Traffic and Highway Engineering
5th Edition
ISBN: 9781305156241
Author: Garber, Nicholas J.
Publisher: Cengage Learning
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Chapter 4, Problem 18P
To determine
The adequacy of the number of test runs using the floating-car technique.
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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?
For a spot speed study in which 100 observations were obtained, the mean speed was 52 km/h and the standard deviation was 4.6 km/h. (BO0K: Traffic % Highway engineering, N. Gruber SI unit)
What is the margin of error on the estimate of true mean speed obtained from this sample?
What is a reasonable estimate of the 85th percentile speed based on the information available?
An 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?
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- engineer 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_forwardQ1 (a) 10,000 vehicle speed traffic data were collected during the weekday on route FT050 at Batu Pahat, Johor. Suggest how to quantify and describe the basic characteristic of this data. Then explain how the method you suggested can help others to understand the data. ii. Consider the following data from 11 truck speed data climbing a hilly road. Compute 5 (FIVE) basic statistics of the sample speed as following: Sample mean Median а. b. с. Variance d. Range Standard error of the mean е. Speed (km/h) 25 Truck 1 35 3 55 4 15 40 6. 25 7 55 8. 35 9 45 10 11 20arrow_forwardConsider only a single lane of a highway. Based on extensive data from an urban freeway it is assumed thatfree-flow speeds (i.e., there are no jams) can best be represented by a Normal distribution with mean andstandard deviation 119 km/h and 13.1 km/h, respectively.1. What is the probability that the speed of a randomly selected vehicle is between 100 and 120 km/h?2. What is the expected number of vehicles between two vehicles that exceed the posted speed limit of100 Km/h? You can use the Z table for calculating the final answer. You can also write your final answer in form ofR functions or as PDF/CDF of statistical distributions with correct arguments.arrow_forward
- Q1 (a) i. 10,000 vehicle speed traffic data were collected during the weekday on route FT050 at Batu Pahat, Johor. Suggest how to quantify and describe the basic characteristic of this data. Then explain how the method you suggested can help others to understand the data. (4 marks) ii. Consider the following data from 11 truck speed data climbing a hilly road. Compute 5 (FIVE) basic statistics of the sample speed as following: Sample mean Median а. b. с. Variance d. Range Standard error of the mean е. Speed (km/h) 25 Truck 1 2 35 3 55 4 15 40 6. 25 7 55 8. 35 9. 45 10 11 20arrow_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 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 responsearrow_forwardAt an impaired driver checkpoint, the time required to conduct the impairment test varies (exponentially distributed) depending on the compliance of the driver, but takes 60 seconds on average. If an average of 30 vehicles per hour arrive (according to a Poisson distribution) at the checkpoint, determine the average time spent in the system.arrow_forward
- 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?arrow_forwardA spot speed study was conducted on a freeway on which the mean speed and standard deviation were found to be 72.4 km/h and 5.4 km/h, respectively. What is the range of values that would be expected to contain the middle 95% speeds 1 what is top and the lowest rangearrow_forwardThe 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_forward
- The average speed of vehicles on an expressway is being studied. a. Suppose observation on 50 vehicles yielded a sample mean of 65 km/hr. Assume that the standard deviation of vehicle speed is known to be 6 km/hr. Determine the two-sided 99% confidence intervals of the mean speed. b. In part (a), how many additional vehicles' speed should be observed such that the mean speed can be estimated to within + 1 km/hr with 99% confidence? C. Suppose John and Mary are assigned to collect data on the speed of vehicles on this expressway. After each person has separately observed 10 vehicles, what is the probability that John's sample mean will exceed Mary's sample mean by 2 km/hr? d. Repeat part (c) if each person has separately observed 100 vehicles instead?arrow_forwardQuestion 3: (a) A section of highway is known to have a free-flow speed of 95 km/h and a capacity of 3300 veh/h. Your summer student indicates that the average time in between passing vehicles was 1.6 seconds during an hour of monitoring. If the linear speed-density relationship applies, what was the space-mean speed of the vehicles during the hour of monitoring?arrow_forwardAt an impaired driver checkpoint, the time required to conduct the impairment test varies (according to an exponential distribution) depending on the compliance of the driver, but takes 60 seconds on average. If an average of 30 vehicles per hour arrive (according to a Poisson distribution) at the checkpoint, determine the average time spent in the system in minutes/vehicle. Answer in whole number.arrow_forward
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