A pedestrian was taken to hospital after being struck by a transport truck at Dundas Street and Adelaide Street Monday morning.
London police say the 20-year-old man was riding a skateboard westbound on Dundas just before 10 a.m. when he collided with a southbound truck.
He was sent to hospital with life-threatening injuries and remains there in critical condition.
The intersection was closed in all directions for much of the day while police investigated the collision.
Also on Monday morning, a man and two young children were taken to hospital after being struck by a van in east London.
Emergency crews were called in around 8:30 a.m. after a man crossing Dundas at First Street with a baby and young boy was struck by a white van turning left onto Dundas.
Witnesses say the driver of the van was visibly upset after the collision.
A City of London lifeguard and members of a paving crew in the area comforted the children and provided first aid to the man until paramedics arrived.
All three suffered non-life threatening injuries.
The driver of the van has since been charged with careless driving.