What is Runway Occupancy Time and Why Does it Matter?

Runway occupancy time (ROT) is just what it sounds like: the amount of time that a runway is occupied or not usable by another aircraft. For arrivals, this is generally measured from the time the aircraft touches down until the time the aircraft is clear of the runway. For departures, the time starts when the aircraft enters the runway and stops as soon as the aircraft leaves the ground. What factors increase average runway occupancy times? Weather, inexperienced pilots, aircraft size, poor airport design, construction, and runway contaminants are just a few possibilities.

Runway Occupancy Time

A group of researchers at George Mason University performed a study in 2009 at Dallas-Fort Worth International Airport using the installed ASDE-X (airport surface detection equipment, model-x). According to the ASDE-X Wikipedia article, "the data that ASDE-X uses comes from a surface movement radar located on the airport traffic control tower or remote tower, multilateration sensors, ADS-B (Automatic Dependent Surveillance-Broadcast) sensors, terminal radars, the terminal automation system, and from aircraft transponders. By fusing the data from these sources, ASDE-X is able to determine the position and identification of aircraft and vehicles on the airport surfaces, as well as of aircraft flying within 5 miles (8 km) of the airport...".  Using this equipment, the researchers from George Mason University discovered that the mean average arrival runway occupancy time was between 47.6 seconds and 56.4 seconds. The researchers stated that, "according to simple laws of physics, the higher the momentum, the more force/time it takes to decelerate the aircraft to the point where it can get off the runway." Heavy sized aircraft average runway occupancy time was 7.9 seconds to 8.8 seconds longer than any other sized aircraft. Now, you may be thinking, would 8 seconds really make a difference?

Six airlines along with the Melbourne Airport in Australia created a program called Airport Capacity Enhancement or ACE which, according to their website, identifies and addresses capacity constraints and makes changes to ultimately decrease runway occupancy time. According to their program, just five seconds lost per aircraft can result in a decrease of two arrival/departure slots per hour. So by decreasing ROT, airports and Air Traffic Control can allow more aircraft to arrive and depart each day, thereby increasing revenue. The ACE Program article proposed that one of the ways to decrease ROT was through informing pilots of the issue and asking them to help. For arriving aircraft the pilots can use certain taxiways at specific speeds for faster runway evacuation. For departing aircraft, they suggest that pilots complete checklists " in due time to [minimize] checks on the runway" and to react promptly when requested to line up and wait or to take off.


During winter operations at airports that observe snow and ice each year, SRE ROT or Snow and Ice Removal Runway Occupancy Time becomes important. The amount of time that snow removal equipment, chemical depositing trucks, and surface friction measuring equipment are on a runway can cause significant  flight delays. Airports should reference Advisory Circular (AC) 150/5220-20A regarding Airport Snow and Ice Control Equipment. The AC gives guidelines on how much snow equipment is needed based on the size of priority 1 surfaces (main runways and taxiways) and the size and amount of aircraft the airport services. Denver International put out a presentation regarding their improvement in snow removal operations which includes an objective to reduce runway occupancy times. The PowerPoint is impressive and there are some really great photos, not to mention that Denver achieved a decreased ROT through their efforts.

From DIA Presentation

Runway Occupancy Time is affected by many different factors. Anything that delays an aircraft taking off or landing or vacating a runway increases ROT. Increasing ROT can put kinks in Air Traffic Control flow and cause delays all over the country. If increased ROT is a chronic issue at a specific airport, it results in less available time for more airplanes to arrive and depart. Both of these outcomes cost airlines, airports, and every other company working for these entities money. The aviation industry must always strive to keep ROT low.

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