VMT Assessment for Projects Reviewed by the Tahoe Regional Planning Agency (TRPA)

4. VMT Assessment

The Vehicle Miles Traveled (VMT) assessment process plays a crucial role in evaluating the transportation impact of projects within the Tahoe Basin, as overseen by the Tahoe Regional Planning Agency (TRPA). VMT is a key measure used to assess the amount and distance of automobile travel attributed to a particular project, providing insight into transportation network efficiency and its broader implications for environmental sustainability, air quality, and energy consumption. This section details the methodologies, criteria, and standards applied in conducting a comprehensive VMT assessment to ensure compliance with TRPA regulations and environmental thresholds.

4.1 Definition and Importance of VMT

VMT represents the total distance traveled by vehicles associated with a project and is typically calculated by multiplying the number of vehicle trips generated by the project by the average trip length. Unlike direct measures of traffic operations such as congestion or delay, VMT is an indicator of network efficiency, particularly when expressed as a function of population or employment, such as VMT per capita. Higher VMT is generally associated with lower land use density and greater reliance on automobiles due to increased travel distances between origins and destinations.

Beyond its role in transportation planning, VMT serves as a proxy for several environmental and infrastructure concerns. It is commonly used to estimate mobile air pollution emissions, greenhouse gas (GHG) emissions, energy consumption, and roadway maintenance requirements. Given its significance, TRPA integrates VMT analysis into its environmental impact assessments to monitor and mitigate the transportation effects of proposed developments.

4.2 TRPA’s Environmental Threshold Standard for VMT

TRPA enforces an environmental threshold standard for VMT to ensure that development within the Tahoe Basin aligns with regional sustainability goals. Compliance with this threshold standard is achieved through the quantification and mitigation of VMT impacts associated with proposed plans and projects. The guidelines outlined in TRPA's regulatory framework provide detailed instructions for analyzing VMT impacts in both long-range planning efforts and individual land development projects.

To streamline the VMT assessment process, TRPA’s guidelines specify various aspects of VMT analysis, including:

• Screening Criteria: Identifying projects that are expected to have a less-than-significant impact on VMT without requiring a detailed analysis.

• Standards of Significance: Defining thresholds that determine whether a project’s VMT impact is considered significant and requires mitigation.

• Analysis Methodology: Establishing standardized procedures for calculating daily VMT generation.

• Mitigation Strategies: Outlining measures that must be implemented to reduce VMT impacts to acceptable levels.

4.3 Screening Criteria for VMT Assessment

Screening criteria are applied to quickly determine whether a project is likely to generate significant VMT impacts. Projects that meet the screening criteria must calculate their VMT generation and pay a mobility mitigation fee to offset additional VMT. However, they are not required to meet the standard of significance for their specific project type. In some cases, projects may opt to implement mitigation measures to reduce their mitigation fee.

TRPA Code of Ordinances Section 1.4 specifies the following categories of projects that are typically screened from further VMT analysis:

• Affordable housing projects that meet specific criteria.

• Projects generating low VMT, which are unlikely to exceed significance thresholds.

• Transit, active transportation, and other transportation-related projects that contribute positively to regional mobility.

• Projects analyzed under an existing area plan, ensuring that their transportation impacts have been previously accounted for.

Screening aims to streamline the VMT impact assessment process by exempting projects with minimal transportation impacts or those that provide net benefits (e.g., affordable housing) from undergoing complex analysis. Instead, these projects contribute to regional VMT mitigation efforts through financial contributions.

4.4 Evaluating Mixed-Use Projects

Mixed-use projects require a holistic approach to VMT analysis. Since these developments include multiple land use types, their aggregated VMT generation must be calculated by assessing each land use individually and summing the results. The calculation follows the formula:

Mixed-Use Project-Generated VMT = VMT for Land Use 1 + VMT for Land Use 2 + …

Affordable housing components that qualify under the screening criteria should be excluded from the total VMT calculation for mixed-use projects. This ensures that these projects are evaluated fairly and do not face unnecessary regulatory burdens.

4.5 Evaluating Redevelopment Projects

For projects replacing existing developments, net VMT generation is the primary consideration. The analysis compares the existing average daily VMT with the projected VMT under the proposed redevelopment. The net impact is calculated as:

Redevelopment Project Net Average Daily VMT = Proposed Project Average Daily VMT - Existing Project Average Daily VMT

If a redevelopment project leads to a net reduction in VMT, it may be presumed to have a less-than-significant transportation impact. However, this presumption does not apply if the site has been vacant for more than 60 months prior to project approval.

4.6 Evaluating Plans, Ordinances, and Amendments

Policy changes, such as amendments to plans or ordinances, must be assessed based on their potential impact on trip generation and trip length. If a policy proposal has no effect on vehicle travel (e.g., changes to exterior lighting standards), it does not require a VMT analysis. However, proposals that expand development areas or modify land use policies must estimate VMT impacts using the prescribed methodologies. Proposals exceeding 650 daily VMT are ineligible for screening and require detailed analysis.

4.7 Standards of Significance

TRPA’s Initial Environmental Checklist identifies a transportation impact as potentially significant if a project generates more than 650 daily VMT. If a project surpasses this threshold, it must undergo further evaluation using the following criteria:

• Screening compliance: Projects meeting the screening criteria are deemed to have less-than-significant VMT impacts with payment of mitigation fees.

• Standard of significance compliance: Non-screened projects must meet specific VMT reduction thresholds based on their land use type.

The table below summarizes the standards of significance for various land use types:

Projects meeting these standards are considered to have no significant environmental impact upon payment of their mitigation fees.

4.8 Special Considerations for Mixed-Use and Redevelopment Projects

For mixed-use projects, VMT impacts may be assessed either by considering the total project effect or by evaluating each land use separately. Internal trip capture within the project site should be factored in before determining significance.

For redevelopment projects, a net decrease in VMT may allow the project to be presumed to have a less-than-significant impact. However, this presumption applies only if the prior land use was active within the last 60 months.

By applying these comprehensive assessment methods, TRPA ensures that transportation impacts are effectively managed, contributing to the sustainability of the Tahoe Basin.

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