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the safest path
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One of the main reasons people have accidents at high speeds is that they are a) driving too fast and b) dont find the apex in the bend.

Bends in roads should be designed to follow the apex of that specific turn calculated accoriding to the speed limit +/- 20%

 — shinobi, Dec 21 2006

Apex http://en.wikipedia...i/Apex_%28racing%29
from the wikipedia [st3f, Dec 21 2006]

Speed limits are usually determined based on how the road was constructed, not the other way around.
 — BJS, Dec 21 2006

agreed BJS, but there are more fatal accidents than I am comfortable with, so clearly the system isn't entrely effective, and needs a change
 — shinobi, Dec 21 2006

 I'm a little confused by the language in this idea. In racing terms, the apex is the point of the bend where the inside tyres touch, nearly touch or go well over the kerb (depending on the type of kerb, car and race). You can't follow an apex. It isn't a line.

 The reason why drivers touch the apex in a race (a point that changes depending on the car, road, tyres, conditions and driving style) is (simplistically put) to make the driven radius wider than the road's actual radius. The racing line isn't anything magical -- it's just the best way of using the a track surface.

 To create a road can be driven faster (not necesarily a good idea) means increasing the radius of the turns and the width of the lanes (because little errors get bigger at speed).

To create a road that can be driven safer (something I'm greatly in favour of) means many things. Too me it means making roads predictable and speed limits and warnings consistent.
 — st3f, Dec 21 2006

Could you help me understand how not finding the apex in a bend makes you crash. I'm a little fuzzy on that point.
 — jhomrighaus, Dec 21 2006

 right, well in racing terms, an apex is defined as "the point a car should touch on the inside of a turn when following a proper line ".

 so im saying, make the road follow this imaginary line that pretty much only F1 drivers can see.

vis a vis, a medium left, wouldn't be a smooth L shaped bend, but rather one with a more angles.
 — shinobi, Dec 21 2006

 shinobi, I don't believe that you understand the racing line (either that or I don't understand you). It is not a magic line. It is just the fastest way around a particular piece of tarmac.

 Step 1: I take Michael Schumacher round a corner (telling him to go fast) and mark the line he takes.

 Step 2: I then alter the road layout so that the path that Michael took will be in the centre of the lane.

 Step 3: I take Michael back to the altered corner to check that I've made the changes correctly.

 He will take a different line. The original line he took was the fastest for that piece of tarmac. Now that the corner layout has changed, the racing line will also have changed.

 The racing line, apexing at a corner is the fastest way around a particular piece of tarmac. Change the tarmac and the line will change.

Following steps 1 to 3 iteratively will result in a piece of tarmac with a gradually increasing radius, eventually turning into a straight line.
 — st3f, Dec 21 2006

I think this idea is basically to make roads with more gradual turns so the speed limit can be increased to how fast people normally drive (over the speed limit). But this would only lead to people driving even faster which would still be just as dangerous, it would actually be more dangerous because of the higher speed if there was a crash.
 — BJS, Dec 21 2006

 Generally racing drivers fit somewhere between two extremes. Some trust the car a lot and go for as close to a constant radius - greater than the road's radius - as possible throughout the curve. Some are more cautious and prefer a gradually-increasing radius, i.e. a part-spiral path, a technique known as late-apexing.

 With some cars one would be nuts not to late-apex. The original Porsche 911 is considered an example of such a car. One turns more tightly during the first part of the curve, when one is going more slowly, then gradually relaxes the line as one accelerates through the curve. This is generally a safe and sensible approach to cornering.

The trick would then be to build the road to the abovementioned part-spiral path. If the road takes traffic in both directions, one would need two spiral segments, one within the other. The result would be that the road would be wider at one point about a quarter of the way along the curve. One might introduce a built or painted island at this point.
 — Ned_Ludd, Dec 22 2006

[BJS] has a point. Narrow, fiddly roads can also be more fun, and are then more fun at lower speeds. But curves cambered the wrong way, and curves with suddenly-tightening radii, can catch one unawares.
 — Ned_Ludd, Dec 22 2006

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