Steve A. responded to my first post, and I said I would address his comments. So here goes.
SA) I have mixed feelings about that left tire track lane position. Here's why:#1 - it tends to be smoother at the center of the lane.
CS) I'm jealous! Most of my roads are coated with Chip-Seal. After a good hot summer, the tires wear a much smoother surface. There is a particular type that Ellis county favors that fails to stick to the under-surface if not pressed down firmly by passing traffic. It becomes an extraordinarily rough surface between the tire tracks. When light permits I will take some photos.
SA)#2 - As vehicles tend to pass closer to the cyclist (on average) if one is traveling in the left tire track. This is simply due to the fact that the road is only so wide.
CH) Correct. If the motorist overtakes in the next lane. They are more prone to straddle pass (where they share part of your lane with you) when in the right tire track. Motorists have hours and hours of practical training of keeping their vehicle within a lane. I have more confidence that they will accurately judge their clearance when there is a lane marker between us!
SA)#3 - An overtaking vehicle has less total time to get back into the proper position the further it has to move left to pass.
CS) I am not really concerned about this. It is the duty of the vehicle operator to pass with due care. Besides, how hard is it to pass a bicycle anyway?
SA)#4 - If I look at the Sousa data, passing separation is best when traveling in the right tire track. That's consistent with the observation that one should position oneself so that the overtaking motorist makes a correct move with the minimum need for thought. Moving further to the left doesn't cause any added impact on the automatic motorist response.
CS) First the actual difference in the observed distance between the two lane positions is about four feet, with six to seven feet the closest pass from further out in the lane. (Note, the data is from the right tire track to the center of the lane.) There were no straddle passes observed from the most commanding positions. I am comfortable with that, but then, I was a bicycle racer in my youth. I may have a greater tolerance for objects being in close proximity than other cyclists.
Second, overtaking traffic is not my primary concern. I face much greater peril from what is ahead of me. I have better sight lines from the left side of the lane. I think I am likely to have better success at avoiding right hooks from there as well.
SA)#5 - Riding too far to the left encourages a pass on the right side of the cyclist.
CS) Yes, this behavior caught me by surprise when I first began riding exclusively in the left tire track. It is surprisingly common. I inspire such overtakes about every week. They are most common on state highways when a shoulder is present, but like you I've had a number of them off in the grass as well. One of them was on the road that is pictured on the previous post!
Curiously, they seem to give me more room on that side!
Another common objection I hear about is that such an "aggressive" lane position displays "arrogance" and is designed to annoy motor vehicle operators.
On the roads I commonly travel on, motorists cannot overtake me without encroaching the oncoming lane, so no matter what position in the lane I take, they must wait for a gap to pass me safely.
The fact that a motorist cannot reason this out and gets upset is neither my fault nor my problem. He may pass me or not as he wishes. It remains his duty to pass slower traffic in a safe manner and in due care.