All I can say is to just grit and do it, the confidence will come. I have a particularly nasty mile on my commute where I have to travel on a 45 mph 3 lane highway, in between the right lane (interstate on-ramp/off-ramp combination) and middle lane (straight lane), or more accuratley, in the middle lane. That is no joyride, cars are wizzing by pretty fast, but I did build confidence, it just takes doing it and asserting yourself, they will get the idea..... And if they don't, hopefuly you won't feel anything.