2.0

Defining the Transition Regions on a Template
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8 Pick the transition region point from your drawing.
To define an area on the template to be stretched, you need to pick two key
points on the template for each transition region, the region point and the
control point:
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The control point determines the place on the template where the horizontal
or vertical alignment is attached. It is the point on the template that is
moved to the desired offset or elevation.
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The region point determines the outer edge of the region to be stretched. To
achieve the surface modification when a transition is applied to a template,
any surface line that is intersected by the vertical plane of the region point is
modified between that point to the next point on the surface toward the
centerline.
In many situations the control point and region point use the same location.
For example, the outer edge of pavement of an asphalt surface that leads up
into a crown at the centerline would be defined as both the region point and
the control point.
If these points are defined at two different locations, then the region point must
always be closer to the centerline than the control point. For example, if you
want to stretch a center median island that has a curb structure, you need to
locate the control and region points at different locations in order to avoid
stretching the curb as well as the median.
If the horizontal transition alignment for the median is defined along the path
of the edge of pavement where it meets the face of curb, locate the transition
control point at this location. However, if you also located the region point at
this same location, the curb structure stretches as the median becomes wider,
creating an extremely wide curb.
To force the stretch to be applied at the back of curb, define the region point at
the back of curb while maintaining the control point at the face of curb. This
situation could also be resolved by defining the horizontal transition alignment
along the back of curb that would allow you to define both the region point
and control point at the back of curb.
NOTE
When transitioning is applied to a template, everything on the outside of
the transition region will move to follow the transitions change in offset or
elevation.
9 Specify which type of surface transition to use: Dynamic or Pinned.
A typical template has a central portion where the surfaces cross the centerline,
such as a median or the traveled lanes of a template without a median. Because
the surface crosses the centerline, it can have both a left and right transition
control affecting it. For this situation, there are two options that control the
way in which the transitioning affects the template surface: Pinned and
Dynamic. With the Pinned option, the inner vertex of the region segment is
always held while the segment is stretched. With the Dynamic option, the
grade of all segments between the control points is held. Each half of the central
surface is moved to the specified offset or elevation and then the surfaces are
joined by trimming off the overlapping segments or by extending the segments
so that they meet. The Dynamic option only affects the central portion of the
template and the surfaces must cross the centerline. If the transition lines come
together so that the surfaces between the inner most transition lines disappear,
then the next transition regions can become dynamic.