For a given road, the estimated safe stopping sight distance is 95 m and the overtaking sight distance is 420 m. What is the intermediate sight distance?
- A190 mCorrect
- B285 m
- C420 m
- D840 m
Solution
Concept
Calculation of intermediate sight distance
Formula
ISD = 2 × SSD
Step-by-step solution
1. Intermediate Sight Distance (ISD) is defined as twice the safe Stopping Sight Distance (SSD). 2. Calculating ISD = 2 × 95 m = 190 m. Answer: A
Explanation
Intermediate Sight Distance (ISD) is defined by highway standards as twice the Stopping Sight Distance (SSD) when overtaking sight distance cannot be provided. Calculating ISD as 2 multiplied by 95 m yields a value of 190 m. Therefore, option A correctly provides the calculated intermediate sight distance.
Why the other options are wrong
NONE
Shortcut
Intermediate Sight Distance (ISD) is always equal to twice the Stopping Sight Distance (ISD = 2 × SSD).
Common mistake
Selecting option B or C by taking 1.5 times SSD or using OSD instead of calculating Intermediate Sight Distance as twice the SSD.
Correct answer: A) 190 m