Expand Arm Geometry and click on the Approach tab.
The Design Speed is the design speed of the section of road leading up to the roundabout.
The Central Gap Width is the distance between the offside definition lines of the approaching lanes and the departing lanes.
The Deviation Offset defines the section of road that follows the original alignment before horizontal deflection is applied.
Deflection (or centre line offset) is the distance that the alignment is adjusted to the left or right of the zero deflection point. Zero deflection occurs when the alignment meets the ICD on a bearing that passed through the centre of the roundel. Deflection is used to adjust driver's speed.
The Approaching Lanes is the number of lanes of traffic approaching the roundabout and would normally be less than or equal to the number of circulatory lanes. Select a profile from the drop-down list.
The Approaching Lane Width is measured between definition lines. On a road with no centre gap, the offside definition line is the centreline.
The Departing Lanes is the number of lanes leaving the roundabout onto this road. Select a profile from the drop-down list.
The Departing Lane Width is measured between definition lines. On a road with no centre gap, the offside definition line is the centreline.
In all cases the Max and Min values represent the limiting values from the adopted design standard and the Default value will be used when the roundabout is first placed. A default value MUST be provided but Max and Min may be blank if there is no limiting value.