Assuming every vehicle owner follows the law and insures their vehicles, making insurance follow the vehicle instead of the driver ensures that every vehicle that could be driven is insured. It’s also easier to ensure compliance with vehicles being insured than drivers – for example, no insurance, no registration or tags (license plates) – a very visible signal that there’s something not right with a particular vehicle being on the road. But there’s no way to know at a glance if someone driving down the road is insured.
Some countries separate drivers and vehicles and and each obtains insurance separately. Even in the US which mandates insurance on vehicles only, drivers who don’t own cars can still purchase auto insurance that covers their personal liability above whatever the limits of the insurance is on any particular car they may be driving.
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