Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks (2017) / Chapter Skim
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Pages 31-42
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31 C h a p t e r 4 4.1 Organizing the Speed and Volume Data (Conflation) "Conflation" is the process of matching probe speed data to roadway volume data for subsequent analysis.
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32 Guide for Identifying, Classifying, evaluating, and Mitigating truck Freight Bottlenecks to use different location referencing systems and time-reporting periods. The specific issues associated with linking databases are: • Point versus segment data.
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Organize Data 33 might be based on pavement type, which might change several times within that uniform traffic volume segment and might not have the same end point as the volume-based system. • Different time-referencing approaches.
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34 Guide for Identifying, Classifying, evaluating, and Mitigating truck Freight Bottlenecks an agency plans to use for its bottleneck analysis (e.g., NPMRDS or other vendor)
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Organize Data 35 Figure 4-4. Example of preliminary cubic data structure.
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36 Guide for Identifying, Classifying, evaluating, and Mitigating truck Freight Bottlenecks A separate cube would exist for each direction of travel for a given roadway. Each cell of the cube describes a specific aspect of what happens on that road segment at that time period.
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Organize Data 37 and apply that pattern to the AADT and truck percentage estimates submitted under HPMS. See the Texas A&M Transportation Institute case study highlight above for reference to the appropriate appendices for calculation procedures and an application of these methods.
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38 Guide for Identifying, Classifying, evaluating, and Mitigating truck Freight Bottlenecks to the same granularity of the travel-time data, which are available throughout the year in this example. The short-term volume count must be adjusted seasonally (hour of day, day of week, and month of year)
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Organize Data 39 Roadway/Area Type Key Steps for Roadway Segmentation All Roadways Short segments should be combined into a reporting segment where traffic levels and resulting congestion patterns are relatively consistent. Reporting segments are almost always defined uniquely for each direction of travel.
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40 Guide for Identifying, Classifying, evaluating, and Mitigating truck Freight Bottlenecks structure. All data that describe what is happening on the roadway needs to be incorporated into that structure.
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Organize Data 41 Another example is crash data. It is often relatively easy to assign crash data to a specific road segment and time period.
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42 Guide for Identifying, Classifying, evaluating, and Mitigating truck Freight Bottlenecks More specifically, AASHTO spells out validation criteria for vehicle count, classification, and weight data from detector sources. In some cases, quality control by visual inspection is valuable.
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