What is a vertical curve calculation used for?


Quick Answer

Vertical curve calculations are used most frequently in road, highway and railroad design. In addition to vertical curves, horizontal curves are another transition element in the design geometry of highways.

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Full Answer

A vertical curve allows for a vertical transition between sloping roads and thus provides a gradual inertial transition over which the altitude change can occur.

Symmetrical parabolic curves make up the majority of vertical curves used in road design. This predominance is the result of a correctly designed symmetrical parabolic curve minimizing the inertial loads on road vehicles as they move through the curve. In addition, many official tables such as those of the American Association of State Highway and Transportation Officials are only applicable to symmetrical parabolic curves.

Circular curves are the easiest vertical curves to design and construct, and they are used most often in the design of low-speed roads and railroads.

A third type of vertical curve is the asymmetrical parabolic curve, which is the least frequently used vertical curve. The asymmetrical parabolic curve comprises two different parabolic vertical curves joined at their midpoints.

Within the parabolic formulation, sag curves and crest curves are the two types of vertical curves. Sag curves are used in valleys and where the gradient change is positive, while crest curves are used for hills and where the gradient change is negative.

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