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MindTap Engineering for Garber/Hoel's Traffic and Highway Engineering, 5th Edition, [Instant Access], 1 term (6 months)
5th Edition
ISBN: 9781305577398
Author: Nicholas J. Garber; Lester A. Hoel
Publisher: Cengage Learning US
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Question
Chapter 4, Problem 3P
To determine
(a)
The number of spot speed observations collected
To determine
(b)
The sample size
Expert Solution & Answer
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Speed data collected on an urban roadway yielded a standard deviation in speeds
of 4.8 mi/h.
(a) If an engineer wishes to estimate the average speed on the roadway at a 95%
confidence level so that the estimate is within 2 mi/h of the true average, how
many spot speeds should be collected?
(b) If the estimate of the average must be within 1 mi/h, what should the sample
size be?
An engineer, wishing to determine the travel time and average speed along a sectionof an urban highway as part of an annual trend analysis on traffic operations, conducteda travel time study using the floating-car technique. He carried out 10 runs andobtained a standard deviation of ±3 mi/h in the speeds obtained. If a 5% significancelevel is assumed, is the number of test runs adequate?
An engineer wishing to obtain the speed characteristics on a bypass around her city at a confidence level of 95%, and an acceptable limit of 2.0 km/h collected a total of 104 spot speed samples and determined that the variance is 4.8 km/h. Has the engineer met with all of the requirements of the study?
1.What is the variance in this question; 'the lambda'?
2.What is acceptable error in this question
3.What is the minimum number of observations to meet the requirements of the study
4.
Has the engineer met with the requirements of the study?
File a YES or NO response
Chapter 4 Solutions
MindTap Engineering for Garber/Hoel's Traffic and Highway Engineering, 5th Edition, [Instant Access], 1 term (6 months)
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- For a specific rural road segment in northeast Colorado, the total number of crashes as well as the number of fatal crashes have been recorded. Using the data provided with a traffic analysis within two standard deviations (or 95% confidence interval), determine if this site should be flagged for further study. Data: Length of road segment = 2 mi. AADT = 11,350 veh/day Total number of injury crashes for past 5 years = 55 Total number of fatal crashes for past 5 years = 5 Total number of property-only crashes for past 5 years = 100 Average number of statewide injury crashes for rural roads over past 5 years = 1.30 per 106 VMT Average number of statewide fatal crashes for rural roads over past 5 years = 0.02 per 106 VMT Average number of statewide property only crashes for rural roads over past 5 years = .033 per 106 VMT Weighted average crash rate of injury crashes for rural Colorado roads = 3 Weighted average crash rate of fatal crashes for rural Colorado roads = 8 Weighted…arrow_forwardAn engineer, wishing to determine the travel time and average speed along a section of an urban highway as part of an annual trend analysis on traffic operations, conducted a travel time study using the floating-car technique. He carried out 10 runs and obtained a standard deviation of ±3.4 mi/hin the speeds obtained. If a 5 percent significance level is assumed, is the number of test runs adequate?arrow_forward3 During a traffic speed survey, the following observations were recorded when a vehicle passes a 50 m long road section XY. Vehicle Time of Passing X (seconds) Time of Passing Y (seconds) 1 4.5 5.8 6.1 6.3 7.5 23 4 5 2.0 3.5 4.0 4.5 5.5 Determine the following: (i) Average time mean speed (ii) Average space mean speed using the above data (iii) Also verify the results obtained in (ii) above using relationship between the time mean speed and space mean speed.arrow_forward
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