Jones and DeMille Engineering has successfully designed and constructed
many roads using roadway design reports and AutoCAD Civil3D design workflow. Geometric
design of roadways first starts by collecting and analyzing data including, but
not limited to: traffic data and applicable design criteria. Traffic data is used to classify a roadway,
select geometric design criteria, and design pavement or other surfacing
The data is organized into a Project Design Criteria (PDC)
document which defines scope and critical geometric design standards. The PDC generally includes criteria for: design
speed, lane width, shoulder width, bridge width, horizontal alignment, superelevation,
vertical alignment, grade, stopping sight distance, cross slope, vertical
clearance, lateral offset to obstruction (clear zone), and structural capacity.
Data for maps and drawings is collected and incorporated into
Civil3D design software. Base drawings
contain existing ground surface, existing conditions, topography information,
parcels, utilities, and other potential impacts to the route design. Design drawings contain the design alignment
and profile which defines the main horizontal and vertical route that typically
represents the construction baseline of the roadway.
The Project Design Criteria (PDC)
is used to apply constraints placed on the alignment and profile in Civil3D. This includes speed and super elevation
parameters. Typical sections (assemblies)
are created to define the cross-sectional component of the design and are built
by connecting individual subassembly objects, thereby helping to simulate the
geometry and material makeup of the road as well as helping to define how it
interacts with surrounding features along the route.
A model is created using corridors
in Civil3D. Corridors are dynamic 3D
models built from the combination of horizontal (alignment), vertical
(profile), and cross-sectional (assemblies) design elements. The corridor model is used to calculate
earthworks and quantity takeoffs, to perform sight and visual analysis, to
generate surfaces, and to extract information for construction purposes. Individual corridor sections may be examined
to help accommodate unique or localized design conditions. To achieve a better design it may be
necessary to optimize design in Civil3D by adjusting one or more of the
corridor components. For example, the
design profile may be adjusted to better balance cut and fill volumes.
The Project Design Criteria (PCD)
and Civil3D model is used to develop a roadway design report. The roadway design report generally includes
summaries of data including: topographical information, traffic data (ADT), design
criterial, and engineer’s opinion of probable cost. The report also includes information exported
from Civil3D including: earthwork reports, cross section information, and other
required design information.
The above described workflow yields
a well-designed roadway model, plans, and roadway design report which can be
used for bidding, construction, or planning purposes. The construction model
created in Civil3D can easily be exported in other formats for use with
additional design software or construction machine control.