Horizontal Curves Panel - Simple Mode
The Horizontal Curves Panel allows dynamic modification of the currently selected Horizontal IP or curve (visible in the Plan Window). It is activated by selecting the Window - New Window - Horizontal Curves menu or by clicking the 
button on the Standard toolbar. See also Horizontal Curves.
In Simple Mode, many features are disabled to reduce complexity. It is often used for private access roads.
To switch to Advanced Mode:
Advanced Mode includes spiral curves, more super-elevation control and design speed. This option is disabled in some products.
Open the Road Class Specifications dialog by clicking the 
button on the Curves Panel. Unselect the Simple Curves option and press OK. The Curve Panel will close and then re-open in advanced mode.
Title bar
At the top of this window is a description line showing the curve number and stationing of the currently selected curve or IP if applicable.
Curve Parameters
Note: curve parameter controls are disabled until the circle radio button is selected (see below).
Radius
Defines curvature. When you change Radius, the IP and Tangent Parameters update instantly. If the curve does not fit the available tangents, the Apply button will be disabled and a warning will be reported.
Super-Elevation (%)
Allows you to change the super-elevation of the curve.
Transition Length
The Transition Length is both the super-elevation runoff length and the curve widening transition length. If you are not using Super-Elevation or Curve Widening, the Transition Length has no effect.
Super-elevation runoff is defined as the distance from zero cross-fall (flat) to full super-elevation on the outside lane. If the normal cross section has a crown, then an additional transition is required from crown to zero cross-fall (the start of Super-elevation runoff ) - this transition is called the Tangent Runout and it occurs outside of the transition length.
The Tangent Runout length is calculated so that the rate of change of cross-fall is the same as in the Super-elevation Runoff. For example if the full super-elevation is 6% and the Transition Length (= Super-elevation Runoff) is 60m, then the rate of change of cross-fall is 10m/%. If the crown slope is 2%, then the Tangent Runout will be 20m. In this case, the total transition length is 80m, 20m more than the value specified in the Transition Length field.
Overlapping curves
The software will not allow you to design adjacent curves that have curved segments overlapping. However, it is reasonable to design curves with overlapping transition zones.
Note: If the transition zone of a curve overlaps that of an adjacent curve, then the super-elevation and curve widening will be calculated from a linear combination of the two curves. If you design an "S" curve (a short tangent between a Left and a Right hand curve) then the super-elevation transition will not include a crown section - the cross-fall will rotate continuously from one side to the other.
Transition Fraction
Allows you to change where the transition starts.
For a circular curve, the Super Elevation Runoff may start before the curve BC (begin curve) and end after; similarly, at the end of the curve, the transition starts before the EC (end curve) and ends after. The Transition Fraction is the amount of transition that happens outside the curve (before BC and after EC). For example, if Transition Length is 90 feet:
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If Transition Fraction is 1.0, the Super Elevation Runoff starts 90 feet before the BC point and full super-elevation is reached at BC
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If Transition Fraction is 0.667, a common standard, the Super Elevation Runoff starts 60 feet before BC and full super-elevation is reached 30 feet beyond BC.
Widening, Inside/Outside
Small radius curves require lane widening to accommodate large vehicle off tracking. The curve widening values are added to the normal lane widths in the curve region. Inside and outside depend on the direction of the curve. For a right hand curve the inside is on the right hand side of center line while the outside is on the left. For a left hand curve, inside is left and outside is right.
Note that your cross section template must have curve widening built in for these values to have any effect. Widening is accomplished by lengthening template legs that have the "apply curve widening" property. Some templates may not respond to curve widening if no such legs exist.
Automatic Widening
If an Auto box is checked, the associated Widening field is disabled and the value is extracted from a table. The 
button pops up the Automatic Curve Widening Options dialog box, allowing you to read in a new Curve Widening Table and/or change the way the table is interpreted.
No Curve / Circle radio buttons
These radio buttons define whether a curve exists.
Select Circle (the only type of curve supported in Simple mode) to define a curve and to enable the other curve parameter controls (above).
Select No Curve to remove a curve and to disable the controls.
Apply
Saves changes to the above values, and updates alignment and all windows to show the result.
If the Apply button is not available, it means one of two things:
1 The curve has not been changed from the one already applied.
2 The curve can't be applied to the current alignment. In this event the reason will be reported left of the Apply button; for example "Curve does not fit tangents".
Toolbar
Previous Curve, Next Curve Moves the current selection to the previous or next IP or curve along the horizontal alignment. Any changes made to the current curve or IP are lost unless you have Applied them.
Note that when a curve is selected, the Current Point displayed in the other windows is the EC (End Curve) point.
Road Class Parameters
Set/Get Default CurveThe first button saves the parameters for the current curve as the new Default Curve.
The second button retrieves the Default Curve parameters. Once your Default Curve is defined, creating a new curve requires two button clicks: Get Default Curve and Apply.
Default Curves (Vertical and Horizontal) are saved with your template table; they are saved with your document and can also be saved externally in a TPL file. Open and update your standard template table files (Normal.tpl and possibly others) to make default curves available in new projects.
Auto-generate Curves
HelpOpens the help browser with this page displayed.
IP and Tangent Parameters
Arc Length
Shows the arc length of the current curve (0.0 if No Curve).
Delta
Shows the delta angle (change in azimuth) of the current IP/curve.
BC / EC / IP or IP- / IP / IP+
If a curve is defined, these fields display the BC (Begin Curve), EC (End Curve) and IP (Intersection Point) coordinates of the currently selected curve.
If a curve is not defined, they show the coordinates of the previous, current and next IPs.
The incoming and outgoing azimuths are also displayed.
Note that you can use the X and Y fields to change the position of the current IP. You must Apply your changes before they take effect.
Add IPAllows you to Add a Horizontal IP. This button is disabled if you haven't Applied changes made to the current curve/IP.
Edit IPAllows you to Modify a Horizontal IP. After you exit the Modify Horizontal IP dialog box, you must Apply your changes before they take effect.
Delete IPDeletes the current IP (and curve if defined).
