If you're injured and immobile, you might not be able to reach under the seat or into the glove compartment for that matter -- my bug out bag is in the trunk, but my Hyundai has a pass-through into the trunk by having the back seats fold down, so if you are mobile enough to reach under the seat you are probably mobile enough crawl into the back seat and get into the trunk, unless you are unconscious of course. If you're pinned in the vehicle, you're just up that proverbial creek, so to speak. Better have that cell phone handy!