Understanding Width or Offset Targets

Another type of target used in corridor design is referred to as a width or offset target. As the name suggests, this type of target is used to vary the width of an object or the distance between a point and the centerline (also known as offset). For example, an alignment can be used as a target that controls the outside edge of a lane. As the path of the alignment moves away from the road centerline, the lane widens. As the path of the alignment moves toward the road centerline, the lane narrows (see Figure 9.9).

Figure 9.9  A width or offset target (in red) applied to a corridor to widen the lane and create a pull-off area

Tying In Proposed and Existing Elevations

The concept of daylighting is found throughout all types of land development. As I’ve mentioned, one of the fundamental activities of land development is changing the shape of the land. This means that portions of the development will have new elevations that are above or below the existing elevations. Since things such as roads and parking lots are not much good underground and are not able simply to float in midair, there must be some way of transitioning between new elevations and existing elevations. The most economical material that can be used to construct that transition is soil, but soil is not stable on steep slopes. Therefore, the transition between new and existing elevations is done with relatively mild slopes such as 3:1 (three units horizontal to one vertical) or milder. One of the most important components of your land development design will be this tie-in between proposed elevations and existing elevations.

In addition to alignments, you can use feature lines, survey figures, and 3D polylines as width or offset targets. Lane widening is probably the most common use of a width or offset target, but there are many other uses. For example, you can use a width or offset target to control the location of a ditch, the width of a shoulder, or the distance between a shoulder and a guardrail.

Applying Corridor Targets

• Understanding Surface Targets
• Understanding Width or Offset Targets
• Understanding Slope or Elevation Targets
• Applying Subassemblies That Can Use Targets
• Assigning Targets

Download Exercise File :

• Applying Corridor - Metric     --- ( 2.18 MB )
• Applying Corridor - Imperial  --- ( 2.05 MB )