Turbo Roundabout Vehicle Envelopes Design Method

Generates and edits roundabout designs by applying design guidelines (see Design Guidelines) to user-drawn reference geometry by ‘driving’ the design vehicles through the design to determine the locations of the road edges.

Vehicle Envelopes Design Methods Note: TORUS creates road edges based on vehicle envelope geometry which represents the minimum space for the design vehicle to maneuver. To generate an approximation of roundabout refined edges from the vehicle tire track envelope, use the Refine Edges tool.

Pavement Markings Note: When you use the Edit Roundabout tool to select a roundabout, all pavement markings edited using GuideSIGN Markings features will be reset to their default state.

Note:

• For the purposes of describing the software, it is assumed that Right-Hand Traffic is selected under Traffic Direction in Design Guidelines' General Category. If Left-Hand Traffic is selected, the descriptions with references to a right/left turn path should be interpreted in the opposite direction.

• This tool requires the presence of user-drawn lines and/or arcs to become reference geometry for the roundabout design. Using the line and/or arc tools in AutoCAD or MicroStation, draw the reference geometry that represents the roundabout’s approach leg centerlines.

  • The reference line length defines the maximum limits of the corresponding splitter island envelope.
  • The reference line defines the separation of the traffic flow directions and normally aligns parallel with the straight section of the median closest to the center of the roundabout.

• It is recommended that you create a new design guideline appropriate for the current design (see Design Guidelines' New Design Guideline).

For an example of how the Generate Roundabout tool works, please play the Generate Roundabout tutorial (for information on how to play a tutorial, see Tutorials -> Play).

Generate Roundabout / Edit Roundabout Dialog Box

In the dialog box, move the mouse pointer over the controls to view the associated tooltip and then reference the controls described below.

Design Guideline Section

Design Guideline

Select the desired Transoft Vehicle Envelopes design guideline from the list.

View

Click this button to view the selected design guideline.

Note:

• As you select a design guideline, its parameters are automatically applied to the current roundabout. To return to the previous design guideline parameters, select the original guideline in the Design Guideline list.
• After you place the central island and add at least one approach leg, you will be able to select only those design guidelines that use the same design method as the current design guideline.

Spiral Starts Section

Number of Spiral Starts

Override the number of spiral starts specified in the current Design Guidelines' Turbo Block Category. In a turbo roundabout, this is how many unique circulating lane starting points there are. This number also determines the number of axes lines there are in the turbo roundabout.

Primary Axis Angle

Allows you to override the primary axis angle value set in the current guideline. The primary axis angle is the angle measured between the spiral start leg that the primary axis is assigned to and the primary axis. Specify the primary axis angle value in the box or click one of the following buttons:

Button	Option	Click to...
	Get Primary Axis	Extract the angle from a picked element in the drawing area to set the primary axis angle.
	Rotate Primary Axis	Rotate the primary axis from the center of its spiral.

Note: Increasing or decreasing the primary axis angle will increase or decrease the overall size of the turbo roundabout depending on the direction rotated and the traffic direction setting.

Central Island Section

Easting and Northing

Specify the location of the central island in the drawing. The Easting value determines the distance eastwards of the roundabout center from the origin. The Northing value determines the distance northwards of the roundabout center from the origin. As you move the pointer in the process of placing the central island, TORUS dynamically updates the values in the Easting and Northing boxes.

Button	Option	Click to...
	Move Central Island	Move the roundabout central island to a new location. After you click the button, click the roundabout, move it to the desired location, and then click to place the roundabout and return to the Generate Roundabout dialog box.

Hint: The optimal location for a roundabout central island is the point through which all reference lines pass. If a reference line cannot be aligned through the center point, you may shift the central island so that the reference line can pass through the central island to the left of the center point.

Inner Radius

Specify a value to override the default inner radius value from the current Design Guidelines' Turbo Block Category. The inner radius is the distance from the center of the sector's central island to the inside edge of the innermost circulating lane.

Button	Option	Click to...
	Configure Circulating Lanes	Override the circulatory offsets or fixed lane widths specified in the current Design Guidelines' Circulating Lanes Category.

Truck Apron

Button	Option	Click to...
	Draw Outer Truck Apron	Turn the outer truck aprons on/off. These are located between the approach and departure legs at the inscribed circle diameter (see Roundabout Illustration Legend). Use Evaluate Movements to specify which movements are involved.
	Draw Truck Apron	Turn the truck apron on/off. By default, this feature is turned on.

Display Properties

Button	Option	Click to...
	Show Construction Lines	Turn the construction lines off. To change the color and line style of the construction lines see Properties' Turbo Roundabout Category).
	Show Axes Lines	Turn the axes lines off. To change the color and line style of the axes lines see Properties' Turbo Roundabout Category).

Circulating Lane Widths Section

Select how the circulating lane widths are drawn. By default, the selection is retrieved from the current Design Guidelines' Circulating Lanes Category.

• When Effective Lane Widths is selected, the circulating lane widths are determined by adding the internal and external circulatory offsets to the width of the circulatory design vehicle's off-tracking.
• When Fixed Lane Widths is selected, the lane widths specified in the current Design Guidelines' Circulating Lanes Category are used.

Note: Click Configure Circulating Lanes to override the circulatory offsets or fixed lane widths specified in the current Design Guidelines' Circulating Lanes Category.

Footprint Section

A footprint offset is the distance from the edges which can be used to approximate the additional space for sidewalk, utilities, and rights-of-way when evaluating the space for a roundabout location. To have a footprint offset added to the roundabout, select the Draw with offset check box, and then specify the desired safety buffer width value in the corresponding box. By default, the Draw with offset check box is cleared, and no safety buffer is added.

Toolbox Section

Button	Option	Click to...
	Add Legs	Add one or more approach legs to the roundabout.
	Delete Leg	Delete an approach leg from the roundabout.
	Edit Legs	Edit approach legs' parameters.
	Replace Leg Reference Geometry	Replace the reference element of an approach leg by picking a different reference element in the drawing. Note: An alternative to using this tool is modifying the reference geometry of an approach leg directly in the drawing by using object grips. If you drag a grip of a line, an arc, or a polyline reference element, the roundabout design will update accordingly.
	Set Secondary Leg Reference Geometry	Pick a second reference element for the exit lanes of an approach leg.
	Rotate Leg	Rotate an approach leg around the center of the central island by moving the mouse pointer around the central island as desired.
	Save Roundabout Template	Save the current roundabout design as a template so that it can be used with the Roundabout Wizard tool. Note: This button is only available when the roundabout has at least three legs.
	Save Design Iteration	Save the current roundabout design as an iteration so it can be recalled later.
	Generate Roundabout Report	Generate a roundabout summary report.
	Markings	Turn markings on/off, and/or change the arrow and/or yield line type used in pavement markings.