Creating NURBS Roadways

Roadway objects can be used to modify the site model. Roadway objects can be drawn with the various roadway tools on the Objects palette, or by drawing a polyline and then selecting the Objects from Polyline command (see Creating Objects from Polylines).

One of the most flexible roadway objects is the Roadway (NURBS) tool, which uses NURBS curves to define the road shape. The Roadway (NURBS) object, while easy to edit, does not represent accurate alignments of low-speed roadways, which are typically constructed with arcs (constant radius) and tangents (straight lines); VectorWorks Landmark provides these roadway objects (see Creating a Road).

A suggested process for using the Roadway (NURBS) object is:

Create the road in Top/Plan view

Select the Send to Surface command to set the road to the existing terrain

Select Redistribute and Smooth Curve from the Object Info palette of the selected roadway once or twice to smooth out the road slightly, so it does not follow every hill and valley in the existing terrain

Manually reshape the road in 3D as required (to match other road elevations, garage elevations, etc.)

Only select Redistribute Stations for more or fewer stations annotated in Top/Plan view. Fewer stations are easier to work with when sketching and reshaping, but a road construction company might require more stations to be specified. Redistribute Stations is also useful to ensure that the station spacing is equal after reshaping the road.

 

To create a road with the Roadway (NURBS) object:

1.	Click the Roadway (NURBS) tool from the Site Planning tool set.

The following modes are available.

See NURBS Curves

2.	Click in the drawing file to set the start point of the road, and then click to set the position of each additional NURBS vertex. Double-click the last point to complete creation of the roadway (NURBS) object.

The roadway (NURBS) object properties dialog box opens. Click OK to accept the default settings.

3.	The roadway (NURBS) properties can be edited in the Object Info palette.

 

Parameter	Description
Z height	Adjusts the elevation of the entire road
Road Length	Displays the length of the road
Paving Width	Specifies the overall width of the paved road surface (without curbs)
Paving Height	Specifies the road paving thickness (without curbs)
Curb Width	Specifies the curb or shoulder width
Curb Height	Specifies the curb or shoulder height
Left Guardrail	Adds a guardrail to the left side of the road
Right Guardrail	Adds a guardrail to the right side of the road
Show Stations	The NURBS curve vertices are used as the station points; select to display the station points. In 2D, stations display as loci with text displaying the point elevation. In 3D, the stations display as round stakes.
Create Pad for DTM	Select for the Roadway (NURBS) object to create its own pad modifier
Create Fence for DTM	Select for the Roadway (NURBS) object to create its own fence modifier, which controls the zone in which the terrain transitions between the existing elevation and the road elevation
Fence Method	Specify whether to create an offset or slope fence
Fence Offset	When creating an offset fence, specify the distance from the road to the control fence
Fence Slope	When creating a slope fence, specify the batter slope
Paving Class	Select the class for the paved portion of the road
Curb Class	Select the class for the curb or shoulder
Redistribute Stations	Redistributes the stations at a specified spacing interval
Redistribute and Smooth Curve	Redistributes the station points at a specified spacing interval and smooths the NURBS curve
Send Stations to Surface	Click to set the Z value of the stations to the surface of the DTM. The stations can be set to either the surface of the existing DTM, or to the surface of the proposed DTM, which may have been altered by modifiers. If the stations are sent to the surface of a proposed DTM which has been changed by modifiers, it may be necessary to deselect Create Pad for DTM and Create Fence for DTM for the Roadway (NURBS) in order to prevent site modifier errors caused by crossing pads or fences.
Align Stations Vertically	Sets the elevation of the indicated station points to a specific plane. As the starting and ending stations are indicated, a red line previews the included station points. The % Grade indicates the grade that will be set between station points.
NURBS curve parameters	Edits the roadway NURBS curve

4.	If necessary, use the 3D Reshape tool to modify the locations of the vertices after object creation, or use the vertex editing controls on the Object Info palette to move the vertices or change the degree of vertices.

5.	Update the site model. Select the site model and click Update from the Object Info palette.