Dilemma Zone Calculation Let π π X c β denote the maximum distance from the – [Free] B24
Dilemma Zone Calculation Let π π X c β denote the maximum distance from the stop line from which a vehicle is able to clear the intersection, and π π X s β 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
π¦ Dilemma Zone Analysis in Traffic Engineering
π¨ 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 β Minimum stopping distance
- Xc β Maximum clearing distance
If Xs > Xc, a Dilemma Zone exists, increasing the chance of indecision and collision.
β Step 1: Convert Speed
Speed = 40 mph β V = 40 Γ 1.467 = 58.68 ft/sec
β Step 2: Calculate Xs (Minimum Stopping Distance)
- Reaction time: 1 sec
- Deceleration: 10 ft/sΒ²
Reaction Distance: V Γ tr = 58.68 Γ 1 = 58.68 ft
Braking Distance: VΒ² / (2a) = (58.68)Β² / 20 = 172.27 ft
Total Xs = 58.68 + 172.27 = 230.985 ft
β 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 β 0.216 Γ 40 = 7.36 ft/sΒ²
V Γ (ty + tr) = 58.68 Γ 4 = 234.72 ft
(W + L) / a = 73 / 7.36 = 9.93 sec
Xc = 234.72 β 9.93 = 176.745 ft
π΄ Step 4: Dilemma Zone Length
Dilemma Zone = Xs β Xc = 230.985 β 176.745 = 54.24 ft β 54 ft
π§Ύ 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 β |