In general, any insurance bought after another insurance plan can only cover what is not already insured by the first plan.

Anything else is actually illegal in the UK (it's a tax loophole, because you are paying for insurance (which isn't usually charged sales tax) for a risk that ends up being zero because another insurance policy ends up covering it).

But they could offer a protection plan that is not tied to your personal insurance in any way and relieves you of the burden of getting your insurance company involved at all. That's what car rental LDW plans do.

"We offer the Loss Damage Waiver so you don't have to worry or stress about driving our vehicles. The LDW isn't insurance, but it can protect you from the cost of damage to the Hertz’ car. By purchasing the LDW, you will not be responsible for any loss or damage that occurs to the car so long as you weren't using the car in a prohibited manner."

https://www.hertz.com/rentacar/productservice/index.jsp?targ...

Turo wants you to buy a protection plan from them, but then if there is a loss, the plan you just bought is not available to you until you exhaust all options and financial compensation via your own insurance carrier.

Yeah, this is a good point! I'd rather be protected than not, but it would be far better for Turo to offer primary instead of secondary insurance.