher baseline risk of a proximity event, the risk increased at a lesser rate compared with that of uncontrolled airspace. The findings of this study serve as a proof-of-concept for the use of ADS-B in studying collision risks and aircraft interactions. The study offers a glimpse of the relationship between airspace saturation and midair collision risk, and can be repeated and built upon to provide further insight into the factors affecting midair collision risks at other airports or on a larger scale.


The authors would like to thank Kristoffer B. Borgen for the development and use of the UKF and interpolation software used for this study. The authors would also like to thank Adam Baxmeyer and Christopher Morris of the Purdue University airport for their assistance with maintaining the ADS-B receiver at the airport.



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