1. Alignment

An alignment is a three dimensional refernce line consisting of a series of straight and curved segments. It  serves as a reference for linear projects such as roads, pipelines, transmission lines, etc. Most alignments have horizontal and vertical components, Figures A-1 and A-2, each related but having their own geometric elements and specific design constraints.

 gen 01

 Figure A-1
Horizontal Component

 gen 02
 Figure A-2
Vertical Component


Although most contemporary alignment design is done digitally in three dimensions, it is still important to understand the geometry of the individual components.
The remainder of the chapter will concentrate on geometry for road alignments.