Chapter 12

Superelevation

Superelevation and cant tools have matured greatly since the early releases, and theAutoCAD® Civil 3D^® 2013 software has added even more functionality.

Before you can understand the superelevation tools, you should have a good grasp of alignments, assemblies, and corridors. You may want to refer to the corresponding chapters for a refresher on those topics before attempting to put superelevation or cant into practice.

In this chapter, you will learn to:

• Add superelevation to an alignment
• Create a superelevation assembly
• Create a rail corridor with cant
• Create a superelevation view

Getting Ready for Super

Several pieces need to be in place before superelevation can be applied to the design. You will need a design criteria file appropriate for your locale, design speeds applied to an alignment, and an assembly that is capable of superelevating.

There are a lot of abbreviations and terminology thrown around when it comes to superelevation, so let's take a look at that first.

When an assembly is applied without superelevation, the geometry comes directly from the original design, as shown in Figure 12.1.

Figure 12.1 An example assembly without superelevation

As the assembly begins its entrance into a curve with superelevation applied to it, it will first start to lose its normal crown. Figure 12.2 shows the same assembly at the End Normal Crown (ENC) station.

Figure 12.2 At the End Normal Crown (ENC) station, the default lane slope starts to change.

When the assembly has one side flattened out, as shown in Figure 12.3, it is called Level Crown (LC).

Figure 12.3 Level Crown entering a left-hand turn

When the assembly straightens out into a plane that matches the inside lane, it is called Reverse Crown (RC), as shown in Figure 12.4.

Figure 12.4 Reverse Crown (RC)

If accommodations have been made for shoulder slope rollover and breakover removal, the shoulder will shift as well. The left image of Figure 12.5 shows where the superelevated lane becomes steep enough to cause an outside rollover problem with the outside shoulder. The shoulder begins to adjust to increase the safety of the road. The right image of Figure 12.5 shows the change in the lower shoulder.

Figure 12.5 Begin Shoulder Rollover (BSR) (left) and Low Shoulder Match (LSM) (right)

Finally, the lane gets to its maximum slope at the Begin Full Super (BFS) station. As you can see in Figure 12.6, all the geometry adjustment has taken place.

Figure 12.6 Begin Full Super (BFS)

On the way out of the curve, you will see the geometry transitioning back to its original design. It will pass through End Full Super (EFS), Low Shoulder Match (LSM), Reverse Crown (RC), Level Crown (LC), Begin Normal Crown (BNC), and finally back to Begin Normal Shoulder (BNS).

Now that you are familiar with the terminology and abbreviations Civil 3D uses, let's get started on some design.

Design Criteria Files

Having the correct design criteria file in place is the first step to applying superelevation to your corridor. These XML-based files contain instructions to the software on when to flag your design for geometry problems both horizontally and vertically. Design criteria files are the brains behind how your road behaves when superelevation is applied to the design.

Several design criteria files are supplied with Civil 3D upon installation. The out-of-the-box standards include AASHTO 2001 and AASHTO 2004 for both metric and Imperial units. Several of the country kits include design criteria files for your locality if you are outside of the United States. If country or state kits do not exist for your situation, you can create your own, user-defined files.

To create your own design criteria:

C:ProgramDataAutodeskC3D 2013enuDataCorridor Design Standards

C:ProgramDataAutodeskC3D 2013enuDataRailway Design Standards

Inside the Design Criteria Editor (Figure 12.7), you will see three headings: Units, Alignments, and Profiles. The Units page tells Civil 3D what type of values it will be using in the file. The Alignments page is used for checking design, creating superelevation, and widening outside curves. The Profiles page provides tabular data for minimum K value used to check vertical design.

Figure 12.7 Inside the Design Criteria Editor

Civil 3D will graphically flag alignments when the design speed specified in the alignment properties has a radius less than the value specified in the Minimum Radius Table. The Minimum Radius Tables from AASHTO use superelevation rates in the table names, but this does not lock you into that rate for applying superelevation to the corridor. In other words, just because you use a more conservative value in your radius check, that doesn't mean you can't superelevate at a steeper rate. The tables are independent of one another.

Also in the Alignments page you will find the superelevation attainment equations. These equations determine the distance between superelevation critical stations. Familiarize yourself with the terminology and locations represented by these stations, as shown in Figure 12.8.

Figure 12.8 Superelevation critical stations and regions calculated by Civil 3D

In the following exercise, you will modify an example design criteria file and save it:

1. Open the Highway 10 Criteria.dwg (Highway 10 Criteria_METRIC.dwg)file, which you can download from this book's web page at www.sybex.com/go/masteringcivil3d2013.

2. Select the Highway 10 alignment that already exists in the drawing.

3. From the Modify panel on the context tab, select Design Criteria Editor.

4. Click the Open button at the top of the dialog, and browse to the _MasteringExample.xml (_MasteringExample_METRIC.xml) file, which is part of the dataset you downloaded for this chapter.

5. Expand the Alignments category, and expand the Superelevation Tables area.

There is only one superelevation table in this example for 4% maximum slope.

6. Right-click on Superelevation Tables, and select New Superelevation Table.

7. Double-click the new table and rename it Example 6% Super.

8. Right-click on Example 6% Super, and select New SuperelevationTypeByTable.

9. Expand the new section, right-click SuperelevationTypeByTable, and select New Superelevation Design Speed, as shown in Figure 12.9.

Figure 12.9 Adding a design speed to the design criteria file

When you expand the SuperelevationTypeByTable section, you will see that Civil 3D has placed a new design speed with a default of 10mph in the listing.

10. Double-click the Design Speed 10 and change the design speed to 30 mi/hr (50 km/hr).

Notice that you only need the numeric value; Civil 3D fills in the rest of the table name for you.

11. Highlight your example design speed.

The right side of the dialog will have an empty table containing columns for Radius and Superelevation Rate.

12. Select the first row of the table. Click the first field in the Radius column to start entering data. Add several radius and superelevation values, as follows:

Curve radius (feet)	Curve radius (meters)	Superelevation %
300	90	6
1000	300	4.5
1500	450	3.2
2000	600	2.6
4000	1250	NC

When you have completed your data entry from the table, your Design Criteria Editor will resemble Figure 12.10.

Figure 12.10 Adding example data using the Design Criteria Editor

13. Add a note in the Comment field that reads Example Data Only!

14. Click the Save And Close button at the bottom of the editor.

15. Click Save Changes and exit when prompted.

Ready Your Alignment

Superelevation stations are connected to alignment curves. The design speed from the alignment properties is needed at each curve to specify which superelevation rate tables to use from the design criteria. The design speed has an effect on the distance between superelevation critical stations and the cross-slope used when the road is at full-super.

It is a good idea to get your alignment geometry and design speed locations finalized before attaching superelevation. If a change is made to your alignment, the superelevation stationing will be marked as out of date.

Super Assemblies

As a general rule, if the lane subassembly has the word “super” somewhere in its name, it will respond to superelevation. If you want to verify that the lane you are choosing will behave the way you want it to in a superelevation situation, you can right-click it from the tool palette and access the subassembly help.

As long as you stay away from the Basic tab, all of the shoulder and curb subassemblies have parameters you can set to dictate how the assembly is to behave when an adjacent lane superelevates.

Most subassemblies that are capable of superelevating are intended for use where the pivot point for the cross section is at the center crown of the road. When the pivot point is at the center of the road, the baseline profile dictates the final elevation of the crown of the road. Figure 12.11 shows an example of a two-lane highway (top image) and a four-lane divided highway (bottom image) that are designed to be used with the superelevation tools.

Figure 12.11 Two-lane road ready for super; four-lane road used in super

Axis of Rotation Support

The axis of rotation (AOR) subassembly can be used when the centerline of the road is not the pivot point for superelevation. The “flag” symbols (as shown in Figure 12.12) indicate potential pivot points on the assembly.

Figure 12.12 AOR subassemblies used on an undivided, crowned roadway

The flag symbols on LaneSuperelevationAOR indicate where the lane can be pinned down and used as a pivot point. When the axis of rotation is not the centerline of the road, the lane geometry is used to determine the change in elevation that will occur as a result.

When building assemblies with LaneSuperelevationAOR you may see warnings appear, as shown in Figure 12.13.

Figure 12.13 A warning symbol on an assembly using LaneSuperelevationAOR

Here are some of the warnings you may encounter:

You can still add assemblies with warnings to a corridor; however, the superelevation may not behave as expected.

The Tipping Point

In some design situations that use superelevation, the crown of the road is not the ideal pivot point. In the following example, you will create a four-lane divided highway that pivots inside the curve rather than at the crowns during superelevation.

1. Open the file AOR Assembly.dwg (AOR Assembly_METRIC.dwg).

2. Zoom into the assembly that was started for you in this drawing.

Note that a generic link has been placed on each side as a spacer for the subassemblies that you will be adding in the next steps.

3. Open your subassembly tool palette (Ctrl+3 will work) and find the Lanes tab.

4. Select the LaneSuperelevationAOR subassembly.

5. In the Advanced Parameters of the properties, set Side to Right and Use Superelevation to Right Lane Outside.

6. Place the subassembly on the right side, using the generic link marker as its “hanger.” Press Esc to complete the placement of the generic link.

7. Select the newly placed subassembly, choose the Subassembly: LaneSuperelevationAOR contextual tab ⇒ Modify Subassembly panel, and click Mirror.

8. Click to attach the mirrored subassembly to the left side of the subassembly you just placed.

A dialog will appear confirming that you want to place the mirrored subassembly on the same side. Click OK.

9. Select the newly placed subassembly and view its AutoCAD properties.

10. Change the Use Superelevation parameter to Right Lane Inside, as shown here.

11. Repeat steps 4–10 for the left side of the assembly.

Be sure to use the subassembly parameters to the correct superelevation property. Note that the inside lane must have Use Superelevation set to Left Lane Inside and the outside lane must be set to Left Lane Outside.

12. On the tool palette, switch to the Generic tab. Select the MarkPoint subassembly, change Point Name to MEDIAN, and place it by clicking the red circle on the inside right edge of the pavement.

13. On the Medians tab, select Median Depressed, and change Marked Point Name to MEDIAN.

14. Leave all other parameters at their defaults and place the median on the inside left of the subassembly as shown here. Press Esc when complete.

15. As the final step in building this assembly, select both of the original generic link spacers and set the Omit Link property to Yes.

If time permits, add the ShoulderExtendAll subassembly to the outermost edges using the default settings. Press Esc when complete.

16. Select the alignment that runs through the project.

17. On the Alignment contextual tab, click Superelevation ⇒ Calculate/Edit Superelevation, and click the Calculate Superelevation Now option when notified that no data exists.

18. Set Roadway Type to Divided Crown With Median.

19. Set the pivot method to Inside Of Curve.

20. Set the median treatment to Distorted Median, and click Next.

21. On the Lanes page, set the normal lane width to 12′ (4 m) and the normal lane slope to -2.00%.

22. Place a checkmark next to Symmetric Roadway, and click Next.

23. On the Shoulder Control page, leave the settings at their defaults, and click Next.

24. On the Attainment page, set the active criteria file to Autodesk Civil 3D Imperial (2004) Roadway Design Standards.xml (Autodesk Civil 3D Metric(2004) Roadway Design Standards.xml).

25. Set the superelevation rate table to AASHTO 2004 Customary eMax 6% (AASHTO 2004 Metric eMax 6%) using the 4 Lane Transition Length table.

26. Toggle on Automatically Resolve Overlap, and click Finish.

27. In Prospector, select the corridor Route 66, right-click, and select Rebuild.

28. Select the corridor in plan and enter the Section Editor to examine your corridor.

You should observe that superelevation is occurring based on our specified pivot point of inside the curves. Close the Section Editor when you can't take anymore awesomeness.

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Applying Superelevation to the Design

Civil 3D takes into account other factors such as curve station locations and assembly geometry. Superelevation information is associated with the alignment, but is handed in a separate calculation area. In this section you will put all the pieces in place that are needed for the software to dynamically apply superelevation or cant to your design.

Start with the Alignment

To begin applying superelevation to the design, select your alignment:

1. Open the Highway 10 Super.dwg (Highway 10 Super_METRIC.dwg) file, which you can download from this book's web page.

2. Select the Highway 10 alignment that already exists in the drawing.

3. From the Alignment contextual tab, select Superelevation ⇒ Calculate/Edit Superelevation.

4. When prompted by the dialog, click Calculate Superelevation Now.

5. On the Calculate Superelevation – Roadway Type page, select the Undivided Crowned radio button.

6. From the Pivot Method drop-down, choose Center Baseline, as shown in Figure 12.14, and click Next.

Figure 12.14 Roadway type specification for superelevation

7. On the Lanes screen, verify that the Symmetric Roadway check box is selected.

8. Set Normal Lane Width to 12′ (4 m), and set Normal Lane Slope to -2.00%, as shown in Figure 12.15, and click Next.

Figure 12.15 Lane information

9. On the Shoulder Control screen, make sure the Calculate check box is selected on the right side of the page.

Only the Outside Edge Shoulders should be active. Since this is an undivided road, the options for the Inside Median shoulders are grayed out.

10. Set Normal Shoulder Width to 6′ (2 m), and set Normal Shoulder Slope to -5.00%.

11. For Shoulder Slope Treatment, set the following:

• Set the Low Side option to Breakover Removal.
• Set the High Side option to Default Slopes.
• Place a check mark next to Maximum Shoulder Rollover and set the value to 8.00%.

Your Shoulder Control screen should look like Figure 12.16.

Figure 12.16 Shoulder Control and Breakover Removal parameters

12. Click Next.

13. On the Attainment screen, click the ellipsis button to verify that the design criteria file is set to Autodesk Civil 3D Imperial (2004) Roadway Design Standards.xml (Autodesk Civil 3D Metric (2004) Roadway Design Standards.xml).

14. Set the superelevation rate table to AASHTO 2004 US Customary eMax 4% (AASHTO 2004 Metric eMax 4%).

15. Set the transition length table to 2 Lane.

16. Set the Attainment method to AASHTO 2004 Crowned Roadway.

17. Place a checkmark next to Curve Smoothing and set the Curve Length to 50′ (20 m).

Leave all other settings at their defaults, as shown in Figure 12.17.

Figure 12.17 Finalizing the superelevation on the Attainment screen

18. Click Finish.

You should now seethe superelevation table appear inside Panorama with the data resulting from the wizard. Examine your alignment; you should now have labels showing the superelevation critical stations created by the wizard.

As you click in the table, you will see helpful glyphs showing you which superelevation station and corresponding curve you are editing, as shown in Figure 12.18.

Figure 12.18 Superelevation table with glyphs in the graphic

Transition Station Overlap

It is not uncommon to have overlap warnings in your superelevation table. You should resolve the transition station overlap before you continue your design.

Overlap occurs when there is not enough room between curves to fully transition out of one curve and back into the next. Transition station overlap will always occur when a reverse curve or compound curve exists in your alignment. As you can see in Figure 12.19, Curve 1 does not complete its transition out until station 16+82.56, but according to the attainment calculations, Curve 2 will begin affecting the shoulder starting at station 15+35.24.

Figure 12.19 Superelevation table showing overlap between two curves

You have several options for fixing superelevation overlap:

• You can choose to have Civil 3D rectify the overlap for you.
• You can manually modify the stations in the table.
• You can change the stationing for superelevation by modifying the superelevation view, which we will discuss later in this chapter.

To have Civil 3D clear the overlap for you, click the warning symbol that appears in the Superelevation Tabular Editor. Civil 3D resolves overlap by omitting noncritical stations and/or by compressing the transition length between certain stations. In the case of a reverse curve, Civil 3D will pivot the road from full-super to full-super, without transitioning back to normal crown. Be sure to verify that the software has made the update that meets the requirements of your locale.

Preserving Your Manual Edits

You may spend hours getting your superelevation stations to work out correctly. However, it just takes one wrong button click to blow away all your time-consuming edits to the tabular input. To save you from yourself (or the click-happy intern), back up your superelevation tables by exporting them to a file. You'll find the Export Superelevation Data button at the top of the tabular input.

When you need to reimport the superelevation data, clear any data and click Import From File.

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Oh Yes, You Cant

In the civil engineering industry, the terms superelevation and cant are often used interchangeably. Inside Civil 3D, the terms have distinct meanings (Figure 12.20).

Figure 12.20 Example cant data table

Superelevation tools in Civil 3D are used for roads where the cross-slope changes within a curve are expressed by a percentage. Unlike superelevation, cant is expressed as a difference in height between the outer and inner rails.

Workin' on the Railroad

Cant tools are new to Civil 3D 2013 and are specifically designed for rail. In order to work with cant, the following must be in place:

Alignment Type Set to Rail

Normally, you would set the alignment type when you first define the alignment. If you forget to set this initially, you can change it at any time in the alignment properties on the Information tab.

Alignment Design Speed

Like motorways and superelevation, rail requires a design speed in order to apply cant. Cant design standards are provided with the software, and can be edited in the same manner as other design criteria files.

Cant Calculated

Like superelevation, cant is attached to an alignment and its curves. As seen in Figure 12.21, the icon's location in the Alignment contextual tab should be reminiscent of the superelevation button.

Figure 12.21 Accessing the Cant Calculation tools from the Rail Alignment contextual tab

Rail Assembly

When working with an assembly for rail, the type must be set to Railway. You can set this on assembly creation, or in the assembly properties after the fact. There is one subassembly that is purpose-built for cant, the Rail subassembly, as shown in Figure 12.22. If you are working with a drawing created in a previous release, make sure you replace the old assemblies with this new rail subassembly to ensure cant takes place.

Figure 12.22 The new rail subassembly

Creating a Rail Assembly

You will find the Rail assembly in the Bridge And Rail tab of the tool palettes. The following exercise will walk you through creating a typical rail bed design:

1. Open the drawing Rail.dwg (Rail_METRIC.dwg), which you can download from this book's website.

This drawing contains an alignment and design profile.

2. On the Home tab ⇒ Create Design panel ⇒ Assembly, click Create Assembly.

3. Name the assembly Rail w Service Road.

4. Set Assembly Type to Railway, and click OK.

5. Click to place the assembly anywhere in the graphic.

6. Open the tool palettes if they are not already open. In the subassembly tool palettes, locate the Bridge And Rail palette, and click Rail Single. In the Properties palette:

A. Set the Subballast width to 20′ (6 m).

B. Set the Subballast Side slope to 0.001:1.

Leave all other parameters at their defaults.

7. Click the assembly to place the RailSingle subassembly.

8. Switch to the Basic palette, and click GenericPavementStructure.

This will be our service road, constructed out of the same material as the subballast.

9. Enter the following data into the Properties palette, remembering that the codes are case-sensitive:

A. Set Side to Left.

B. Set Width to 8′ (2.5 m).

C. Set Depth to 1′ (0.3 m).

D. Set DeflectOuterVerticalFace to Yes.

E. Set Outer Edge Slope to 2:1.

F. Set TopLink Codes to Top, and set BottomLink Codes to Datum.

G. Set Shape Codes to Subballast.

10. When your Parameters resemble Figure 12.23, click to place the GenericPavementStructure to the left of the rail subassembly.

Figure 12.23 Placing an assembly to represent additional subballast for a service road next to the rail bed

11. Remain in the GenericPavementStructure tool, but change the width to 0.1′ (0.03 m).

12. Click to place the structure on the right side of the rail subassembly.

13. Switch to the Generic palette, and click LinkSlopeToSurface.

14. Set Slope to -50 and click the “tip” of the generic pavement structure on both sides of the assembly.

Your completed assembly will look like Figure 12.24.

Figure 12.24 Your completed rail assembly

15. Save and close the drawing.

Applying Cant to the Alignment

Like superelevation in a roadway alignment, cant is related to a rail alignment. The following exercise will walk you through applying cant to the alignment. You should experience a distinct déjà-vu feeling if you completed earlier exercises involving applying superelevation to the alignment.

You should observe that your section views show the cant applied to the design.

Superelevation and Cant Views

Superelevation and cant views are a graphic representation of the roadway or rail superelevation. Grip edits to the graphical view will also edit the superelevation stations. The view itself is not intended for plotting. The superelevation view plots station against lane slope to form a sort of profile of the left and right edges of the pavement.

At first glance, the superelevation view may seem difficult to read, but with a little explanation it can shed a lot of light on what is going on with your lane slopes. Figure 12.25 shows the superelevation diagram for a two-lane road that contains a reverse curve. The superelevation graphic plots the station value against the percent cross-slope of each edge of pavement. The upper line shows the behavior of the right edge of the pavement, and the lower line shows the left edge of the pavement.

Figure 12.25 The superelevation view

Where no superelevation is applied, the graph data is flat. As the assembly twists into position during superelevation, the distances between the lines become greater as the right edge slopes up to a maximum superelevation of 5.6%. You can also see in Figure 12.25 how Civil 3D has resolved overlap between the two curves. Neither line goes back to the default position at -2.00% until the end of the alignment. The crisscross in the center indicates that the roadway transitions directly from one max super to the other.

Place the view into Civil 3D by selecting the alignment and clicking Superelevation ⇒ Create Superelevation View. To simplify the view and make it easier to edit, you can choose which lanes to show or hide at the bottom of the view, as shown in Figure 12.26. You should also change the colors for left and right edge of pavement by clicking the ByBlock option and changing it to the color of your choice.

Figure 12.26 Creating a superelevation view

To modify superelevation data using the graphic, click on it to activate the numerous grips. Figure 12.27 shows a close-up of some of the grips you will see.

Figure 12.27 Grip-editing is another method for fine-tuning your superelevation stationing.

The diamond-shaped grips can be slid in one axis to modify stationing (the horizontally oriented grips) or slope (the vertically oriented grips). The rectangular grip can be moved to reduce the maximum lane slope when it is in a full-super state.

The Bottom Line