I ride on a highway that has a very narrow bridge, no shoulder, no sidewalk. It's just at the growing edge of town, so it's pretty busy for its size. At first, I stayed right once my wide shoulder disappeared. Wrong. Buzzed on a bridge is no fun. Now, I try to time a gap in traffic to take the lane early enough that drivers coming up behind me have time to slow from 100km/h to 30 km/h. Fortunately, it's a short bridge, so I'm often over it before motorists have totally caught up to me. I keep watch in my mirror the whole way, and I'm ready to dive right if it looks like trouble (hasn't happened yet... everyone seems to see me fine).

Note on taking the lane... if you're travelling into the setting/rising sun, you may be very difficult to see. If I'm squinting, I know I may be invisible, so I keep a very close eye on my mirror if I'm travelling into the sun. I also keep a very close watch out for motorists turning left into my path if I have the sun at my back.