My favorite parkway in the US (at least for now) is the Baltimore-Washington Parkway. It's a National Park. It's gorgeous during the spring and fall with leafy trees exploding in color. No billboards too.
Spain also prefer no billboards along their highways - at least, the one time I visited. Our tour guide pointed it out. The only billboards were from the Barcelona Olympics, I believe.
>>system+(OP)
When not commuting on metro, I always favored 295 even if traffic was slightly worse. It’s been decades, but I still vividly recall the trees being calming, even with traffic.