Introduction

Forecasting Approaches

Selecting a Method

Descriptions of Available Methods

Key Inputs and Outputs for Each Method

References

List of Acronyms

Selecting a Method

This section provides summary information on each method that should assist the user in selecting an appropriate method. The methods are loosely placed in four groups, as follows:

1. Off-the-shelf TDM/TCM analysis software. These are software packages that can be acquired for free or at a low cost. They have been designed to analyze a variety of strategies aimed at reducing travel impacts (TDM programs) and/or reducing emissions (TCM programs). While the software itself is readily available, the user must generally obtain locality-specific data from the MPO.
2. Customized TDM/TCM analysis software. These software packages have similar objectives as those in category 1, but require some customization of the software to apply locally. As a result, a greater initial investment is required to develop the model. The benefits may include greater accuracy and ease of use, since the models can be tailored to local data and needs.
3. Sketch-plan workbook approaches. These are not software packages, but instead are worksheets or examples of calculations by other agencies to assess the emission impacts of CMAQ-type projects. They may cover strategies not addressed by existing software packages, but they can become cumbersome to apply for multiple projects.
4. Specialized software tools and methods. These are software packages or methods designed to analyze one or more specific strategy types. While the methods address only a limited set of CMAQ strategies, they generally address these strategies with greater depth and accuracy than more general models. The range of customization and level of effort in this group varies significantly.

Table 2 summarizes each of the 19 methods. Table 3 identifies the types of CMAQ strategies addressed by each method. Table 4 provides a summary analysis of some key characteristics of each method, including:

• Availability, or the cost and level of effort in obtaining the model in a format that can be applied locally to analyze strategies;
• Ease of application, or the level of effort in using the model and in obtaining any data necessary to analyze specific programs;
• Technical robustness, or the validity or accuracy of the underlying data and computational techniques embedded in the model;
• Range of strategies addressed, or the extent to which a single model is capable of analyzing a broad range of CMAQ strategies; and
• Self-sufficiency, or the extent to which the method is capable of addressing the various analytical steps required, including the estimation of both travel benefits and resulting emission changes as a result of project implementation.

To further assist the user of this report, Key Inputs and Outputs for Each Method provides a listing of methods by type of strategy addressed. For each method, the basic inputs required to describe the strategy are identified (e.g., for transit service, percent change in transit fare or frequency of service). This should assist the user in identifying whether the model is capable of evaluating the specific strategies proposed for CMAQ funding.

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