Mastering AutoCAD® Civil 3D® 2010

434 CHAPTER 12 THE ROAD AHEAD: ADVANCED CORRIDORS

Figure 12.7

Set the Ditch Foreslope

subassembly to follow

the swale centerline

alignment and profile.

11. Click OK to dismiss the Target Mapping dialog. Click OK again to dismiss the Corridor

Properties dialog and rebuild the corridor. When viewed in 3D, the corridor should now

look like Figure 12.8.

Figure 12.8

The adjusted corridor

Note that the corridor has been adjusted to reflect the new target alignment and profile.

Also note that you may want to increase the sampling frequency. You can view the sections

using the View/Edit Corridor Section tools. You can also view the corridor in 3D by picking

it, right-clicking, and choosing Object Viewer. Use the 3D Orbit tools to change your view of the

corridor.

Modeling a Peer-R oad Intersection

When you’re using the corridor model, an important distinction to make is that even though

you’re building a model, you aren’t designing it. Technically speaking, you could build the model

and design the intersection simultaneously; however, most users who attempt to ‘‘figure it out’’

as they’re constructing the model find the task tedious and frustrating.

MODELING A PEER-ROAD INTERSECTION 435

The first step is to figure out how your intersection works. Give yourself some modeling guide-

lines, trends, and design constraints (but not actual hard elevations just yet), either onscreen or on

a small plotted schematic (see Figure 12.9).

Figure 12.9

Plan your intersection

model in sketch form.

Constant grade

around curbline

Grades adjust to match

road centerline profiles

Normal

cross section

Normal

cross section

Normal

cross section

High point

in middle

Crowned

from CL out

Next, plan what alignments, profiles, and assemblies you’ll need to create the right combination

of baselines, regions, and targets to model an intersection that will interact the way you want.

Figure 12.10 shows a sketch of required baselines. Baselines are the horizontal and vertical

foundation of a corridor, as you saw in Chapter 11. Each baseline consists of an alignment and its

corresponding finished ground (FG) profile. You may never have thought of edge of pavement

(EOP) in terms of profiles, but after building a few intersections, thinking that way will become

second nature. The Intersection tool on the Create Design panel of the Home tab will create EOP

baselines as curb return alignments for you, but it will rely on your input for curb return radii.

Figure 12.10

Required baselines for

modeling a typical inter-

section

Baseline: Edge of Pavement Left

Baseline: Main Road

Baseline: Edge of Pavement Right

Baseline: Second Road

Figure 12.11 breaks each baseline into regions where a different assembly or different target

will be applied. The next exercise will give you hands-on experience in splitting regions along a

corridor baseline as a precursor to building an intersection automatically. Once the intersection

has been created, target mapping as well as other particulars can be modified as needed.

436 CHAPTER 12 THE ROAD AHEAD: ADVANCED CORRIDORS

Figure 12.11

Required regions for

modeling an intersection

created by the Intersec-

tion tool

Region with intersection assembly

targeting Second Road Centerline

Region with typical assembly that

leaves off left lane and curb

Region with typical assembly

Region with typical assembly

Region with intersection

assembly targeting

Main Road Centerline

Using the Intersection Wizard

In Chapter 11, you learned briefly about regions. A baseline consists of a combination of an align-

ment and a profile, whereas assemblies are applied to specific regions. By default, every baseline

has one region, which you created in Chapter 11 whenever you made a new corridor. If certain

zones of a baseline require the application of a different assembly, you split a baseline into multiple

regions. The Intersection tool will do this for you automatically.

On the basis of the schematic you drew of your intersection, your main road will need two

assemblies to reflect two different road cross sections. The first assembly, as shown in Figure 12.12,

is the typical or ‘‘normal’’ case. The bulk of your neighborhood will use this typical assembly along

straight pieces that aren’t intersections, widening areas, or similar structures.

Figure 12.12

A typical assembly will

be applied to all ‘‘nor-

mal’’ regions.

The next assembly (see Figure 12.13) is a right lane–only assembly that you’ll apply through

the intersection. On the basis of your sketch, this particular main road won’t maintain a full crown

through the intersection; however, the right half of the road will be normal.

Figure 12.13

Right lane–only assem-

bly