Selected Intersection Properties

Rebuild method - Auto is the default setting that allows the intersection and corresponding surface to rebuild automatically after each change that affects it. Select Show empty to hide the surface in graphic views while you make edits. The surface cannot be automatically or manually rebuild in this state. Select By user to suspend the process of rebuilding the intersection and surface until you select Rebuild Intersection.

Type - The options K, Y, T, or O depend on the number of intersecting legs.

Parent corridor for the masses - When you calculate material volumes for a corridor, it will include the volumes for the connected intersection if you select the associated corridor here.

State - In some situations, intersections can be defined from more than one intersection point. The read-only definition used is shown here (e.g., Valid (multiple point)).

Vertical adjustment - Select Yes to automatically adjust the vertical geometry of secondary road/roundabout legs so that they follow a certain rule when joining to the main road/roundabout’s central island.

Interpolation method - Shows the method used to add interpolation lines when forming the surface:

• None
• Parallel
• Centered

Main road method

• Derived - The main road edge is computed as a derived line from interpolation lines. (The interpolation line is an s-curve, so this derived line will also be close to the s-curve option) However, this derived line method is recommended if the vertical geometry of the main road includes curvy elements (arcs/parabolas) at the intersection area. The Derived method maintains the lane slope in the case there is a sag curve at intersection area.
• S-curve - The main road edge connects the two main road leg edges with an s-curve (both horizontal and vertical).

In addition, when there is T-intersection, the connection 3-1 in T is the main road edge. There is a new method "Main road derived". In this option, the connection 3-1 is not computed using a connection method, but the main road edge is taken as it is (derived or s-curve) to use in connection.

Note: If the chosen main road method is "Derived", then always the "Main road derived" in T-intersection's connection 3-1 must be used. When Horizontal turning method is "Main road derived", then the vertical method is the same as well.

(roundabouts only)

Style - Circular is the default for round islands. Select Non-circular for oval islands. Then adjust the two different radii below.

Radius - Use this to control the size of the inner circle/center island. The overall size of the intersection is impacted by this, as the lane and shoulder width stay the same.

Radius 2 - For non-circular roundabouts, there are two radius boxes. This shows the long radius to the inner circle of the roundabout.

Direction - For non-circular roundabouts, this is the direction between the two focal points of the roundabout. The roundabout can be rotated by changing this value.

Focal point distance - This shows the distance between the two focal points of the non-circular roundabout.

Lane width - This shows the distance between the inner circle (radius above) and outer circle. This value is constant all the way around the roundabout.

Note: If your intersection connects to a corridor that defines lanes (using instructions tagged with the Lane edge code), the Lane width and Lane slope properties do not appear here; these properties are controlled by the parameters in the corridor template instructions. See Create Corridor Template Instructions for more information.

Lane slope - This shows (or lets you specify) the slope of roundabout lanes. A negative value means that the lane slopes down in outbound direction. This value is constant all the way around the roundabout.

Width of inner shoulder - This shows the distance from the inner circle to the inner area line (shoulder of the inner circle). This width is part of the total lane width.

Slope of inner shoulder - This shows (or lets you specify) the slope of the inside shoulder of a roundabut. The default value is the same as the Lane slope above. A negative value means that the shoulder slopes down in outbound direction. This value is constant all the way around the roundabout.

Width of outer shoulder - This shows distance from the outer radius to the outer area line (shoulder of the outer circle). This width is part of the total lane width.

Curb height - This shows the vertical distance from the flow line to the top of curb.

(roundabouts only)

Tilting

1. Outer circle
2. Inner circle

When using either of these tilting methods:

• Automatic tilt all circles
• User-dfined tilt all circles

the inner shoulder and inner circle should be elevated based on the tilted surface (plane). To do so, these two parameters are required:

• Vertical offset from outer circle to inner shoulder
• Vertical offset from inner shoulder to inner circle

The lane and inner shoulder will still have varying slopes all the way around, but with different offsets from the base plane.

• Automatic tilt outer circle - This is the default setting to control the slope of a roundabout's outer circle: the outer radius is tilted according to the elevation legs of the intersection. If there are 3 legs, the tilt will match the elevation of those legs. If there are more than 3 legs, the match will be optimized (least square best match). Then the inner radius of the roundabout will be "back calculated", meaning that the vertical alignment will be found by the slope of the roundabout lane. In this way, the slope of the lane will be correct if it is computed by difference of elevation between inner and outer radius of the roundabout (perpendicular to inner radius alignment). The program tries to fit the roundabout's outer circle so that the vertical difference between it and the incoming alignments. is as small as possible. This uses the leg elevation at the location where the outer circle intersects.

  

• User-defined tilt outer circle - Select this to activate vertical adjustment functionality for the roundabout and then specify the slope and direction of the outer circle. The tilt can now be defined by a slope and tilt direction that you specify in the boxes below. The delta elevation for each leg is shown below. As opposed to the automatic method above, this method for roundabout tilt lets you manually specify the slope and direction of a roundabout's outer circle and have the inner circle's tilt computed automatically.

   

  

• No tilt outer circle z reference - Select this to prevent the roundabout's outer radius from being tilted. Select this to specify the tilt of the outer circle and have the inner circle computed automatically based on the slope value of the lane. The lane slope is used to compute the tilt of the outer circle. This means that the vertical alignment will be defined as a horizontal line segment with an elevation equal to the elevation of the intersect point. The inner radius vertical alignment will be computed the same way, as if tilted.

  

• Automatic tilt inner circle - Select this method for roundabout tilt to use the leg elevations where they intersect the inner circle to automatically find the best fit tilt.
• User-defined tilt inner circle - Select this to specify the tilt of the inner circle and have the outer circle computed automatically based on the slope value.
• No tilt inner circle z reference - Select this to keep the inner circle horizontal based on the top elevation of the outer circle.
• Automatic tilt all circles - Select this method to automatically control a roundabout's slope. The outer circle defines the 'plane' by finding the intersection points with incoming road alignments. These alignments define the slope and direction of the tilt of the outer circle. The inner circle and shoulder are parallel with the plane defined by outer circle. In addition, there also is a couple of properties for offsetting these two inner lines.

  - Vertical offset inner shoulder - Specify this vertical delta between inner shoulder and inner circle when using the User-defined tilt all circles tilt method described above.

  - Vertical offset inner circle - Specify the vertical delta between the inner circle and inner shoulder when using the User-defined tilt all circles tilt method described above.

  These properties are used to lift up/down both those inner lines.

• User-defined tilt all circles - Specify the tilt (slope and direction) of both the inner and outer circles manually, and optionally the vertical offset between inner and outer circle (see Vertical offset inner shoulder and Vertical offset inner circle below). Lane and inner shoulder slopes are calculated automatically.

Slope - This shows either the automatically calculated or user-defined slope of the entire roundabout.

Tilt direction - This shows the bearing of the high side of the tilt, which you can control if the tilt is user-defined. The zero (0) bearing is north, and bearings are measured clockwise.

Vertical offset inner shoulder - Specify this vertical delta between inner shoulder and inner circle when using the User-defined tilt all circles tilt method described above.

Vertical offset inner circle - Specify this vertical delta between inner shoulder and inner circle when using the User-defined tilt all circles tilt method described above.

Delta elevation, Leg < > - For a user-defined tilt, this shows the deviation between the automatically calculated tilt and the one you have specified.

(roundabouts only)

Easting, Northing - This shows the 3D coordinate of the roundabout's center island. Normally this will be the intersection point where the alignments/corridors converge. The center point can be moved slightly off center, but if the point specified is too far away from the actual center, the intersection cannot be updated. By moving this point, the roundabout may appear eccentric according to the intersection point of the alignments/corridors.

Elevation - This shows the mean elevation of the intersection point. Normally this will be the mean value of the alignment elevations at the point. This value can be changed, which will lift up or drop down the whole roundabout.

Selected Road Intersection Leg Connection Properties

Main horizontal turning method - This method is called 'Touch roundabout double radius'. It computes a tangent point to the outer radius of the roundabout by using the two radii values R1-R2 (Turn radius 1 – Turn radius 2).

Turn radius 1 - The first of the two radii. The value of this radius is the smallest, normally around 15.0 m.

Turn radius 2 - The second of the two radii. The value of this radius is the largest, normally in the interval from 50-100.0 m.

Main vertical turning method - The vertical method is called 'Copy'. The method connects the vertical alignment to the elevation of the outer roundabout at the tangent point. No other methods are available in this case.