Junction Upgrade in Civil 3D

This post outlines a workflow for upgrading an existing junction using Civil 3D. The incoming and outgoing lanes of the junction are to be widened to accommodate HGV movements while maintaing the existing main road crossfall along the widened portion.

First lets take a look at the existing junction...

First create centreline alignments for both roads and create surface profiles for each sampling existing ground. Next use the junction design wizard to create our proposed curb return and offset alignments. We are only going to use the horizontal curb return geometry created by the wizard – untick the options to create curb return and offset alignment profiles... 

...and also the option to create the corridor.

A warning message appears to inform us that we are using dynamic surface profiles. Continue with the dynamic profiles.

The wizard creates offset and curb return alignments...

The curb return alignments rely on the offset alignments for their geometry. In order to be able to edit and stretch the curb returns to suit our design we will first have to stretch out the offset alignments to give ourselves enough room to work with.

This needs to be completed for both roads. Next we add turn in lanes to the junction to model the widenings. Select the junction marker and select edit curb returns from the ribbon. Tick to add widen lane for each of the incoming lanes for both curb returns.

Completed curb returns below:

Next we need to extend out the existing main road cross fall so that we can determine the levels along the widened curb return alignments. To do this we create a temporary corridor using the widenmatchslope subassembly. This will allow us to target the existing road surface at the crown and existing road edge and then continue this slope out wide enough to extend past the new widened section - giving us our proposed levels along the widened alignments.

First create the assembly:

The assembly properties are set as below:

Most of the values are set to zero - we are going to use corridor targets for the insert and sample points. We are not overlaying the existing road and we are not adding a widen lane with this assembly so these values are set to zero. The only value we set is the width for the widen portion, this is set at a value that will be wide enough to cover the widened area. Setting a number of values to zero like this will result in a strange looking layout assembly. The appearance of this is not important, it is the behaviour we are interested in.

Create a temporary corridor using this assembly, the main road centreline alignment and existing profile. In the target mapping set the insert point as the edge of existing road and the sample point as the existing road centreline for both the width and offset targets. Also target the existing ground surface.

The temporary corridor can be seen below:

Now create a surface on this corridor and set style to all off. To ensure that our corridor is extending the existing road cross fall correctly we can project the corridor surface onto our side road profile and check as below:

We then create a profile along each of the curb return alignments sampling both the existing ground and temporary corridor surfaces. This should look something similar to below:

We can see the existing ground surface profile in green and the corridor surface in purple. We need to manually draw our design profile using these as a guide. On the left in the profile above we can see where the NE curb return is running along the edge of the main road. The existing road surface is blank for a portion where we are outside the extents of the survey and then on the right we see where we are tying back into the side road. When drawing our design profile we can trace over the temporary corridor surface and tie back into the existing ground at the end of the curb return on the side road. See below:

Repeat this process for the SE curb return. Next we create a curb return assembly.

This will need to contain a subassembly with the ability to target horizontally and vertically. We then build our junction corridor using the curb return alignments as the baselines. The first pass of the NE curb return corridor below:

We need to set two corridor targets - the existing main road edge (surveyed 3D polyline) and the side road alignment and profile

These two targets can be added together - the default behaviour is that Civil 3D looks for the nearest one. Set these for both the horizontal and vertical targets.

Complete the SE curb return in the same manner and the finished corridor appears as below:

Found this useful? Need to learn more? Check out our Advanced Junction Design course HERE

Connecting to MapInfo files in Civil 3D & Map 3D

There are a couple of ways of connecting to MapInfo data in Civil and Map 3D... 

1. Use the MAPIMPORT command
2. Download the free FME FDO provider to allow connectivity to MapInfo files through the standard Map and Civil 3D FDO

We will explore both methods here and also look at the pros and cons of both.

1.  Using the MAPIMPORT command.

On the command line type MAPIMPORT. Browse to the data files and change the files of type to suit.

Select the files and click OK. In the import dialog box for each layer under the data column, click where it reads none and select to create object data - this will add the object data present in the MapInfo files as attributes to the AutoCAD objects (tip here to create polylines instead of mpolygons is to set the MAPUSEMPOLYGON variable to OFF) created on import.

After importing the data we can inspect the properties of the imported objects. Below we see that the selected polyline has been placed on an AutoCAD layer with the same name as the MapInfo file it was imported from. Also we can see that the object data has been added as an attribute to the polyline - the province name in this case.

The data is imported in AutoCAD format. The control of the display of the imported objects is achieved through use of AutoCAD commands - layers, draw order etc... as you would with any AutoCAD objects. We cannot perform any GIS analysis on the data - for example to stylize or query the objects based on the attached attribute data. In summary importing using the MAPIMORT command is useful to create AutoCAD drawings from the MapInfo files but leaves us limited in terms on controlling the display of and analysing the data.

Using the FDO connection provides us with more control over the data...

2.    Use the FDO data connect

The out of the box FDO in Map and Civil 3D does not allow connectivity to MapInfo files. Luckily there is a add-on that will enable connection to 9 additional formats including MapInfo TAB, MIF/MID and SPATIALWARE...

The add-on, developed by Safe Software, is free and can be downloaded from the following link:

http://www.safe.com/solutions/for-applications/autodesk/autodesk-autocad-map-3d/fme-fdo-provider/

Once installed you can access the new connections through the FDO in Map or Civil 3D. On the command line type MAPWSPACE and press enter twice. This brings up the Map workspace. Click on DATA icon and connect to data...

...here you will see the usual data connection formats plus an extra one entitled Add FME connection. Double click on this and select MapInfo Tab as the file format. Browse to the files, select and open.

Back in the data connect dialog box select the tick boxes to display the schema and click on Add to Map

The selected files are added as Map 3D layers to the drawing... 

...this allows you to control the draw order easily through Map task pane by dragging and dropping layers to change their order.

You can also easily control the display of layers by checking or unchecking the tick box beside each.


You an also view the object data associated with each layer in table format. In the table you quickly zoom to a particular feature by right clicking on one and selecting zoom to.

You can use the style button to control and edit the display of each layer. We can make use of the information in the data table to enhance layer appearance. For example in this case I have imported a MapInfo file containing elevations. We can edit the style of this layer to show ranges in elevation and give more depth to our drawing.


To do this, first change the draw order of the layers to bring the layer you are going to stylise to the top. Highlight the layer in the Map Workspace and click on style, select new theme and choose the property upon which you wish to stylize the layer. Then change the colour of the style range to suit.

Once this is complete the layer style will update automatically in the drawing.

In summary using the FDO data connect in Map and Civil 3D provides you with far greater control over the data than using MAPIMPORT, for both display and GIS analsyses.

Customising Cross Sections

A query that has come up regularly (on overlay jobs) is how to display proposed levels on cross sections at specified offsets from the baseline... (and then get them out to csv file)


For this example I am using the UKIE country kit:


First add a new band to your cross section in the section view properties < bands tab - Select the 'Surface Levels at Major Interval (Section 1)' band style from the list as shown and click 'Add'.

Untick 'Match major/minor increments to vertical grid intervals'. Set the 'major interval' for your band to the desired offset. The display of the minor interval labels is turned off by default for this band.

Set the band to read the desired surface and your sections should display levels at offsets from baseline.

While it is one thing to have these levels displayed on cross sections; how do we get them out to csv file for setting out? This takes a bit more working around. There may be an easier way to achieve the following so please post it if you know how...


Create your final corridor with finished ground surface. Create a new assembly. On the 'Generic' tab of the toolpalettes select the 'LinkOffsetonSurface' subassembly and set the following properties:


Offset from Baseline: 2.5m
Point Codes: 2.5m right

Leave other options at default. Build a new (dummy) corridor using this assembly, the road centreline alignment and associated profile. In the corridor properties < parameters tab < set all targets and set the target surface to the surface you want to sample.

Now we can extract the points using reports. In your Toolspace under:  Toolbox tab < Reports Manager < Corridor < use the 'Section Points Report'

In the report dialog box select your dummy corridor (the linkoffsetonsurface one) and you should see your point code listed under the list of features. Set the station interval and click create report. You can then copy from here into excel and edit as necessary.


There are other reports in the toolbox that will produce something similar but i have found this one easiest to edit in excel afterwards. Also as an alternative you could create cogo points from your dummy corridor, place them in a point group and export them directly to csv file. Using the report above produces a better result as it will give points across your corridor at each chainage. Exporting from point group only gives easting northing and not chainage.


Also why not add the linkoffsetonsurface subassembly to your design corridor assembly rather than creating a new assembly for it?


If you add the linkoffsetonsurface subassembly to your design corridor assembly you cannot reference the corridor finished ground surface in the targets. This is because a circular reference will be created – both the corridor and the assembly would be trying to reference objetcs from eachother. The solution is to create a separate assembly as above.


I had originally posted this on the UK & Ireland Civil 3D user forum at http://civil3dukie.com