2.0

Table Of Contents
Chapter 3 Working with Profiles and Vertical Alignments
206
Drawing a Sag Vertical Curve Based on a
Given Velocity
One method of drawing a sag vertical curve is to specify a velocity.
To draw a sag vertical curve based on a given velocity
1 From the Profiles menu, choose FG Vertical Curves to display the Vertical
Curves dialog box.
NOTE
You can only use this command with a sag curve.
2 Select the Comfort option by clicking its name in the Description list. You can
also click the Comfort icon, and then click OK.
NOTE
If you do not see the graphic representation of the curve type you want to
create, then click the Next or Previous button at the bottom of the Vertical
Curves dialog box.
3 Select the tangents that represent the grades coming into and out of the PVI.
4 Press ENTER to accept the default design value (55 miles per hour for imperial
units and 88.51 kilometers per hour for metric units), or type a new value.
The command calculates the appropriate length of the curve.
5 Press ENTER to accept this length, or enter a new value.
If you enter a new length, the Comfort option recalculates the design velocity
and draws the curve with the specified length.
The following illustration shows the parameters used in calculating a vertical
curve based on design velocity:
Designing a vertical curve by velocity
The following formula is used to calculate the length of the sag vertical curve:
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where:
V = the design speed (mph)
A = the grade change (absolute value)