The Stopping Sight Distance (SSD) of a vehicle depends on which of the following factors? 1. Total reaction time of the driver. 2. Speed of the vehicle. 3. Efficiency of the brakes. 4. Longitudinal friction between the tyre and the road. Which of the statements given above are correct?
- A1 and 2 only
- B2 and 3 only
- C1, 2 and 4 only
- DAll of the aboveCorrect
Solution
Concept
Stopping Sight Distance (SSD)
Formula
SSD = 0.278 Vt + V² / [254 (f ± n)]
Step-by-step solution
1. Identify the two main components of Stopping Sight Distance (SSD): lag distance (distance traveled during reaction time) and braking distance (distance traveled after applying brakes). 2. Analyze the formula SSD = 0.278 Vt + V² / \[254 (f ± n)\], noting that driver reaction time (t), speed (V), brake efficiency, and longitudinal friction (f) all directly influence SSD. 3. Verify that all four listed factors affect the stopping sight distance and choose Option (d) as the correct answer.
Explanation
Stopping Sight Distance (SSD) is the total distance needed for a vehicle to safely come to a complete stop. It consists of lag distance (the distance traveled while the driver reacts) and braking distance (the distance traveled after applying the brakes). Therefore, SSD directly depends on all four factors: the driver's reaction time, vehicle speed, brake efficiency, and longitudinal friction between the tires and the road surface.
Shortcut
To easily remember all the factors affecting Stopping Sight Distance (SSD), use the mnemonic "RSBF" (Road Safety Depends on Four): - Reaction Time (t): Time taken by the driver to react. - Speed (V): Speed of the vehicle. - Brake Efficiency (η): Condition and performance of the brakes. - Friction (f): Longitudinal friction between tyres and road surface.
Common mistake
A common mistake is selecting option C by assuming brake efficiency is not included in standard Stopping Sight Distance formulas, or selecting option A by focusing only on driver reaction time and vehicle speed while ignoring braking and friction factors. In reality, brake efficiency directly affects the braking distance required to stop the vehicle safely.
Correct answer: D) All of the above