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Cost-Effective Performance Measures for Travel Time Delay, Variation, and Reliability (2008) / Chapter Skim
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Pages 55-68

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From page 55...
... The literature search, agency interviews, and case studies conducted during the course of this project suggest that use of travel time and delay data for planning purposes is currently C H A P T E R 8 Using Travel Time Data in Planning and Decision Making
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From page 56...
... Yet travel time and delay statistics can be useful in helping analysts, decision makers, and the general public to understand the potential payoff of different capital and operating investments in terms that are most immediately relevant to daily trip-making of system users. 8.4.1 Using Travel Time and Delay Measures Transportation project complexity and costs are continuing to grow significantly.
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From page 57...
... Example before-after comparison of different travel time measures. know the average travel time (or total daily delay)
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From page 58...
... The list goes on, but the principle remains: if the tools are important for decision-making, improving the tools must be a priority. Research projects, such as these and many others like it, ultimately provide planners with the necessary tools to estimate and apply travel time performance data in a broad variety of situations.
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From page 59...
... Chapters 4 through 7 describe specific analyses that can be performed using travel time and delay data. Exhibit 8.3 presents a recommended short list of measures for reporting travel time, delay, and reliability.
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From page 60...
... travel time for travel planning purposes Percent Variation Intensity, Variability Region, Subarea, Section, Corridor % of average travel time required for on-time arrival of given trip, similar to Planning Time Index 95th Percentile Duration, Variability Section or Corridor Trip duration in minutes and seconds Exhibit 8.3. Recommended measures for reporting travel time, delay, and reliability.
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From page 61...
... Step 6. Process Baseline Results • Set reasonableness bounds for data and eliminate outliers; • Set travel time standard (free-flow, speed limit, or other)
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From page 62...
... • Compute desired metrics, selecting from initial list; and • Prepare report and graphics. (Chapter 3)
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From page 63...
... against which additional travel time is considered delay; • Compute mean and variance for travel time and delay; • Compute confidence intervals for mean travel time and mean delay; • Compute desired reliability metrics; and • Identify deficient segments and facilities (Chapter 5)
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From page 64...
... Step 2. Determine Study Bounds • Decide if O-D times, facility times, or segment times desired; and • Decide on length of analysis periods and time slices within analysis period.
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From page 65...
... against which additional travel time is considered delay; • Compute mean and variance for travel time and delay; • Compute confidence intervals for mean travel time and mean delay; • Compute desired reliability metrics; and • Prepare report and graphics. (Chapter 3)
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From page 66...
... against which additional travel time is considered delay; • Compute mean and variance for travel time and delay; • Compute confidence intervals for mean travel time and mean delay; • Compute desired reliability metrics; • Identify deficiencies; and • Prepare report and graphics. (Chapter 3)
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From page 67...
... available for analysis; • Select desired analytical approach (e.g., sketch planning, 4-step, mezoscopic, HCM, micro-simulation) ; and • Revisit accuracy requirements, proposed analytical approach, and number of candidate improvements if inadequate resources or time.
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From page 68...
... ; • Compute reliability metrics as desired; • Determine confidence intervals for results; • Estimate cost-effectiveness of each candidate improvement; • Determine if candidate improvements are sufficient to meet operator standards; and • Select final list of improvements. (Chapters 3 and 4)
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Key Terms

  • determine required
  • future deficiencies
  • prepare report
  • existing deficiencies
  • accuracy requirements

  • determine agency
  • study bounds
  • travel time
  • agency performance
  • set travel

  • additional travel
  • compute desired
  • compute confidence
  • time standard
  • set reasonableness

  • process baseline
  • baseline results
  • available detector
  • select metrics
  • conduct baseline

  • lane miles
  • considered delay
  • reasonableness bounds
  • intensity region
  • detector data

  • prepare data
  • baseline data
  • determine desired
  • determine sampling
  • data covers


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