Road Plan Tool

Road Plan Tool button

The Road Plan Tool is the primary tool for creating and laying out roads. It allows for creation and manipulation of the 2D reference curve that the road layout is based on. The height of the road can be manipulated independently using the Road Height Tool. Intersections are created automatically where roads overlap.

Roads and Terrain Surfaces

Roads automatically participate in the terrain surface graph. For more information about this interaction, refer to the Surface Tool.

Create a New Road

  1. Click the Road Plan Tool button.

  2. If another road is already selected, click away from any road to unselect it.

  3. Optionally, click the desired road style in the Assets Browser to build a road of a particular style. If no road style is picked, a basic default style will be used.

    1. For more information about road styles, refer to the Road Style Assets documentation.

  4. Right-click at the location you want to start a new road.

  5. Right-click additional times to create additional road control points to extend and shape the road.

Move Road Control Point

  1. Click the Road Plan Tool button.

  2. Click the road you want to edit. The road is highlighted, and the control points are displayed and connected by light blue lines.

  3. Click and drag the desired control point to move it.

  4. Optionally, you can click to select the point, and then type a precise position in the Attributes Panel.

Note

The end control points and the first interior control points have some special properties when roads are connected end-to-end:

  • Moving the end control point of one of the roads will move the end of the connected road and update the first interior control point of the other road to ensure that the road directions remain aligned at this end, as shown here:

  • Moving the first interior control point of one of the roads will move the first interior control point of the other road (by rotating it about the end point) to ensure that the road directions remain aligned at this end, as shown here:

Insert New Control Point Within Existing Road

  1. Click the Road Plan Tool button.

  2. Click the road you want to edit.

  3. Move the mouse cursor over the blue control line at the location you want to insert a node.

  4. Right-click to insert a new node within the control line of the road.

Adjust Radius of Road Curve

By default, the circular arcs in the road curves will fit in the space available. If a smaller curve radius is desired:

  1. Click the Road Plan Tool button.

  2. Click the road you want to edit. The road is highlighted, and the control points are displayed and connected by light blue lines.

  3. Click the control point closest to the circular arc you want to modify. The attributes of the selected control point will appear in the Attributes Panel.

  4. Adjust the Max Radius value to the desired radius. If you do not see anything change, then try a lower value, because Max Radius will limit the maximum radius of the arc.

Adjust Curvature of Road Curve

See Explicit Road Curves.

Extend Existing Road

You can extend an existing road in either direction by adding more control points, as follows:

  1. Click the Road Plan Tool button.

  2. Click the road you want to extend. The road is highlighted, and the control points are displayed and connected by light blue lines.

  3. Click the control point on the end of the road you want to extend.

  4. Right-click to create a new control point and extend the road.

Note

For optimal performance, avoid very long individual roads. Keeping individual roads under 500 m is recommended. To create stretches of road longer than 500 m, use multiple roads connected end-to-end. Refer to Create New Road Connected End-to-End With Another Road and Connect Two Roads End-to-End.

Create New Road Connected End-to-End With Another Road

In a similar fashion to extending an existing road, you can also create a new road that connects end-to-end with an existing road. The visual result is similar to extending the existing road, but there are some important situations where end-to-end roads are needed:

  • To avoid extremely long roads for performance reasons

  • To create a road loop or self-intersecting road

You can create an end-to-end road that connects with an existing road as follows:

  1. Click the Road Plan Tool button.

  2. If another road is already selected, click away from any road to unselect it.

  3. Click the lavender road node line at the end of a road.

  4. Right-click to create a new control point, which creates a new road that extends off the existing one.

Connect Two Roads End-to-End

Similar to the steps above, you can extend a road and simultaneously connect it to the end of an existing road as follows:

  1. Click the Road Plan Tool.

  2. Click the road you want to extend. The road is highlighted, and the control points are displayed and connected by light blue lines.

  3. Click the control point on the end of the road you want to extend.

  4. Right-click the lavender line at the end of another road.

Create Road Loop

You can create a closed loop road by combining the steps above or by using the Road Circle Tool.

Note

Closed loops require at least three separate roads. You cannot form a loop from a single road.

  1. Create the first road by using the Create a New Road steps.

  2. Create the second road by using the Create New Road Connected End-to-End With Another Road steps.

  3. Create the final road by using the Create New Road Connected End-to-End With Another Road steps, followed by the Connect Two Roads End-to-End steps to end the road.

Delete Road Control Point

  1. Click the Road Plan Tool button.

  2. Click the road you want to delete the point from. The road is highlighted, and the control points are displayed and connected by light blue lines.

  3. Click the control point you want to delete.

  4. Press the Delete key, or select Edit > Delete from the Main Menu.

Delete Road

  1. Click the Road Plan Tool button.

  2. Click the road you want to delete.

  3. Press the Delete key, or select Edit > Delete from the Main Menu.

Create Intersection

At-grade intersections are created automatically in RoadRunner wherever two or more roads cross.

Four-Way Intersections

To create a four-way intersection, create two roads that fully overlap:

T-Junctions

To create a T-junction, create two roads where one ends within the extents of the other:

Ramps and Splits

To create onramps, offramps, and road splits, refer to the Slip Road Tool documentation.

Self-Intersections

A single road should not overlap itself. If you need to create a road that loops back on itself, either chop the road with the Road Chop Tool, or create roads connected end-to-end:

Roads may not cross themselves

Instead, create two or more roads connected end-to-end

Double-Crossings

You might observe issues with lane markings when two roads cross each other twice (that is, two at-grade intersections are formed between the same two roads).

Avoid double-crossing roads. If you need to create a double-crossing situation, either chop one of the roads with the Road Chop Tool, or initially create one of the roads using two end-to-end roads.

Avoid roads that cross each other twice.

Instead, split one of the roads in two

(Note the lavender bar indicating an end-to-end connection.)

Note

Intersections are only created when the roads have similar heights at the crossing locations. To adjust road heights, use the Road Height Tool.

Explicit Road Curves

By default, new roads will be created out of straight lines and circular arcs. Roads created in this method are called "Automatic." It is sometimes desirable to instead define a road curve as an explicit set of straight lines, circular arcs, clothoids (spirals), and parametric cubics (hermite curves).

Roads created in this method are called "Explicit." Each line, arc, spiral, or cubic is called a "Segment." The Explicit Road Curve also allows you to set the tangents of the road at each control point. Editing the control points of an explicit curve is done the same as with an automatic curve.

Building Roads With Explicit Curves

Explicit curves can be used to create a road with a very specific profile (for example, a 50 m linear section, followed by a 20 m spiral with specific starting and ending curvatures, followed by a 30 m arc with specific curvature, and so on).

To build such a road, follow these steps:

  1. Click the Road Plan Tool button.

  2. Create a new road using these steps: Create a New Road.

  3. Convert the new road to explicit form using these steps: Make Road Curve Explicit.

  4. Adjust the type and properties of the first road section.

  5. For each new section you want to add to the road:

    1. Add a new section using these steps: Extend Existing Road.

    2. Adjust the type and properties of the new road section.

Make Road Curve Explicit

  1. Click the Road Plan Tool button.

  2. Click the road you want to change.

  3. In the Attributes Panel, press Convert to Explicit.

Make Road Curve Automatic

  1. Click the Road Plan Tool button.

  2. Click the road you want to change.

  3. In the Attributes Panel, press Convert to Automatic.

Note

Converting an explicit curve to an automatic curve can slightly change the curve and insert additional points.

Change Tangent of Explicit Curve

  1. Click the Road Plan Tool button.

  2. Click the road you want to change.

  3. Click and drag one of the tangent control points and move it to set the desired tangent.

Note

Setting tangents on a road may change the type of the segments connected to the affected control point.

Change Type of Segment

  1. Click the Road Plan Tool button.

  2. Click the road you want to change.

  3. Click the segment you want to change.

  4. In the Attributes Panel, select the Type of the segment. This will automatically constrain the segment's points and tangents to match the type.

Change Length of Segment

  1. Click the Road Plan Tool button.

  2. Click the road you want to change.

  3. Click the segment you want to change.

  4. In the Attributes Panel, adjust the Length of the segment to the desired length.

Note

You can set the length of a segment only if the segment is a line, arc, or spiral.

Change Curvature of Segment

  1. Click the Road Plan Tool button.

  2. Click the road you want to change.

  3. Click the segment you want to change.

  4. In the Attributes Panel, adjust the Curvature (for circular arcs) or Start Curvature/End Curvature (for spirals).

Note

You can set the curvature of a segment only if the segment is an arc or spiral.