Geometry > Approach Geometry

Approach Geometry

The widths and radii of the approach roads.

Topics covered

Approach Geometry
Approach Geometry has six parameters displayed in the main window on the first data table.
Leg name
Legs are numbered counterclockwise for right hand driving. Leg 1 can be chosen arbitrarily, but it helps avoid mistakes if a convention is adopted.
Graphical Geometry Editor
The column of buttons after Leg Names calls the graphical geometry editor.
This is the whole circle bearing taken in a counterclockwise direction for right hand side driving (RHD).
Grade Separation G
Grade Separation is not used in the HCM model.
Approach Half Width V
This is the narrowest width of the approach road prior to any widening (flaring) up to the roundabout entry.
Number of Approach Lanes nv
A maximum of 4 lanes (40 ft) is permitted.

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