Road positioning in bends
Discussion
Please excuse my weak art efforts to describe what I am talking about. This is only a rough sketch & says more about my artistic limitations on the PC than anything else I fear.
If you look at the picture & assume no sufficient lateral vision.
To take a path that leads you to the middle of the road mid bend (red line) you have to come off the nearside line prior to having full vision of both sides of the road (before you can be sure that there isn't anything heading towards that could meet you in that position). ie you are heading towards potential conflict as one should assume that anyone towards would be positioned towards the crown mid bend. If you held the nearside line (green line) until you could see both sides of the road (at point X), by the time any smooth steering would take reasonable effect you'd be through the bend anyway & would be coming away from the n/s line effectively after exiting the bend. If you have fantastic lateral vision, (can see the whole road surface) you could take the the full apex (blue line).
If you look at the picture & assume no sufficient lateral vision.
To take a path that leads you to the middle of the road mid bend (red line) you have to come off the nearside line prior to having full vision of both sides of the road (before you can be sure that there isn't anything heading towards that could meet you in that position). ie you are heading towards potential conflict as one should assume that anyone towards would be positioned towards the crown mid bend. If you held the nearside line (green line) until you could see both sides of the road (at point X), by the time any smooth steering would take reasonable effect you'd be through the bend anyway & would be coming away from the n/s line effectively after exiting the bend. If you have fantastic lateral vision, (can see the whole road surface) you could take the the full apex (blue line).
Edited by vonhosen on Sunday 6th August 13:00
Good drawing - I would take the red line every time - and if you draw a line from the point you want to see and put a x on the red line you be at a better angle to see the entire corner and you would sooner from your starting position plus you would be at less of a lateral force - and need less perifiral vision - this drawing only further goes to prove the point that hanging around the out side is not worth it and a danger in it's self!
townrow said:
Good drawing - I would take the red line every time - and if you draw a line from the point you want to see and put a x on the red line you be at a better angle to see the entire corner and you would sooner from your starting position plus you would be at less of a lateral force - and need less perifiral vision - this drawing only further goes to prove the point that hanging around the out side is not worth it and a danger in it's self!
If we look at the limit of your vision (pale blue line), by taking the red line path you are starting to move towards a potential area of conflict, with the as yet unseen vehicle towards, by coming off the wide line before you had vision of both sides of the road. Despite it being on it's own side of the road you are reducing the safety margin significantly. If you hold the green line until you can see both sides of the road (at point X) you are maximising the safety margin.
Move time on & I would rather be in the position of the pink car (on green line) than the blue car (on the red line), maximising my safety margin.
Edited by vonhosen on Sunday 6th August 16:57
Do the outer lines on those diagrams represent the entire carriageway VH? If so, I think the examples you show don't really represent the common sensible choices. I'd only use both sides of the road when I had complete visibility and was in a hurry. The decision I'd be making in normal driving is where to position myself within my part of the carriageway.
GreenV8S said:
Do the outer lines on those diagrams represent the entire carriageway VH? If so, I think the examples you show don't really represent the common sensible choices. I'd only use both sides of the road when I had complete visibility and was in a hurry. The decision I'd be making in normal driving is where to position myself within my part of the carriageway.
They are the entire carriageway.
On road the full apex will make very little difference to speed/time over the green line. The full apex is more about balance (less cornering forces) & smoothness than increased speed.
As I said the artwork, ergo accuracy of the lines is not going to be of a high standard. It is more about illustrating the point that you shouldn't be making a decision to head towards an area that has a higher degree of potential conflict before you have the vision to say that there is none.
My advice is stay on the wide (green) line until you can see all of the road on the exit side clearly.
The full apex (blue line) should only be taken where you have complete view of the road on exit side, for a very good distance, prior to arrival at the bend. Any doubt over that hold the wide line. I tell candidates if they couldn't see a snake on a roller skate (let alone a Lotus Elise) coming the other way, they shouldn't be coming off the line.
Of course you have to weigh in many factors, such as nearside junction/depth of vision into it & n/s road surface quality, before deciding on line of approach. Generally though the more n/s position I have to sacrifice on approach (with no lateral vision) the more speed I am also going to sacrifice.
Edited by vonhosen on Sunday 6th August 17:49
townrow said:
Good drawing - I would take the red line every time - and if you draw a line from the point you want to see and put a x on the red line you be at a better angle to see the entire corner and you would sooner from your starting position plus you would be at less of a lateral force - and need less perifiral vision - this drawing only further goes to prove the point that hanging around the out side is not worth it and a danger in it's self!
The wider position provides earlier vision than the shallow line (where you have no lateral vision) & from a safer position as shown in previous diagrams with the potential oncomer.
Edited by vonhosen on Sunday 6th August 21:32
I've just completed a performance road driving day with Drivetrain and I was taught exactly what vonhosen is stating here. On a right hand bend keep to the outside (green) line (where safe to do so), I kept getting my knuckles rapped by John (the instructor) when I took the racing (red) line, like I was used to.
Edited by daz9100 on Sunday 6th August 21:17
Good helpful illustrations from Von - all as taught to me by John Lyon and documented in his 'Porsche Driving Book'. This point is not really covered by Roadcraft (P 120 only deals with the nearside position at the entry to the bend) and slightly better by the IAM Pass Your Advanced Driving Test.
John's book says: "The correct position for approach to a blind right-hand bend is again eighteen inches from the nearside, provided there is no hidden nearside danger. This position gives you the greatest safety margin from oncoming traffic, as well as maximum line of sight. Remain in this nearside position all the way round the bend until you have a complete view of the road surface. As the view opens up return with minimum steering deflection to the safety lime position".
And for a gradual right-hand bend: "Remain in the approach position, eighteen inches from the nearside, until the view begins to open up. Then smoothly and gradually straighten out the curve at the exit, to ease the car away form the nearsdie towards the centre line, just where it begins to straighten: but only if this position does not crowd oncoming traffic......stay into the nearside until your view is complete."
I used to find holding the nearside position until the view opened up uncomfortable - it sacrifices the most stable line, and leaves little space for the car to understeer away from the intended course (not a problem with correct entry speed of course). But I accept the logic, and now it comes naturally.
John's book says: "The correct position for approach to a blind right-hand bend is again eighteen inches from the nearside, provided there is no hidden nearside danger. This position gives you the greatest safety margin from oncoming traffic, as well as maximum line of sight. Remain in this nearside position all the way round the bend until you have a complete view of the road surface. As the view opens up return with minimum steering deflection to the safety lime position".
And for a gradual right-hand bend: "Remain in the approach position, eighteen inches from the nearside, until the view begins to open up. Then smoothly and gradually straighten out the curve at the exit, to ease the car away form the nearsdie towards the centre line, just where it begins to straighten: but only if this position does not crowd oncoming traffic......stay into the nearside until your view is complete."
I used to find holding the nearside position until the view opened up uncomfortable - it sacrifices the most stable line, and leaves little space for the car to understeer away from the intended course (not a problem with correct entry speed of course). But I accept the logic, and now it comes naturally.
7db said:
Great pics, Von.
Do you have a big book of these for different situations? Was most impressed by Andy Morrison when he pulled out a book of almost every possible corner, laminated and ready to draw lines on. Very helpful.
Do you have a big book of these for different situations? Was most impressed by Andy Morrison when he pulled out a book of almost every possible corner, laminated and ready to draw lines on. Very helpful.
I just knocked them up in MS paint while sitting here
(I do have lots of laminated pics, pens & paper in the mobile office though)
Edited by vonhosen on Monday 7th August 21:47
18 inches from the side of the road! If i new you where talking about margins as large as thet I would never have mentioned a thing - If you can't get your car within that margin you should not be on the road anyway.
I completly understand the reasons for what you are saying about the line and naturally I do as you say on any corner that feels unsafe - but as rule most corners on our roads have so much room it feels unecassary to this.
I grew up in Cornwall with tight twisty lanes - that taught me you never whats coming rule - then moved to london and learnt you never who is coming rule! And what you teach would be great if everyone was made to take it!
I completly understand the reasons for what you are saying about the line and naturally I do as you say on any corner that feels unsafe - but as rule most corners on our roads have so much room it feels unecassary to this.
I grew up in Cornwall with tight twisty lanes - that taught me you never whats coming rule - then moved to london and learnt you never who is coming rule! And what you teach would be great if everyone was made to take it!
townrow said:
18 inches from the side of the road! If i new you where talking about margins as large as thet I would never have mentioned a thing - If you can't get your car within that margin you should not be on the road anyway.
On a very narrow road surely you have no scope for positioning anyway - it is essential to be close to the nearside until you have a full view of the road. As I understand it, the reason for keeping a margin from the edge of the road is to avoid drains and debris etc which would reduce grip.
StressedDave said:
7db said:
If only Dave could datalog the pink car's progress...
I've got plenty of representative data... and even such modern things as measures of radius and path
Wondered where you had got to. Conversation with Mike the other night about whether you were right or wrong ended in a draw. You have me to thank...
Assume that you'll be posting up some data to show a car tightening its line under power soon...
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