2.0

Table Of Contents
Drawing Vertical Curves for Ditches and Transitions
227
5 Accept the calculated length of the curve, or enter another one using one of the
following methods:
n
Enter a smaller length to have the vertical curve pass above the indicated
point in a crest curve, and below the selected point in a sag curve.
n
Enter a greater length to have the vertical curve pass below the indicated
point in a crest curve, and above in a sag curve.
The command draws the curve. If the command cannot construct a vertical
curve through the point you selected, an error message appears stating that the
function is undefined for the argument.
Drawing a Sag Vertical Curves Based on the
Headlight Data
To draft a sag vertical curve with given grades, sight distance, and
headlight data
1 From the Profiles menu, choose DT Vertical Curves to display the Vertical
Curves dialog box.
2 In the Description list, select the Headlight option. You can also click the
Headlight icon, and then click OK.
3 Select the tangents that represent the grades going into and out of the PVI.
4 Enter the value for the headlight sight distance.
5 Accept the default values for the headlight height above pavement and
maximum headlight angle, or enter new values.
The length of the curve is calculated. To view the formulas used to calculate the
length of curve, see Drawing the Vertical Curves Based on Curve Length in
this chapter.
6 Accept the calculated length of curve, or enter a new value.
If you enter a new length, the Headlight option recalculates the headlight sight
distance and draws the curve with the length specified.
The final headlight sight distance is displayed and the curve is drawn.