University of Virginia Library

THE SPLINE LINE:

You will be manipulating transitions during the design of your
road at Birdwood or your project next Fall. While you are refining
"Your Road", ask what might be the next refinement in striving for
the perfect line of grace and movement. What mathematical derivation

might lead to the absence of tangents altogether? And what
might we call that line?

Let me share an experience with you:

Soon after I was called into the office from the Tree Gang in
1951, I was amazed to see a "spline and set of spline weights."
As students, we had not seen those tools much less used them during
our time in school. I was fascinated by the skill with which Mr.
VanGelder and Mr. Hanson adjusted the direction and subtle refinements
of road centerlines. This was the magic of everchanging curvature
that Prof. Albrect had described to us. To my disappointment, I
neither acquired the skill that Mr. VanGelder and Mr. Hanson had
nor was my curiosity satisfied in the potential of the "spline
line." Very soon I found myself drawing road alignment for the
Bureau Engineers in terms of tangents and circular curves onto
which they imposed their mysteries to convert my crude line to
geometrics. The fascination for the "spline line" continued through
the years and to this day I want to master that highest of park
road geometrics, "The Line Without Tangents."

I don't know the procedure for calculating the "spline line";
although Nick Annese shows me that Clarke and Rapuano uses the
method as standard procedure. Perhaps Ol' Ben could learn from
those designers who use it.

In this day of computers the calculations could be done quickly.
Programming the computer is quite another matter...and I lack the
skill to do that. To those of you who are interested and possess
the skills in programming, I would encourage you to explore the
geometrics of the "spline line". Surely the spline line geometrics
will lead to a refinement of the methods I have presented to you
in this course.