As an example of the use of CADD files and design software, the Ohio Department of
Transportation (ODOT) has stated that this is the preferred method of preparing plans.
ODOT has adopted MicroStation and GEOPAK as its standard drafting and design
software (Ref. 8). (Note: The preferences mentioned here are those used by ODOT
and are cited here only as an example. This is not intended to be an endorsement by
the authors. Other agencies use a variety of similar programs.) The standards referenced
in the ODOT manual have been developed and tested using the software versions
listed on the web site www.dot.state.oh.us/cadd/GPKStandards. For a more detailed
explanation and background of the use of CADD in ODOT plan development, the reader
may view the CADD Manual at www.dot.state.oh.us/cadd/CaddManual.
All highway CADD software programs are based on a two- or three-dimensional
coordinate system that assigns coordinates of a specific point to a number or alphanumeric
label. Groups of points make up alignments or property boundaries or roadway
centerlines, pavement edges, curbs, sidewalks, etc., in the two-dimensional “plan”
view. In the three-dimensional environment, these points have “elevation” values to
go along with their x-y plan view coordinates. Likewise, in roadway profiles, similar
points make up the vertical profile of a roadway. This also is a two-dimensional