…about where they should position themselves within a lane.
Most traffic lanes are designed to accommodate a single line of vehicles. Motorists rarely have more than a few feet of lateral movement available to them within that single travel lane. It never occurs to them to consider where in the lane they ought to be laterally, their only concern is that they remain within the lane itself.
Many states have codified it into law. Texas demands that a driver “shall drive as nearly as practical entirely within a single lane”.  So with only being required to keep it between the lines, few if any auto drivers have thought about where they ought to be within that lane.
Motorcyclists and bicyclists have broader choices about what it means to travel “entirely within a single lane” than automobile operators. Many common traffic hazards can be avoided with proper lane position for such narrow vehicles. On the other hand, improper lane positions can increase the hazards they are exposed to.
People who only drive automobiles would never think that it would be proper or safe to share any travel lane side-to-side with a truck, with another car or even with a motorcycle. And yet they expect to share the lane side-to-side with bicycles all the time.
SHARING THE LANE
Because our streets, roads and traffic laws are based on the principle that a travel lane is for a single line of vehicles, “sharing the lane” means, in most instances, that you travel behind the vehicle in front of you until it is safe to pass.
To enhance traffic through-put, slow vehicles are required to use the rightmost lane then available. That is, to form a single line of vehicles in the right-most lane. There is no motor vehicle, anywhere, that is required to share a lane side-by-side with another vehicle other than the bicycle.
It is against the law to share a lane side-by-side with a motorcycle.
Singling out bicyclists as a vehicle that must share a lane side-by-side with other traffic was obviously an attempt to make motoring more convenient. But the lane sharing law has exceptions, lest the rule imperil cyclists.
Many conditions exist that make sharing a lane side-by-side dangerous for a cyclist. It is often things like debris, potholes at the side of the lane, parked cars and the like. These sort of things can make what appears to a motorist as a wide lane to actually be narrowed for the cyclist, that is, making it a narrow lane.
The share the lane side-to-side rule cannot be interpreted to compromise a cyclist’s safety.
WHAT IS A NARROW LANE ?
A narrow lane is a lane that is too narrow for a large vehicle and a bicycle to share side-by-side, or two small cars to travel down together side-to-side. A lane that is wide enough to share when the speed of both vehicles is slow may not be safe to share side-by-side at higher speeds.
The slower moving vehicle has the right to refuse to share the lane side-by-side if that driver deems it unsafe. It is always the duty of the faster vehicle to overtake the slower one in a safe manner and with due care. Even if the bicyclist chooses a lane position that encourages overtaking within the same travel lane, it is the passing vehicle that is at fault if the cyclist is hit or is caused to fall.
NARROW LANE POSITIONS
Perhaps you are a motorist, and you are wondering what are some of the considerations that go into why a cyclist chooses the lateral lane position he does. Or perhaps you are thinking of riding a bicycle on the public streets, and this is all new for you. Here are some of the things we are concerned about as cyclists when deciding where to ride in the travel lane. It has been adapted from the Texas Motorcycle Operators Guide.
In some ways the size of a bicycle can work to your advantage. Each traffic lane provides a bicycle with three paths of travel; The right tire track, centered in the lane and the left tire track.
Your lane position should:
• Increase your ability to see and be seen.
• Avoid others’ blind spot.
• Avoid surface hazards.
• Protect your lane from encroachment from other drivers.
• Communicate your intentions.
• Avoid wind blast from other vehicles.
• Provide an escape route.
Select the appropriate position in the lane to maximize your space cushion and to make yourself more easily seen by others on the road. In general, there is no single best position for riders to be seen and to maintain a space cushion around them. No portion of the lane need be avoided–including the center.
Position yourself in the portion of the lane where you are most likely
to be seen and you can maintain a space cushion around you. Change
position as traffic situations change. Ride centered or on the right tire track if vehicles and other potential problems are on your left only. Remain centered or in the left tire track if hazards are on your right only. If vehicles are being operated on both sides of you, the center of the lane is usually your best option.
The greatest potential for conflict between you and other traffic is at
intersections. An intersection can be in the middle of an urban area
or at a driveway on a residential street–anywhere traffic may cross
your path of travel. Cars that turn left in front of you, and cars on side streets that pull into or across your lane, are the biggest dangers.
There are no guarantees that others will see you. Never count on “eye contact” as a sign that a motorist will yield. Too often, they look
right at a cyclist and still fail to “see” him. The only eyes that you can count on are your own. If an automobile can enter your path be ready to avoid them if they do. Good drivers are always “looking for trouble”– not to get into it, but to stay out of it. For bicycle drivers, that means ignoring traffic behind you and concentrating your attention to where the dangers lie- ahead of you.
Increase your chances of being seen at intersections. Ride in a lane position that provides the best view of oncoming traffic. Provide a space cushion around you that permits you to take evasive action.
As you approach the intersection, select a lane position to increase your visibility to motorists. Be where they are scanning for traffic. Select the right-most lane for your destination. If there is a right turn only lane, for example, ride in the center of the right-most through lane. Watch out for oncoming left turners who will be inclined to “shoot the gap” in any traffic in the lane next to you. Cover your brakes to reduce reaction time.
If you approach a blind intersection, move to the portion of the lane that will bring you into another driver’s field of vision at the earliest
possible moment. For example, on a street with curb side parking, move to the left portion of the lane–away from the parked car–so the driver on the cross street can see you as soon as possible. Remember, the key is to see as much as possible and remain visible to others while protecting your space.
Many cyclists ignore these precepts without coming to harm. Which helps illustrate how safe cycling in a prudent and lawful manner really is.
Proper lane positioning will make a trip on a bicycle less stressful and more relaxing. You will be amazed at how courteously you will be treated by motorists when you claim your rightful place on the public road.
 Sec. 545.060.(a) An operator on a roadway divided into two or more clearly marked lanes for traffic shall drive as nearly as practical entirely within a single lane and may not move from the lane unless that movement can be made safely.