I suspect if they looked at attached garages and their toll when cars are left running the incident will be higher. How many people have died because of attached garages? Folks can help mitigate this by having carbon monoxide detectors in their garage and in the house. Car manufactures tho should have this built in, if the car is not running and the CO level inside get's too high, shut it off and sound the car alarm. The only challenge is that CO sensors seems to need replacing more than the life of the car and of course the price of car will go up and those without the need will be upset.
I wonder how many people died because they locked their keys in a running vehicle in the garage, called a locksmith, but didn’t think about CO entering the house while they waited.
At the rate of 2 per 100’s of millions of people per year, these scenarios become plausible.
