Someone was driving my vehicle and the ABS lights came on and suddenly the brakes were barely working. They are a family member but I have a car insurance policy for my car only and they have a car insurance policy for their car only. If they are in an accident in my vehicle, will my car insurance go up? Does this law vary by state? Would it be safer to tow the vehicle in case it gets totaled?
I found this really good article* written by an insurance trial lawyer that I feel can help answer this question.
*The article is US focused, the OP didn't mention their country of origin though "by state" suggests the US.
He goes into detail about how different types of coverage (liability, comprehensive, collision, etc.) "follow" the driver or the vehicle. However, throughout the article he states that exceptions exist and so it is best to refer to your insurance policy.
I think this is a relevant quote (emphasis mine):
So Does Insurance Follow the Car or the Driver?
As we have seen, this is usually not the right question to ask. However, that won’t prevent inquiring minds from asking – over and over. An answer to the question that isn’t going to be universally correct, therefore, is that insurance that follows the car usually has the vehicle listed in the policy. If anyone who has your permission drives the car, that person is probably covered by virtue of the fact that the car is covered. However, as we’ve seen, this kind of insurance does not cover everyone. There are qualifications for the drivers covered. Other types of coverage such as collision or comprehensive insurance will usually follow the car. These coverages will usually not “follow the driver” to any vehicle which the “covered” driver operates.
Clearly the author is stating that in usual cases car insurance covers other drivers as long as the insurance holder gives them permission. This means that should a collision occur and the OP's insurance gets a claim filed against it their rate will most likely go up. However there are always exceptions and conditions.
I do think the author sums up questions such as the OP's well with this statement:
In most cases, therefore, the right question to ask would be “Is there insurance coverage under these specific facts?”
To answer this question the OP really needs to thoroughly review their insurance policy, probably with their agent so that there are no misunderstandings/misinterpretations.
The first two comments by Solar Mike and Weather Vane are mistaken. Insurance follows the car, not the driver (in the USA, that is, I'm not familiar with other countries). You can lend your car to anyone and insurance will cover it as if you were driving in the event of an accident. It is true, however, that if someone like a son or daughter regularly uses your car, some insurance companies expect to be notified and your premium may be increased.
Whoever drives your car, an accident claim will likely increase the cost of your insurance premium. And, yes, laws can vary by state. It is best to call your insurance company and request a written copy of your premium. Read it carefully.