what would a tarp do to help? i'm certain i'm overlooking something, because it's not like cars are generating heat to be reflected by a tarp, unless you mean

what would a tarp do to help? i'm certain i'm overlooking something, because it's not like cars are generating heat to be reflected by a tarp, unless you mean a driven car, thus warm, covered by a tarp, would maintain its heat longer in -50c ?