Provincial police are urging drivers to be aware of their surroundings after a deadly day for motorcyclists.

In the last 24 hours, OPP West Region says officers have responded to four motorcycle crashes.

Three have been fatal.

"People, these are not accidents, they're collisions," says Insp. Shawn Johnson in a video posted to Twitter. "They don't happen by accident, they happen as a result of somebody doing or not doing something that jeopardizes somebody else's safety."

One such incident happened in Middlesex County, just east of London, where a rider was struck by a vehicle that crossed the centre line.

That rider was pronounced dead in hospital.

Another serious crash between a van and motorcycle happened in Norfolk County. That driver was airlifted to hospital with "life-altering injuries," the OPP said on Twitter.

"In these collisions, three people have lost their lives," Johnson says. "Imagine that: three families without their loved ones tonight."

Johnson asks drivers to do their part to prevent tragedy on Ontario roads.