ACRP 04-08: Improved Models for Risk Assessment of Runway Safety Areas

Airplane amid airport construction


The purpose of Airport Cooperative Research Program (ACRP) 04-08 was to expand on ARA’s earlier work on ACRP 04-01 (Aircraft Overrun and Undershoot Analysis for RSA) and to provide a risk-based assessment tool that is rational and accounts for the variability of several risk factors associated with aircraft overruns and undershoots. Current standards for runway safety areas (RSAs) are fairly rigid because they depend only on the type and size of aircraft using the runway. As such, these standards do not directly account for numerous factors that may lead to aircraft overruns, undershoots, and veer-offs. In many instances, standard RSAs are not feasible because of constraints such as obstacles or land unavailability. In such cases, it is essential to have analysis tools that allow for the evaluation of other alternatives to minimize risk, to the extent practicable, in relation to site-specific conditions.


ARA served as the prime contractor on ACRP 04-08 to improve and validate models and to develop software for analyzing RSAs. The primary function of the models is to support airfield planning and risk management actions for RSAs that do not comply with standard dimensions.

ARA based the improved model on updated accident and incident data, incorporated a runway criticality factor to consider the safety margins available for operations, and extended the analysis to the portion of safety areas not included in the original ACRP study (i.e., the evaluation of veer-off accidents/incidents). ARA also complemented the existing accident/incident database with historical information related to overrun and undershoot accidents and incidents from 2007 and 2008. Additionally, we added information on veer-off events from 1982 to 2008. Based on the new database, ARA updated overrun and undershoot models and created models for veer-off events. One key feature of the new ARA-developed models is a runway criticality factor that allows airports to take into consideration the safety margins provided by longer runways.

The ARA research team incorporated the risk models developed in this project into user-friendly analysis software to facilitate entering operation conditions and to provide a quantitative or qualitative assessment of overrun, undershoot, and veer-off risks associated with specific aircraft operation conditions. The software is flexible to incorporate the analysis of multiple obstacles, non-standard RSA configurations, and the presence of engineered material arresting systems (EMAS).


The results of ACRP 04-08 provide airport engineers and planners with an RSA analysis tool that can be used to support safety risk assessments and actions. The approach 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 near the RSA.

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