Definition

Precise taxi instructions given to a pilot/crew in stages as the aircraft proceeds along the taxi route.

Use

Progressive taxi instructions are issued on a step-by-step basis and are used:

• When requested by the pilot/crew (e.g. to mitigate increased safety risks by overly long taxi-clearances, complex aerodrome layouts or reduced visibility or due to unfamiliarity with the aerodrome).
• When deemed necessary by the air traffic controller (e.g. due to construction works, closed taxiways, etc.).
• During reduced visibility, especially when the taxi route is not visible from the tower.
• In accordance with local instructions (i.e. if so prescribed by the relevant manual).

Benefits

• Reduced taxi clearance content reduces the chance of overloading pilots working memory potentially leading to confusion, misunderstanding of taxi routing and wrong hear- and readback.
• Reduce the chance of a runway incursion, especially at complex aerodromes or when runway crossings are involved.
• Reduce the chance of an pilots/crews losing situational awareness at night, in reduced visibility, 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

• Progressive taxi instruction must not infer a clearance to cross a runway.
• Progressive taxi instruction might mean an increased workload for the air traffic controller due to the controller diverting a lot of attention to a single flight. The associated risks need to be considered and effectively mitigated.
• "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.
• While providing a clear safety benefit for pilots 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 pilot/crew request for progressive taxi instructions may mean that the pilot/crew is unsure about their position. Therefore, the use of a pilot’s report for confirming their location might not be advisable.