This answer is inconsistent with the OP, which should have been worded more clearly if "you" (the original driver) were allowed to stay behind. Instead of saying "You can only take one person", it perhaps should have said the car can only fit two people. A satisfactory puzzle requires a clear statement of conditions.
I think one could disagree with this answer. Just because a shadow is 2-dimensional does not mean it doesn't touch the air. When a shadow appears on a surface, such as a wall or floor, what else could it touch except that surface and the air? This presumes one is talking about a shadow defined as a shape/image, just as a painting is an image. Does a painting not touch the air? Can one not touch a shadow?