11. Vertical Design

Question 1

What is the variable “r”?

Answer 1

the rate of grade change per station (%/station)

Question 2

What is the rate of vertical curvature?

Answer 2

K=1/r = L/(g_2 - g_1)

K= the distance required to achieve a 1% change in grade.

Question 3

How to solve minimum length of crest vertical curve to satisfy AASHTO stopping sight distance?

Answer 3

Given design speed, look up K in Table 3-35, use L=KA.

Question 4

How to solve minimum length of crest vertical curve to satisfy AASHTO passing sight distance?

Answer 4

Given design speed, look up K in Table 3-36, use L=KA.

Question 5

Design criteria for a sag vertical curve are?

Answer 5

1. Headlight sight distance
2. Passenger comfort
3. Sight distance under overhead structure
4. Drainage control
5. General appearance

Question 6

What is the equation to calculate the slope for a given station on a vertical curve?

Answer 6

S = g_1 + r(x)