Explanation A-8. Which of the speed-related measures is used in fundamental rela

Question

Explanation A-8. Which of the speed-related measures is used in fundamental relationships of traffic flow theory? a. Space Mean Speed b. Travel time c. Pace d. Spot Speed e. Time Mean Speed PART B: 1-3 Problems- Please provide the solution for each of the following questions. (If you need extra space feel free to add more pages and attach them accordingly.) B.1-Adriver is driving uphill on a 3 % grade at 30 mph on a dry pavement when suddenly a person steps from behind a parked car in the path of the driver, at a distance of 85 ft. Can the driver stop in time with emergency braking assuming a deceleration rate of 14.8 ft/s and a reaction time of 1.2 seconds? Solution:

Explanation / Answer

Velocity, V = 30 mph = 30 x 1.6 kmph = 48 kmph

Reaction time, t = 1.2 seconds

friction, f = 0.38 ( by imterpolation from : f = 0.35 for V = 20 kmph and f = 0.4 for V = 100 kmph)

Grade, n = 3%(upward)

So, Stopping Sight Distance , SSD = 0.278Vt + V2 / 254(f+0.01n)

= 0.278 x 48 x 1.2 + 48x48 / ( 254 x ( 0.38 + 0.01 x 3))

= 38.5 m

Distance from Driver of the vehicle to the person stepping on the road = 85 ft

= 85 / 3.28 m = 25.9 m < 38.5 m

which is not safe.

When the driver is applying emergency break at a deceleration rate of 14.8 ft/s2 , then the distance at which the car will just stop = (30 x 1.47)2 / (2 x 14.8) = 65 ft < 85 ft

After 1.2 sec of reaction if the driver apply the emergency break, it will not be safe to stop the car in time.

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