Each visibility sightline is defined in a separate page.
Click the New button on the Visibility page or select the required sightline from the expanded list. The Sightline page or dialogue is displayed.
Select a sightline Type from the drop down list.
Enter a Name for the sightline. Typically, this might be the same as the type. This is what is displayed in the Roundabout Properties for you to select.
Enter the Visibility Distance which may be a fixed distance but is more likely to be based upon vehicle speed and may be defined in a table depending upon the standard.
If the visibility distance is fixed, select Fixed Distance and type the value in the edit field provided.
If the distance is listed in a table, select Based on Table and click the [...] button to select the table.
If the distance is calculated from an equation, select Based on Equation and click the [...] button to select the equation.
If Visibility Distance is set to anything other than Fixed Distance then you will need to specify the Speed which may be set to a fixed distance or various values from your design.
If the speed is fixed, select Fixed Speed and type the value in the edit field provided.
Otherwise select one of the alternative options listed in the dropdown list box. Note that the speed generally refers to the subject but in some cases refers to the object, e.g. the Previous Entry Visibility type uses the speed of the vehicle on the previous entry to determine the visibility distance.
Select the Subject Icon, the icon (if any) that you want to use for the viewer.
Select the Subject Position, the road lane in which the viewer should be placed.
Select the Subject Lateral Offset, the offset of the viewer within the selected lane. This may be the centre of the lane or offset from the nearside or offside road marking or kerb. If you select an offset then you must enter the value in the edit field provided.
Select the Subject Longitudinal Offset, the offset along the lane from a specified feature. This may be an offset from the give way line or from a crossing (if one exists) or, in the case of circulatory sightlines, an angular offset expressed as a whole circle bearing (WCB). In all cases, you must enter an offset value in the edit field provided.
Enter the Subject Eye Height, the height of the viewer above ground level.
Select the Object Icon, the icon (if any) that you want to use for the target point.
Select the Object Position, the location of the object or target point.
Enter the Object Height, the height of the viewed object above ground level.
Select Hatch Visibility Area if you want the visible zone to be hatched. If this is not selected, you will see just the extents of the visible zone.