First and foremost, bikes do not travel in a straight lines. The act of balancing a bike is a constant input of steering adjustments to bring the bike back under the rider. These adjustments can be imperceptible, but they are always going on. Your mind and body does it constantly, without thinking about it; in fact, thinking about it makes more difficult.
When you change pace, change handlebar positions, or even turn your head in conversation, you make even more of these subtle steering adjustments, so a straight line becomes a band that is actually 3-6” wide. The need for these micro-adjustments and subtle steering inputs is why I always encourage a rider to be relaxed; the tense rider with locked arms is going to make more handling mistakes.
Another reason that riding the white line is an error is that it becomes your focus point, and your bike will alway follow your eyes. Looking at the white line, and focusing on it and the edge of the road, increases, rather than decreases your chances of riding off the road. If the pavement on the edge of the road and white line begins to break up, inexperienced riders tend to focus on that the broken edge of the pavement, rather than looking at where the wheel should be going.
Riders focused on the white line or road edge are typically looking a much shorter distance ahead, and do not spot road hazards soon enough to smoothly avoid them with small adjustments; rather they are forced to make quick adjustments, and then over-correct, and then over-correct again.
This is compounded when road hazards come up to the left of the white line, because now the riders avoidance options are halved; they may only have the option of hugging the side of road even tighter or riding off the edge.
Finally, a riding position on the extreme edge of the road will actually encourage cars to pass you. This is why safety instructors and advocates have spoken for years about riding the right hand tire track of the traffic lane, to “claim” the lane, and force overtaking cars accept you in the flow of traffic.
Even if you are not comfortable in the right hand track, you should ride in a physical space that gives you adequate maneuvering room on either side of your wheel, at least 12” to 16” from the edge of the road. A good way learn this space is to look down your right arm, and your right hand and brake lever should be inside white line, rather than over it.
By riding farther away from the white line or road edge, you can:
- ride more relaxed and confident, knowing you have good surface on both sides of your wheel.
- look further down the road, and make more gradual adjustments for road hazards.
- claim more of the lane to be a part of traffic.
One further note; it is extremely hazardous when a rider with a white line fixation is in the middle of a pace line. Along with hazards mentioned above, this greatly increases the chance of overlapping wheels, and erratic breaks in the pace. All riders in a paceline should be in the same line, and that line should be well clear of the edge of the road.