Limit Point Analysis—Or, Driving to Stop Safely within the Distance You Can See to Be Clear

About four years ago, I had the pleasure of taking advanced street driving training from Advanced Drivers of North America (ADNA). Until then, I had never heard of one of the mantras of UK driver training, which is “Always drive so you can stop safely within the distance you can see to be clear on your own side of the road.”

It was like a blinding flash of revelation. So simple, yet so true. Why on earth isn’t this a mandatory part of drivers education in the United States? Some driving instructors in America might teach such wisdom to their students (and if you do, congratulate yourself). But if you’re an instructor and don’t, you should add it right away.

To understand this concept more fully, I need to descend briefly into some jargon—limit point analysis, which sounds dreadfully dry and technical, but it’s actually pretty easy. Visualize a road that you travel regularly that has a curve in it. As you enter that curve, what you can see around that curve might be quite limited if it is a sharp bend. Where the roadway disappears from view is your “limit point,” or “vanishing point.” As you continue around the curve, that limit point steadily travels away from you, and as the curve straightens out, the roadway and surrounding landscape opens up and you can see much more.

What you must keep in mind at all times is this question: “If an obstacle were to appear in the roadway or in my lane at any moment, could I safely stop in time without having to swerve outside my lane into the path of an oncoming vehicle, or even on my side of the road into a dangerous car-rolling ditch?” If the answer is no, then you should rethink (or start thinking) about your speed, vision, braking, and acceleration at all points of the curve—entrance, through it, and after it.

The crux of the matter lies in three crucial questions:

1. What can be seen? (A parked car, an oncoming car?)
2. What cannot be seen? (A broken-down vehicle around the corner, animals, or fallen rocks?)
3. What can be reasonably expected to happen? (A vehicle coming around the curve on the wrong side of the road?)

Not surprisingly, you should always expect the unexpected.

This sort of thing is much easier to illustrate through video rather than writing. Here are two excellent ones on the subject: The first one is short, concise video by Steev Stamford, who outlines 3 different types of limit points, including the fact that not all limit points are caused by bends but also by elevation changes (crests) in the roadway. https://www.youtube.com/watch?v=CSSEkhwVap8

The second one is a longer explanation from a motorcyclist’s perspective, courtesy of Roadcraft Nottingham: https://www.youtube.com/watch?v=WkAtWiRq8Q0. This second one goes into excellent detail and more fully explains the dangers of “chasing the limit point” and other hazards. Both of these videos were filmed in Great Britain, where they do drive on the other side of the road, but the basic principles remain the same regardless.

One last detail: Positioning yourself properly (or “presenting yourself”) in your lane is a critical part of limit point analysis. Always position yourself as far to the outside curve edge as safely possible to maximize your limit point distance. Having full headlights on (not just daytime running lamps) also really helps announce your presence that much sooner, especially if others are catching glimpses of you through the trees on double-bend roads.