One month before the OC Transpo double-decker she was driving slammed into an awning at Westboro station, killing three and injuring many more, Aissatou Diallo was involved in another crash that left five passengers injured.

CBC has learned new details of that earlier incident from internal reports obtained through access to information, including that Diallo claimed to have lost control of her vehicle before it crashed into a parked bus.

That earlier collision happened on Dec. 10, 2018, at St-Laurent station.

According to the incident reports obtained by CBC, Diallo was behind the wheel of an articulated bus making its way up a ramp from St. Laurent Boulevard when she turned left toward the station and apparently lost control. The bus slid and collided with the parked bus. Paramedics and firefighters arrived a short time later.

In one of the reports, Diallo told the investigator that "She wasn't able to [steer] it out of the slide and tried to brake, but the brakes were not responding," according to the report. She had been on duty for seven hours at the time of the collision.

The investigator quoted Diallo as saying the "accident happened real quick." The other driver wrote in his statement that "all I felt was the hard [impact] then another when bus hit the concrete wall."

In her signed account, Diallo wrote that the roads were slippery at the time of the collision, but the investigator and the driver of the parked bus reported dry roads. Environment Canada reported only a trace amount of snow had fallen that day.

The driver of the bus that Diallo crashed into made this drawing of the collision for investigators.It was among the collision reports obtained by CBC News through access to information. (CBC)

Split lip, hurt knees

The other driver was the only occupant of the parked bus, but Diallo had 30 passengers aboard. Five were injured in the collision, including one with a split lip from striking a seat, another woman who hurt her jaw on a seat and others with sore knees or shins from the impact.

Two of those injured passengers were assessed by paramedics, and one was transported to hospital.

Diallo's bus suffered damage to its bumper, windshield and mirror, and the parked bus had broken windows and body damage.

The city initially refused to provide any of the records from the Dec. 10 crash to CBC, which appealed to the Information and Privacy Commissioner of Ontario. In early October, the city provided some of the records.

The records still being withheld include Diallo's detailed notes about the Dec. 10 crash. None of the records obtained by CBC includes any mention of retraining or disciplinary measures taken against Diallo.

'Refesher training'

Earlier this year, CBC obtained data on the 140 OC Transpo collisions resulting in injuries during 2017 and 2018. In most of those crashes the injuries were minor with no one taken to hospital.

When asked for comment, the city said it doesn't discuss labour issues involving specific employees, and declined to say if Diallo underwent retraining or faced discipline.

When collisions occur, the city said it determines whether retraining is necessary on a case by case basis.

"Refresher training generally takes places on a one-to-one ratio with an operator and instructor that includes at minimum four hours of training and a road evaluation by a certified instructor," said Jim Hopkins, the city's chief safety officer, in an email.

"Depending on the results of the investigation, additional communication, coaching, training, as well as disciplinary action may be provided to individual specific operators with the goal of preventing a re-occurrence."

He confirmed the bus involved in the St. Laurent crash had received regular maintenance and inspection.

CBC reached out to Diallo's lawyer, but received no response.

Ten months after the crash, authorities haven't yet said what they believe happened at Westboro station, but some passengers later told CBC they felt the bus slide before it left the Transitway and collided with the shelter.

Diallo has been charged with three counts of dangerous driving causing death and 35 counts of dangerous driving causing bodily harm stemming from the Westboro crash. Her lawyer has appeared on her behalf and Diallo has been deemed to have entered a not guilty plea, but no trial date has been set.