If I recall correctly, early designers of roller coasters had problems with "jerk" when making looping roller coasters. Loops were constructed by joining a straight section of track to a circular section with no transition. Apparently the high jerk caused severe injury to many of the riders.
There is a curve for which the transition from one radius of curvature to another is as gradual as possible. I too have forgotten its name however it can be formed by bending a length of material of constant stiffness (such as a garden hose) into a loop by holding only its ends.
I don't think the occupants of a car would guide it through a path that would cause them discomfort. So even if a road did have a jump in radius of curvature, the path traced out by a car wouldn't. (Unlike a roller coaster, a car doesn't have to travel out any particular path).
-Patch
From: [EMAIL PROTECTED] To: [email protected] Subject: Re: How DO they do that? Date: Sun, 11 Feb 2001 13:20:33 EST I love this list's digressions! 8-) Trivia question: You can't join a straight road to a circular road tangentially else the third derivative (d/dt of the centripetal acceleration) will be infinite. So, what curve is used to join the straight road to the circular road? If no one knows, I don't remember the answer but can find it. John Bercovitz
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