Comprehensive Analysis Methodology for Transportation, Access, and Environmental Impact in Projects Reviewed by the Tahoe Regional Planning Agency (TRPA)

4.3 ANALYSIS METHODOLOGY

If Vehicle Miles Traveled (VMT) analysis is required, various methodologies are available, including the TRPA Project Impact Assessment (PIA) Tool, quantitative assessments, and qualitative assessments. The transportation analyst shall consult with TRPA staff to determine the most appropriate methodology based on the project's location and characteristics.

Regardless of the selected methodology, consistency in the method, data source, and approach is essential to ensure an "apples-to-apples" comparison between significance standards, project VMT forecasts, and VMT reduction forecasts, in accordance with the OPR Technical Advisory guidance.

VMT Forecasting Approach

VMT forecasting considers either VMT generation or VMT effect depending on the land use type:

Determining VMT Generation

VMT generation represents the VMT from trips that start or end at the project site. It is calculated for:

• Screening criteria determination.

• Assessing whether a residential, tourist accommodation, or public service project meets the significance standard.

• Calculating the mobility mitigation fee for screened and non-screened projects.

VMT Generation Calculation

VMT generation is estimated using the following formulas:

Determining VMT Effect

VMT effect assesses the project’s influence on VMT from surrounding land uses or trip lengths within the existing transportation network. Analysts must quantify and analyze changes in vehicle travel due to commercial, recreation, transportation, and other projects.

For example, adding a retail use may reduce overall trip lengths, leading to a net decrease in VMT effect. Analysts should use a model or method sensitive to the project's changes in trip making, comparing pre-development and post-development VMT within the affected area (e.g., market shed).

The selected methodology must be reviewed with TRPA Transportation staff before analysis begins, ensuring appropriate tools are used for accurate VMT impact estimates.

Determining Average Trip Lengths and VMT per Resident

TRPA has divided the Tahoe Basin into 79 PIA Zones, each with associated VMT per resident and average trip length data. This information is embedded in the PIA Tool and detailed in Appendix C.

Determining the Standard of Significance

Projects that are not screened must be compared to the standard of significance. If a project’s impact is below this standard, only the mobility mitigation fee is required. Projects exceeding the threshold must provide mitigation to reduce VMT to the standard of significance.

Standard of Significance Calculation

Determining the Mobility Mitigation Fee

The mobility mitigation fee is calculated based on VMT generation:

Mobility Mitigation Fee = Fee Rate * Net Average Daily VMT

The fee is apportioned as follows:

• 90% at the origin/production end of the trip

• 10% at the destination/attraction end of the trip

Mobility Mitigation Fee Rates (2021)

Using the PIA Tool

The PIA Tool assists in assessing:

• Whether a project meets screening criteria.

• Calculation of the required mobility mitigation fee.

• VMT generation estimates for residential, tourist accommodation, and public service projects.

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