Toronto police are investigating a serious collision that left a 54-year-old man with life-threatening injuries after he was struck by a TTC bus in Scarborough on Wednesday night.The incident occurred around 9:35 p.m. near the intersection of Eglinton Avenue and McCowan Road. According to police, the man was waiting near a TTC bus stop on the north sidewalk of Eglinton Avenue when he was hit by the bus.The victim was transported to the hospital, where he remains in critical condition.Traffic Services officers are leading the investigation and are appealing to the public for assistance. Investigators are asking anyone who may have witnessed the collision or who has dashcam or security footage from the area to come forward.