Driving at night can be annoying because the range of light intensities is huge. Driving along a dark road you want your eyes adapted to the dark, then along comes a car with bright headlights and you lose your night vision. The rearview mirror also has this issue: it tends to be full of bright headlights, but if you switch it to "night mode" then it is so dark you can't see anything but the headlights. I think something that could darken the brightest stuff while leaving less bright things alone would really help night driving.

One solution I think would be some kind of adaptive windshield tinting. A fast responding photosensitive darkening chemical, sensitive only in one direction, would allow the windshield to limit bright lights aimed at the driver's eyes without much affecting portions of the field of view that were not actually bright. The idea is that at every spot on the windshield there is a direction from which bright light would hit the driver's eyes, so each spot blocks light only when there's excessive light from that single direction. It would look pretty weird from the passenger's seat, but I think the driver is far enough from the windshield that even different driver heights and seat to wheel distances wouldn't make it too innacurate.

I suspect rapidly darkening and lighting in response to varying light levels is possible, but requiring the sensitivity to be only to a specific direction might be impossible or way too expensive.