Like others have said...
1. Wear bright clothing. I see so many people with dark clothing on bikes, its a pet peeve. Well... that and a creaky drive train
2. Plan your tour ahead of time, identifying low traffic roads. You may need to go miles off the straight shot route, but so what, the goal of touring is not to win the tour.
3. Be aware of conditions, get a mirror, listen, you see a big truck coming or a house pulling a car (Road Vermin) or cars backing up, consider pulling over to let them pass.
4. Get a very bright rear light that flashes, e.g. hot shot. If caught on busy road switch it on, it makes a difference.
5. On low visibility days, have a front light on that flashes brightly.

We are not the only people that have travelled >150,000 mi over the years on bike and not died or had a major accident.