| As you drive on a straight, two-lane rural road with a speed limit of 55 mph (design speed 70 mph) you notice a car has stopped in your lane due to a fallen tree that completely blocked the road. The back of the car is 683-feet from you when you first notice the problem. For this problem, you may assume your vehicle has a standard deceleration rate of 11.2 ft/s2. a.) Assuming the road grade is reasonably level, if your reaction time is the assumed 2.5 seconds, would you be able to stop before hitting the car in front of you? (Hint: Since you are not told the vehicle speed you should assume it is traveling the design speed.) b.) Since you pride yourself on your quick thinking and fast reactions, assume your personal reaction is actually 1.25 seconds. Would you be able to stop before hitting the car? c.) If you did have the fast reaction time of 1.25 seconds but the grade of the road was - 4.3% at that location, would you be able to stop before hitting the car? d.) Finally, the deceleration rate of 11.2ft/s2 is based on comfortable deceleration for most drivers. It is likely that if you "slam on the brakes” you will be able to stop with a higher deceleration rate. What minimum deceleration rate would be needed to successfully stop, assuming a 2.5 second reaction time and a 0% grade? Why do we not use this value in designing stopping sight distance?
| As you drive on a straight, two-lane rural road with a speed limit of 55 mph (design speed 70 mph) you notice a car has stopped in your lane due to a fallen tree that completely blocked the road. The back of the car is 683-feet from you when you first notice the problem. For this problem, you may assume your vehicle has a standard deceleration rate of 11.2 ft/s2. a.) Assuming the road grade is reasonably level, if your reaction time is the assumed 2.5 seconds, would you be able to stop before hitting the car in front of you? (Hint: Since you are not told the vehicle speed you should assume it is traveling the design speed.) b.) Since you pride yourself on your quick thinking and fast reactions, assume your personal reaction is actually 1.25 seconds. Would you be able to stop before hitting the car? c.) If you did have the fast reaction time of 1.25 seconds but the grade of the road was - 4.3% at that location, would you be able to stop before hitting the car? d.) Finally, the deceleration rate of 11.2ft/s2 is based on comfortable deceleration for most drivers. It is likely that if you "slam on the brakes” you will be able to stop with a higher deceleration rate. What minimum deceleration rate would be needed to successfully stop, assuming a 2.5 second reaction time and a 0% grade? Why do we not use this value in designing stopping sight distance?
Chapter2: Loads On Structures
Section: Chapter Questions
Problem 1P
Related questions
Question
Transcribed Image Text:|
As you drive on a straight, two-lane rural road with a speed limit of 55
mph (design speed 70 mph) you notice a car has stopped in your lane due to a fallen tree that
completely blocked the road. The back of the car is 683-feet from you when you first notice
the problem. For this problem, you may assume your vehicle has a standard deceleration rate
of 11.2 ft/s2.
a.) Assuming the road grade is reasonably level, if your reaction time is the assumed 2.5
seconds, would you be able to stop before hitting the car in front of you? (Hint: Since
you are not told the vehicle speed you should assume it is traveling the design speed.)
b.) Since you pride yourself on your quick thinking and fast reactions, assume your
personal reaction is actually 1.25 seconds. Would you be able to stop before hitting
the car?
c.) If you did have the fast reaction time of 1.25 seconds but the grade of the road was -
4.3% at that location, would you be able to stop before hitting the car?
d.) Finally, the deceleration rate of 11.2ft/s2 is based on comfortable deceleration for
most drivers. It is likely that if you "slam on the brakes” you will be able to stop with
a higher deceleration rate. What minimum deceleration rate would be needed to
successfully stop, assuming a 2.5 second reaction time and a 0% grade? Why do we
not use this value in designing stopping sight distance?
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