I'm 5'1" and even though I slide the seat belt anchor all the way down and sit on an extra cushion the belt slides towards my throat as I drive. I think shoulder width and boobs have an effect also, (mine are sort of medium) and of course when I was heavily pregnant that raised other issues (put it across your hips, not your belly! And drive carefully so you don't have to slam the brakes because your bladder is already ready to burst!) but of course manufacturing engineers take the lazy misogynistic way out by pretending women don't exist.

From a quick search, it seems like it's not as simple as getting a harness and using it in my car, I'd have to also get aftermarket seats and possibly further alterations to the vehicle. Not a bad idea, though, and something to keep in mind when I'm ready for a new car.