Do you usually ride on roads when not on tour? If so why are you more worried about safety on tour. I always figured that I was safer on tour than around town at home traffic wise.

BTW just my opinion, but I suspect that folks who are greatly worried are more likely to have accidents despite or maybe even because of taking extra measures. I have found that to be true in other pursuits. If it really worries you or her I'd either try real hard to get over it or else not tour. Bicycle touring is a pretty safe activity IMO, but I wouldn't do it if I was worried the whole time. I'd advise doing some riding on similar roads to what you will tour on and if it bothers you/her much I wouldn't tour until it didn't.