The Transportation Safety Board said procedures and runway layout contributed to a “troubling pattern” of runway incursion at Toronto’s Pearson International Airport, risking the lives of travellers at Canada’s busiest airport.

“Why does this keep happening?” asked TSB Chair Kathy Fox. To get at the answer, the TSB conducted a special investigation into repeated incidents at Pearson.

An incursion happens when an aircraft or vehicle mistakenly ends up on an active runway. There were more than 450 incursions in Canada last year, most at smaller airports, where student pilots make mistakes. But that was not the case in Toronto Pearson, which is only open to professional pilots.

The TSB focused on a complex set of parallel runways at the south end of the airport, 06L/24R and 06R/24L, and found 27 incursions between 2012 and 2017.

“Pearson International airport traffic is tightly controlled and monitored, and all 27 incursions examined involved flight crews who understood they needed to stop, and that they were approaching an active runway,” said Fox. “Despite all the visual cues, including lights, signage and paint markings, professional crews were not stopping in time as required, thereby risking a collision with another aircraft on the other runway.”

The TSB found issues large and small. Among them:

• Warning lights not oriented the right way or not bright enough to catch a pilot’s attention
• Pilots were distracted as they performed other tasks as they approached the adjacent runway
• Stop lines that were farther from the runway than was the case at other major airports, so pilots weren’t expecting them
• Controllers unable to get pilots’ attention when they were mistakenly entering the adjacent runway

The TSB said the incursions happened even to experienced pilots who were aware of the risk. In many cases, the incidents involved pilots flying for regional airlines based in the United States, who were less familiar with the particular layout at Pearson. It sent a letter last year warning of the danger, which helped reduce the number of incursions in 2018.

A recent investigation by Western Aviation News found at least 24 significant incursions in Toronto over the last two years that could have led to a collision, many at the parallel runways, including one incident in 2017 where a passenger jet passed just overhead a plane that had stopped on the runway. If the departing plane had been much larger or heavier, it likely would not have been airborne in time to avoid a calamity.

The map below shows where significant runway incursions happened in Toronto in 2017 and 2018, based on data supplied by NAV CANADA. The points in orange represent incursions in 2017, and the points in blue are incursions in 2018. Click on each marker to read details of what happened.

The TSB recommended four changes to improve the situation:

• Controllers use clearer language to warn pilots
• Regulators and airlines amend their standard operating procedures to have pilots complete checklists only once they’re clear of all active runways so they can focus their attention outside the aircraft
• The GTAA make physical changes to the taxiway layout to reduce the risk of incursion, by changing taxiway design or building new exit routes

Fox noted that Pearson was the only major airport in North America to have the space, but not have a parallel taxiway between the active runways to reduce the risk.

“Ultimately it’s up to the GTAA to decide what physical changes are made,” said Fox. Until then, she said changing procedures would have to suffice.

The GTAA said in a statement it welcomed the findings, but did not commit to making any changes to the airport’s layout.

“In addition to specific enhancements to our runways and taxiways, new lighting systems, and mandatory LED backlit signage,” the authority said in a statement, “we have also provided up-to-date safety information and educational outreach to these carriers about our operations.”

Fox said she was hopeful the GTAA would take the time to evaluate the recommendations and come to a decision, although it is not required to respond, unlike federal regulators.

The TSB stopped short of recommending runway status lights be installed at Pearson. RWSL act as an automated warning system to pilots and shine red when there is a risk of conflict.

“That’s certainly an option,” said Fox. But since the TSB had already issued an advisory on status lights, the TSB did not feel the need to reiterate the point in this case.

The Federal Aviation Administration in the United States has been far more aggressive in its approach to runway incursions since 2017.

Runway status lights have been successfully installed at 20 of the busiest airports in the United States, including Orlando, Los Angeles and Dallas-Ft. Worth. Each system cost $7 million or more, which was paid by the FAA.

“Fixing these complex issues won’t be easy, which means all those involved must work together,” said Fox. “Because clearly, more needs to be done—so that all flight crews see the cues and react as required.”

WATCH: The French Department of Transportation explains how runway status lights work at Paris-Charles de Gaulle (in English).