18.1. Overview

Try these first

1. 1.

   What is a valley curve?

   Hint

   Think about what happens when a road goes downwards.

2. 2.

   What shape is preferred for valley curves?

   Hint

   Remember the name has two words; what does it relate to?

3. 3.

   What are valley curves primarily used for?

   • To increase vehicle speed
   • To accommodate road gradients
   • To improve aesthetics

   Hint

   Think about how roads deal with hills and valleys.

4. 4.

   True or False: Valley curves are only necessary during the day.

   • True
   • False

   Hint

   Consider what happens after dark.

5. 5.

   A new road is to be constructed through a steep valley. If the descending gradient is n = 1 in 25 and the ascending gradient is n = 1 in 30, calculate the required length of the valley curve for a design speed of 80 km/h. Assume c = 0.6 m/sec³ and SSD = 127.3m.

   Hint

   Break down the problem using comfort and safety criteria as you learned about.

6. 6.

   Discuss what factors would lead to the decision to use a longer or shorter valley curve based on gradient changes and nighttime visibility.

   Hint

   Consider how gradients impact perceived visibility and safety needs.