Air transportation safety recommendation A18-07

 Recommendation A18-07 in PDF [147 KB]

Taxiway design and conspicuity

Background

Air transportation safety issue Investigation A17O0038 examined 27 runway incursions that occurred between June 2012 and November 2017 at 2 closely spaced parallel runways known as the “south complex” at Toronto/Lester B. Pearson International Airport (CYYZ), Ontario. The 27 cases studied were not the only incursions at CYYZ during that period. However, their number and similarity raised concern and led the TSB to examine them more closely as a group, in order to determine their systemic underlying causes and contributing factors and to assess the degree of ongoing risk.

All of the incursions occurred on the inner runway (Runway 06L/24R) after the flight crews involved had landed on the outer runway (Runway 06R/24L), had been instructed by air traffic control (ATC) to hold short of Runway 06L/24R, and, despite intending to stop, had missed the visual cues depicting the runway holding positions.

The taxiway layout between the runways has several characteristics that are uncommon compared to those at other airports, both within North America and internationally. The runways are spaced a relatively short distance (305 m [1000 feet]) apart, and the rapid exit taxiways (RETs) provide direct access to the adjacent runway without first progressing to another transitional surface. The runway holding positions are located immediately following a 65° curve and are situated at greater distances from the protected inner runway than they are at other airports.

Regional airlines that are based in the United States and that operate regional jets were involved in a disproportionate number of the incursions, both in total and in terms of the rate of incursions per landing. This was likely due to foreign flight crews being unfamiliar with the uncommon taxiway layout between the parallel runways at CYYZ and to the increased speed at which their smaller aircraft types often approached the runway holding positions.

It is for these reasons that some foreign flight crews did not anticipate the location of the stopping position on each RET and so did not direct their attention outside the aircraft at the required time to identify the visual cues indicating the runway holding positions.

Most of the flight crews were aware of the south complex areas at increased risk for runway incursions because they are designated as “hot spots” on the airport charts supplied to crews. However, that guidance, together with limitations in operators’ requirements for taxi briefings, did not bring crews’ attention to specific strategies to mitigate the risk of incursion. Instead, the crews followed their usual routines after exiting the landing runway and proceeded with their post-landing checks. The timing of those tasks distracted them at a point when limited time was available to recognize the visual cues requiring them to stop, and contributed to their overlooking those cues.

In the occurrences examined in this study, ATC recognized the incursions quickly and took appropriate actions that either caused the incurring aircraft to stop or reduced the severity of the consequences. As a result, most of the aircraft did not reach the inner runway surface. Of the 3 that did reach the surface, 2 were at an intersection beyond the point at which the departing aircraft presented a risk of collision. In the 3rd case, ATC cancelled the takeoff clearance for the departing aircraft before it began its take-off roll.

In another occurrence, ATC instructed the incurring aircraft to stop before it had reached the runway surface, then immediately told the departing aircraft to abort its takeoff. The crew of the departing flight did not recognize the instruction to abort because the phraseology was unfamiliar and because it was not repeated as they were used to; as a result, they continued their departure. The incurring aircraft stopped before reaching the runway surface, and the departing aircraft overflew the intersection without further event.

International guidance for the prevention of runway incursions recommends that, once areas presenting a hazard of incursion have been identified, strategies to manage or mitigate that risk should be implemented and should include awareness campaigns, additional visual aids, alternate routings, or, ultimately, the construction of new taxiways.

Various awareness campaigns and advisories have been issued since 2012, and visual aids have undergone progressive but significant improvements. Those strategies have likely resulted in periodic, but not permanent, reductions in the incidence of incursions.

Revising the post-landing procedures of flight crews may lead to increased vigilance and reduced distraction, but it is unlikely to eliminate crews’ expectations that visual cues will be situated in common locations or induce crews to reduce their taxiing speeds so that they have more time to recognize the cues.

All but one of the applicable strategies recommended by international guidance have been implemented on the south complex; the remaining strategy is to make physical changes to the taxiway layout. A change of this scale may be required to increase the distance and taxiing time between runway holding positions, reduce the taxiing speeds of aircraft approaching hold-short locations, and prevent direct access to adjacent runways from RETs. Among the possible reconfigurations for achieving these objectives is the addition of an intermediate taxiway between the runways and parallel to them, as found at numerous airports with parallel runways, and the re-situating of visual cues in common locations.

The Board concluded its investigation and released report A17O0038 on 31 January 2019.

TSB Recommendation A18-07 (January 2019)

The taxiway layout between the closely spaced parallel runways at Toronto/Lester B. Pearson International Airport (CYYZ) has several characteristics that are uncommon when compared with those at other airports, both within North America and globally. The runways are spaced a relatively short distance apart, and the rapid exit taxiways provide direct access to the adjacent runway without first progressing to another transitional surface. The runway holding positions are located immediately following a 65° curve and are situated at greater distances from the protected inner runway than is seen elsewhere.

These uncommon characteristics, and the short distance between the runways, present significant challenges for flight crews. When exiting the landing runway, crews are normally occupied with other tasks and, because they are using a rapid exit taxiway, the aircraft is usually travelling at taxi speeds that are faster than typical. A flight crew's unfamiliarity with these uncommon characteristics, the short amount of time and distance available, and distraction due to other tasks reduces their ability to identify the runway holding positions. As demonstrated by the occurrences covered in this investigation, if these positions are not identified, aircraft can incur on the other active runway and potentially collide with another aircraft.

International guidance recommends many strategies to address runway incursions. All but one of these have been implemented on the south complex at CYYZ; the remaining strategy is to make physical changes to the taxiway layout.

A change of this scale may be required to increase the distance and taxiing time between runway holding positions, to reduce the taxiing speeds of aircraft approaching the hold-short line, to prevent direct access to adjacent runways from rapid exit taxiways, and to re-situate visual cues in common locations. Among the possible reconfigurations that may address these factors is the inclusion of an intermediate parallel taxiway between the runways, as found at numerous other airports with parallel runways.

It is recognized, however, that a change this significant cannot be made overnight, and simpler incursion mitigation strategies may need to be implemented, or current strategies improved, in the meantime. Although much has been done over the past few years to improve the conspicuity of the runway holding positions, options still remain, such as altering the type, amount, or intensity of the runway holding position lighting, which may further improve the likelihood that flight crews identify the cues and stop before incurring on the runway.

Therefore, the Board recommended that

the Greater Toronto Airports Authority make physical changes to the taxiway layout to address the risk of incursions between the parallel runways and, until these changes can be made, make further improvements to increase the conspicuity of the runway holding positions.

TSB Recommendation A18-07

The Greater Toronto Airports Authority’s response to Recommendation A18-07 (August 2019)

The GTAA has carefully considered the TSB’s Report and is working diligently to assess solutions to address the TSB’s recommendation. The GTAA has identified several design concepts for field test in the Fall 2019, including a significant enhancement to the lighting, runway/taxiway hold position markings, and painted information markings located on the high-speed runway exits to increase the conspicuity of the hold positions. The objective of the test in the Fall 2019 is to finalize the design concept for an operational trial in 2020, and full installation during planned runway rehabilitation activities in 2021. We are also reviewing and analyzing longer-term design solutions.

The design concepts and field testing have been developed in full consultation with Toronto Pearson’s Local Runway Safety Team (LRST). The LRST is a multi-stakeholder group that includes airline representatives, the TSB experts, Transport Canada, pilots and airline pilot associations (e.g. ALPA, IFALPA), Nav Canada, and the Canadian Business Aviation Association. It is the GTAA’s view that the LRST represents the most appropriate forum to address the TSB’s recommendation, as it is capable of dynamic and iterative evaluation of options.

The GTAA considers this ongoing work relating to design and concept testing and that of the LRST to be meaningful progress in addressing the TSB’s recommendation to the GTAA.

TSB assessment of the Greater Toronto Airports Authority’s response to Recommendation A18-07 (March 2020)

The Board is encouraged that the Greater Toronto Airports Authority is reviewing and analyzing longer-term design solutions to address the deficiencies identified in the report, and the resultant recommendation to make physical changes to the layout.

As well, from observing the consultations in collaboration with the local runway safety team, the TSB acknowledges that progress is being made towards making further improvements to increase the conspicuity in the area of the runway holding positions, including the recent addition of RWY AHEAD painted markings, which were installed in November 2019.

While this progress is notable, until these improvements are completely implemented as planned in 2021, and until longer-term physical design solutions are analyzed and adopted, the risk of runway incursions on the south complex will remain.

Therefore, the Board considers the response to Recommendation A18-07 to be Satisfactory in Part.

Next TSB action

The TSB will continue to monitor the progress of the conspicuity improvements, and await further information regarding analysis of the longer-term plans. The TSB will reassess the deficiency on an annual basis or when otherwise warranted.

This deficiency file is Active.

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