Traffic and Highway Engineering
5th Edition
ISBN: 9781305156241
Author: Garber, Nicholas J.
Publisher: Cengage Learning
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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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Students have asked these similar questions
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?
Please solve and explain step by step, thank you
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?
Chapter 4 Solutions
Traffic and Highway Engineering
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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 obtain the speed characteristics on a bypass around her city at a confidence level of 95%, and an acceptable limit of 1.0 mi/h collected a total of 130 spot speed samples and determined that the variance is 25 (mi/h)2 . Has the engineer met with all of the requirements of the study?arrow_forwardAn engineer wishing to obtain the speed characteristics on a bypass around her city at a confidence level of 95%, and an acceptable limit of + 1.0 mi/h collected a total of 130 spot speed samples and determined that the variance is 25 (mi/h). Has the engi- neer met with all of the requirements of the study?arrow_forward
- Complete answerarrow_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_forwardQ3. The below Table shows the time and distance for 10 vehicles recorded during a traffic survey. Choose the correct answer of the following (Four only): 1. The Average Spot Speed of the sample in the Table equals: a. (68.5) Km/hr c. (19.21) Km/hr e. (18.9) Km/hr (20 Marks Time (sec) 5.0 Distance (m) b. (190.21) Km/hr d. (67.9) Km/hr f. None of them Distance/time (m/sec) 20.00 100 5.6 100 17.86 5.6 100 17.86 4.8 100 20.83 2. The Time Mean Speed (TMS) of the sample in the Table equals: a. 68.5 (Km/hr) c. 19.21 (Km/hr) e. 18.9 (Km/hr) 6.1 100 16.39 5.3 100 18.87 b. 190.21 (Km/hr) d. 67.9 (Km/hr)- f. None of them 5.9 100 16.95 5.2 100 19.23 4.5 100 22.22 5.0 100 20.00 3. The Space Mean Speed (SMS) of the sample in the Table equals: a. 68.5 (Km/hr) d. 67.9 (Km/hr) Total 53 1000 190.21 b. 190.21 (Km/hr) e. 18.9 (Km/hr) c. 19.21 (Km/hr) f. None of them 4. The Average travel Speed of the sample in the Table equals: a. 68.5 (Km/hr) d. 67.9 (Km/hr) b. 190.21 (Km/hr) e. 18.9 (Km/hr) c. 19.21…arrow_forward
- 3 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_forwardA construction zone on a highway has a posted speed of 40 kmph. The speeds of vehicles passing through this construction zone are normally distrbuted with a mean of 45 kmph and a standard deviation of 4 kmph. a.) What is the probability that a vehicle passing through the construction zone exceeds the posted limit? b.) What is the probability that a vehicle passing through the construction zone is travelling at speeds between 38 and 49 kmph? c,) For the next 30,000 vehicles passing through the construction zone, how many will be passing through the zone with speed less then 50 kmph?arrow_forwardengineer wishing to determine the travel time and average speed along a section of an urban highway as part annual trends 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 mi/h in the speeds obtained .if 5% significance level is assumed is the number of test runs adequate?arrow_forward
- The city received a complaint of afternoon traffic speeding in a residential area. The city suspected this was related to students leaving a nearby school. The first action taken by the city was to quantify the facts by conducting a spot speed study. The city decided to use the stopwatch method because of their limited resources. The Speed (mph) 21.4 22.2 23 24 Frequency of Vehicles 3. 25 26.1 27.2 28.9 30 31.5 33.3 35.2 37.5 9. 11 13 posted speed limit is 30 mph. The study was conducted on a Wednesday and started at 3:00 p.m. The time was selected to correspond to the period when most students leave the school. The study continued until a sample size of 100 9 10 10 9. 40 42.8 vehicles was measured.arrow_forward4-14 Table 4.10 shows data obtained in a travel time study on a section of highway using the moving-vehicle technique. Estimate (a) the travel time and (b) the volume in each direction at this section of the highway. Chapter 4 Traffic Engineering Studies 149 Table 4.10 Travel Time Data for Problem 4-14 No. of No. of No. of Vehicles Vehicles That Vehicles Run Travel Traveling in Орposite Overtook Overtaken by Test Vehicle Direction/ Time Test Number (min) Direction Vehicle Northward 5.25 100 2 2 2 5.08 105 2 1 3 5.30 103 3 1 4 5.15 110 1 5.00 101 6. 5.51 98 7 5.38 97 1 1 8 5.41 112 2 3 5.12 109 3 1 10 5.31 107 Southward 1 4.95 85 1 2 4.85 88 1 3 5.00 95 1 4 4.91 100 2 1 4.63 102 1 5.11 90 1 1 7 4.83 95 8 4.91 96 3 1 9 4.95 98 1 2 10 4.83 90 1arrow_forwardLinear regression analysis was performed on a set of traffic data using speed and density measurements from a highway segment. The following equation was developed. ?? = 57.5 − 0.457?? Use this equation, as well as the fundamental relationship equations to answer the following questions. What is the free-flow speed for this data? What is the jam density of this data? What is the maximum flow of this highway segment? What is the mean speed at this maximum flow?arrow_forward
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