PRIN.OF HIGHWAY ENGINEERING&TRAFFIC ANA.
7th Edition
ISBN: 9781119610526
Author: Mannering
Publisher: WILEY
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Chapter 2, Problem 24P
To determine
The speed of the car when the stopped traffic is hit if the coefficient of rolling resistance is constant at
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A car is traveling up a 3% grade, with the speed of 85mph, on a road that has good, wet pavement. A deer jumps out onto the road and the driver applies the brakes 290-ft from it. The driver hits the deer at a speed of 20mph.If the driver did not have antilock brakes, and the wheels were locked the entire distance, would a deer-impact speed of 20mph be possible? (Hint: check the braking efficiency) [Use Theoretical Stopping Distance]
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Chapter 2 Solutions
PRIN.OF HIGHWAY ENGINEERING&TRAFFIC ANA.
Ch. 2 - Prob. 1PCh. 2 - Prob. 2PCh. 2 - Prob. 3PCh. 2 - Prob. 4PCh. 2 - Prob. 5PCh. 2 - Prob. 6PCh. 2 - Prob. 7PCh. 2 - Prob. 8PCh. 2 - Prob. 9PCh. 2 - Prob. 10P
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- A car is traveling up a 2% grade at 70 mi/h on good, wet pavement. The driver brakes to try to avoid hitting stopped traffic that is 250 ft ahead. The driver's reaction time is 0.5 s. At first, when the driver applies the brakes, a software flaw causes the anti-lock braking system to fail (brakes work in non-anti-lock mode with 80% efficiency), leaving 80 ft skid marks. After the 80 ft skid, the anti-lock brakes work with 100% efficiency. How fast will the driver be going when the stopped traffic is hit if the coefficient of rolling resistance is constant at 0.013? (assume minimum theoretical stopping distance and ignore aerodynamic resistance)arrow_forwardA car is traveling at 60 mi/h on good, wet pavement. It has a wheelbase of 110 inches with the center of gravity 50 inches behind the front axle and at a height of 24 inches above the pavement surface. Determine the percentage of braking force that the braking system should allocate to the rear axle.arrow_forward1. A driver is travelling at 50 mph is 80 m from a wall ahead, if the driver applies the brake immediately at t=2 secs, and begins slowing down at 10m/s^2.a. Find the distance from the stopping point to the wall.b. Determine the braking time or the time during deceleration.c. Determine the average skid resistance, assuming brake efficiency of 70%. 2. A two lane road with design speed of 80 kph has horizontal curve of radius 480 m. Design the rate of superelevation. By how much should the outer edges of the pavement be raised with respect to the center line, if the pavement is rotated with respect to the center line and the width of the pavement at the horizontal curve is 7.5 m?arrow_forward
- A car is approaching toward an intersection with speed 45 mph. The road has a downhill grade of 1%. When the car is at a distance of 250 ft from the intersection, the signal turned yellow. If the driver applies brake and the reaction time of the driver is 1.5 s, will the driver be able to come to a complete stop? Justify your answer with calculations. Assume braking friction coefficient of 0.35.arrow_forwardcompute the braking distance for a car moving at an initial velocity of 80 kph and a final velocity of 60 kph. slope of roadway is +6% the coefficient of friction between road pavement and tries is 0.17, and the perception time is 3/4 seconds.arrow_forwardAn automobile’s braking distance from 108 km/h is 75 m on level pavement. Assume the braking force is independent of grade. Determine the automobile’s braking distance from 108 km/h when it is going up a 5° incline. The automobile’s braking distance from 108 km/h when it is going up a 5° incline is _____m.arrow_forward
- A driver is traveling at 90 mi/h down a 3% grade on good, wet pavement. An accident investigation team noted that braking skid marks started 410 ft before a parked car was hit at an estimated 45 mi/h. Ignoring air resistance, and using theoretical stopping distance, a. If the car’s antilock braking system was effective (no sliding wheels on the pavement), what would the crash speed be?arrow_forwardThe rated speed of a highway curve of 200 ft radius is 40 mph. If the coefficient of friction between the tires and the road is 0.26, (a) What is the maximum speed at which a car can round the curve without skidding?arrow_forwardA student trying to test the braking ability of his car, determined that he needed 32 ft. More to stop his car downhill on a particular road than uphill when driving at 55 mph. Assuming that the coefficient of friction between the tires and the pavement is 0.30. Determine the braking distance downhill and the percent grade of the highway at that section of the road.arrow_forward
- A level test track has a coefficient of road adhesion of 0.80, and a car being tested has a coefficient of rolling friction that is approximated as 0.018 for all speeds. The vehicle is tested unloaded and achieves the theoretical minimum stop in 180 ft (from brake application). The initial speed was 60 mi/h. Ignoring aerodynamic resistance, what is the unloaded braking efficiency?arrow_forwardA vehicle weighing 2000-lb is traveling 30 mph at 5% upgrade with rate of 6 ft/sec². The vehicle has a frontal cross-section area of 20 ft. The roadway has horizontal alignment, and a badly broken and patched asphalt surface. Assume the drag coefficient = 0.3, air density = 0.076 lb/ft³. Find the curve resistance if the horsepower required to accelerate the vehicle is 100 hp.arrow_forwardA driver is traveling at 90 mi/h down a 3% grade on good, wet pavement. An accident investigation team noted that braking skid marks started 410 ft before a parked car was hit at an estimated 45 mi/h. Ignoring air resistance, and using theoretical stopping distance, what was the braking efficiency of the car? If the car’s antilock-braking system was effective (no sliding wheels on the pavement), what would the crash speed be?arrow_forward
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