In order to support the Aerodrome Design Working Group reviewing of ICAO taxiway to object separation standards, a statistical study about ICAO code C taxiway separations was undertaken by the French Civil Aviation Technical Centre (STAC).
The study aimed at assessing risks associated with current code C taxiway separations, using deviation data collected on code E taxiways at Charles-de-Gaulle Airport (LFPG). The study used statistical extreme values analysis to calculate overrunning and aircraft-object collision probabilities, in order to determine associated risk levels.
Results were compared with an FAA/Boeing Cooperative Research and Development Agreement (CRDA) study about ADGIII / ICAO code C taxiway separations, and with an analysis of taxiway excursion reports from 1980 to 2011.
The study showed that the current code C taxiway to object separation is safe, and that for both French and FAA study risk models based on extreme value theory appear conservative compared to accidentology.