Curves are essential in connecting two tangents or straight lines in transportation routes. This is because curves will give a shorter distance to travel and more safety for passage. And just like observed in any transportation system, curves are noticed on both the horizontal plane and vertical plane - horizontal curves and vertical curves.
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| courtesy of Wikipedia |
The two general types of horizontal curves are circular and transition curves. The third type is the combination of these two general types. Circular curves are:
- Simple curves - the most common and recommended type of circular curve. This curve is comprised of a single arc between two tangents.
- Compound curves - a curve made of two or more simple curves with same or different raddii. Its differentiation from the other type is the locations of centers for this curve are all on the same side of the alignment.
- Reversed curves - similar with compound curves however, the location of the centers of curves comprising this curve are located in opposite sides of the alignment.
- Broken-back curves - a curve which is not recommended for highways works due to danger it poses to most drivers. This curve comprises of a small tangent between two arcs with centers on the same side of the alignment.
Spiral curves are used to make a transition on the curve used especially if there is a sudden change in curvature. Due to its purpose, spiral curves are also called transition curves, or easement curves.
