On roads with restricted width or on single lane roads, when two-way movement of traffic is permitted, the minimum stopping sight distance should be equal to ___________
- A2 × stopping sight distanceCorrect
- B3 × stopping sight distance
- C4 × stopping sight distance
- D5 × stopping sight distance
Solution
Concept
Sight distance on single-lane two-way roads
Formula
Minimum Sight Distance = 2 × SSD
Step-by-step solution
1. For single-lane roads with two-way traffic, opposing vehicles share the same lane. 2. Both vehicles need stopping distance upon sighting each other: SSD for vehicle 1 + SSD for vehicle 2. 3. Therefore, minimum sight distance required = 2 × SSD. Answer: A
Explanation
On single-lane roads or roads with restricted width where two-way traffic movement is permitted, two approaching vehicles moving towards each other require space to come to a complete stop safely. Therefore, the minimum sight distance provided must be equal to 2 × Stopping Sight Distance (SSD).
Why the other options are wrong
B) 3 × SSD exceeds the requirement and is not defined in IRC standards. C) 4 × SSD is incorrect. D) 5 × SSD is incorrect.
Shortcut
Single lane + Two-way traffic = 2 × SSD.
Common mistake
Confusing with intermediate sight distance (ISD), which is also 2 × SSD, but thinking single lane only needs 1 × SSD.
Correct answer: A) 2 × stopping sight distance