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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2017. Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks. Washington, DC: The National Academies Press. doi: 10.17226/24807.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2017. Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks. Washington, DC: The National Academies Press. doi: 10.17226/24807.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2017. Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks. Washington, DC: The National Academies Press. doi: 10.17226/24807.
×
Page 3
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2017. Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks. Washington, DC: The National Academies Press. doi: 10.17226/24807.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2017. Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks. Washington, DC: The National Academies Press. doi: 10.17226/24807.
×
Page 5
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2017. Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks. Washington, DC: The National Academies Press. doi: 10.17226/24807.
×
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2017. Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks. Washington, DC: The National Academies Press. doi: 10.17226/24807.
×
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2017. Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks. Washington, DC: The National Academies Press. doi: 10.17226/24807.
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Page 8

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

1 S u m m a r y The demand for truck transportation increases alongside population growth, economic growth, and increases in trade. As truck transportation shares infrastructure with passenger vehicles, increases in demand for truck transportation negatively impact passenger traffic. Similarly, increases in passenger traffic negatively impact truck transportation. The com­ bination of truck and passenger traffic outstripping capacity is a key driver of congestion, which is experienced as truck bottlenecks in the freight community. Truck bottlenecks also can be caused by issues ranging from vehicle size and weight restrictions to roadway geom­ etry to weather impacts and to truck bans. To address the issue of truck bottlenecks system­ atically, national, state, and regional transportation agencies are developing methodologies to define, identify, quantitatively measure, and mitigate truck bottlenecks. This is the first step in empowering decision makers to develop cost­effective solutions to address different types of truck freight bottlenecks. This Guidebook provides state­of­the­practice information to transportation profession­ als on identifying, classifying, evaluating, and mitigating truck bottlenecks. The bottleneck analysis described in this Guidebook is focused on utilizing truck probe data rather than traditional travel demand models. The primary application for the methodologies is evalua­ tion of truck bottlenecks for prioritizing investment decisions. Examples of truck bottleneck analysis and notable practice highlights are provided throughout the Guidebook and are intended for two primary audiences: 1. Transportation planners that are conducting freight­related analysis or developing freight­ related planning documents and 2. Research and operational staff that are interested in developing freight bottleneck analyses relevant for transportation planning processes. For these audiences, the Guidebook is designed to serve the following purposes: • Define a common language related to truck freight bottlenecks; • Classify truck freight bottleneck categories based on causal and contributing factors; • Describe truck bottleneck state­of­the­practice; • Provide highlights from several case studies related to truck bottlenecks; • Describe data sources used for truck bottleneck analysis; • Provide a spatially scalable methodology for identifying truck freight bottlenecks; • Describe quantitative measures for truck freight bottleneck categories for determining bottle­ neck severity, impact, and ranking and subsequent decision­making; • Describe mitigation options for truck freight bottlenecks; and • Describe how to integrate freight bottleneck analysis into the planning process. This Guidebook embraces a broad term for “truck freight bottlenecks” as any condition that acts as an impediment to efficient truck travel, leading to travel times in excess of what would Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks

2 Guide for Identifying, Classifying, Evaluating, and mitigating Truck Freight Bottlenecks normally occur. This definition encompasses a wide range of events and conditions, all of which add time to the delivery of truck freight shipments, from the time those shipments leave their origin to the time they arrive at their destination. The Guidebook describes two methodologies: 1. A travel speed­based delay methodology and 2. A process­ or operation­based delay methodology. The methodologies are scalable in multiple ways, and this allows the agency performing the analyses to use its available data resources regardless of the source or size of those resources. In addition, the same analytical approach works whether the analysis is performed for an entire state highway network, a regional network, or even a specific city. The recommended approach can be applied to a single road segment, multiple roads within a geographic corridor, an entire region, to all roads in the state, or to all roads in a multistate region. Travel Speed-Based Delay The travel speed­based delay methodology consists of six generalized steps, as shown in Fig­ ure S­1. Several of these steps can be performed simultaneously in terms of computer processing, but are discussed separately in different chapters in this Guidebook. As shown in Figure S­1, the first step in the travel speed­based delay truck bottleneck method­ ology is to identify, collect, quality check, organize, and link the various data sources available to the agency that are needed to identify and quantify bottleneck locations. This step involves con­ flation to match probe speed data to roadway volume data for subsequent analysis. Conflation is the process of combining geographic information from overlapping sources, while minimizing redundancy and reconciling data conflicts. It is necessary for computing performance measures for truck bottleneck analysis when the speed and roadway volume data are provided on differ­ ent networks. The process of conflation is facilitated by using a geographic information system (GIS) to import and compare segments of the roadway speed data network with the traffic vol­ ume inventory. By combining vehicle speed and truck and passenger car volume data, agencies can compute when and where congestion occurs along with the relative size of the delays (in vehicle­hours and truck­hours) that each congestion location causes. It also is possible to track the frequency with which congestion forms. For analysis purposes, these different referencing systems must be connected during confla­ tion. All the data to be used in the bottleneck analysis must be transformed into a common data structure that describes the conditions, such as speed, weather, and work zones, to be found on defined road segments during defined time periods. To analyze truck bottlenecks across multiple dimensions, this Guidebook describes a cube structure, as shown in Figure S­2, that incorporates traffic speed, travel time, and volume data, as well as all other data needed to describe what is happening on the roadway. If these different variables (i.e., car travel time, car speed, car travel rate, truck travel time, truck speed, and truck travel rate) are thought of as the third dimension of the above matrix structure, the data struc­ ture can be envisioned in the cube, where: • The vertical axis of the cube is time (and date); • The horizontal axis is the roadway segmentation (location) in the order in which a vehicle would drive a given road (the left most column being the first road segment traversed, followed by the second column, and continuing to additional columns); and • The depth of the cube consists of different variables.

Summary 3 NPMRDS = National Performance Management Research Data Set. NOAA = National Oceanic and Atmospheric Administration. RWIS = Road Weather Information System. TT = travel time. Identify Available Data (Chapter 3) Conflate Data Time Location (Chapter 4) Essential Bottleneck Data NPMRDS (or other speed data set) Volume Data Trucks Cars Data to Estimate Causes of Delay Crash data Incident data Weather NOAA RWIS Construction Time of closures Lane restrictions Road closures Truck restrictions Infrastructure Bridge heights Grades Horizontal curves Bridge weight limit Processing Sites Border crossings Enforcement sites Special event days Select Road Segmentation Desired for Analysis (Chapter 4) Create Data Analysis Structure (Chapter 4) Transform Data Into Desired Analysis Units (e.g., mph vs TT) (Chapter 4) Quality Assurance and Missing Data Handling (Chapter 4) Compute Delay (Chapter 5) Compute Delay by Influence Factors (Chapter 5) Summarize Delay By Time, Location, Influences (Chapter 5) Rank Delays (Chapter 6) System Creation System Operation Data SourcesBottleneck Determination Work Flow Perform Field Analyses (Chapter 6) Develop Mitigation Options (Chapter 7) Figure S-1. Travel speed-based bottleneck identification and quantification methodology.

4 Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks A separate cube would exist for each direction of travel for a given roadway. An initial step in the travel speed-based process is to conduct an analysis that defines the size and scope of the travel speed-based congestion bottleneck problem throughout a study area. The next step is to select a subset of the identified bottleneck locations to perform more detailed analyses to examine the effectiveness of different approaches to mitigating those bottlenecks. These detailed analyses can take into account key details about each study location (e.g., current local transportation improve- ment plans) that cannot be readily incorporated into an automated statewide analysis. With the aid of a GIS, these statistics can be displayed graphically to highlight the key delay locations. The cubic structure allows simple computations of travel speed delay by location and time period for any given roadway for which volume and speed data are available. With the aid of a GIS, these statistics can be displayed on a map to highlight the key delay locations. Figure S-3 provides an example of how a large volume of vehicle delay data was displayed on Interstate 65 in Indiana. The y-axis shows the mileposts along I-65. The x-axis is the number of vehicle-hours of travel less than 45 miles per hour (mph). The multicolored waves in the figure represent the amount of delay at each milepost on the Interstate. Moving from left to right along the waves provides the delay for each month in the year from January to December. Process-Based Truck Delay Another major category of bottleneck causes of is process-based truck travel delay, which includes locations that either force trucks to use longer, more circuitous paths than passenger cars would take if making that same trip, or require trucks to carry less cargo than they would Note: NPMRDS is noted in this example, but any travel time (or speed) data source could be used. (WSDOT = Washington State Department of Transportation; WITS – Washington Incident Tracking System; SPD = speed.) Figure S-2. Schematic of data analysis structure with congestion causation factors.

Summary 5 Figure S-3. Vehicle delay on Interstate 65 in Indiana.

6 Guide for Identifying, Classifying, Evaluating, and mitigating Truck Freight Bottlenecks otherwise carry if not legally restricted from doing so. Both situations force trucks to travel addi­ tional miles, increasing the cost of freight delivery as a result of both additional labor hours and additional mileage driven. In addition, higher truck­miles of travel (TMT) increases fuel use and produces negative environmental emissions. A key difference between the methodology for process­based truck bottlenecks and travel speed­based truck bottlenecks is that process­based truck bottlenecks require an understanding of impacted truck trips, given the truck restriction. Therefore, the analysis for process­based truck bottlenecks is sometimes referred to as a “trip­based” analysis in contrast to the “facility­ based” analysis described earlier for travel speed­based truck bottlenecks. The methodology for estimating process­based delay is shown in Figure S­4. The methodol­ ogy includes a system creation component and a system operation component. The system cre­ ation component includes identifying available data and identifying truck trips impacted by the operations­based delay. The system operation component estimates the delay of the impacted truck trips, ranks bottlenecks by type, and then develops mitigation options associated with each type of delay. The cubic data structure also can be used as an effective tool for identifying the costs of many process­based delays. In this case, it must be used in concert with additional information that describes the size of truck movements, the nature of those movements, and data on the loca­ tions and attributes of the specific truck restrictions being evaluated. For example, using GIS software, the cube analysis structure can help compute travel times and travel­time reliability over alternative travel paths. Once the data analysis cube for travel speed­based and process­based delays has been con­ structed, it is possible to compute the wide range of delay­related performance statistics that can be used to rank and quantify truck freight bottlenecks. To identify the potential causes of truck Figure S-4. Process-based truck bottleneck classification and quantification methodology.

Summary 7 bottlenecks, it is necessary to link the variables that describe potential bottleneck factors to the time and location data that describe vehicle volume and speed. The desktop analysis described above can be combined with field analysis to fully analyze select bottlenecks. In many cases, the field analysis relies on the same tools and reports that are available to the desktop analysis but involves a deeper examination of a limited number of road­ way segments. The field analysis also typically incorporates additional data into the bottleneck analysis that may not be available for an entire study area. In other cases, these additional data must be collected specifically for the field analysis. In still other cases, agency staff that work in the area can describe in detail some of the contributing causes of local bottlenecks. Taking advantage of this local knowledge is an important part of the field analysis process. In the end, these additional data sources are developed to provide more depth to the analysis about why observed bottleneck patterns are occurring and how those delays might best be mitigated. After causation has been evaluated, ranking supports the prioritization of mitigation actions. No one ranking system is appropriate for all uses. Each performance measure (e.g., truck delay, total delay, expected travel rate or reliability, or the frequency with which congestion occurs) can be used to effectively rank locations. Each of those resulting rankings will likely be different. What these different rankings indicate is that the importance of any one bottleneck changes depending on which bottleneck attributes are most important to an individual decision maker. The Guidebook also provides a section on mitigating truck bottlenecks in which is described that there are a large number of potential approaches to mitigating the identified truck bottle­ necks. A selected approach typically is a function of the following considerations: • The causes of the delays, • The geographic and geometric attributes of that location, • The operational characteristics of the roadway, • The organization of the agencies working on that facility and other facilities that influence the operation of that roadway, • The operational systems currently implemented on the road (or in the larger region that have been demonstrated effective and/or have public support), and • The type of funding available. Typically, mitigation for truck bottlenecks can be divided into a number of categories on the basis of the basic causes/attributes of delay. These include the following: • Recurring congestion (too much traffic volume), • Nonrecurring congestion or delays, • Geometric deficiencies, • Operational deficiencies, and • Event congestion. Each of these causes of delay requires different types of mitigation, and the design and imple­ mentation of those mitigation efforts depends on the organization and operational relationships of the various transportation agencies and political jurisdictions that operate the road or that provide services in that geographic region. The Guidebook covers different possible mitigations related to bottlenecks caused by roadway design and geometrics, different types of volume and congestion limitations, disruption such as incidents and weather, and policy restriction such as truck size weight rules. The Guidebook also describes approaches for focusing mitigation by sorting bottlenecks based on if the bottlenecks are for trucks only or if they impact all vehicles. The truck­only bottlenecks often involve road geometrics limitations for large vehicles, which are detailed in the Guidebook. The use of trans­ portation agencies’ asset inventories is presented as a tool to tie infrastructure­related truck bottlenecks to roadway attributes.

8 Guide for Identifying, Classifying, Evaluating, and mitigating Truck Freight Bottlenecks Finally, the Guidebook describes how truck bottleneck analysis can be incorporated into typi­ cal planning studies. The typical planning study is composed of existing and future conditions, identification of needs and solutions, analysis of solutions/recommendations, and outreach. For bottleneck analysis to be fully considered, it should be a part of each of these activities in a number of different ways. Table S­1 shows how typical components of these studies can include specific elements of the truck bottleneck analysis. Task in Planning Study Incorporation of Truck Freight Bottleneck Analysis Existing Conditions Essential data collected for bottleneck analysis (speed and volume) can be used as part of the description of existing conditions. See Chapters 3 and 4 of this Guidebook. Desktop analysis to identify and quantify bottlenecks (Chapter 5 of this Guidebook) can be used to describe existing conditions for trucks on the road network. Future Conditions Travel demand models can be augmented by using bottleneck analysis as the source of delay estimates in base year, then increasing delay proportional to increases in volume-to-capacity (V/C) ratios provided by travel demand models. Identification of Needs The causal analysis described in Chapter 6 can be used to identify needs in the system. For example, if a large percentage of truck bottlenecks are caused by crashes, then this indicates the need for safety improvements. Identification of Solutions to Consider Mitigation options described in Chapter 8 of this Guidebook can be used as a source of solutions to consider for the planning study. Field analysis described in Chapter 7 of this Guidebook also can be used to identify solutions. Analysis of Solutions and Development of Recommendations The ranking of causes of bottlenecks (see Chapters 6 and 7 of this Guidebook) can be used to prioritize solutions that are recommended. For example, if the majority of truck bottlenecks at a particular location is based on weather, then solutions that are targeted toward improving the road’s ability to handle inclement weather may be given a 30 percent increase across a scoring method for solutions. Outreach Draft results of bottlenecks analyses should be presented to public- and private-sector stakeholders to validate locations of bottlenecks, severity of bottlenecks, potential causes of bottlenecks, and mitigation options to consider for addressing bottlenecks. Table S-1. Incorporation of truck freight bottleneck analysis into planning studies using generic tasks.

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TRB's National Cooperative Highway Research Program (NCHRP) Research Report 854: Guide for Identifying, Classifying, Evaluating, and Mitigating Truck Freight Bottlenecks provides transportation agencies state-of-the-practice information on truck freight bottlenecks using truck probe data rather than traditional travel demand models. The report embraces a broad definition of truck freight bottlenecks as any condition that acts as an impediment to efficient truck travel, whether the bottleneck is caused by infrastructure shortcomings, regulations, weather, or special events. The comprehensive classification of truck freight bottleneck types described in this report provides a standard approach for state departments of transportation, metropolitan planning organizations, and other practitioners to define truck freight bottlenecks and quantify their impacts.

This project produced the following appendices available online:

  • Appendix A: Selected Details of State-of-the-Practice Review
  • Appendix B: Short Summaries of Selected Case Studies
  • Appendix C: Data Quality Control Examples
  • Appendix D: Additional Performance Measure Discussion and Analysis Procedures
  • Appendix E: Truck Bottlenecks and Geometrics
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