Principles of Highway Engineering and Traffic Analysi (NEW!!)
6th Edition
ISBN: 9781119305026
Author: Fred L. Mannering, Scott S. Washburn
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 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)
A car is traveling up a 1.5% grade at 65 mi/hr on good, wet pavement. The driver brakes to
try to avoid hitting a cone on the road that is 300 ft ahead. The driver's reaction time is 1.5
second. When the driver first applies the brakes, a software flaw causes the braking
efficiency to lower to 0.8 for 100 ft. After the initial 100 ft, the braking efficiency returns
to 1.0. How fast will the driver be going when the cone on the road is hit if the coefficient
of rolling resistance is constant at 0.015? (Assume minimum theoretical stopping distance
and ignore aerodynamic resistance.)
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]
Chapter 2 Solutions
Principles of Highway Engineering and Traffic Analysi (NEW!!)
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- 1. A car is approachin an intersection with velocity 35 mph. When the car is at a distance of 200 ft from the intersection, the signal turned yellow. If the driver decides to break, will he be able to stop safely? The driver's reaction time is 1.5 s. Assume the road surface as leveled. The maximum braking effort is applied. Will your answer change, if the grade of the road surface is downhill 3%? A car is at a distance of 200 ft from an intersection stop line when the signal turned yellow. What should be the minimum speed of the car (miles/hour) if the driver decides to apply brake and is just able to stop at the line? Use reaction time of 1.5 s and the road surface has zero grade.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_forwardA car is driving at 75 mph down a 4.0 % grade on poor, wet pavement. The car's braking efficiency is 90%. The driver saw an object which is 480 ft away and applied the brake, and his reaction time was 1.0 second. The car's antilock braking system (ABS) works. Just after seeing the object, which of the following is closest to the distance (in ft) traveled before applying the brake? (Assume theoretical stopping distance ignore air resistance and let yb= 1.04 and fr = 0.015). 153 ft B) 127 ft 135 ftarrow_forward
- abäi 25 Q4) A driver is travelling at 45 mph. He is 60m from a traffic light when he sees turn yellow. His reaction time, before stepping on the break is 0.5 seconds. What steady deceleration while breaking will bring him to a stop * ?right at the lightarrow_forwardA 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_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, a. If the car’s antilock braking system was effective (no sliding wheels on the pavement), what would the crash speed be?arrow_forward
- bäi 25 Q4) A driver is travelling at 45 mph. He is 60m from a traffic light when he sees turn yellow. His reaction time, before stepping on the break is 0.5 seconds. What steady deceleration while breaking will bring him to a stop * ?right at the lightarrow_forwardThe car's braking distance from a velocity of v= 96 km/hr is 45 m on a level pavement. Assuming that the braking force is independent of the grade of the pavement, determine the car's braking distance from the same velocity when it is (a) Going up a 10-percent incline (b) Going down an 8° inclinearrow_forwardA car traveling at 45 mph on a poor, wet pavement has a braking efficiency of 87%. The brakes were applied 100 feet before hitting an obstacle in the road. The road is uphill for 40 feet and then is level for the remainder of the way. The car had a maximum coefficient of road adhesion in the sloped portion of the poor, wet roadway and but as soon as it started going on the level portion its coefficient of road adhesion reduced to 0.3. Assuming that the car struck the obstacle at 30 mph, what was the grade of the hill? Assume practical stopping distance equation applies.arrow_forward
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