Selected Leg Connection Properties

Traditional T- X or Y intersection

Name - This is the name of current road intersection leg connection. By default, connections are numbered Connections 1-2, Connections 2-3, etc., but if necessary, the names can be defined more specifically.

Horizontal turning method - This shows the method used to compute the horizontal connection between two legs. For the traditional T-intersection, there are four methods:

• R - This method computes a single radius between two connection lines.

  

• 2R-R-3R - This method computes a triple-curve between two connection lines. The radius is known and the angles of 2R and 3R. The middle arc length (angle) is unknown and is computed.

  

• 3R-R-6R - This method computes a triple-curve between two connection lines. The method is similar to the 2R-R-3R method.

Additional properties:

- Delta angle 1 - Specify the angle that determines the length of 3R arcs.

- Delta angle 2 - Specify the angle that determines the length of 6R arcs.

• 3R-R-6R imitating LA-I standard - This method works similar to the "3R-R-6R" method above, but uses different (and optimized) angle values in the arcs (3R and 6R). This affects the length and the shape of the output result. The NB turn radius is not used in this method; the radius is estimated.

  

  Turn radius - This shows the radius that is used in the horizontal methods.

Vertical turning method - This shows the method used to compute the vertical connection between two legs. The vertical curve is limited to the horizontal length of the corresponding curvature.

For traditional T-intersections, there are five methods:

• Linear connection - This method draws a straight line between the start and end point of the curvature. The method generates a tangential break both in the beginning and end of the curvature.

  

• Curve connection - This method computes a double arc/parabolic curve between the start and end point of the curvature. The method generates a tangential continuous curve both in the beginning and end of the curvature.

  

• Linear low point - This method draws a double straight line between the start and end point of the curvature. This method computes a low point (as the additional properties describe). The method generates tangential breaks both in the beginning, middle, and end of the curvature.

  

  Additional properties;

  Delta elevation - The depth of the pit where the lowest point is located.

  Delta ratio - Relative position along the curvature to position the lowest point.

• Curve low point - This method computes a four arc/parabolic curve between the start and end point of the curvature. This method computes a low point as the additional properties describes. The method generates a tangential continuous curve both in the beginning and in the end of the curvature.

  

  Additional properties;

  Delta elevation - The depth of the pit where the lowest point is located.

  Delta ratio - The relative position along the curvature to position the lowest point.

• Linear slope transition - This method computes a vertical connection curve between two connection lines such that the slope of the from-leg is linearly changed (by linear interpolation) to match the grade of the to-leg in the connection point.

Maximum vertical grade check - Select Yes if you need to do a grade check on the vertical alignment in the connection curvature. The maximum grade is set to 8 % in the grade check method.

Roundabout tangent connection double radius

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 radius values R1-R2 (Turn radius 1 – Turn radius 2).

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

Turn radius 2 - This is the second of the two radii. The value of this radius is the largest, normally in the interval from 50-100 m.

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

Roundabout contra curve connection

Name - This is the name of current road intersection leg connection. By default, connections are numbered Connections 1-2, Connections 2-3, etc., but if necessary, the name can be defined more specifically.

Main horizontal turning method - This method is called 'Contra inner circle'. It computes a copy of the outer radius of the roundabout as long as it is a part of the roundabout alignment. In computing access and exit geometry to the roundabout, traditional methods from the leg connection are used, such as:

• R
• 2R-R-3R
• 3R-R-6R
• 3R-R-6R imitating LA-I standard

Main vertical turning method - The vertical method is called 'Copy'. In this case, the method copies the vertical alignment from the outer radius of roundabout. In computing the access and exit geometry to the roundabout, traditional methods from a leg connection are used, such as:

• Linear connection
• Curve connection
• Linear low point
• Curve low point
• Linear slope transition

In radius - This is the access radius that is used in the horizontal methods.

Incoming horizontal turning method - This is the access method used in the horizontal method.

Incoming vertical turning method - This is the access method used in the vertical method.

Out radius - This is the exit radius that is used in the horizontal methods.

Outgoing horizontal turning method - This is the exit method used in the horizontal method.

Outgoing vertical turning method - This is the exit method used in the vertical method.

Roundabout tangent connection

Name - This is the name of current road intersection leg connection. By default, connections are numbered Connections 1-2, Connections 2-3, etc., but if necessary, the name can be defined more specifically.

Main horizontal turning method - This method is called 'Touch roundabout'. It computes a tangent point to the outer radius of the roundabout. This means that the turning radius is a variable and will be computed by this method.

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

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.