Tell him, Peter!
Tell me what? This?:
http://www.mctourguide.com/lane-positioning/Lane Position 1
All things being equal, lane position 1 would be the default lane position on a two lane road. The rider is able to scan further ahead and behind to determine hazards. Drivers ahead and behind have the rider in the primary rear view mirror and in full frontal view respectively. Most importantly, oncoming traffic can see the rider far sooner than if the rider is hidden by a car in front. Something else I personally feel is that there is more “room to run” than anywhere else on the road. There is more pavement left and right of the rider to use to avoid hazards. To put these considerations to the test, watch as you drive or ride, for a rider who has chosen lane position 3 behind a car or some vehicle large enough to hide the bike (there are unfortunately plenty out there). The rider only becomes visible at the last instant as the car in front passes you. For that rider, it is not unusual for a driver coming the other way, itching to pass the car in front, to move out into the oncoming lane only to see there is a bike right where they thought there was nothing. Bad news for the bike.
To sum up, as a general rule lane position 1 gives you the highest conspicuity, highest visibilty and the most dominance of any other position on the roadway. As a single rider, you are in the best position for a left turn, however must move to lane position 3 for the best position for a right turn. Lane Position 2
The center of the road is often described by some as “the grease strip” and that it should be avoided at all times. Except for very particular circumstances, this is not true. Unfortunately the statement malignes what can be the safest place to be. Certainly at or near intersections the roadway can be covered in oil dripping from countless cars waiting at red lights. On the open road and less busy city streets clear of intersections, this is not the case. This means a rider must survey his or her situation if considering riding in lane position 2. The advantages of lane position 2? You are farther away from oncoming traffic and the curb. It is a decent place to be when rounding a blind curve or approaching a blind hill, allowing fair visibility and conspicuity at the same time and at the same time allowing “room to run” if things change on either side (i.e. driver over the line or car parked on the side of the road). Disadvantages? You are hidden by cars ahead from on-coming traffic to some degree, there is sometimes more debris in the center of the road, you are not in the primary mirror of the driver in front and perhaps less visible to following drivers. To make safer left and right turns you must move to positions 1 and 3 respectively.
Lane Position 3
This position is usually the least desireable position for normal riding because of poor visibility, conspicuity and dominance. You are close to the curb or parked cars and there is usually a lot of debris (read: gravel or sand) in that position if there is a curb. It is a very good place to be in blind corners and approaching blind hills, although it must be kept in mind that there can also be hidden hazards on the curb side once rounding the corner or cresting the hill. It is the best position to make a right turn, claiming the lane as your own prior to the turn (bicycles and even cars will tend to deek in between you and the curb if they think they can). It is often suggested to move over to lane position 3 when being approached by a large truck, bus or other that may produce a significant wind blast. Something to consider is that if the wind blast is that strong that it may disturb the bike, being in lane position 3 only places you about four feet further away (negligeable reduction in wind blast) but also four feet closer to the curb. If the wind blast is that bad, I personally don’t like being too close to the side of the road. Thankfully, unless there is a severe cross wind, it is not usually all that bad and in all cases, easy to manage using counter steering. Junk falling off a truck is more of an issue and again, lane position 3 leaves you very little “room to run”.
Keeping in mind I've already given the answer "where you can best see and be seen", but the above clearly states my point. Thanks for the brash remarks to some. Some of you that disagree with the above have been in many accidents. I wonder if it's starting to make sense now?