Precise taxi instructions given to a pilot unfamiliar with the airport or issued in stages as the aircraft proceeds along the taxi route.
Progressive taxi instructions are issued on a step-by-step basis and are used:
When requested by the pilot (e.g. due to unfamiliarity with the aerodrome).
When deemed necessary by the air traffic controller (e.g. due to construction works, closed taxiways, etc.).
In accordance with local instructions (e.g. during reduced visibility if so prescribed by the relevant manual).
Reduce the chance of a runway incursion, especially at complex aerodromes or when runway crossings are involved.
Reduce the chance of an aircraft getting lost at complex or unfamiliar aerodromes.
Reduce the chance of an aircraft being at a wrong place (e.g. wrong taxiway intersection, ILS sensitive area, getting stuck and needing pushback, etc.).
Issues and considerations
Increased workload for the air traffic controller. Giving progressive taxi instructions means that the controller should divert a lot of attention to a single flight.
"Tunnel Vision" – it is possible that the controller gets so preoccupied with one aircraft that they may neglect other situations and have their situational awareness reduced.
Increased frequency occupancy. Breaking the taxi clearance into several parts means several calls and readbacks, which may result in a frequency congestion (i.e. several stations that need to or try to transmit at the same time). This, in turn, easily leads to frequency blocking, need for repetition and further increase of the occupancy.
Overuse of progressive taxi instructions may lead to reduced efficiency of the traffic flow due to the increased controller workload, frequency occupancy and possibility for aircraft holding for further taxi instructions at an intermediate position.
A request for progressive taxi instructions may mean that the pilot is unsure about their position. Therefore, the use of a pilot’s report for confirming their location is not advisable.