I love polarized sunglasses for driving. Cutting glare from the road, the rear window of the car in front of you, bodies of water etc is a great thing. Unfortunately, the instrument displays in my Prius are also polarized, and are very hard to read with polarized sunglasses on.
It finally occurred to me that I only need the polarized part for looking out the windshield. The instruments are all below the windshield, so if I made something that was polarized on the top and not the bottom, I’d be able to see it all. Fortunately, I’ve been hacking (and collecting) polarized clip-on sunglasses for years, so the old sunglasses box had a good stash of stuff to begin with. I chose a pair with lenses riveted to a wire bridge that normally clips over the top of a plastic glasses frame. (OK, probably from the 60s.)
Of course they had to be somehow custom fitted to the current glasses frame. I bent the wires so they just clipped over the metal nose bridge of the glasses to hold them on. Spreading the wires so they touched the metal lens frames would keep the sunglasses from sliding from side to side, but offered little resistance to sliding up and down or tilting. By making the tops of the sunglass lenses 1/8″ or so higher than the glasses frame, I had room to epoxy two small scraps of plastic on the tops of those lenses, making a positive vertical stop and providing tilt-resistance to boot. The extra also provided a little additional darkening of the sky above the official field of view. In retrospect, it could have been an even larger overlap.
After the glue dried and they’d been tweaked into their final resting position, I sat in the car with the still-full-size sunglasses on and drew a line with a Sharpie where I wanted the bottom edge of the lenses. I tried to take into account sometimes wanting to tilt my head back if my neck was stiff and being willing to raise my head a little to see the instruments in return for not having an undarkened band above the instrument panel. Then I cut a little below the line.
I tried them out and they delivered just what I wanted: polarized view of the road and unobstructed view of the speedometer and nav screen. (Yeah, yeah, they look kinda strange. Oh well.) I wish I’d thought of this years ago!