Route planning typically happens when stationary — or if you have passengers, they'll obviously use the systems onboard (or on their personal devices) to do navigation.
But if you're driving alone, and no-one else is navigating for you… you'll have to stop.
the problem isn't that you're doing something with your free hand and sparing some mental capacity--else the manual transmission would be outlawed--it's that if you have a poorly designed car, you have to look away for long enough to lose track of what's happening around you.
good on you for realizing when you can't safely operate your car. but me, i just bought a car i can operate safely.
What makes you believe I think I can't safely operate my car? I don't know what “mirror checks” you mean?
I understand a lot of people don't and this significantly increases the rate of vehicle collisions and other accidents.