I've been doing some research on "inattentive blindness". This phenomena has only recently been more heavily researched by psychologists, but it has important implications for cyclists.
The long and short of it is this: people may not see what is directly in their field of vision. That means you! Pretty scary stuff, huh?
It has long been my belief that riding on a shoulder is more dangerous than riding in traffic. I have held that with many distractions to the driver already present, they simply do not pay attention to anything on the shoulder of the road. It's as if their mind decides that only what is in "my lane" is important, and that only relates to the space between the white line on the right and the yellow line on the left. Anything on the other side of those lines only becomes important when it crosses that perceptual barrier.
At intersections, which are perhaps the most dangerous place to cycle, I always take the full lane. In fact, I take the lane about a block away from the intersection and I ride in line with the drivers' heads, that is, near the center line. I believe that drivers wanting to turn right on red, or who are anxiously waiting for their light to turn green will be looking at that exact spot, so that they can see the eyes of the driver of another vehicle. I want them to see my eyes, and therefore, me. In fact, I usually don't wear dark glasses if I'm only riding in town so that they really can see my eyes.
We have been successful in having legislation passed which requires drivers to give us 3 feet of space when they pass us. (Now if we could only be successful in having it enforced.) However, if I ride on the shoulder, then in many cases, I encourage drivers to ignore the rule. If the shoulder is only 3 feet wide or less, I am mathematically unable to get that 3 feet of space between my left shoulder and their right fender IF they continue on a straight path without moving over. And THEY WON'T MOVE OVER BECAUSE THEY DON'T HAVE TO; YOU ARE NOT ON THE ROAD! The law becomes moot. And when they hit you they will say they didn't see you, and that will be that.
Similarly, if you hug the white line, allowing them to squeeze by without moving, you create the same situation. It seems counter intuitive, but the safest place would be directly in front of them, in line with other drivers. Since that would not be legal in most cases, and would stir up a hornet's nest of ire from drivers everywhere, we have to take the next best place.
Use the rule of thirds. Mentally divide the lane into three sections. On most occasions, ride within the third that is on the right side of the lane, without hugging the white line. Try to stay far enough to your left to force drivers wanting to pass you to move over a little. Obviously, on a very wide road, you will not be able to do that, nor would you want to. You will have to trust your guardian angel on those roads.
Look ahead. If there is debris, a poor road surface likely to cause you to crash, or a narrow roadway with no room to share, move over to the middle third. Ride as quickly as you are able, then move back as soon as possible. Use hand signals to indicate your movements. Ignore honking.
Finally, at intersections, or when making a left turn, use the left third of the road. Remember, if you are stopped for a left turn, cars behind you may not perceive you as well. Track standing may not be your best option. Keep your left arm out and add some movement to help their ability to notice you. Most of you will not have a blinking signal on the rear of your bike, especially in the daylight, so stay alert and turn as quickly as it is safe to do so.
Being seen is your responsibility. That's important enough to repeat it. Being seen is your responsiblility. One of our members refers to my bike as a "freakin' Pee Wee Herman bike" because of all the lights, reflective tape, etc. So what? In town, I wear a reflective vest and reflective ankle bands and on the open road I wear a hi-viz/reflective Sam Browne sash, with a hi-viz/reflective triangle along with reflective ankle bands. (For added protection, I've added a blinky to the triangle.) I have a light mounted on my helmet and two on my bike for night riding. Yeah, I look like a dork. I hope that's what every driver who sees me thinks. And I hope every driver sees me. And you, too.