I did a solo cross-USA ride in 2007, Maryland to Calif. Some roads were rather hairy and frightening. I've also bicycle commuted to my work across various jobs over 30 years, from Philly to San Diego and points in between (not religiously in all weather but probably 30% of the time). I tell folks my most important safety item for bicycling is my rear-view mirror, I don't leave home without it. I don't mean one of those little things attached to the helmet, I mean a nice stable one attached to the handlebars. You may see me on occasion (especially on hot days) bicycling without a helmet, I almost never use my lights, but you'll never see me on a bicycle without a rear view mirror. I've never had to ditch because of what I saw coming at me, but many times I pull farther onto the shoulder or even stop and pause given what I saw coming from behind.

You can see my 2007 X-country day-by-day diary here: https://www.crazyguyonabike.com/doc/?o=1mr&doc_id=2579&v=LL

Yeah same here. Just this week, the CFO of Sports Basement was among a group of riders struck and killed by a box truck driver who was high on meth. They were riding in a group with a support car and it still didn’t help. Just awful.

Provided that you have wide tires, appropriately low gearing on the bike, and no strict schedule, then you can choose unpaved routes across much of the world where you will almost never see other cars. Or, even if there are occasional cars, the terrain would force them to move at so slow a speed they don’t pose a danger.

I would suggest doing it in Europe where many countries have dedicated cycle paths that are separated from the main roads. Much less risky, much more enjoyable.