If it's actively raining and you are moving, it seems to clear just fine without a wiper. You still see beads of rain on the glass but it's fine. I was out for a short drive this morning (15 mins, average speed 60-80km/h) and the window had been wet from morning mist, but it was no longer raining. By the time I got back it was still wet but a little clearer. I could still see cars behind me just fine.