In roadway design situations involving varying pavement widths,
Assign Template Point Centerline is an effective way to control the
edge of pavement horizontal alignment as well as any other element
in the template. This command assigns centerline (.CL) files to
template ID points, independent of the main centerline, thereby
controlling the horizontal location. Besides controlling the
template grades, you can also control the tie point where the
cut/fill slope intersects the existing ground by entering TIE for
the Template Point ID.
The assignment of Template ID points to centerline files (.CL)
is stored in Template Point Centerline files (.TPC). These files
are then used by the Process Road Design and Road
Network commands. The slope to these template points is based
on the parameters defined in Design Template. Subgrades can
be made to follow template IDs if their offset distances are
defined not by distance but by reference to the template ID. For
example, with a grade ID of EOP and a subgrade that goes one foot
past this grade, the subgrade distance can be defined as EP+1 so
that the subgrade follows the template point centerline
adjustments.
The commands that process Template Point Centerlines such as
Road Network will make the template grades follow the template
point centerlines including along their curves for the output of
the template 3D polylines and road TIN surface. This way Template
Point Centerlines can be used to create rounded medians and
edge-of-pavements that follow alignments that are independent of
the main centerline as shown here.
There are a few key settings to a road
design with medians as shown here.
First you are prompted to create a new Template Point Centerline
file (.TPC) or edit an existing one.
Next the Define Template Alignments
dialog is presented, showing a list of existing Template
ID-Centerline assignments. Use the Add, Edit and Delete buttons to
manage the list of template point centerlines. The Report function
creates a report of the template point centerlines in the standard
report viewer. The Reference Template is optional for setting the
road template (TPL) to use for selecting the template point
description from a lookup list.
The Add and Edit buttons bring up the Template Point Centerline
Settings dialog. First, set the Template Point Description
which refers to the Template ID for an element in the Template
(TPL) defined by the Design Template command. Next, pick the
Specify Centerline File button, to choose the file (.CL) to assign
to the Template Point ID. Alternatively, you can use the Screen
Pick button to select a polyline from the drawing that the program
will use to generate a centerline. Specify if this assignment is
for the Left or Right side of the main centerline.
The Adjust Next Outside Grade Distance controls how
template elements are affected that are outside from the current
Template Point Description. This option controls whether to hold
the grade distance or grade offset from the main centerline for the
outside template elements. When this option is on, the outside
grade distances are adjusted by the same amount that the template
point centerline adjusts the horizontal alignment. When this option
is off, the outside grade distances remain set by their distance
defined in the template. For example, consider a template that has
an inside median grade (MED) followed by an edge-of-pavement (EP)
and the MED has a template point centerline. When this option is on
and the template point centerline shifts the MED out 2 feet, then
the EP grade is reduced by 2 feet so that the EP offset from the
main centerline isn't affected. When this option is off and the MED
is shifted out 2 feet, then EP grade distance doesn't change and
the EP offset from the main centerline is shifted out 2
feet.
The Skip Travel Lane for Parallel Grades applies to a
grade for a travel lane that is outside a grade being adjusted by a
template point centerline. This option controls whether this
outside grade is adjusted to by parallel with the template point
centerline or the road main centerline.
The Skip Grade When Centerline Missing means that the
template will only contain the element at stations that have a
template point centerline for it. The Additional Grades To Skip
specifies other related template elements to skip in this case. The
option applies to template elements like intermittent medians that
you only want included in the template for stations where they have
a template point centerline defined.
Here are two sections along the
roadway, illustrating the varying lane widths on the right side of
the main centerline. These sections are created by Process Road
Design with the TPC set in the input files and these sections
are viewed with the Section File
Editor command.
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