The importance of taxiing times in the A-CDM Light (Advanced ATC Tower) certification

6 September 2021

The A-CDM & A-CDM Light concept


Airports are very busy places where the various stakeholders have key roles and a common goal: safely and efficiently manage the flow of departing and arriving flights.

With an anticipation of 3 hours, the airport collaborative decision-making (A-CDM) process allows all stakeholders to benefit as soon as possible from the same shared information in order to make informed decisions. Milestones and flight information are updated and shared in order to have precise block departure times (OBT) and take-off times (TOT) for better anticipation of the situation. This information sharing leads to better management of traffic flows at the level of the European Eurocontrol NM network.

Avec une anticipation de 3 heures, le processus de prise de décision collaborative aéroportuaire (A-CDM) permet à toutes les parties prenantes de bénéficier le plus tôt possible du partage des mêmes informations afin de prendre des décisions éclairées. Les jalons et les détails de vol pertinents sont mis à jour et partagés afin d’avoir des heures de départ bloc (OBT) et des heures de décollage (TOT) précises pour une meilleure connaissance de la situation. Ce partage d’informations conduit à une meilleure gestion des flux de trafic au niveau du réseau européen Eurocontrol NM. 

In the light version of A-CDM (A-CDMLight or Advanced ATC Tower), this translates into a need for internal communication from the airport, to partners but also to the network, departure information, includes:

  • A reliable take-off time estimate (TTOT).
  • Reliable departure procedure information (SID) ;

This information sharing leads to better management of traffic flows at the level of the ATFM network.


The importance of taxiing times in the A-CDM Light


The taxiing time and the reliability of the take-off time


Taxi time is the time spent by an aircraft between the runway and the parking lot.

For a departing flight, Taxi-Out Time (EXOT) is the time spent between parking P and the take-off point on runway D.




For an arriving flight, Taxi-In Time (EXIT) is the time spent taxiing from landing point A on the arrival runway to parking P.




In a classic management of the departure flow, for regional airports, the Taxi-Out Time is an important and sometimes very variable part of the take-off time estimate. In fact, on the airport side, a set of operations (cleaning, carrying snacks and lunches, boarding passengers, etc.) must be carried out for an aircraft to be ready for departure. This time when the aircraft is estimated to be ready for departure (TOBT) is associated with the Taxi-Out Time (EXOT) in order to estimate the target take-off time (TTOT).




This clearly illustrates that, in order to provide a reliable take-off time to partners as well as to the network, the estimation of the taxiing time is essential, in addition to the communication of an objective block departure time (TOBT) by airport assistants.


Classic method of estimating the driving time (MTB)


Variable Ride Time (MTB) is a table-based ride time estimation model where multiple inputs are combined to estimate the ride time. Commonly used input variables are:

  • The runway information used by the aircraft;
  • The airplane parking lot;
  • The flow of the plane (departure / arrival);
  • The type of the plane.

This basic model meets the need for most regional airports which have a simple taxiway topology.

It should be noted that this method can be limiting when the number of airplanes on the taxiway increases or when the airport process induces a non-linear behavior on the taxiing time. In this case more advanced algorithms, but requiring increased maintenance, can be deployed.


Simplified monitoring of the accuracy of MTB riding time estimates thanks to AirportKeeper


AirportKeeper allows dynamic construction of MTB tables on the basis of the historical realized rolling time






Once built, the accuracy and relevance of these tables are monitored by the application, and automatically warn platform administrators in the event that the configured accuracy thresholds are not met. AirportKeeper then offers help in updating these tables, in order to facilitate decision-making and guarantee optimal updating of the values, always on the basis of the historical running times achieved.

Thanks to this functionality, AirportKeeper allows a simple and reliable installation of the taxiing time tables. This feature is one of the many aids that make it easier to obtain A-CDM Light (Advanced ATC Tower) certification at airports where AirportKeeper is deployed.