QQuestionAnatomy and Physiology
QuestionAnatomy and Physiology
# Dilemma Zone: Example
A driver traveling at the speed limit of $\mathbf{3 5} \mathbf{~ m p h}$ was cited for crossing an intersection on red. He claimed that he was innocent because the duration of the amber display was improper and, consequently, a dilemma zone existed at that location.
1) Using the following data, determine whether the driver's claim was correct.
2) Determine if the driver is innocent. Given he kept 37 mph speed and he was 0.33 second into the red light when he crossed intersection.
Amber duration $= 4.5 \mathrm{~s}$
perception/reaction time $= 1.5 \mathrm{~s}$
deceleration $= 10 \mathrm{ft} / \mathrm{s}^{2}$
Car length $= 15 \mathrm{ft}$
Intersection width $= 50 \mathrm{ft}$
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Answer
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Step 1: Determine the distance needed to stop the car within the amber duration.
d_{decel} = \frac{(37 \frac{miles}{hour} * \frac{1 hour}{3600 \frac{seconds}{hour}})^2}{2 * 10 \frac{feet}{second^2} * \frac{4.5 seconds - 1.5 seconds}{1 second}} = 67.72 feet
The driver has a perception/reaction time of 1.5 seconds, during which they will continue at their initial speed. After this time, they will begin decelerating until they stop. First, calculate the distance traveled during the perception/reaction time: where Substituting the given values: Next, calculate the distance needed to stop the car during the amber duration: where Substituting the given values:
Step 2: Calculate the total stopping distance.
d_{total} = d_{reaction} + d_{decel} = 8.17 feet + 67.72 feet = 75.89 feet
Add the distance traveled during the reaction time and the distance needed to stop the car during deceleration:
Final Answer
The driver is not innocent, as they crossed the intersection 0.33 seconds after the amber light turned red.
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