A motorcyclist has been critically injured in a collision on Highway 401 in Ajax, police say.

It happened on the westbound lanes of the highway at Westney Road.

Ontario Provincial Police Sgt. Kerry Schmidt said a 25-year-old man driving a motorcycle at high rates of speed slammed into the back of an SUV.

The motorcyclist was taken to a trauma centre with life-threatening injuries.

Schmidt said motorists should expect delays in the area for the investigation.

He reminded motorists that highways are not for racing. He said officers saw a group of motorcyclists lane splitting at 254 kilometres per hour.

“So Formula One is tomorrow in Monaco. The 401 is a highway in the GTA, and we currently have motorcycles travelling at high rates of speed,” he said.

“This is not a race track. This is not the way to be using our highways here where everyone is trying to get through to their destinations here safely. You know this kind of behaviour is obviously very dangerous, potentially life-threatening and deadly.”