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Cost-Effective Performance Measures for Travel Time Delay, Variation, and Reliability (2008) / Chapter Skim
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Pages 25-33

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From page 25...
... Exhibit 3.2 highlights typical agency or third-party travel time and delay data collection programs. The FHWA publication, Travel-Time Data Collection Handbook is an excellent source of information on the strengths, weaknesses, and costs of various travel-time data collection methods.
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From page 26...
... The results can be aggregated weighting the average travel times according to the number of trips represented by each super-district. 3.3.2 Sampling Strategies for System Monitoring If it is desired to develop travel-time information for the regional freeway system (or surface street system)
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From page 27...
... MPOs MPOs conduct travel behavior surveys every 5 to 10 years in which they ask travel-time information. MPOs involved in congestion management may commission annual surveys of peak-period speeds and travel times on specific road segments.
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From page 28...
... Prospective survey where the traveler is contacted in advance and asked to record all trip making the next day are generally more precise than retrospective surveys. Good for obtaining OD trip times.
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From page 29...
... Possible to extrapolate travel time from speed data, depending on accuracy need. Vehicle signature matching, under development; may generate travel-time data in the long term.
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From page 30...
... , N−1 = The Student's t statistic for the probability of two-sided error summing to alpha with N − 1 degrees of freedom; and s = The standard deviation in the measured travel times and the square root of the variance. Exhibit 3.5 illustrates the minimum number of observations required for various target levels of precision, expressed here in units of the standard deviation of the measured travel times or delay times.
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From page 31...
... Exhibit 3.5. Minimum observations to obtain desired confidence interval.
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From page 32...
... . 3.5.3 Computation of Confidence Intervals (Travel Time and Delay)
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From page 33...
... Chapter 6 contains more detailed directions for data sampling and calculation of travel time/delay variance and reliability measures using estimated data, rather than observed or TMC data.
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Key Terms

  • road segment
  • travel time
  • mean speed
  • confidence intervals
  • typical agency

  • confidence interval
  • sampling plan
  • state highway
  • loop detectors
  • custom data

  • volume data
  • sampling strategies
  • time travel
  • count stations
  • major urban

  • speed data
  • collection methods
  • trip time
  • congestion management
  • reliability measures

  • mean travel
  • average travel
  • trip times
  • collection plan
  • resources required

  • planning application


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