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 Motorcycle Safety
 Roadcraft
 POSITIONING
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Nigel A
Male Junior Member
68 Posts


TAUNTON, Somerset
United Kingdom

(None)

Formerly BMW 80RT

Posted - 06/16/2009 :  9:01 AM                       Like
Positioning is a key element in riding or driving safely. You can get away (quite literally) without it but, with it the opportunity for safety, view and stability are greatly enhanced. Positioning is integral with System because there are only two things you can do at any moment to either enhance or degrade safety, that is change position (i.e also direction) snd/or speed. There is, quite literally, nothing else you can do with a moving vehicle.

There is an article (another more or less straight out of the D12 Manual) called Safety, View and Stability, The Keys to Positioning, which anyone is welcome to have by sending a private message to me with their current email address. The more people who have this the more discussions we can have on the subject.

(Deleted or Lost)

Posted - 06/21/2009 :  12:13 PM
I highly recommend that article, which is a little above even the Roadcraft treatment, reflecting the Devon and Cornwall Police Force's high level of commitment to safety in the light of real world experience.
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rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 06/28/2009 :  6:56 AM
quote:
Originally in the SVS article

Now let's look at the average persons ability to judge and adjust speed for bends. Do you think its fairly good or not? Add to that drivers who tend to use the performance of their cars, or lorries (!) and what then? Well obviously the exit area of a bend is one where the danger is potentially greatest. So in ideal circumstances where would you like to position your vehicle now on the approach to a right hander when looking at safety? Yes, you would like to be as far away from it as possible wouldnt you, which means on the nearside




Nigel, in the basic rider course I was taught to enter and exit a turn in a way consistent with the above. I will use a 2 way road for illustration since it has the addition of the center line as a reference point. I am referring to a bend in the US that curves to the left in my use of the term nearside but the references to position relative to the center line would hold true for a curve in either direction. You enter on the nearside (the point furthest away from the bend center line), move towards the crown (center line) while in the bend, and then exit towards the nearside (again, the point furthest away from the bend center line).

I personally formed the opinion that when closest to the center line I would be most at risk. I am having trouble resolving, in my mind, the exit as posing the greatest risk. I hope I have not taken the quote above out of context. If I have please correct me.

Can you clarify why the exit point might be where one is most at risk?

Edited to clarify the curve / bend direction.


Edited by - rayg50 on 06/28/2009 7:27 AM
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James R. Davis
Male Administrator
17282 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 06/28/2009 :  9:06 AM Follow poster on Twitter  Join poster on Facebook as Friend  
There will be a great deal of confusion for people who drive on the right-hand side of the road when they try to understand the logic of Roadcraft positioning.

quote:
Originally in the SVS article
--------------------------------------------------------------------------------
Now let's look at the average persons ability to judge and adjust speed for bends. Do you think its fairly good or not? Add to that drivers who tend to use the performance of their cars, or lorries (!) and what then? Well obviously the exit area of a bend is one where the danger is potentially greatest. So in ideal circumstances where would you like to position your vehicle now on the approach to a right hander when looking at safety? Yes, you would like to be as far away from it as possible wouldnt you, which means on the nearside



This instruction makes no sense to us as it seems to suggest that this is the safest path in a right turn:


That is simply not true. What you mean is that this is the safest path in a left turn:



Discounting the fact that to you right is left and vice versa, what your instruction really means is that the apex of your path should be closest to the where the radius of the turn is shortest. That is true regardless of the direction of the turn.

In other words, in the States, a right turn path should look something like this:



But even if the wording as to direction were to be adjusted for the culture reading it (or changed per my suggestion to make it culture independent), the rationale used in the quote seems rather odd and, frankly, wrong.

I'll agree that if the curve is 'blind', meaning that you cannot see the exit from where you enter it, your greatest danger lies near the end of that curve as it is a complete unknown. But for all curves with fully visible sight lines, the greatest danger, it seems to me, is precisely at the same point as your apex lies - near the center of your path of travel - because that is where the 'other' driver is most likely to be should he have misjudged his speed and wandered beyond the center line.

For that reason, it is imperative from a safety point of view to have a margin of lateral path changing capability when at or approaching the apex. Translating that, I mean that you have the flattest possible path at the apex instead of having a 'fastest' path through a turn.

For illustration purposes, that means in the States a right turn, using a late entry (late apex) path would look like this:



And a late entry (late apex) left turn would look like this:



These late entry turn paths accomplish a sharper turn angle near the beginning of the turn, where visibility is best and have a flatter (smaller) turn angle near their apex so that lateral adjustments can be made if necessary to avoid colliding with a vehicle that has encroached on the center line.
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gymnast
Moderator
4263 Posts
[Mentor]


Meridian, Idaho
USA

Harley-Davidson

Sportster Sport

Posted - 06/28/2009 :  9:49 AM
Note- I am beginning to see a trend whereas the combination of terminology differences and the fact that the US (and virtually all of North and South America) drive on the opposite side of the road, is leading to confusion. Imagine the potential for confusion if the specific diagrams and terminology commonly used in the US were going to the UK unchanged in terms of specificity and vehicle position diagrams. I see two other specific areas where some of the terminology used and concepts upon which Roadcraft are based cause some difficulties as this "exercise proceeds. These differences are not trivial, yet they are at the root of the differences between driving in the UK and driving in the USA.

1. USA traffic laws differ those in the UK and this in turn guides all aspects of driver behavior and interaction. You cannot simply lay the template of one system upon the other and expect a perfect fit. This becomes problematic when giving specific advice without having specific knowledge of "the rules". If and effective information exchange is to take place, those providing advice need to have a high level of knowledge pertaining to the vehicle code and terminology of the other. For information pertaining to the USA, "The Uniform Vehicle Code" and "The Model Traffic Ordinance" are good resources. Note that individual state and municipal codes may differ from the court tested models.

A second major difference that is problematic is the difference in the way the highway systems are engineered. This goes far beyond the differences between the side of the road we drive upon and includes many differences in the type of configurations encountered, the engineering standard right on through the more mundane such as signs signals and markings. A good source of information that guides Civil Engineers in matters pertaining to all physical aspects of the US roadway system is "The Traffic Engineers Handbook".

My comments above are not meant to be argumentative, or qualitative as there are many ways to build, regulate, and use a roadway system. The evolution of a nations roadway systems is a part of the factors that have influenced that nation. It should be noted that different countries or groups of countries have approached the various aspects of engineering, enforcement, and education of user in sometimes significantly different ways.





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rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 06/28/2009 :  12:14 PM
My question may have failed miserably as quite possibly my mental translation of "left" to "right" driving. Listed below is a part of a response to a private email, early this week, where I had described my difficulty and Nigel responded.

quote:


Thanks for your message. Now that I realise that the conversion from driving on the left to driving on the right has been more problematic than I thought it might be, then I can ensure that it is all US orientated in the future ...




I read the articles prior to this exchange. My quote from the article may have been out of context. Mea culpa if that should be the case.

quote:

You enter on the nearside (the point furthest away from the bend center line), move towards the crown (center line) while in the bend, and then exit towards the nearside (again, the point furthest away from the bend center line).



I was trying to describe what the illustration below shows.




And my confusion is based on the above mental picture. To me being near oncoming traffic adds to my risk. However if the article is referencing a turn such as this



Then I would agree the exit point would have the highest risk for me since it would expose me to oncoming traffic that might encroach on my part of the road, which may be the point the SVS article was trying to make.

Sorry for "borrowing" the illustrations. I have no way of creating my own.

Most definitely sorry if I jumbled the turn intended. I will be more careful in the future although I try to be careful now.

Ray

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rioguy
Ex-Member

Posted - 06/28/2009 :  7:34 PM
Unfortunately, I don't have the article, so I can only respond based on what I see here.

It's actually a surprise when I see a curve with good visibility here except on the interstate. I saw precisely one today. I recall it, because it kind of startled me a little. It was a right curve and yes, I did move to the right as depicted in the diagram.

There are two basic rules I follow in curves aside from basic control and tracking rules of thumb.

1. Always be at a speed to where I can stop safely on my side of the road on the road I can see. (This one is from Roadcraft.)

2. Always be at a speed where I can adjust my track anyplace on my side of the road with complete comfort. (Because sooner or later you will have to.)

(Note: These speeds will always be near or below the speed limit for me.)

The problem with diagrams is that what the person imagines when they draw the diagram may be quite different than what the person who sees the diagram imagines. Both are quite different than what is seen on the road as they don't have the pink dotted lines there for us.

So we don't end up disagreeing when we actually agree, take some time to review this video several times. I'm the lead rider. Niebor is the second rider. First critique my track and see if it disagrees with what you imagine when you the diagrams in the previous post.

The second part is more complicated. The road will tell you when it's time to switch tire tracks. At the point where the distance one can see starts to extend, it's safe for someone at the speed limit to both switch tire tracks and to gradually start accelerating as visibility extends. The actual term here is "limit point" according to Roadcraft. That's deserving of another thread, so I won't go into it.

Now for a contrary opinion on the left turn:




If you are the guy following what I imagine to be the suggested path, you will be the one hanging over or close to the centerline when I'm making a right turn coming the other direction. If I see you, no problem, I can duck inside in plenty of time, but that reduces my forward visibility in the turn and I'd be forced to slow a bit to remain safe.

I'd suggest one of two tracks.

1. The one that forks to the right if there is oncoming traffic to maintain separation.

2. The one that forks to the left if the road straightens or there is a right curve coming up.

Now a contrary opinion on the right turn:



Staying in the left tire track until visibility opens up will maintain maximum visibility throughout the curve. As visibility opens up, one can stay in the left tire track if it can clearly be seen there is no oncoming traffic. Or move right if there is oncoming traffic or a subsequent left turn.

In a right turn, it's crucial to maintain visibility of as much of the road as possible for as long as possible. Gravel and football sized rocks are very common here as well as bicycles. When people buy property on a blind curve, they don't hesitate to put a driveway right in the middle of it.

These may not actually be contrary opinions. The video may show exactly what was imagined when the diagrams were drawn.
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rayg50
Male Moderator
2082 Posts
[Mentor]


NYC, NY
USA

Honda

Shadow Spirit 750DC

Posted - 06/28/2009 :  9:39 PM
quote:


... These may not actually be contrary opinions ...




I personally do not see a contrary opinion. I view yours as a reasonable application of the theory I believe those lines represent.

I believe the lines as drawn accurately depict what I have come to believe has been recommended in words on this forum as the better way to negotiate a turn.

If you assume, perfect weather, perfect road, absolutely no chance of "debris" on the road, 360 degree unobstructed view for a mile, perfect bike, perfect tires, no living moving organism other than you within 50 miles, a curve that is perfection, in short, absolutely nothing to hinder you from negotiation the turn however you might choose.

Would you still follow the path you drew or would you seek to follow the path represented by the original line?

I personally would seek to follow the path shown by the original lines. As real life crept in would I adjust the line to better account for it? Possibly to one you have drawn? You bet.

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aidanspa
Male Advanced Member
1739 Posts
[Mentor]


Omaha, NE
USA

Harley-Davidson

Road King

Posted - 06/28/2009 :  10:17 PM
quote:
Originally posted by rioguy

First critique my track and see if it disagrees with what you imagine when you the diagrams in the previous post.

Rioguy - Thanks for the video, very insightful. Your track is not at all what I imagine when thinking of the outside/inside/outside or delayed apex turns described in the previous post. Those turns are designed to enhance stability by having the flattest possible path at the apex.

You track appeared in the video to stay near the center of your lane through the entire curve, with an adjustment to one side or the other at the exit depending on the curve direction. You confirmed that with your drawings. Niebor's track appeared from the camera position to be more in line with the outside/inside/outside line discussed above.

What do you find is the benefit gained from staying in the center track through curves?
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James R. Davis
Male Administrator
17282 Posts
[Mentor]


Houston, TX
USA

Honda

GoldWing 1500

Posted - 06/29/2009 :  6:25 AM Follow poster on Twitter  Join poster on Facebook as Friend  
Here we see yet another concern - oversimplifying a discussion.

My path diagrams were designed to illustrate ONLY the logical concern of left or right turns, and the value of having as flat a curve (minimum lean angle) at the apex to give you the maximum ability to change your path laterally. They IMPLY that you are trying to ride that turn at the fastest speed possible. Clearly that is NOT either the way I advocate riding on public roads or handling curves in general.

The more rational focus of 'positioning' is to provide both best sight lines and best possible buffer space when and where it is most likely to be needed. A different path drawing would be in order for those considerations and you can be sure that they would NOT imply fastest speed possible.
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rioguy
Ex-Member

Posted - 06/29/2009 :  9:04 AM
James,

Thanks for the clarification. I think we agree that nothing we suggest implies riding faster than the legal limits. The idea is to reduce our risk as much as we can for each situation.


Shortly after graduating from BRC, I went back and asked a coach on what lane position I should maintain in the city. He said "It depends on the conditions." The answer was totally unsatisfactory to me at the time. Now my answer to the same question about a curve would be "It depends on the conditions."

The SVC article mentions three considerations.

1. Stability
2. Safety
3. View

I then goes on to say stability is often subservient to the other two.

1. What is stability? Keith Code in one of his videos stated that stability is reduced by accelerating or decelerating. It can also be reduced by turning inputs. A key is not to do them together in a way that can result in loss of control.

But he is focused on racing. We aren't. If I'm in a curve, I'm not afraid to slow SLIGHTLY if my sight line is reduced or I see a decreasing radius turn. This DOES reduce stability, but not in a way likely to cause problems. If more than a slight adjustment is needed, I'll find a line where I can straighten my path, brake and then resume a good path.

There is also nothing wrong with a SLIGHT acceleration in a curve. If my sight line extends, I may accelerate GRADUALLY to either the speed limit or to the point where it stops extending. Always keeping enough room to stop on my side of the road in the distance I can see.

For an example of just how much maneuvering one can do, I made this video. The first 3 minutes has the view from a camera on a tripod and it looks quite tame. The last 3 minutes has the view from the handlebars and appears quite violent. Especially if you watch the horizon. The magnitude of the corrections are greater than would normally be experienced on the roads. The purpose of the video is to give practice avoiding objects in the road in a way that is more abrupt than what will normally be done on the road. This gives the rider confidence to make normal adjustments.

Stability could become the primary factor in situations where traction is reduced. For instance, if I see a patch of snow, I would sacrifice visibility in order adjust my path to take a straight path through it and be able to brake before it. (Snow is still a possibility in the passes.)

2. Safety: By definition, in Roadcraft, safety as it applies to the road in this situation is something that causes an IMMEDIATE threat to safety. For instance, a rock in the road, a car coming the other direction, or a bicyclist. In this case, one must sacrifice some stability or some view in order to avoid the immediate threat. It generally involves a lateral movement in the riders position on the lane. However, it could also include slowing.

3. Visibility: Being able to see a sufficient distance is the part of riding in twisties that usually determines my lane position. Sometimes it demands being totally to the outside of the curve. Sometimes the center track is good enough and is chosen for other considerations. Sometimes I have to sacrifice a lot of it to avoid a threat. In this case, I'll slow if practical.

To say there is ONE perfect track would be incorrect. And nobody has said that. I'm not even sure it would be totally correct to say there is a preferred track. However, one has to start someplace.

My preference is to plan a curve to enter on the outside of the curve as this gives me the greatest forward visibility. Instability which might be caused by adjusting lateral position in my lane is normally not a concern as I ride at the speed limit. An adjustment to any point in the lane should be safe as far as stability is concerned. I then adjust my position as needed for safety and visibility factors.

How does one learn all this?

For newer riders, I'd focus on counter-steering and just making it around the curve. I'd select areas where the speed limits are slow and there is good visibility in curves.

For experienced riders, I'd suggest slowing down while incorporating new concepts. Isolate them and practice one at a time. For instance, one could plan a ride where they maximize their forward visibility at a speed where the other factors won't get out of hand due to some task saturation that always occurs when we practice something new. Then they could ride the same route and practice adjusting lane position in places where it's not normally appropriate. The could also practice a mild form of straightening the bike and slowing just a little bit while remaining in their lane.

Back to the basics on Roadcraft

1. Information - gather as much information about the curve as you can prior to entering the curve.

2. Position - choose a position based on stability, safety and view.

3. Speed - Choose a speed that won't require you to slow in the curve

4. Gear - Ideally, the gear would stay the same throughout the curve. This can be an issue downhill. Select a gear that won't cause one to accelerate while coasting downhill.

5. Acceleration - Limit acceleration (both throttle and brakes) while in the curve. Acceleration may be done gradually as visibility opens up. Acceleration can be a little faster as you straighten up the bike.

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gymnast
Moderator
4263 Posts
[Mentor]


Meridian, Idaho
USA

Harley-Davidson

Sportster Sport

Posted - 06/29/2009 :  9:15 AM
Rioguy, when reviewing your video I see no problems in path, positioning, or pace. I tend to choose a path that provides the greatest separation from potential hazards and this is particularly true when site lines are limited and the roadway shoulders are limited or non existent. While some may avoid the center lane position in curves, when riding in curves, I tend tend to use it "generously" so as to provide as much space cushion and as many maneuver options as possible. On a track, in competition, the chosen path is based on setting up the next corner and minimizing lap times. Track techniques are not necessarily good street techniques and may in fact lead to a path which compromises positioning and separations available for a space cushion.
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