Traffic and Highway Engineering
5th Edition
ISBN: 9781305156241
Author: Garber, Nicholas J.
Publisher: Cengage Learning
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Question
Chapter 4, Problem 5P
To determine
The range of values that would be expected to contain the middle 95 percent of speeds
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A 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 range
A 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 range
2. what is the lowest range
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?
Chapter 4 Solutions
Traffic and Highway Engineering
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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?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_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 accompanying data show spot speeds collected at a section of highway located in a residential area. Using the student's t test, determine whether there was a statistically significant difference in the average speeds at the 95% confidence level.arrow_forwardThis is a three-part question. Data obtained from aerial photography showed eight vehicles on an 800 ft-long section of road. Traffic data collected at the same time indicated an average time headway of 3.7 sec. Part A. Determine the density on the highway in vehicles per mile. Part B. Determine the flow on the road in vehicles per hour. Part C. Determine the space mean speed in mph.arrow_forwardFor 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?arrow_forward
- 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 responsearrow_forwardData obtained from aerial photography showed nine vehicles on a 720 ft-long section of road. Traffic data collected at the same time indicated an average time headway of 4.2 sec. Determine the following. (a) the density on the highway (in veh/mi) veh/mi (b) the flow on the road (in veh/h) veh/h (c) the space mean speed (in mi/h) mi/harrow_forwardA 12 ft long loop detector has observed six vehicles that have crossed the device in a 148 second period, for the following durations: 0.44; 0.48; 0.5; 0.41; 0.49; and 0.55. The six vehicles are 18, 21, 20, 23, 17 and 19 ft respectively. Calculate: b. What is the % lane occupancy?arrow_forward
- The data shown below were obtained by time-lapse photography on a highway. Use regression analysis to fit these data to the Greenshields model and determine The mean free speed The jam density The capacity The speed at maximum flow Speed(mi/h) Density (veh/mi) 14.2 85 24.1 70 30.3 55 40.1 41 50.6 20 55 15arrow_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_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
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