Which of the following is most nearly the distance from the edge of roadway that must be free from obstructions to provide the required stopping sight distance for a horizontal curve with a 2,000-foot radius and a stopping sight distance of 570 feet?
Explanation
Answer: A - 20.3 is the required distance from the edge roadway that must be free from obstructions to provide the required stopping sight distance for a horizontal curve with a 2,000-foot radius and 60 mile per hour design speed.
Solution: Use the middle ordinate equation for simple horizontal curve
M = R [1-cos (90SSD/ΠR)]
Where R = 2,000 feet
SSD = 570 feet
Therefore
M = 2,000[1-cos (90)(570)/Π(2,000)]
= 2,000[1-cos (8.16)] = 20.3 feet
