Rotary parameters

You can find the rotary parameters spread over several tabs. The number of Roadway... tabs that are actually available to you varies depending on the number of roadways specified in the General tab.

General

Position

Select a value in the list and then click the buttons to move the rotary by the value selected beforehand.

Remove road / Add road

These buttons define the number of roadways in the rotary. You can enter two to five roadways. The number of Roadway... tabs changes accordingly.

options

You can specify the roadway width, the distance to the island in the middle and the radii. These settings can be made for each roadway of the rotary. Then select the check boxes for the relevant roadways and click Apply. Now you can change the values and modify the selection of roadways. Then click Apply again.
This way, you can define geometric values globally for all roadways. The positions of the roadways and the Alpha and Beta angles, however, can only be specified in the tab of the relevant Roadway.
If you do not want to make additional assignments, close the dialog box.

Outer radius / Inner radius / Roadway width

Define the dimensions of the rotary’s geometric elements.
For information on the individual elements, see Overview of the main elements.

The outer radius must be between 12.25 and 22.50 m. Make sure that the rotary is large enough for all types of vehicles. Rotaries out out town require a larger outer radius than rotaries in town.
You can also click an existing circle to be used for the outer radius.

The inner radius, which is limited by the outer radius, must be at least 0.90 m. It defines the island area in the middle that cannot be crossed by vehicles. The inner radius is calculated based on the outer radius minus the rotary’s width (roadway width plus width of road stripping).
When you enable the Inner radius acc. to VSS option, the program uses fixed values for the inner radius. These values are in compliance with the Swiss SN 640263 standard.

The roadway width is limited by the outer and inner radii and depends on the size of the rotary. The roadway width and the width of road striping (if necessary) define the rotary’s width. For safety reasons, you should avoid rotaries with very large width values. It is advisable to not exceed a roadway width of 5.50 m.

Roadway ...

Position

Enter an angle in [grd] or use the arrows. You can also enable the Road striping option and click a line that ends within the rotary. When this option is already active, click this button to select a different line.

Geometric elements

For information on the individual elements, see Overview of the main elements.

Options

Entry and exit settings can be defined separately. Enter the Beta angle and specify how the roadway shoulder is to be displayed.
Define the tangent distance (‘b’), which is used to calculate the tangent for the Beta angle. In addition, enter the delta angle.
Specify whether exact circle segments, lengthened circle segments or full circles are to be used to represent the roadway shoulder.

Roadway width
Entry / exit – central part

Enter the roadway width here. The outline and dimensions of the roadway’s island in the middle are obtained from the entry and exit radii as well as the roadway widths you have defined.
For safety reasons, it is advisable to enter a roadway width of 3.00 to 3.50 m for entries and 3.50 to 4.50 m for exits.

Radius at circle / entry

Enter the radii based on which the roadway shoulder is created. You can make separate settings for entry and exit.
For entries, set the Radius at circle to approximately 10.00 m (in town) and 12.00 m (out of town). The Radius at entry should be approximately five times this value.
For exits, set the Radius at circle to approximately 12.00 m (in town) and 14.00 m (out of town). Here, the Radius at entry should be approximately four times this value.

Beta angle

You can use the slide bar to define the angle separately for entry and exit. Alternatively, use the RIGHT and LEFT arrows to move the slide bar by specific values.

See Information on the Beta angle.

Offset to circle

Define the offset from the edge of the rotary. You can make separate settings for entry and exit. The offset should be at the height of the pedestrian crossing or approximately 7.00 m from the edge of the circle.

Alpha angle

You can use the slide bar to define the angle between the roadway of the rotary and the roads leading to the rotary separately for entry and exit. Alternatively, use the RIGHT and LEFT arrows to move the slide bar by specific values.

As specified in the rotary standards, the Alpha angle is the difference between 200 [grd] and the angle defined here.