I'd say it depends on what kind of person your wife is. My longtime girlfriend got a little anxious about my commuting, especially when I used to have to bike in the dark. I also did a lot of training rides at night because I lived in the south and after dark the weather would be perfect
But, have since moved to an urban center and she now bikes to school daily. I got her hooked on riding casually and now that we live in a city she bikes to school every day. She's on her bike more often than I am! Shorter rides, but she pushes me to do more. She's a really logic based girl so I used the facts of biking safety vs. driving safety and she got on board. Also, we're really into preserving our health so we can be old and wrinkly together--lay that on your wife. "Honey, it's really about my health. I want to make my daily life a workout so that I can be sure to live as long as possible so that we can grow old together!"
My biggest tip, don't share your dramatized close call stories with her, even if she is the first person you see when you get off your bike right after that ride. Save it for your biking buddies over a few beers.
