Dilemma Zone Calculation Let ๐ ๐ X c โ denote the maximum distance from the – [Free] B24
Dilemma Zone Calculation Let ๐ ๐ X c โ denote the maximum distance from the stop line from which a vehicle is able to clear the intersection, and ๐ ๐ X s โ denote the minimum distance from the stop line where the vehicle can stop completely after the beginning of the yellow interval.
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Answer
๐ฆ Dilemma Zone Analysis in Traffic Engineering
๐จ What is the Dilemma Zone?
A Dilemma Zone is the area before an intersection where a driver cannot safely decide whether to stop or go when the traffic light turns yellow.
It exists between:
- Xs โ Minimum stopping distance
- Xc โ Maximum clearing distance
If Xs > Xc, a Dilemma Zone exists, increasing the chance of indecision and collision.
โ Step 1: Convert Speed
Speed = 40 mph โ V = 40 ร 1.467 = 58.68 ft/sec
โ Step 2: Calculate Xs (Minimum Stopping Distance)
- Reaction time: 1 sec
- Deceleration: 10 ft/sยฒ
Reaction Distance: V ร tr = 58.68 ร 1 = 58.68 ft
Braking Distance: Vยฒ / (2a) = (58.68)ยฒ / 20 = 172.27 ft
Total Xs = 58.68 + 172.27 = 230.985 ft
โ Step 3: Calculate Xc (Maximum Clearing Distance)
- Yellow time: 3 sec
- Reaction time: 1 sec
- Intersection width: 55 ft
- Vehicle length: 18 ft
Acceleration: a = 16 โ 0.216 ร 40 = 7.36 ft/sยฒ
V ร (ty + tr) = 58.68 ร 4 = 234.72 ft
(W + L) / a = 73 / 7.36 = 9.93 sec
Xc = 234.72 โ 9.93 = 176.745 ft
๐ด Step 4: Dilemma Zone Length
Dilemma Zone = Xs โ Xc = 230.985 โ 176.745 = 54.24 ft โ 54 ft
๐งพ Final Summary
| Parameter | Value |
|---|---|
| Speed (V) | 58.68 ft/sec |
| Minimum stopping distance (Xs) | 230.985 ft |
| Maximum clearing distance (Xc) | 176.745 ft |
| Dilemma Zone length | 54 ft |
| Dilemma Zone Exists? | Yes โ |