We've tried this. It doesn't really keep the pizza hot, it just prevents the pizza box from coming in contact with a cold seat in the winter. Plus, you'd have to have a car that comes with seat warmers in the first place. If you just happen to have an oven with a "warming shelf" or whatever the hell it's called just count on putting the pizzas in there for 10 minutes before digging in. That's all the time you need to give it for that fresh-tasting temperature, and it gives you a chance to get the rest of the meal together, beer, soda "pop", to you some of you heathens , whatever.