I'm all for acceptable public transportation to be the norm, but until then cars work fine. Roads also weren't originally built for bikes. I actually don't know how many of the bigger cities look now, and I imagine most of them have bike lanes, but places like where I live have bikers just taking the right lane because there's no extra space. There also isn't enough space to expand the road to make room for both of us. Ultimately they're a huge hazard because they're difficult to see and hear. I really don't think they should ever mix cars and bikes. Or at least not in high capacity areas. Also you're desire to exercise is completely your own, I'm glad you enjoy it, but it's a personal choice.