I saw a similar thread on Reddit about 12 years ago and one of the suggestions near the bottom that didn’t have any comments on it is something I’ve incorporated into my daily life and it has made a huge difference: Adjust your car mirrors so you have no blind spots.
Most people have their side mirrors adjusted where they can see a portion of their own car in the mirror. This leaves you with large blind spots. To adjust them where you have no blind spots, sit in the driver’s seat and lean your head over to the left as far as you can (basically putting your head on the window), then adjust the driver’s side mirror to where you can just barely see your car in it. Then lean your head over to the passenger side about the same amount and adjust that mirror.
When adjusted properly if you can see a car in your rearview mirror, you shouldn’t be able to see that car in your side mirrors, but as soon as a car is no longer visible in the rearview mirror it should be visible in one of your side mirrors. Then when it is no longer visible in your side mirror it should be in your peripheral vision.
It takes some getting used to, but once dialed in and you’re used to it then it makes changing lanes a breeze. It also helps at night if someone behind you has bright lights because you’ll only see them in one mirror instead of all 3.