Runway Incursion Severity Categorization (RISC) Model

Current FAA Runway Incursion Severity Categories Operational dimensions affecting runway incursion severity: Available Reaction Time Evasive or Corrective Action Environmental Conditions Speed of Aircraft and/or Vehicle Proximity of Aircraft and/or Vehicle Increasing Severity Category D Little or no chance of collision, but meets the definition of a runway incursion. Category C Separation decreases, but there is ample time and distance to avoid a potential collision. Category B Separation decreases and there is a significant potential for collision. Category A Separation decreases and participants take extreme action to narrowly avoid a collision, or the event results in a collision.

Proposed Severity Categories “A” = A very serious incident in which a collision was narrowly avoided. “B” = An incident in which separation decreases and there is significant potential for collision, which may result in a time-critical corrective/evasive response to avoid a collision. “C” = A minor incident characterized by ample time and/or distance to avoid a collision. “D” = Insufficient information, inconclusive or conflicting evidence precludes severity assessment

Background The categorization of the severity of runway incursions is a tool to help represent risk in the system. Risk = probability of an event x severity of the outcome In order to be defensible, ratings need to be valid and reliable. Valid = an “A” is really an “A” Reliable = an “A” is always an “A” Inter-rater: An “A” for Peter is an “A” for Paul Over time: An “A” today is an “A” tomorrow

Components of the Model A rating is assigned based on the closest proximity (CP) and the factors that contribute to the variability of that proximity (probability of a collision). CP - both horizontal and vertical - is measured at the end of the conflict OR the point at which all parties are aware of the situation and have the aircraft under control at taxi speed or less.

Components of the Model (continued) Assumptions Some scenarios are more serious at the same CP than others (e.g, head-on is worse than tail-chase) There are factors that increase the variability of the response and resulting CP, for example: Actions with short response time Larger aircraft (more variable stopping distance) Contaminated runways

Benefits of the Model Rankings are reliable – same event will result in the same rating every time. Reliable ratings are necessary to have confidence in trends of system performance. Counts of types of scenarios (e.g., crossing in front of a takeoff, landovers) is automatic.

How the Model Works Rater is asked a series of questions and selects answers to classify the event as a scenario For example, what was the aircraft doing? (taking off, landing, taxiing, stopped) If taking off, did the aircraft takeoff or abort takeoff? What did the other aircraft or vehicle do? (For example, crossed runway, crossed hold short line, etc) Rater enters additional information about the event into three categories: visibility, avoidance maneuver, human error.

Information Selected by the Rater Ceiling and Visibility, RVR, Day/Night Aircraft type Types of human error – pilot error, controller error, communication error Avoidance maneuvers (initiated/commanded) Characteristics of avoidance maneuver (for example, point at which go-around was initiated)

Aircraft Type Aircraft Type = FAA weight categories S = less than 12,500 lbs S+ = 12,500 – 40, 999 lbs L = 41,000 – 254,999 H = or greater than 255,000

Avoidance Maneuver Categories Early rotation on takeoff (as reported by pilot) Aborted takeoff (reported distance rolled) Swerve (reported or observed) Hard/maximum braking (reported or observed) Go-around (point at which GAR was initiated/commanded)

Examples of Error Categories - (Degree of Control) Controller unaware of (or forgot about) aircraft or vehicle. Controller forgot runway was closed. Controller misidentified aircraft and issued instruction to wrong aircraft. Pilot took off/landed on wrong runway. Wrong aircraft accepted a clearance. Situation Unawareness

Examples of Communication Factors Total communication failure (e.g., stuck mike) One or more party (e.g., vehicle) not on frequency Completely blocked transmission Partially-blocked (stepped-on) transmission Controller unable to contact aircraft Pilot unable to contact controller  

Example Input: C-150 crossed hold short lines (but did not enter runway) with another aircraft (C-150) taking off. Aircraft taking off rotated normally after passing through the intersection (no avoidance maneuver). Closest horizontal proximity = 100’ as aircraft passed through the intersection Visibility: 10 miles - day Error: Pilot read back “hold short” instruction correctly but then crossed the hold short lines.

Example Output: Rating = 1.0 = “D”

Example of Most Common Scenarios N = 906

Example of Most Common Scenarios (continued) N = 906