Impaired driving appears to be the cause of a four-car collision on the weekend.

The collision happened around 7:30 p.m. on Sunday near Centennial Parkway and Barton Street East.

A driver was heading north on Centennial Parkway when she failed to stop at a red light, police say. She rear-ended the car in front of her, which caused a chain reaction involving two other vehicles.

The driver, a 28-year-old from Maple, Ont., showed signs of impairment, police say. A breathalyzer test revealed her to be three times the legal limit.

She is charged with impaired driving and having more than 80 milligrams of alcohol in 100 millitres of blood.