7.0 Criteria for Selecting the Appropriate Type of Traffic Analysis Tool

This section identifies criteria that can be considered in the selection of an appropriate traffic analysis tool type and helps identify under what circumstances a particular type of tool should be used. Decision Support Methodology for Selecting Traffic Analysis Tools (Volume II) provides a detailed assessment of criteria to be considered when selecting a type of traffic analysis tool.

The first step is identification of the analytical context for the task-planning, design, or operations/construction. Seven additional criteria are necessary to help identify the analytical tools that are most appropriate for a particular project. Depending on the analytical context and the project’s goals and objectives, the relevance of each criterion may differ. The criteria include the following:

1. Ability to analyze the appropriate geographic scope or study area for the analysis, including an isolated intersection, single roadway, corridor, or network.
2. Capability of modeling various facility types, such as freeways, high-occupancy vehicle (HOV) lanes, ramps, arterials, toll plazas, etc.
3. Ability to analyze various travel modes, such as single-occupancy vehicle (SOV), HOV, bus, train, truck, bicycle, and pedestrian traffic.
4. Ability to analyze various traffic management strategies and applications, such as ramp metering, signal coordination, incident management, etc.
5. Capability of estimating traveler responses to traffic management strategies, including route diversion, departure time choice, mode shift, destination choice, and induced/foregone demand.
6. Ability to directly produce and output performance measures, such as safety measures (crashes, fatalities), efficiency (throughput, volumes, vehicle-miles of travel (VMT)), mobility (travel time, speed, vehicle-hours of travel (VHT)), productivity (cost savings), and environmental measures (emissions, fuel consumption, noise).
7. Tool/Cost-Effectiveness for the task, mainly from a management or operational perspective. Parameters influencing cost-effectiveness include tool capital cost, level of effort required, ease of use, hardware requirements, data requirements, animation, etc.

In Decision Support Methodology for Selecting Traffic Analysis Tools, each analytical tool category is evaluated against each criterion to identify whether or not a category of analytical tool is appropriate for use. Figure 2 summarizes the criteria that may be considered in the selection of a tool category.

Figure 2. Criteria for selecting a traffic analysis tool category.

The steps for selecting the appropriate type of analysis tool are:

1. Users should begin by identifying the project’s analytical context (discussed in Section 2.1 of Decision Support Methodology for Selecting Traffic Analysis Tools).
2. Next, users should filter through criteria 1 through 6 to limit the appropriate tool categories to one or two options.
3. Finally, criterion 7 (tool/cost effectiveness) should be used to select the final tool category based on parameters outside of the technical context of the analysis, such as tool cost, training, hardware requirements, etc.

Decision Support Methodology for Selecting Traffic Analysis Tools presents step-by-step guidance for the tool selection process, along with a list of recommended readings. An automated tool that implements the guidance can be found at the FHWA Traffic Analysis Tools Web site at: http://ops.fhwa.dot.gov/Travel/Traffic_Analysis_Tools/traffic_analysis_toolbox.htm

The first step in selecting the appropriate type of traffic analysis tool is the identification of the analytical context of the project. Figure 2 illustrates a typical transportation analysis process, which contains several analytical phases, including:

• Planning: This phase includes short- or long-range studies or other State, regional, or local transportation plans (e.g., master plans, congestion management plans, ITS strategic plans, etc.).
• Design: This phase includes approved and funded projects that are going through analysis of the alternatives or preliminary design to determine the best option for implementation. This phase also includes the analysis of roadway features needed to operate at a desired level of service (LOS). Full design projects (i.e., horizontal/vertical alignments, pavement design, etc.) are not included in this category.
• Operations/Construction: These projects share many similar characteristics with design projects, but are performed to determine the best approach for optimizing or evaluating existing systems.

Table 1 presents the general relevance of each tool category for each analytical context, including planning, design, and operations/construction.

Table 1. Relevance of traffic analysis tool categories with respect to analytical context.

Analytical Context	Analytical Tools/ Methodologies: Sketch Planning	Analytical Tools/ Methodologies: Travel Demand Models	Analytical Tools/ Methodologies: Analytical/ Deterministic Tools (HCM-Based)	Analytical Tools/ Methodologies: Traffic Optimization	Analytical Tools/ Methodologies: Macroscopic Simulation	Analytical Tools/ Methodologies: Mesoscopic Simulation	Analytical Tools/ Methodologies: Microscopic Simulation
Planning
Design	Not Applicable
Operations/ Construction

Notes:  Specific context is generally addressed by the corresponding analytical tool/methodology.
            Some of the analytical tools/methodologies address the specific context and some do not.
            The particular analytical tool/methodology does not generally address the specific context.
           Not Applicable: The particular methodology is not appropriate for use in addressing the specific context.

Before selecting a particular tool, users are strongly encouraged to assess the strengths and weaknesses of the specific analytical tools. Appendix A provides a list of available traffic analysis tools by tool category as of August 2004 (Web site links are also provided for more information).

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