From the Ontario government:
Using either a hand-held or hands-free cell phone while driving makes it four times more likely that you will be involved in a collision. In fact, using a cell phone affects what a driver sees, reduces reaction time and changes the way drivers react ”” especially in heavy traffic.
I followed a Bell Canada service van on my way home last night. The driver was a young male in his early twenties. I could see him on his cell phone through his mirror and I could also see the result in his driving: erratic acceleration, weaving, abrupt stops. Although Kingston enjoys little in the way of traffic congestion, this was a busy time of day on one of the major north/south arteries. And sure enough, the driver — clearly distracted by the cell phone — smashed into the car in front. The driver had not noticed that the traffic flow had stopped.
What made the situation interesting was that he kept talking on his cell phone. He stayed on the cell phone as he left his van to make his way to the car that he had just hit. He paused the call only just long enough to see if the other driver was hurt. And then he resumed his call as he made his way back to the van.