This chapter focuses on taking your corridor-modeling skills to a new level by introducing more tools to your corridor-building toolbox, such as intersecting roads, cul-de-sacs, advanced techniques, and troubleshooting. You will use advanced corridor targets and work with conditional subassemblies.
This chapter assumes that you've worked through the examples in the chapters on alignments, profiles, profile views, assemblies, and basic corridors. Without a strong knowledge of the foundational skills, many of the tasks in this chapter will be difficult.
In this chapter, you will learn to
In the previous chapter, you modeled corridors with one baseline and one region. A question many people ask when working with corridors is, “At what point do I need another region?” The answer is simple: If you need a different assembly, you need a different region.
In the following example, you will step through adding an additional region to an existing baseline:
1001_MultiRegionCorr.dwg
(1001_MultiRegionCorr_METRIC.dwg
), which you can download from this book's web page, www.sybex.com/go/masteringcivil3d2015.
This drawing has been split into two modelspace viewports so that you can observe the results of your efforts in 3D.
On the Parameters tab of the Corridor Properties dialog, notice that there is a baseline containing a single region.
The Corridor Properties dialog temporarily disappears. The drawing contains linework representing the edge of pavement for this network of roadways in this subdivision. You will be using your Endpoint Osnap along with this linework to define multiple regions in this corridor.
The Corridor Properties dialog reappears. Notice the new End Station value.
Notice that the corridor region now stops exactly at the beginning of the curb return; you would not want the curb and gutter, sidewalk, and daylighting to shoot through the intersection on the right side of the road. In this situation you need another assembly, one without curb and gutter on the right. Since it is needed only in the intersection area, you'll add a region that picks up where the first region left off and ends at the end point of the opposite curb return.
This assembly contains a daylighting subassembly, so you'll need to set the surface target.
The new region was added but it is extending to the end of ROAD C, which wasn't the intent. Next, you will split that region in two and assign another assembly to finish this part of the corridor.
If you see a warning dialog referring to 0+00 being outside of the station limits, click OK and continue.
Back on the Parameters tab, you now have three regions listed under your baseline. The last region requires an assembly change since this is the section on the corridor that requires curb and gutter, sidewalk, and daylighting on both sides.
The corridor along ROAD C is nearly complete with the exception of the curb returns, as shown in Figure 10.4.
The files 1001_MultiRegionCorr_FINISHED.dwg
and 1001_MultiRegionCorr_METRIC_FINISHED.dwg
are available on this book's web page for you to check your work.
Instead of moving into building out the regions required for the curb returns, you're going to switch gears for a bit and look at a building a cul-de-sac region. Then after you build the cul-de-sac, you'll learn how to use the intersection tool, which automates the process of creating regions, assigning assemblies, and designating targets.
Even if you never plan to design one in real life, understanding what is going on in a cul-de-sac corridor model will set you on the right path for building more complex models. If you truly understand the principles explained in the section that follows, then expanding your repertoire to include intersections and roundabouts will become much easier.
Up to this point, every corridor you've built has had a single baseline. When you worked with corridor surfaces, you were working with a complex corridor with multiple baselines. A cul-de-sac by itself can be modeled in two baselines, as shown in Figure 10.5. The procedures that follow will work for most cul-de-sacs, including symmetrical, asymmetrical, and hammerhead styles. You will need a centerline alignment and design profile for the road leading into the cul-de-sac as well as an edge of pavement (EOP) alignment and design profile defining the cul-de-sac bulb.
In the example shown in Figure 10.5, the centerline of the road, Baseline 1, will require a typical crowned assembly, which will terminate when it reaches the point in the cul-de-sac geometry where the bulb defining curvature begins. From that point, the baseline is swapped out for an alignment and profile that define the edge of the cul-de-sac.
As you've seen, when assemblies are applied to a baseline, the geometry of the subassemblies project perpendicularly from the baseline. In the example of Figure 10.5, the curb and gutter subassembly as well as the rest of the subassemblies it carries (sidewalk, daylighting) need to be projected from the edge of the cul-de-sac bulb because that's the way their real-life counterparts are built. The assembly used on this baseline will have the curb and gutter subassembly on one side and the lane subassembly on the opposite side (Figure 10.6). The lane subassembly will stretch to meet the centerline alignment and profile as its targets.
It helps to think of the assembly as radiating away from the baseline, from the assembly base outward, toward a target (Figure 10.7). Because the assemblies are applied to the baseline in a perpendicular manner, using the edge of pavement for a baseline in curved areas (such as cul-de-sac bulbs or curb returns) will result in a smooth, properly graded pavement surface.
One of the most challenging parts of complex corridor (i.e., cul-de-sac, intersection, or roundabout) is establishing design profiles for non-centerline alignments. You must have design profiles for both the centerline and edge of pavement alignments, but it does not have to be a painful process to obtain them.
Using a simple, preliminary corridor and the profile-creation tools you learned about in Chapter 7, “Profiles and Profile Views,” you'll find that establishing an edge of pavement profile can go quickly.
In the exercise that follows, you will work through the steps of creating an EOP profile:
1002_EOPProfile.dwg
(1002_EOPProfile_METRIC.dwg
) file, which you can download from this book's web page, www.sybex.com/go/masteringcivil3d2015.
This drawing contains the corridor you worked on in the last exercise, plus an additional baseline and region built for ROAD E. You may also notice that there is an alignment tracing around what would be the edge of pavement in the cul-de-sac for ROAD E.
You will not be adding a boundary at this time.
You should now see a green surface boundary in your drawing.
The profile you are seeing has a large gap in the middle. The two short segments at the beginning and end of this profile show what the proposed grade would be according to the corridor surface, which terminates at the PC and PT of the cul-de-sac bulb. The cul-de-sac alignment actually overlaps the corridor surface so you were able to show the proposed grades in profile view leading into and exiting the cul-de-sac.
Next, you will fill in the large gap with your own profile by snapping to the red profile segments to ensure that you are matching grade at the edge of pavement of your cul-de-sac.
You'll now add a high point along the corridor edge of pavement.
Your profile should look like Figure 10.8.
You now have a proposed profile that is acceptable to use in the cul-de-sac baseline. Check your work against 1002_EOPProfile_FINISHED.dwg
or 1002_EOPProfile_METRIC_FINISHED.dwg
to see how your stations and elevations compare. You do not need to save the drawing file.
You have all the pieces in place to perform the first iterations of this cul-de-sac design.
The following exercise will walk you through the steps to put the cul-de-sac together. You will complete several steps and let the corridor build to observe what is happening at each stage. This exercise will also encourage you to get comfortable using the Corridor Properties dialog to make design modifications.
1003_Cul-de-SacDesign.dwg
(1003_Cul-de-SacDesign_METRIC.dwg
) file, which you can download from this book's web page.Select a baseline:
prompt, click over the cul-de-sac alignment in the drawing.Specify the region start station:
prompt, type 0 ↵ Alternatively, you could snap to the end of the corridor at this location.Specify the region end station:
prompt, type 369.17 (113.26 for metric) ↵. Alternatively, you could snap to the edge of the corridor at this location.The curb return assembly has been wrapped around the cul-de-sac, as shown in Figure 10.9. However, the curve frequency needs to be increased to mimic the curvature of the cul-de-sac bulb. Also, an offset and elevation target will have to be set so that the pavement of the assembly stretches to connect horizontally and vertically to the centerline design of ROAD E.
Select a region to edit:
prompt, click anywhere inside the cul-de-sac portion of the corridor. Be careful not to select inside the “donut hole” in the center of the cul-de-sac.Select a region to edit:
prompt, click anywhere inside the cul-de-sac portion of the corridor. Be careful not to select inside the “donut hole” in the center of the cul-de-sac.The files 1003_Cul-de-SacDesign_FINISHED.dwg
and 1003_Cul-de-SacDesign_METRIC_FINISHED.dwg
are available for you to check your work.
People make several common mistakes when modeling their first few cul-de-sacs:
You can fix this problem by opening the Target Mapping dialog for your region and checking to make sure you assigned the road centerline alignment and FG profile for your targets. Also, check to see if you assigned these targets to the wrong subassembly.
To pinpoint the location of errors, use the Edit Targets tool from the Modify Region panel of the Corridor contextual ribbon. Edit targets one region at a time to avoid confusion.
You can fix this problem by changing the assembly applied to the region to one that was created for the correct side or reversing the alignment.
Now that you have a thorough understanding of cul-de-sacs, you're ready to take on intersections.
The steps that follow apply to all intersections, regardless of whether it is a T-shaped intersection, a four-way intersection, perfectly perpendicular, or skewed at an angle.
When you build your corridor model, chances are that it will not be graded perfectly, and you may need to tweak it to perfect it. This is why you build the model in the first place, so you can easily see if and where the model fails. Design flaws are difficult to catch right away when you're dealing with a two-dimensional model.
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. It helps to create a simple sketch, as shown in Figure 10.16.
Figure 10.17 shows a sketch of required baselines. As you saw in the previous example, baselines are the horizontal and vertical foundations of a corridor. Each baseline consists of an alignment and its corresponding finished ground (FG) profile. You may never have thought of edge of pavement in terms of profiles, but after you build 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 10.18 breaks each baseline into regions where a different assembly or different target will be applied. Once the intersection has been created, target mapping as well as other particulars can be modified as needed.
All the work of setting baselines, creating regions, setting targets, and applying the correct frequencies can be done manually for an intersection. However, Autodesk® AutoCAD® Civil 3D® software contains an automated Intersection tool that can handle many types of intersections.
On the basis of the schematic you drew of your intersection, your main road will need several assemblies to reflect the different road cross sections. Figure 10.19 shows the full range of potential assemblies you may need in an intersection and the design situations in which they may arise.
This exercise will take you through building a typical intersection with a couple of right-turn lanes using the Create Intersection Wizard:
1004_Intersection.dwg
(1004_Intersection_METRIC.dwg
) file, which you can download from this book's web page.
You'll start by building a four-way intersection for ROAD A and ROAD D.
Select intersection point:
prompt, choose the intersection of the two existing alignments. (Hint: The Intersection Osnap will automatically turn on and be active.)Select main road alignment <or press enter key to select from list>:
prompt, click the ROAD A alignment that runs from west to east.
The Create Intersection – General dialog will appear (Figure 10.20).
At this step, the screen should resemble Figure 10.22.
You will be creating right-turn lanes for ROAD A. Notice how the dialog changes when the check box is filled to show widening parameters.
You will see a schematic name of the quadrant listed at the top of the dialog that corresponds to the glyph. As shown in Figure 10.23, the temporary glyph will help you determine which quadrant you are currently modifying.
When you reach the last quadrant, you will see that the Next button is grayed out. This means that you have successfully worked through all four curb returns.
Some locales require that lane slopes flatten out to a 1 percent cross-slope in an intersection. If this is the case for you, you can change the lane slope parameters in the Intersection Lane Slope Parameters dialog (Figure 10.24). In this exercise you will leave this setting at -2%.
Civil 3D performs the task of generating the curb return profile. The profile will be at least as long as the rounded curb plus the turn lanes that are added in this exercise. If you wish to have Civil 3D generate even more than the length needed, you can specify that in the Intersection Curb Return Profile Parameters dialog (Figure 10.25). This dialog is actually a series of dialogs based on quadrant, as was the Curb Return Parameters dialog. According to Figure 10.25, the alignment and profile for the SE - Quadrant curb return will be extended 25′ beyond its PCs and PTs. And how is this useful? You'll find out in the upcoming section called “Manual Intersections.”
You will be keeping all default settings in both the Lane Slope Parameters area (Figure 10.24) and the Curb Return Profile Parameters area (Figure 10.25).
The Corridor Regions page is where you control which assemblies are used for the different design locations around the intersection. Clicking each entry in the Corridor Region Section Type list will give you a preview of what each assembly type should look like and where in the intersection it's applied (as shown at the bottom of Figure 10.26). If your assemblies have the same names as the default assemblies, they will be pulled from the current drawing. Alternatively, you can click the ellipsis to select any assembly from the drawing, which is what you will be doing in this example.
If you didn't have all the necessary assemblies created in your drawing at this point, you could still create your intersection with the default assemblies. You could always modify the default assemblies with your own criteria and subassemblies after they are brought in.
Corridor Region Section Type | Assembly To Apply |
Curb Return Fillets | Curb Returns |
Primary Road Full Section | Full Section |
Primary Road Half Section - Daylight Left | Left Half |
Primary Road Half Section - Daylight Right | Right Half |
Secondary Road Full Section | Full Section |
Secondary Road Half Section - Daylight Left | Left Half |
Secondary Road Half Section - Daylight Right | Right Half |
After a few moments of processing, you will see a corridor appear at the intersection of the roads. Use the REGEN
command if you do not see the frequency lines. Your corridor should now resemble Figure 10.27.
Notice how the region highlighted in the Parameters tab is outlined in the graphic. This will help you determine which region to edit.
To move from region to region without searching through the overwhelming list of baselines and regions, use the Select Region From Drawing button.
Next you will create a three-way intersection.
Select intersection point:
prompt, choose the intersection of the two existing alignments.
You will not be prompted to pick a main/primary road alignment for three-way intersections. The Intersection tool automatically configures the through road as the primary road.
Corridor Region Section Type | Assembly to Apply |
Curb Return Fillets | Curb Returns |
Primary Road Full Section | Full Section |
Primary Road Half Section - Daylight Left | Left Half |
Primary Road Half Section - Daylight Right | Right Half |
Secondary Road Full Section | Full Section |
Secondary Road Half Section - Daylight Left | Left Half |
Secondary Road Half Section - Daylight Right | Right Half |
NorthRiver
and click Save to continue.NorthRiver.xml
file and click Open to import.
This may take a few seconds, so wait for it.
You should have four intersections in addition to your cul-de-sac modeled in your drawing, as shown in Figure 10.29.
The files 1004_Intersection_FINISHED.dwg
and 1004_Intersection_METRIC_FINISHED.dwg
are available for your review.
You will begin this section by visiting an intersection with unusual circumstances that must be built manually. Then we will discuss other issues you can experience with intersections.
1004_Intersection_FINISHED.dwg
(1004_Intersection_METRIC_FINISHED.dwg
) file, which you can download from this book's web page.Select main road alignment <or press enter key to select from list>:
prompt, click the ROAD A alignment that runs from west to east.Corridor Region Section Type | Assembly to Apply |
Curb Return Fillets | Curb Returns |
Primary Road Full Section | Full Section |
Primary Road Half Section - Daylight Left | Left Half |
Primary Road Half Section - Daylight Right | Right Half |
Secondary Road Full Section | Full Section |
Secondary Road Half Section - Daylight Left | Left Half |
Secondary Road Half Section - Daylight Right | Right Half |
The intersection will be created. Event Viewer will open displaying a number of errors, as shown in Figure 10.30.
Upon looking through the errors in Event Viewer, you'll discover that they are all the same error occurring at different stations. Each mentions a target object not being found. The subassembly involved is LaneSuperelevationAOR and the Target name is Outside Elevation. Since the Intersection tool uses profiles for elevation targets, there must be a problem with one of the profiles that the tool created. A quick way to figure out which one(s) would be to examine the intersection in 3D.
Your viewport configuration should be similar to Figure 10.31.
For some reason, you have two quadrants in this intersection that decided to set down at elevation zero. You could spend a lot of time trying to seek out the reasons for this, but if you're like most of us, you're in a time crunch and would like to finish up this roadway model. Before we delve into creating manual intersections, it's important that you look at a couple of things before moving on.
If you look at the profile properties for both the NE and SE quadrants on the Prospector under Alignments Curb Returns, you'll see that the profile is empty of station and elevation data (Figure 10.32), so this is one area where the Intersection tool failed. However, according to the errors, the targeting problems are occurring along the ROAD B baseline, so what is happening there?
If you open up Corridor Properties, scroll all the way down to the bottom of the list on the Parameters tab, select one of the regions, click the Target ellipsis, and open the Set Slope Or Elevation Target dialog for the left lane, you'll see that the “bad” profiles show up for targeting there as well.
Even if you made manual overrides to cause your corridor to use relevant data, you will still receive errors in Event Viewer because the Intersection tool does not want to let go of the profiles and settings it created. The upside to this behavior is that autogenerated intersections will always update. The downside to this behavior is when you are in situations like this where the tool failed in an area and you need to make manual adjustments. The best thing to do here is to “turn the intersection off.” The Intersection tool did do a lot of the heavy lifting for you, so all is not lost.
Examine the contextual ribbon. Notice the tools for editing offset, curb return, lane slopes, and curb return parameters. If any of the parameters set in the Intersection wizard need to change, these tools can be used to reconfigure the intersection.
The contextual ribbon closes, the intersection marker and label disappear, and the entry for this intersection on Prospector will no longer be found.
The next step is to re-create the two curb return profiles with relevant station and elevation data.
If you take a look at the profile, the surface that is being displayed in profile is doing exactly what your corridor is doing: taking a dive down to elevation 0 where the quadrant begins and ends. Here is where you get to fill in the gap again.
Select profile view to create profile:
prompt, select the profile view for the curb return.You have created an actual profile that can be used in the NE quadrant of this intersection. Next, you'll address the SE quadrant.
Event Viewer will pop up.
Although the right viewport is now showing a good-looking intersection, you'll want to take the following steps to ensure that Event Viewer isn't picking up any more problems with the corridor.
Select a region to edit:
prompt, select the RG - Full Section region along ROAD B north of the intersection, as indicated by Figure 10.34.
Neither of these targets are needed since you are not widening the road in this area.
The Select a region to edit:
prompt should still be active.
The Select a region to edit:
prompt should still be active.
Now if you were to clear the events out of Event Viewer and rebuild the corridor, you would receive no errors. It's better to reserve the error list for those items that you need to address.
The files 1005_ManualIntersection_FINISHED.dwg
and 1005_ManualIntersection_METRIC_FINISHED.dwg
are available for your review.
The best way to learn how to build advanced corridor components is to go ahead and build them, make mistakes, and try again. This section provides some guidelines on how to “read” your intersection to identify what steps you may have missed.
Fix this problem by editing your subassembly to swap the lane to the other side of the assembly. If the assembly is used in another region that is correct, just make a new assembly that is the mirror image of the other assembly and apply the new one to the alignment.
Since so many design elements rely on the alignment as their base, it is better to add a new assembly rather than reversing the direction of the alignment.
Fix this problem by making sure your baseline profile exists where you need it, and make note of the station range. Set your station range in the corridor to be within the correct range.
Now it's time for you to fill in another kind of gap in the corridor. You will be filling in the corridor between the intersections you created.
1005_ManualIntersection_FINISHED.dwg
(1005_ManualIntersection_METRIC_FINISHED.dwg
) file, which you can download from this book's web page.Select a baseline:
prompt, place your cursor over the ROAD A alignment and left-click.
The Select A Baseline dialog opens. The command ascertains that there are four baselines associated with ROAD A. The first three on the list belong to the three intersections on ROAD A.
Specify region start station prompt
, snap to the diamond grip, as shown in Figure 10.42.
When selecting the region start station, it must be an earlier station than the region end station that you will select next.
Specify region end station prompt
, snap to the diamond grip, as shown in Figure 10.43.
Your new baseline-region should resemble Figure 10.44.
The Add Region command is still active.
Optionally, you may repeat steps 8–9 to fill in the gaps in this corridor along the remaining areas of ROADs B, C, and D.
The files 1006_FillingCorridorGaps_FINISHED.dwg
and 1006_FillingCorrodorGaps_METRIC_FINISHED.dwg
are available for your review.
In Chapter 9, you completed a road-widening example with a simple lane transition. Earlier in this chapter, you worked with intersections and cul-de-sacs. These are just a few of the techniques for adjusting your corridor to accommodate a widening, narrowing, interchange, or similar circumstances. There is no single method for building a corridor model; every method discussed so far can be combined in a variety of ways to build a model that reflects your design intent.
Another tool in your corridor-building arsenal is the assembly offset. In Chapter 8, “Assemblies and Subassemblies,” you had your first glimpse of an offset assembly, but in the example that follows you will have a chance to use one for a bike path design.
Notice in Figure 10.45 how the frequency lines in the corridor are running perpendicular to the main alignment. The bike path is an alignment that is not a constant offset through the length of the corridor. In this scenario, the cross section of the bike path itself is skewed. This could prove problematic when computing end area volumes for the bike path pavement. This is the result of using an assembly where all of the design is based on one main baseline assembly.
There are several advantages to using an offset assembly instead of creating an additional, separate assembly. The offset assembly requires its own alignment and profile for design. In the corridor that results, a secondary set of frequency lines is generated perpendicular to the offset alignment, as shown in Figure 10.46. Additionally, you can use a marked point assembly to model the ditch between the bike path and the main road.
There are many uses of offset assemblies besides bike paths. Typical examples of when you'll use an assembly offset include transitioning ditches, divided highways, and interchanges. The assembly in Figure 10.47, for example, includes two assembly offsets.
When you use an assembly with an offset in your corridor, you must assign an alignment and profile to it. The only restriction to the offset assembly is that it can't use the same alignment or profile as the main part of the assembly. In the case where you want your offsets to follow the same elevation, you will need to use the Superimposed Profile tool to effectively make a copy of the desired profile.
In this exercise, you will model a bike path with an assembly offset:
1007_BikePath.dwg
(1007_BikePath_METRIC.dwg
) file, which you can download from this book's web page.You'll see an incomplete assembly called Road With GR And Bikepath.
Specify offset location:
prompt, click to the left of the Road With GR And Bikepath assembly, leaving enough room for the bike lane and ditch.
Your result should look like Figure 10.48. The warning symbols indicate that you can no longer use the assembly for roads where superelevation occurs at points other than the centerline. Superelevation at the crown will still work, which is the situation used here.
Your assembly should now look like Figure 10.49.
Next, you will use a MarkPoint assembly to set the stage for building a ditch between the bike path and the main road.
Your marker will look like Figure 10.50. Note that the point code defaults to MarkedPoint in the subassembly parameters but can be renamed as needed.
The offset assembly will now look like Figure 10.51.
The completed assembly will look like Figure 10.52.
Next, you will create a corridor using this new assembly. You need to have completed the previous exercise before proceeding:
In the Baseline And Region Parameters dialog, notice that the Offset – (1) is not associated with an alignment (your numbers may vary).
The Bike Path alignment is slightly shorter than the main USH 10 alignment, which would cause the “waterfall” effect explained in Chapter 9.
Your completed corridor will resemble the example shown earlier in Figure 10.46.
You may want to change your annotation scale to 1″ = 1′ (1: 1 for metric users) to get an unobstructed view of your masterpiece.
At each station, the offset assembly ties back to the main assembly because of the use of the LinkSlopeBetweenPoints subassembly. Your design in the Section Editor should resemble Figure 10.53.
Completed versions of these drawings (1007_BikePath_FINISHED.dwg
and 1007_BikePath_METRIC_FINISHED.dwg
) are located with the rest of the dataset for your review.
You'll now take advantage of some of the corridor utilities found in the Launch Pad panel (Figure 10.54) of the contextual tab.
The utilities on this panel are as follows:
There are many uses for the utilities outlined in this section. Once you get the hang of using some of the corridor utilities, you should find that they are straightforward. In the exercise that follows, you will dabble in the corridor utilities:
1008_CorrUtils.dwg
(1008_CorrUtils_METRIC.dwg
).Select a Corridor Feature Line:
prompt, click the south daylight line (this will be the line that is not a constant offset from the centerline alignment).
The Select A Feature Line dialog will appear if you click the daylight line in a cut or fill region. This is because Civil 3D makes two distinct feature lines in these areas. Recall from Chapter 9 that feature lines are formed as a result of marker points with the same name in the assembly connecting together at frequency stations. In other words, why do you have two feature lines here? Because the daylight subassembly creates two marker points at the catch point.
You want the Daylight feature line because it is continuous through the length of the corridor. Daylight_Cut appears only in the cut areas (red) and Daylight_Fill appears only in the fill areas (green). Where the corridor transitions from cut to fill (or fill to cut), you will see a yellow line. Only the Daylight feature line will appear in the transition regions.
Select a Corridor Feature Line:
prompt. If you accidentally exited the Feature Lines From Corridor command, start it again from the Launch Pad panel. Click the daylight line on the north side of the road.Completed versions of this exercise are available with the rest of the dataset.
You've gained some hands-on experience using alignments and profiles as targets in an intersection and in a cul-de-sac design. Civil 3D adds options for corridor targets beyond alignments and profiles. You can use grading feature lines, survey figures, or polylines to drive horizontal and/or vertical aspects of your corridor model.
Imagine using an existing polyline that represents a curb for your lane-widening projects without duplicating it as an alignment, or grabbing a survey figure to assist with modeling an existing road for a rehabilitation project. Better yet, what if the object you are targeting is visible to the corridor drawing only as an XRef? The next exercise will lead you through an example where a lot-grading feature line is integrated with a corridor model through an external reference:
1009_FeatureLineTarget.dwg
(1009_FeatureLineTarget_METRIC.dwg
) file, which you can download from this book's web page. Note that the file 1009_XREF.dwg
(or 1009_XREF_METRIC.dwg
) must be extracted to the same folder as the main file in order to see it for use in this exercise.
This drawing includes a completed assembly and a partially completed corridor. Your task will be to use the feature lines that run through the project as targets in the corridor. These lines are in an external reference file.
The Target Mapping dialog appears.
The Set Width Or Offset Target dialog appears.
Select feature lines, survey figures or polylines to target:
prompt, select the north feature line to the left of the alignment and then press ↵.
The Set Width Or Offset Target dialog reappears, with an entry in the Selected Entries To Target area.
If you stopped at this point, the horizontal location of the feature line would guide the Slope-Left subassembly, and the vertical information would be driven by the slope set in the subassembly properties. Although this has its applications, most of the time you'll want the feature line elevations to direct the vertical information. The next few steps will teach you how to dynamically apply the vertical information from the feature line to the corridor model.
Select feature lines, survey figures or 3D polylines to target:
prompt, select the north feature line to the left of the alignment again and then press ↵.
The Set Slope Or Elevation Target dialog reappears, with an entry in the Selected Entries To Target area.
The corridor will rebuild to reflect the new target information and should look similar to Figure 10.58.
Once you've linked the corridor to these feature lines, any edits to the feature lines will be incorporated into the corridor model. You can establish this feature line at the beginning of the project and then make horizontal edits and elevation changes to perfect your design. The next few steps will lead you through making some changes to this feature line and then rebuilding the corridor to see the adjustments.
This opens the external reference so you can modify the feature lines.
1009_XREF.dwg
or 1009_XREF_METRIC.dwg
), save and close the drawing.
After the external reference closes, you should be back in the corridor drawing. A message will appear in the lower-right corner of your screen indicating External Reference File Has Changed.
1009_XREF.dwg
(for metric users, 1009_XREF_METRIC.dwg
).The corridor will rebuild to reflect the changes to the target feature lines.
See 1009_FeatureLineTarget_FINISHED.dwg
(1009_FeatureLineTarget_METRIC_FINISHED.dwg
) to view a completed version of this exercise.
Edits to targets—whether they're feature lines, alignments, profiles, or other Civil 3D objects—drive changes to the corridor model, which in turn drives changes to any corridor surfaces, sections, section views, associated labels, and other objects that are dependent on the corridor model.
If you really understand what went on earlier in this chapter, you are almost ready for roundabout design. You may want to wait to tackle your first roundabout until after reading Chapter 14, “Grading.”
The same concepts apply to a roundabout as for a standard road junction, but you will have several more regions, baselines, and corresponding profiles.
The following sections will help you prepare files for roundabout design. We will not take you through every detail of corridor creation, but once you master the topics of intersection design, a roundabout is an extension of the same concepts.
A roundabout is best done in several corridors:
Based on your existing ground surface, determine the general direction that you want water to flow away from the center of the roundabout. Use grading tools and a feature line to create the general drainage direction of the roundabout.
Chapter 14 will go into much more depth on creating grading. You will certainly want to have an understanding of grading basics before you tackle a roundabout.
Create a feature line that represents the highest elevations. In the example shown in Figure 10.59, the feature line slopes downward and acts as a ridge to separate water flow. The grading tools are then used to create grading objects and a corresponding surface model called Roundabout Grading.
The Roundabout Grading surface will be the basis for your profile elevations through the rest of the design process.
Roundabouts need alignments to guide the design for the same reasons that an intersection needs them. Alignments will be baselines and targets for the approaches and rotary. Create alignments manually with the tools you learned to use earlier in this chapter, or start with the handy roundabout layout tool.
The roundabout layout tool creates horizontal data based on the location of the center of the roundabout and the approach alignments.
In the exercise that follows, you will create the Civil 3D alignments needed to create a roundabout:
1011_RoundaboutLayout.dwg
(1011_RoundaboutLayout_METRIC.dwg
) file, which you can download from this book's web page.Specify roundabout center point:
prompt, use your Intersection Osnap to select the point where the alignments intersect.
The alignments leading into the roundabout are often referred to as approaches.
Select approach road:
prompt, select all four alignments leading into the roundabout, and press ↵ when you have finished.
You now see the Create Roundabout – Circulatory Road page of the wizard, shown in Figure 10.61.
Autodesk Civil 3D Imperial Roundabouts Presets.xml
. Metric users should be using Autodesk Civil 3D Metric Roundabouts Presets.xml
.
C:ProgramDataAutodeskC3D 2015enuDataCorridor Design Standards
folder. Browse to either the Imperial or Metric units folder and select the correct roundabout presets XML file. Click Open to return to the Create Roundabout dialog.This will be the radius from the center of the roundabout to the outermost circular edge of pavement. This will also adjust other settings in the dialog.
Now, you'll design the approach road exit and entry geometry. The options in the Create Roundabout – Approach Roads page of the wizard (see Figure 10.62) can be set independently for each approach, or you can click Apply To All, which will set the geometry for all four approaches.
The final screen of the Create Roundabout Wizard deals with pavement markings and signage. Notice that you can specify your own blocks for the signs that will be placed in this process.
Everything created in this last step is an AutoCAD polyline or block. The polylines have a global width set to indicate pavement marking thicknesses. These thicknesses are set in the Markings And Signs page (Figure 10.64).
Your roundabout should resemble Figure 10.65. Since standards vary by region, the metric drawing will have slightly different default pavement markings.
Finally, you will add a turn lane in the NW quadrant of the roundabout. When you're creating slip turn lanes, remember that the turn radius must be large enough to fillet the exit and entry roads without overlapping the other alignments.
When selecting the approach entry and exit alignments, you need to click the shorter approach alignments created by Civil 3D rather than the original approach road. For this reason, the exercise has you select inside the islands, just to be sure.
Your roundabout will now look like Figure 10.68.
The completed files, 1011_RoundaboutLayout_FINISHED.dwg
and 1011_RoundaboutLayout_METRIC_FINISHED.dwg
, are available for your review if desired.
You now have all the alignments you need to start your roundabout design. At this point, you can add geometry to the alignments and modify what Civil 3D has created for you.
The horizontal layout is complete, but the roundabout design is far from done. No vertical data has been created; that is up to you.
This is as far as we will take you in this book in regard to building a roundabout step by tedious step. Rest assured, however, that if you have truly mastered corridors, the technique for completing a roundabout is similar to that used for any intersection.
The remainder of this chapter gives you an overview of how to accomplish the rest on your own.
All profiles need to meet at the elevations inside the traveled way in the circular pavement area of the roundabout. Therefore, the main circle design comes first.
To see an example of a completed roundabout corridor, open the drawing 1011_RoundaboutExample_FINISHED.dwg
or 1011_RoundaboutExample_METRIC_FINISHED.dwg
. Use these examples as a guide to “reverse engineer” your own roundabouts when you've mastered other forms of intersections.
You can use any of the circular alignments created by Civil 3D as the basis for this step, as long as your assembly works with the design. Remember to make note of which direction the alignment goes, to ensure that the assembly you create is not backward.
Extract profiles for the main circle design from the Existing Intersection and Roundabout Grading surfaces, as shown in Figure 10.69.
The assembly you create for this preliminary design will also be used in the main design. Decide which alignment will be used as the circular design basis, and create an assembly based on your alignment location and desired geometry, as shown in Figure 10.70.
This assembly can be used in several steps of the process. First, it is used in a preliminary corridor called RAB MAIN. It can also be recycled to be the centerpiece of your main corridor. In the example, the main circle alignment created by Civil 3D, Roundabout_OUTER_EDGE, was used as the baseline for this initial corridor. There are no targets or frequencies set in this corridor. Like the cul-de-sac example earlier in this chapter, this is a preliminary corridor, used to ensure that profiles from the approach roads tie in at the correct elevations.
In the example drawings, a Top link surface was created from the RAB MAIN corridor. At this point, the roundabout will resemble Figure 10.71.
You have all the preliminary surfaces in place, and you have all the alignments you need, so it is time to extract profiles from your various surfaces.
In the 1011_RoundaboutExample_FINISHED.dwg
and 1011_RoundaboutExample_METRIC_FINISHED.dwg
files, the surface profiles for all the approach alignments were created by sampling the existing ground, drainage surface, and preliminary RAB MAIN corridor surface. These profiles will look something like Figure 10.72.
When you create your design, you will see all your design considerations in the profile views. No matter how you decide to tie into existing ground and slope upward toward the surface, your design must tie into the preliminary center surface, as shown in Figure 10.73.
Use techniques you learned earlier in this chapter to assist you. Labels are an especially valuable tool for roundabouts. Keep your profile views organized because you will have at least three for each approach. If you have a slip turn lane, you will have a profile for that as well.
Stretch your legs and go for more coffee. It is time to put this thing together into a completed corridor. When you model the corridor initially, ignore curb islands—you will add them as individual corridors in a later step.
A simple roundabout can be completed using as few as three assemblies. In our example, however, the slip turn lane necessitates a total of four assemblies. In addition to the RAB Main assembly you saw in Figure 10.70, you will need three more assemblies, as shown in Figure 10.74.
These assemblies will be tied to the EOP alignments and profiles as baselines, similar to a traditional intersection. Each quadrant of the roundabout will target at least two alignments and profiles, as shown in Figure 10.75.
Keep in mind the direction of your alignments. If you build the corridor in stages, check the corridor periodically to make sure it is building correctly.
Create a corridor surface from your completed roundabout lanes. You will likely have to use the Add Interactively tool to add the boundary correctly.
The median islands are the last parts to go on the corridor. You can create them using simple grading objects, but since this is a book about mastering skills, and this is a chapter about corridors, you should examine the dynamic way.
Create a simple assembly containing the curb and gutter for the curb islands. This will be the assembly that you use with the median corridors (Figure 10.76).
Each median island will need its own alignment. Take note of the direction of the alignments to make sure they are compatible with the curb island assembly. If necessary, change the direction of the alignments using the Reverse Direction tool in the Modify panel of the contextual ribbon tab. Figure 10.77 shows the bypass island and north island with directions.
The good news is that the elevation data for the medians is already complete. Your main corridor's surface will act as the profile for each individual median. This also means that once the curb return corridors are created, they will be dynamic to the main corridor. After these little corridors are created and surface model information has been obtained, you can set them to Rebuild – Automatic and forget all about them.
Extract a profile for all the curb return alignments from the Top link surface model from the main roundabout corridor, as shown in Figure 10.78. You do not need to see this profile in a view, so you can click OK to extract.
When the design roundabout corridors are complete and surfaces are made, the next step is to merge the surfaces. Create a final surface model and paste the main roundabout design in first. After the main corridor is pasted in, paste the smaller median corridor surfaces, as shown in Figure 10.79. The center median is already taken care of by the first baseline.
Your next step is to use the corridor fine-tuning techniques you learned earlier in this chapter to ensure that your grades are correct and the design is correct. To see an example of a completed corridor using these steps, take a look at 1011_RoundaboutExample_FINISHED.dwg
(1011_RoundaboutExample_FINISHED_METRIC.dwg
), which you can download from this book's web page.
MasterIt1001.dwg
(MasterIt1001_METRIC.dwg
) file, which you can download from www.sybex.com/go/masteringcivil3d2015. Add the cul-de-sac alignment and profile to the corridor as a baseline. Create a region under this baseline that applies the Intersection Typical assembly.MasterIt1001.dwg
(MasterIt1001_METRIC.dwg
) file. You need to have completed the previous exercise before continuing. Add the Second Road alignment and Second Road FG profile as targets to the cul-de-sac region. Adjust Assembly Application Frequency to 5′ (1 m) for tangents and curves.MasterIt1001.dwg
(MasterIt1001_METRIC.dwg
) file. Create an interactive corridor surface boundary for the entire corridor model.3.139.240.244