Taxiway Simulation (TAXSIM)
TAXSIM is a computer simulation of the flow of aircraft through the runway and taxiway network of an airport. The simulator uses a discrete event architecture that models the activity of each aircraft using the airport for a selected period of time. TAXSIM provides a convenient tool for airport planners to evaluate the effects of taxiway layout, aircraft mix, gate assignments, and other factors on surface traffic at the airport.
The simulation operates as follows: an aircraft is created prior to reaching the Outer Marker; it is assigned and scheduled on an active runway for landing; it taxis to one of the airport's gate areas, where it remains for a selected time; it is assigned a departure runway and time; it taxis to the runway and awaits takeoff clearance; and finally, it is removed the simulation after takeoff.
The taxiway structure is represented as a series of taxiway elements. These include links (pieces of a taxiway), nodes (intersections), and gates (either a single aircraft parking position or an area where more than one aircraft can park without restricting entrance or exit of other aircraft in that area). Taxi paths must designate the sequence of taxiway elements traversed by an aircraft from the arrival runway turnoff to the gate, and from the gate to the departing runway threshold. The model allows delaying gate selection, for example, until the aircraft is in close proximity to the gate area, or deferring departure runway selection until after gate residence time.
The inputs to TAXSIM include the taxiway structure, taxi routing information, runway data, aircraft type characteristics, airline data, and aircraft separations. The outputs provide considerable details on the airport activity and congestion, including: total delay, average delay, and average utilization by taxiway segment; average and maximum delay for the taxiways and for the runways; average utilization, average queues, average delay and maximum delay for both arrivals and departures. FTA has applied TAXSIM to airports around the world, including Schipol (Amsterdam), Munich, and the Second Bangkok International Airport.
Due to the unique nature of each airport, TAXIM must be tailored to the specific requirements of each application. FTA has developed a "toolkit" of modules and techniques which are combined to model the airport elements of interest. The extent of modeling and the amount of data required will depend upon the complexity of the airport and the goals of the study.
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