Offset alignments and widenings

Last updated: 2026-01-06

Total video time: 36:22

Exercise file: ali-data-C3D22.zip

Video: ali-offst-widen-00.mp4 2:36

A roadway design consists of 3 main elements; alignment, profile, and cross-section. When combined, provides a 3D layout of the roadway.

  • Alignment is the route of the road, defined by horizontal tangents and curves.
  • Profile is the vertical aspect of the road.
  • Cross-section shows the precision and number of lanes and sidewalks, cross slopes or banks, drainage features, and pavement structures.

 

Offset alignment function helps place identify the lanes, sidewalks, and other geometric physical elements of the road horizontally. Offset alignments are dynamically linked to a parent alignment and dependent on their geometry. Usually it is the centerline of the road. The offset alignment function is perfect for defining linear geometry as the roadway evolves.

Widening regions can be placed along the geometry of the offset alignments and useful for creating bus bays, medians, turn lanes, shoulders, and parking lanes. Offset widening should not be a negative offset value.

Video: ali-offst-widen-01.mp4 5:37

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-All.dwg
    3. Open

Create offset alignment

  1. Ribbon > Home tab > Create Design panel > Alignment dropdown > Create Offset Alignment
  2. Select an alignment:Right-click > Select Alignment dialog box > select alignment 25 OK

    Tip: When there are more than one alignment, right-click and select the alignment from the list in the Select Alignment dialog box.

  3. Create Offset Alignments dialog box

    These settings are based off the parent alignment. We will keep most as is, but they can be edited.

    1. Incremental offset on left: type 12
    2. Incremental offset on right: type12
    3. General tab > Alignment style: dropdown and select RDWY Shoulder Paved
    4. General tab > Alignment label set: dropdown and select _No Labels
    5. OK
  4. Ribbon > Home tab > Create Design panel > Alignment dropdown > Create Offset Alignment
  5. Select an alignment:Right-click > Select Alignment dialog box > select alignment 25 OK
  6. Create Offset Alignment dialog box
    1. Incremental offset on left: type 15
    2. Incremental offset on right: type 15
    3. General tab > Alignment style: dropdown and select RDWY Pavement Edge
    4. General tab > Alignment label set: dropdown and select_No Labels
    5. OK
  7. Ribbon > Home tab > Create Design panel > Alignment dropdown > Create Offset Alignment
  8. Select an alignment:Right-click > Select Alignment dialog box > select alignment 25 OK
  9. Create Offset Alignment dialog box
    1. Incremental offset on left: type 25
    2. Incremental offset on right: type 25
    3. General tab > Alignment style: dropdown and select RDWY Shoulder Aggregate
    4. General tab > Alignment label set: dropdown and select _No Labels
    5. OK

The drawing now contains alignment 25 and offset alignments with object styles. If the parent alignment changes, the offset alignments are dynamically linked and will move along maintaining their offset values.

Video: ali-offst-widen-02.mp4 8:46

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-All-ali-offst-widen-02.dwg
    3. Open

Viewing alignments and offset alignments in Toolspace

  1. Toolspace > Prospector tab

    In Master View, Open Drawings should be expanded and list all drawings. The drawing in bold font is the active drawing.

  2. Expand AliProf-All > expand Alignments > expand Centerline Alignments and Offset Alignments

How to open Alignment Properties dialog box

  • Left click alignment 
  • Contextual ribbon > Modify panel > Alignment Properties
  • Right-click menu > Alignment Properties...
  • Toolspace > Prospector tab > expand Alignments > expand Offset Alignment > right-click alignment > Properties...

Renaming offset alignments

  1. Toolspace > Prospector tab > expand Alignments > expand Offset Alignment > right-click offset alignment 25-Left-12.000 > Properties...
  2. Alignment Properties dialog box
    1. Information tab > Name: type 25-L-ETW (edge of travel way)
    2. OK
  3. Continue down the list for each offset alignment listed in Toolspace.
  4. Right-click offset alignment 25-Left-15.000 > Properties...
  5. Alignment Properties dialog box
    1. Information tab > Name: type 25-L-EPS (edge of paved shoulder)
    2. OK
  6. Right-click offset alignment 25-Left-25.000 > Properties...
  7. Alignment Properties dialog box
    1. Information tab > Name: type 25-L-EGS (edge of gravel shoulder)
    2. OK
  8. Right-click offset alignment 25-Right-12.000 > Properties...
  9. Alignment Properties dialog box
    1. Information tab > Name: type 25-R-ETW
    2. OK
  10. Right-click offset alignment 25-Right-15.000 > Properties...
  11. Alignment Properties dialog box
    1. Information tab > Name: type 25-R-EPS
    2. OK
  12. Right-click offset alignment 25-Right-25.000 > Properties...
  13. Alignment Properties dialog box
    1. Information tab > Name: type 25-R-EGS
    2. OK

Check your work

  1. Left-click furthest left/west offset alignment
  2. Properties palette > Information
    1. Confirm Style: RDWY Shoulder Aggragate
    2. Confirm Name: 25-L-EGS
  3. ESC to end

Save drawing and close drawing

  1. Quick Access > Save ORCtrl + S
  2. Close drawing, left-click X on AliProf-All tab, at the top of Modelspace.

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-4thAve-ali-offst-widen-02.dwg
    3. Open

Renaming offset alignments

  1. Toolspace > Prospector tab > expand Alignments > expand Offset Alignment > right-click offset alignment 4thAve-Left-12.000 > Properties...
  2. Alignment Properties dialog box
    1. Information tab > Name: type 4thAve-L-ETW
    2. OK
  3. Right-click offset alignment 4thAve-Left-18.000 > Properties...
  4. Alignment Properties dialog box
    1. Information tab > Name: type 4thAve-L-EGS
    2. OK
  5. Right-click offset alignment 4thAve-Right-12.000 > Properties...
  6. Alignment Properties dialog box
    1. Information tab > Name: type 4thAve-R-ETW
    2. OK
  7. Right-click offset alignment 4thAve-Right-15.000 > Properties...
  8. Alignment Properties dialog box
    1. Information tab > Name: type 4thAve-R-EPS
    2. OK

Check your work

  1. Left-click furthest left/north offset alignment
  2. Properties palette > Information
    1. Confirm Style: RDWY Shoulder Aggragate
    2. Confirm Name: 4thAve-L-EGS
  3. ESC to end

Video: ali-offst-widen-04.mp4 4:38

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-All.dwg
    3. Open

Open Toolspace palette

The Toolspace palette helps to navigate through, gives details of what Civil3D objects exist in the drawing, and styles or settings that can be selected and are available. Two ways to open the Toolspace palette:

  • Commandline: type Toolspace
  • Ribbon > Home tab > Palettes panel > Toolspace and anchor to left or right side of the drawing area.

Add widening to offset alignment

Adding widening to the road allows more room to get around turns, create off ramps, turn lanes, and bus bays.

  1. Toolspace > Prospector tab > expand Alignments > expand Centerline and Offset Alignments
  2. Offset Alignments > Right-click 25-R-ETW > Add Widening...
  3. Create Widening portion as a New Alignment? [Yes/No]:YEnter
  4. Select start station:38370Enter
  5. Select end station:38462Enter
  6. Enter widening offset:22Enter
  7. Specify side [Left/Right]:REnter
  8. Offset Alignment Parameters dialog box

Changing properties in Alignment Parameters dialog box

Zoom into widening area of the alignment to visually see the changes. The component that is changing will highlight in the drawing.

  1. Transition Parameters at Exit > Transition Length: type 1Enter
    1. Notice transition taper is gone and there's a sharp return.
  2. Transition Parameters at Entry > Transition Length: type 50Enter
    1. Notice start station changed from 383+70.00' to 383+45.00'.
    2. Notice region length increased from 92' to 117'.
  3. Widening Parameters > Start station: type 38350Enter
    1. Notice it maintained the 50' transition length, but moved the station forward and reduced the region length.
  4. Widening Parameters > End station: type 38367Enter
    1. Notice region length decreased.
  5. Transition Parameters at Entry > Taper Input Type: change to By Taper Ratio
  6. Transition Parameters at Entry > Taper Ratio: type 3Enter (it will assume the 1: portion)
    1. Notice widening area in the drawing, measuring 1' in length.

Video: ali-offst-widen-05.mp4 3:16

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-All.dwg
    3. Open

Add widening to EPS alignment

  1. Toolspace > Prospector tab > expand Alignments > expand Centerline and Offset Alignments
  2. Offset Alignments > Right-click 25-R-EPS > Add Widening...
  3. Create Widening portion as a New Alignment? [Yes/No]:NEnter
  4. Select start station:Shift + right-click > Osnap Endpoint > select start station point of previous widening area.
  5. Select end station: Select end station point of previous widening area.
  6. Enter to end command
  7. Enter widening offset:37Enter
  8. Offset Alignment Parameters dialog box
    1. Transition Parameters at Entry > Taper Input Type: change to By Taper Ratio
    2. Transition Parameters at Entry > Taper Ratio: type 3Enter
    3. Widening Parameters > Start station: select Green Box icon - Select from Screen
      1. Shift + right-click > Osnap Endpoint > select start station point of previous widening area.
    4. Transition Parameters at Exit > Transition Length: type 1Enter
    5. Select X to close Offset Alignment Parameters dialog box

Video: ali-offst-widen-06.mp4 2:38

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-All.dwg
    3. Open

Add masking to offset alignment 12-R-ETW

The masking properties allows a selected area or region, along the alignment, to be masked or hidden. Even though the area isn't visible, the information still exists; the stationing and geometry is still active.

  1. Toolspace > Prospector tab > expand Alignments > expand Offset Alignments > Right-click 12-R-ETW > Properties...
  2. Alignment Properties dialog box
    1. Masking tab > Masking regions > Add masking region icon
    2. Specify first station for masking region: type 33000Enter
    3. Specify second station for masking region:OSnap to the start point of the widening transition area. Enter
  3. Alignment Properties dialog box
    1. Masking tab > Masking regions > Add masking region icon
    2. Specify first station for masking region:OSnap to the end point of the widening transition area.
    3. Specify second station for masking region: type 48519Enter
  4. Alignment Properties dialog box
    1. OK

Video: ali-offst-widen-07.mp4 4:04

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-4thAve.dwg
    3. Open

Create offset alignment with widening

  1. Ribbon > Home tab > Create Design panel > Alignment dropdown > Create Offset Alignment
  2. Select an alignment: Left-click alignment
  3. Create Offset Alignments dialog box
    1. Alignment to offset from: 4thAve
    2. Offsets name template: Leave as is
    3. Station range: Check box From start and check box To end
    4. No. of offsets on left: 1
    5. No. of offsets on right: 0
    6. Incremental offset on left: 18
    7. General tab
      1. Site: <None>
      2. Alignment style: RDWY Lane Edge
      3. Alignment layer: P_ALI-Base
      4. Alignment label set: _No Labels
    8. Create Offset Profile tab
      1. Check box Create profile for offset alignment
      2. Leave all other settings as is.
    9. Widening Criteria tab
      1. Check box Add widening around curves
      2. Property Widening to Apply on: Inside Only
      3. Increase in width: 4
      4. Transition length: 50
    10. OK

Edit widening

  1. Left-click offset alignment
  2. Locate Padlock symbol, this is where widening occurs.
  3. Left-click the padlock, this will unlock and allow edits.
  4. Contextual ribbon > Modify panel > Offset Parameters
  5. Offset Alignment Parameters dialog box
  6. As you select each Property type, it will highlight in the drawing. Change the values to edit the widening.

Video: ali-offst-widen-08.mp4 2:02

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-4thAve.dwg
    3. Open

Edit widening parameters

  1. Toolspace > Prospector tab > expand Alignments > expand Offset Alignments > Right-click 4thAve-Left-18.000 > Edit Offset Parameters...
  2. Offset Alignment Parameters dialog box
    1. Nominal Offset: 15Enter

      Info: When entering a value, the placement of the offset decides if the value is positive or negative. Since the offset is to the left, this value will automatically be negative.

    2. Transition In > Transition Length: 45Enter
    3. Widening Region > Increased Width from Standard: 10Enter
    4. X to close box

Video: ali-offst-widen-09.mp4 2:11

Open drawing file

  1. Quick Access > Open
  2. Open File dialog box
    1. Look in: browse to folder dataset is saved.
    2. Select AliProf-4thAve-ali-offst-widen-09.dwg
    3. Open

Edit widening to offset alignment

  1. Left-click the offset alignment
  2. Notice the different grip points along the parent and offset alignments.
  3. Left-click the cyan diamond grip point on the east end of alignment.
    1. Specify stretch point: slide the grip point left/west 20' OR point the grip west and type 20Enter
  4. Left-click the cyan diamond grip point on the west end of alignment.
    1. Specify stretch point: slide the grip point right/east 20' OR point the grip east and type 20Enter
  5. Left-click the cyan plus symbol to create an offset widening area.
  6. Left-click the gray circle grip in transition. Two cyan circle grips appear on either side. Left-click and drag the cyan grips to make a tapered transition.
    1. Notice two gray diamond grips on the parent alignment. These will also adjust to transition ends along the parent alignment.
  7. Left-click the cyan triangle grip point and drag up or down. This will change the offset distance of the widened area.