2.0

Table Of Contents
Chapter 3 Working with Profiles and Vertical Alignments
202
The following equations are used to calculate the stopping sight distance.
If the safe stopping distance (S) is less than the length of the curve (L):
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/
$6
KK
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If (S) is greater than (L):
>@
/6
KK
$
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§
©
¨
¨
·
¹
¸
¸
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where:
L = Length of vertical curve in feet
S = Sight distance in feet
A = Algebraic difference in grade percent
h
1
= Height of eye above alignment surface in feet
h
2
= Height of object above alignment surface in feet
Drawing a Vertical Curve Based on an
Elevation Point
One method of drawing a vertical curve is to specify a high or low elevation
point through which the vertical curve must pass.
To draw a vertical curve based on an elevation point
1 From the Profiles menu, choose FG Vertical Curves to display the Vertical
Curves dialog box.
2 Select the High/Low Point option by clicking its name in the Description list.
You can also click the High/Low Point icon, and then click OK.
NOTE
If you do not see the graphic representation of the curve type you want to
create, click the Next or Previous button at the bottom of the Vertical
Curves dialog box.
3 Select the tangents that represent the grades into and out of the PVI.
4 Specify the high/low point using one of the following methods:
n
Select a point from the screen.
n
Press ENTER and type a numeric value for the elevation.
The command computes the necessary length of curve to pass exactly through
the given elevation.
5 Press ENTER to accept the length of curve required to pass exactly through the
given point, or enter a new length.
If you change the length, the actual curve passes above or below the given point.