Car owners are liable under the Highway Traffic Act for the negligent operation of their vehicles by others. This liability is based on possession of the vehicle. In a recent Ontario case (Fernandes v. Araujo), the owner of an all-terrain vehicle was found liable for the negligent operation of that vehicle on a highway even though the owner expressly prohibited the person from operating the ATV on a highway. The court found that liability flowed from the fact that the person was permitted by the owner to have possession of the vehicle.
Be very careful to whom you lend your vehicle to!