Consider width of road 7.2 m and pedestrian speed of 1.2 m/s, find the green time for pedestrian. Consider initial walk time as 7 s.
- A14 s
- B6 s
- C13 sCorrect
- D26 s
Solution
Concept
Pedestrian green time = initial walk time + time needed to cross the road.
Formula
Gp = twalk + W / vp
Step-by-step solution
1. Crossing time = W / vp = 7.2 / 1.2 = 6 s. 2. Initial walk time = 7 s. 3. Pedestrian green time = 7 + 6 = 13 s.
Explanation
A pedestrian needs some starting walk time plus the time to cross the full road width. The crossing time is the road width divided by the walking speed. Adding both gives 13 s.
Why the other options are wrong
A: 14 s does not match the given data. B: 6 s is only the crossing time; the walk time is missing. D: 26 s is double the correct value.
Shortcut
Green time = 7 + 7.2/1.2 = 13 s.
Common mistake
Taking only W/v (6 s) and forgetting to add the initial walk time.
Correct answer: C) 13 s