Limit Point Analysis – The Road is Telling You More Than You Think

Today, I’m going to be talking about an invaluable technique for safe scooter riding called Limit Point Analysis.

I say this technique is invaluable because application of it really can give us a “free” window into the future: What is happening with the road ahead.
It is often telling us things such as how fast we can safely take that corner, or what safe speed should we be doing right now.
It is often telling us how sharp that curve is up ahead, and whether the curve we are on is beginning to get tighter, or straighten out.

All this is available to us – if only we know where to look. Doesn’t that sound interesting? It sure was to me when I first came across it!

So much for the build-up. Let’s now define what the Limit Point is:

Take a look at the image below:
When we are looking down a road such as this, the effect of perspective makes it seem as if the sides of the roads converge and meet at a point in the distance.
The point where this perceived convergence occurs is the Limit Point.

With a straight road, that point is quite a distance away. With a curved road, that point appears to be a lot nearer.
To illustrate, here is an actual example on a road:
You can see that at the point the red line is showing, we can see no further round the bend. This is the Limit Point.

Now, here is the really exciting part about the limit point: The limit point has the potential to tell us exactly how fast we could safely negotiate that bend. It is like a free guide with local knowledge.

Let’s say we are riding along that road on our scooter, and going round that bend – all the time keeping our eye on that point ahead where the road appears to converge to a point.

There are three things that could happen to that limit point. It could:

  1. Get nearer to us.
  2. Stay the same distance from us.
  3. Move away from us.

The movement of that limit point is telling us what is happening with the road ahead – and what we can do, in the following ways:

  • If the limit point is getting nearer to us, the bend is getting sharper. It is decreasing in radius. We need to ease off the throttle.
  • If the limit point is staying the same distance from us, the bend is staying at the same radius. We should maintain the speed we are currently doing.
  • If the limit point is moving away from us, the road is straightening out. We can begin to accelerate.

Here, in a nutshell, is what we need to do when using limit point analysis in negotiating a curve:

Keep that limit point a constant distance from us, and outside of the distance in which we could safely stop.

In practice, what happens is this:

You approach a curve in the road. At this point, the limit point may be coming towards you quite rapidly.
You slow down to the speed indicated by the movement of the limit point as you enter the curve (i.e. you decrease your speed until the limit point is staying at the same distance from you).
As you continue negotiating the curve, you use your throttle to either slow down if the limit point begins to come towards you, or accelerate to “chase” the limit point if it moves away from you.

By simply playing “chase the limit point” like this, the road itself is telling us the speed at which we can safely negotiate the turn… marvellous!

Before I leave you for today, I’d like to mention just another couple of things about Limit Point Analysis:

A curve in the road isn’t the only thing that has an effect on the limit point. A hill, for example, can cause us to take notice of the limit point, and adjust our speed accordingly.
If we were reaching the brow of a hill which dips sharply on the other side, the limit of our view would be severely restricted. In this case, we would slow down to keep the limit point away from us. As we come over the top of the hill, the limit point would rapidly move away. We can then accelerate safely to resume our speed.

And, finally, I hope you have read my post: Positioning – Part 2. In that, I talked about the best position to be in the road when negotiating bends. Well, here’s a bonus for us: If we use good positioning on a bend, the limit point is further away from us!

What does that mean? We can make better, safer and quicker progress through the bend.
Don’t you love those free bonuses? I do.

Until next time, Scoot Safely!

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One thought on “Limit Point Analysis – The Road is Telling You More Than You Think

  1. Have you stopped to wonder why Alan mentions a hill as an important limit point? I didn’t do an IAM course, but I read the UK Police Drivers’ Manual on which it used to be based, and I did a Defensive Driving course during which my instructor pointed out that knowing the road was no justification for driving any faster than a skilled driver who was experiencing it for the first time. He hammered home the point about hills as follows:

    – over the brow, far enough beyond the Limit Point to be hidden by the dip, there could be a stationary obstacle.
    – if you’re very lucky, it will be a haycart
    – more likely, it is a broken down truck
    – if you’re less lucky, it’s the biggest backhoe that can fit on the road
    – if you’re really out of luck, it’s a tractor with a buckrake, facing you.

    Keep that image in mind.

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