RIM to the Rescue
How the FAA’s Runway Incursion Mitigation Program Is Improving Aviation Safety
By Tom Hoffman, FAA Safety Briefing Magazine
Improving safety at the nation’s airports is a top priority for the FAA. But to truly move the needle with airport surface safety, we must deal with one of its leading nemeses — runway incursions (RIs). In fiscal year 2024 alone, there were 1,757 RIs, nine of which were the more dangerous Category A and B variety where a collision was narrowly avoided or was a strong possibility.
A major contributor to RIs is complex airport geometry; areas where a pilot might get confused about how to properly proceed. You may notice many of these locations labeled as “hot spots” on airport diagrams (e.g., two runway thresholds in close proximity). The FAA is aware of these arrangements and the confusion they sometimes cause for pilots. And while there is solid outreach and guidance for these locations, the FAA needed a specific effort that could focus on complex geometry more quantitatively and develop mitigation strategies that provide more effective and long-term solutions. In 2015 the Runway Incursion Mitigation (RIM) program was established and set out to tackle this very issue. And with nearly 10 years under its belt, RIM is well on its way to being one of the FAA’s most successful safety programs.
Finding the Right Angle on Safety
To get a better idea of how many and what types of geometry issues existed, the FAA’s Airport Technology Research and Development Branch was tasked with conducting a study that would help inventory problematic taxiway geometry (PTG) locations. Often, the PTGs had commonality with existing hot spots. The 2013 study created a database of all pilot deviation and vehicle/pedestrian runway incursions at 520 towered airports reported between Oct. 1, 2007, and Sept. 30, 2013, and overlaid them with the PTGs. In doing so, the report identified 19 of the most common geometry elements associated with a runway/taxiway intersection, known as geocodes. The three most problematic geometries discovered were 1) a short taxiway distance from a ramp/apron to a runway; 2) direct taxi access to runways from ramp areas; and 3) taxiways intersecting a runway at other than right angles. For a full list of these 19 geocodes, see the table below.
The research also plotted the intersection of airport design issues and RIs and helped pinpoint an initial 140 locations for further study. This set the stage for the RIM team, which began validating a subset of these initial 140 locations for inclusion into the program, giving priority to high-incident locations.
Measuring Up
The validation process for RIM locations involves several steps as well as specific criteria that must be met. First, the location must have had three or more RIs in a single calendar year, or average one or more RIs per year during the most recent 10-year stretch. In addition, some of the unique characteristics of a location are reviewed along with the narratives of the incursions. This is designed to help weed out cases that might skew the RI counts at certain locations, such as a vehicle driver who caused multiple RIs in a single incident. Other unique situations, like an air show or a short-term construction project, could indicate RIs that were caused by something other than a taxiway geometry issue.
Runway Incursion:
any occurrence at an aerodrome involving the incorrect presence of an aircraft, vehicle, or person on the protected area of a surface designated for the landing and take-off of aircraft.
The next step is to validate the RIM location in the field. Local FAA staff will do a final assessment of the location and verify the geometry issue still exists. Once that’s complete, the location is entered into the RIM inventory.
The number of RIM locations fluctuates throughout the year, with the current total at approximately 140. “Every year we go through a re-evaluation based on the previous year’s RIs and add new locations if needed,” says Steve Debban, a civil engineer with the FAA’s Airport Engineering Division and RIM program manager. “As we go through the year, we’ll also remove some from the inventory as locations are completed.” Debban adds that locations that fall off are still monitored for effectiveness and could potentially be added back to the list for additional mitigation action based on new data.
We have a lot of people across the country doing what they can to keep pilots safe and to hardwire safety into the system — that’s what RIM is all about.
Squaring that Circle
Once a RIM location is added to the inventory, FAA personnel and local airport sponsors will coordinate to determine the most appropriate mitigation strategies for the location. “While safety is our number one priority, we prefer solutions that won’t hamper the airport operations by causing major issues for air traffic control, fixed-based operators (FBOs), or local users,” says Debban.
With that in mind, airports have a variety of mitigation strategies at their disposal to eliminate problematic taxiway geometries and reduce the likelihood of incursions. Some geometry changes might include reconfiguring a taxiway to intersect a runway at 90 degrees or closing a taxiway or, on rare occasions, a runway. A few non-geometry-related solutions include changes to airfield lighting, signage, and markings. Public outreach and procedure changes can also be appropriate measures in certain cases. Other factors like funding sources and environmental studies must also be considered when exploring solutions. While the mitigation process can be iterative, proper planning and stakeholder communication are essential for all parties to agree on a solution that is both effective and efficient.
Correcting an Acute Issue
Working the RIM process to mitigation completion can be a lot of hard work in many locations, but the results have proven to be extremely worthwhile. By the end of fiscal year 2024, RIM was credited with having mitigated 100 complex airfield locations. Many locations have seen zero RIs post-mitigation, with the total recurrence reduction rate averaging an impressive 80% according to Debban. Mitigations at these locations have also eliminated hot spots from the airport diagram at 32 locations.
Airports that have benefited from RIM run the gamut from small and medium-size general aviation (GA) fields to the much larger part 139 hubs. A few notable success stories have been:
- Fairbanks International Airport (FAI): Runway 20L was shortened to create a more standard configuration for Taxiway Tango.
- Terre Haute Regional Airport (HUF): Runway 18/36 was converted to Taxiway Foxtrot to provide safety improvements with traffic flow.
- Miami Executive Airport (TMB): A more standard taxiway configuration was created for Taxiways Echo and Hotel where they intersect Runway 31.
In the latter example at TMB, FAA lead program manager Pedro Blanco and former program manager Krystal Ritchey, P.E. needed to address several PTGs that resulted in 11 incursions over a nine-year period. Blanco admits that the most challenging part of addressing a RIM location is often the validation process by the sponsor (accepting there is a problem) and the planning effort to determine alternatives with viable options. “These steps entail significant effort in educating local stakeholders and conducting a planning analysis that prioritizes safety and efficiency through airport design standards first, then risk evaluation alternatives,” says Blanco.
Blanco and Ritchey worked diligently with the airport sponsor, stakeholders, and fellow FAA staff to devise a series of changes that the sponsor later approved for construction. The changes were extensive, including shortening a runway, as well as demolishing, extending, relocating, and constructing new taxiways. The hard work paid off as there have been no reported incursions in this area since the project was completed in May 2024. Additionally, other capacity-related tasks were identified during the course of the project that may provide future improvements in taxiway and runway utilization at this busy reliever airport.
Another notable example of a successful RIM project occurred at Bethel Airport (BET) in Alaska. Eight runway incursions took place here between 2019 and 2021 when aircraft turned onto the crosswind Runway 12/30 from the main Runway 1L/19R as opposed to utilizing the nearby taxiway as instructed by the air traffic control tower. “A review of the incursions determined that the connecting pavement between the two runways caused pilot confusion on the ground,” says Rory Bryant, P.E., an FAA airport program manager in the Alaskan Region. In 2022 the sponsor mitigated the existing conditions to increase pilot situational awareness by:
- Reducing the length of the blast pad prior to Runway 30 threshold.
- Applying green paint within the non-movement area between the outer limits of the revised blast pad and Runway 1L/19R shoulder edge.
- Installing a missing runway edge light along Runway 1L/19R to meet the advisory circular standards for runway lighting.
Upon completion of the project, no runway incursions have occurred.
Striking the Right Chord
As mentioned earlier, stakeholder feedback is critical to gaining consensus on a RIM mitigation strategy, particularly during the planning and coordination phases. Some of the information the FAA uses for RIM comes from Aviation Safety Reporting System (ASRS) reports, but most feedback is conveyed via the local Runway Safety Action Team (RSAT) meetings. RSAT meetings are held regularly at towered airports to discuss local safety concerns, review data, and develop targeted action plans to improve surface safety. (Learn more about RSATs.) These meetings give pilots an opportunity to discuss problem areas firsthand and have a seat at the table with any proposed mitigation methods. Some RSATs are designed to specifically cover potential RIM projects, so be sure to keep an eye out and make your voice heard when able.
Debban credits having more data and feedback with being able to better validate the success of RIM mitigations. “For the first few years of the program, our success metrics used to measure pre- and post-incursions against each other, but as we collected more data as the program has matured, we now have enough data to do statistical analyses and have a better understanding of what mitigations are effective,” says Debban. For example, the team is now looking at certain hot spots differently. “Before, hot spots that were very large, and maybe had more than one hold line, would be considered a single RIM location,” he continues. The team now breaks a larger hot spot into separate RIM locations to better mitigate the issue and measure its effect.
By the end of fiscal year 2024, RIM was credited with having mitigated 100 complex airfield locations.
Looking forward, Debban is focused on improving safety strategies for wrong surface events (WSEs). “It’s a challenge finding mitigations for WSEs as they tend to be very site-specific solutions,” says Debban. The FAA’s Technical Center is currently working on a study that will assist the RIM team and the entire FAA in developing a more focused and customized strategy for these events than what exists with current airport design standards.
A Straight Line to Safety
“We have a lot of people across the country doing what they can to keep pilots safe and to hardwire safety into the system — that’s what RIM is all about,” states Debban. He attributes simplicity as a leading factor in the success of the program. “Our society has been reliant on technology solutions and how we can use AI to solve our way out of things. But in this case, it’s about keeping it simple and building the infrastructure in the way it’s supposed to be designed and for the types of aircraft using it.” It’s a successful geometry formula that will help reduce runway incursions now and for years to come.
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Tom Hoffmann is the editor of FAA Safety Briefing. He is a commercial pilot and holds an A&P certificate.
