display using the centerline of the plan view along with its associated elevation.
Although vertical curves consist of a series of closely spaced points in a drawing, they
take on the appearance of a “curve” to the viewer. In a cross-section view, the elevation
component of the point is shown along with its offset reference to the centerline.
The view generated is one in which a “slice” of the roadway is taken as it would look if you took a perpendicular plane to the driver and lifted a section of the road up to see it.
In the world of CADD, all these points are three-dimensional and yet have been used,
as described above, to generate three different combinations of two-dimensional drawings.
These two-dimensional drawings make up the majority of the sheets in a set of
highway construction plans. The value of CADD is that the points are entered only
once, by a described alignment or profile or cross slope in a cross section, and yet have
been recalled in numerous applications throughout the plans—whether in developing
final cross sections, earthwork calculations, intersection details, drainage designs, etc.
CADD software allows the assignment of “names” to various sets of points, such as the
centerline of a roadway or the boundary of a property. It also can assign points that are
closely associated, if not connected, to a group called a layer or level in the CADD
drawing file. One such layer may contain points for a bridge, or even subdivided into
layers for bridge deck, bridge abutment, bridge pier, etc. Other layers can be used for
hydraulics, lighting, signals, or signs. The assignment of points to layers is limited only
by the storage assignment capability of the software and the capacity of the computer
memory itself, which far exceeds that required for most projects. The following sections
describe the components of a basic set of highway plans, without reference to
CADD applications. However, the end product can be completely produced in the
CADD environment.