Override the entry path radius and offsets specified in the current Design Guidelines' Leg Arc Radii Category, Design Guidelines' Leg Offsets Category, Design Guidelines' Leg Biarc Entry Category, and Design Guidelines' Lane Transitions Category.

Configure Entry Path Radius and Offsets 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.

For a description of the elements drawn in the roundabout in this category, see Roundabout Illustration Legend.

For a description of the elements drawn in the turbo roundabout in this category, see Turbo Roundabout Illustration Legend.

Entry Path Radius

Specify the entry path radius value. This is the radius of the path which the design vehicle travels from the entry approach leg to the circulatory path.

Entry Path Radius Start

Specify the entry path radius start value. This is measured from the inscribed circle diameter to the start of the first radius in the biarc entry.

Secondary Entry Path Radius

Specify the secondary entry path radius value. This is the second radius of the path which the design vehicle travels from the entry approach leg to the circulating path.

Internal Entry Offset

Specify the internal entry offset value. This is the distance from the reference element of the approach leg to the closest tire track of the vehicle.

External Entry Offset

Specify the external entry offset value. This is the distance from the approach leg's edge on the entry side to the closest tire track of the vehicle.

Internal Exit Offset

Specify the internal exit offset value. This is the distance from the reference element of the approach leg to the closest tire track of the vehicle.

External Exit Offset

Specify the external exit offset value. This is the distance from the approach leg's edge on the exit side to the closest tire track of the vehicle.

Internal Entry Separator Offset (Turbo Vehicle Envelopes Design Method)

Specify the internal entry separator offset value. This is the distance from the inside lane's outer tire track to the entry lane separator.

Entry Lane Separator Width (Turbo Vehicle Envelopes Design Method)

Specify the entry lane separator width value.

External Entry Separator Offset (Turbo Vehicle Envelopes Design Method)

Specify the external entry separator offset value. This is the distance from the entry lane separator to the outside lane's inner tire track.

Entry Separator Length

Specify the entry separator length value. This is the distance from a line drawn perpendicular to the leg angle line at the intersection of the leg angle and outer construction lines to the end of the separator. The leg angle line is a line projected from the center of the roundabout to where the leg reference line intersects the outer construction line (note that the leg angle line is used in the creation of the roundabout geometry but is never drawn).

Entry Transition Length

Specify the entry transition length value.

Approach Half Width

Select this check box and then specify the approach leg's half width value. As opposed to the constant width of a straight line path, the approach half width of an approach leg with a curved path is the combined width of the maximum track of the design vehicle plus the internal and external exit offsets measured in the approach downstream from any exit flare. The Approach Half Width value will update dynamically as the offset values are modified.

Button	Option	Click to...
	Use Minimum Width	Reset the Approach Half Width value to use the minimum width based on the off-tracking of the design vehicle plus the internal and external entry offsets. This button is only available for effective lane width approach legs.

Lane Widths Section

Specify the width values for the lanes and the median.

Note: This section is only available for fixed lane width approach legs.

Override Curb Vehicle Section

Select this check box to override the design vehicle specified in the current Design Guidelines' Vehicles Category: Road Edges. Select a design vehicle specified for the current design guideline in the list or click Select Vehicle to select from the complete list of Design Vehicles.