Principles Of Highway Engineering And Traffic Analysis
7th Edition
ISBN: 9781119493969
Author: Mannering, Fred L., WASHBURN, Scott S.
Publisher: Wiley,
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Chapter 2, Problem 25P
To determine
The speed of the car just before it impacts the object.
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A car is traveling at 76 mi/hr down a 3% grade on poor, wet pavement. The car's braking efficiency is 90%. The brakes were applied 320 ft before impacting an object. The car had an antilock braking system, but the system failed 200ft after the brakes had been applied (wheels locked). What speed was the car traveling at just before it impacted the object? (Assume theoretical stopping distance, ignore air resistance, and let Frl=0.015)
compute 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.
A motorist travelling at 100 km/hr on a highway needs to take the next exit, which
has a speed limit of 50 km/hr. The section of the roadway before the ramp entry has
a downgrade of 3% and coefficient of friction (f) is 0.35. In order to enter the ramp
at the maximum allowable speed limit, determine the braking distance (expressed in
m) from the exit ramp.
Chapter 2 Solutions
Principles Of Highway Engineering And Traffic Analysis
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, civil-engineering and related others by exploring similar questions and additional content below.Similar questions
- A car is traveling at a speed of 100 ft/s which accelerates 12 ft/s2. The perception reaction time for the driver is 2.40 s. If the maximum grade of the road is -3.7%, compute the following: a. Braking distance in meters b. Lag distance in metersarrow_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_forwardA vehicle weighing a 50 kN is moving at a constant speed around a circular curve. Neglecting the friction between the tires and the pavement and the centrifugal ratio (the ratio of the centrifugal force experience by the vehicle on the curve to its own weight) is 0.30. The degree of the curve is 5 degrees.a. Calculate the centrifugal force.b. Calculate the maximum speed the vehicle could move around the curve (in kph)c. If the skid resistance is 0.15, calculate the maximum super elevation that can be provided for the speed calculated from b.arrow_forward
- 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]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_forwardA vehicle moving at a speed at a speed of 90 kph along an incline surface having aslope of 5%. If the coefficient of friction is 0.20, determine the braking distance.arrow_forward
- 43. A truck was travelling uphill at 50 kph. The brakes are suddenly applied and the truck stopped in a distance of 16.1 m. If the coefficient of friction between the tires and the road surface is 0.4, what is the grade of the road?arrow_forwardIf the car in Example 2.9 had CD = 0.45 and area = 25 ft2, what is the difference in minimum theoretical stopping distances with and without aerodynamic resistance considered (all other factors the same as in Example 2.9)? Example 2.9 EFFECTS OF GRADE ON THEORETICAL MINIMUM STOPPING DISTANCE A car is traveling at 80 mi/h and has a braking efficiency of 80%. The brakes are applied to miss an object that is 150 ft from the point of brake application, and the coefficient of road adhesion is 0.85. Ignoring aerodynamic resistance and assuming the theoretical minimum stopping distance, estimate how fast the car will be going when it strikes the object if (a) the surface is level and (b) the surface is on a 5% upgrade.arrow_forwardA car is traveling at 70 mi/h on a level section of road with good, wet pavement. Its antilock braking system (ABS) only starts to work after the brakes have been locked for 100 ft. If the driver holds the brake pedal down completely, immediately locking the wheels, and keeps the pedal down during the entire process, how many feet will it take the car to stop from the point of initial brake application? (The braking efficiency is 80% with the ABS not working and 100 % with the ABS working. Use theoretical stopping distance and ignore air resistance. Let frl = 0.02 when the brakes are locked, but complete the frl once the ABS becomes active.)arrow_forward
- A 11120 N car is designed with a 310 cm wheelbase. The center of gravity is located 60 cm above the pavement and 105 cm behind the front axle. If the coefficient of road adhesion is 0.6, what is the maximum tractive effort that can be developed if the car is (a) front-wheel drive and (b) rear-wheel drive? From the previous question, how far back from the front axle would the center of gravity have to be to ensure that the maximum tractive effort developed for front- and rear-wheel drive options is equal?arrow_forwardWhile traveling at a constant speed a driver saw a road block 112 m away. He applied the brakes and the car decelerated uniformly at 6.4 m/s2. It stopped 5 m from the block. The driver’s PRT is 2.2 seconds. Sketch and calculate the initial constant speed of the vehicle in kph if;a. The roadway is levelb. The roadway grade is +10%c. The roadway grade is -10%arrow_forwardTwo cars are traveling on level terrain at 60 mi/h on a road with a coefficient of adhesion of 0.8. The driver of car 1 has a 2.5-s perception/reaction time and the driver of car 2 has a 2.0-s perception/reaction time. Both cars are side by side and the drivers are able to stop their respective cars in the same amount of distance after first seeing a roadway obstacle (perception/reaction plus vehicle stopping distance). If the braking efficiency of car 2 is 0.75, determine the braking efficiency of car 1. (Assume minimum theoretical stopping distance and ignore aerodynamic resistance.)arrow_forward
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