CEQA VMT Impact Thresholds
The California Environmental Quality Act (CEQA) Vehicle Miles Traveled (VMT) thresholds are established to evaluate the transportation impacts of projects and ensure that any potential increase in VMT remains within manageable limits. These thresholds help determine the environmental significance of a project's VMT impact, providing a basis for analyzing whether a project contributes to increased transportation-related emissions or urban sprawl. Under CEQA guidelines, VMT thresholds are applied based on project types, such as residential, office, or retail projects, to determine if a significant VMT impact will occur. When evaluating projects in the City of Montebello, the San Gabriel Valley Council of Governments (SGVCOG) baseline VMT metrics serve as reference values for calculating allowable limits and assessing impacts.
Significant VMT Impact Conditions
To identify potential significant impacts, the following threshold-based conditions are applied in the Existing Plus Project scenario:
- Residential Projects: A significant impact occurs if the project’s home-based VMT per capita exceeds 15% below the SGVCOG baseline home-based VMT per capita.
- Office Projects: A significant impact occurs if the project’s home-based work VMT per employee exceeds 15% below the SGVCOG baseline home-based work VMT per employee.
- Retail Projects: A significant impact is recognized if the project would lead to a net increase in the total citywide baseline VMT.
For projects deemed consistent with the Southern California Association of Governments (SCAG) Regional Transportation Plan/Sustainable Communities Strategy (RTP/SCS), cumulative VMT impacts are typically considered less than significant. However, cumulative analysis is generally not necessary for projects that either screen out of detailed VMT analysis or do not generate a substantial VMT impact. Where a cumulative impact analysis is required, the evaluation focuses on whether the project would cause a net increase in citywide VMT.
Cumulative Impact Conditions for All Projects
A significant cumulative VMT impact is identified if the project causes a net increase in cumulative total citywide VMT. This comprehensive approach ensures that all projects are examined for potential long-term impacts on the city’s transportation system, regardless of their type.
VMT Mitigation Measures
In cases where significant VMT impacts are identified, project applicants have multiple options for reducing the project’s transportation footprint, with an emphasis on minimizing single-occupancy vehicle trips and encouraging more sustainable transportation modes. The City of Montebello outlines the following mitigation options:
- Project Design Adjustments: Modify the built environment characteristics of the project to decrease VMT generation.
- Transportation Demand Management (TDM) Programs: Implement TDM strategies aimed at reducing VMT by promoting alternatives to solo driving, such as transit, ridesharing, and active transportation options.
- VMT Fee or Mitigation Banking Programs: Participate in VMT fee programs or mitigation exchanges, if available, to offset the project's VMT through contributions toward reducing VMT from other land uses or transportation programs within the region.
Under the SGVCOG Implementation Study, appropriate TDM measures for the region are listed in the City of Montebello’s guidelines (Attachment D, “VMT Reduction Strategies”). These measures address potential VMT reductions using accepted methodologies; however, it is acknowledged that TDM effectiveness may vary over time depending on tenant engagement and enforcement. Consequently, continuous monitoring may be needed to ensure compliance with mitigation expectations and track performance.
When a project’s traffic study attributes a VMT reduction to a TDM plan, the analysis must document:
- Plan Details: An in-depth description of the TDM measures, including implementation and ongoing maintenance.
- Supporting Data: Empirical evidence or case studies validating the anticipated traffic reduction.
- Roadway Impact Analysis: Calculations for Volume-to-Capacity (V/C) ratios illustrating circulation benefits from reduced VMT.
- Compliance and Enforcement: Monitoring and enforcement methods for the TDM plan.
- Air Quality Standards Compliance: Alignment with South Coast Air Quality Management District (SCAQMD) regulations.
VMT Analysis for Land Use Plans
In addition to individual project reviews, citywide or regional land use plans, such as General Plans and Specific Plans, also require VMT assessments to identify potential long-term transportation impacts. These evaluations help determine if proposed changes in land use could alter travel patterns significantly, impacting regional VMT levels. The analysis for such plans involves comparing the projected VMT in the horizon year (future scenario) with both existing conditions and the no-project scenario.
Assessment Requirements
Land use plans must be analyzed using the SCAG regional travel demand model, which provides accurate estimates of VMT based on anticipated population and employment growth. The following scenarios must be evaluated:
- Base Year Model: Estimates VMT under existing conditions.
- Cumulative Year No-Project Model: Projects VMT for a horizon year without any changes.
- Cumulative Year with Project Model: Projects VMT for a horizon year that incorporates the land use changes proposed under the plan.
For General Plans, VMT is calculated based on trips originating and/or ending in the city, while Specific Plans calculate VMT based on trips within the defined plan area. Metrics used include home-based VMT per capita, home-based work VMT per employee, and total VMT per service population (combined residents and employees).
A significant impact occurs if:
- Plan VMT Exceeds Existing Levels: If the plan’s VMT per capita, VMT per employee, or VMT per service population in the horizon year with project scenario exceeds the metrics under current conditions.
- Plan VMT Exceeds No-Project Scenario: If the plan’s metrics in the horizon year with project scenario exceed those in the horizon year no-project scenario.
Mitigation Strategies for Area Plans
When a significant VMT impact is identified for an area plan, CEQA mandates the implementation of mitigation measures to address and reduce this impact. Possible mitigation options include:
- Increasing Land Use Density and Mix: Promoting a higher density and diversity of land uses can reduce travel distances and encourage non-automotive trips.
- Bicycle, Pedestrian, and Transit Infrastructure Improvements: Prioritizing infrastructure for sustainable transportation options over automobile facilities.
- Reduced Parking Supply: Limiting parking spaces can reduce the appeal of driving alone.
- Employee Commute Reduction Programs: Policies that encourage employees to use alternative transportation modes or work remotely.
- Mandatory On-Site TDM Strategies: Requiring developers to implement TDM measures within project sites to reduce vehicle trips.
VMT Analysis for Transportation Projects
Transportation projects, like those involving infrastructure improvements, also need a detailed VMT analysis if they are likely to increase VMT, such as by adding new travel lanes. Projects that improve vehicular capacity and encourage single-occupancy travel are particularly scrutinized for VMT impacts under CEQA. However, some projects may be exempt from VMT analysis if they are unlikely to raise VMT. For example, transit service enhancements, bikeways, and pedestrian facilities typically promote reduced VMT and are therefore excluded from detailed analysis.
Analysis Requirements
For applicable transportation projects, two tiers of VMT analysis are required:
- Near-Term VMT Analysis: Conducted using the SCAG model, this analysis estimates the impact of a new or expanded facility on citywide VMT in the short term by comparing scenarios with and without the project. The focus is on the net change in total citywide VMT using a boundary-based method.
- Induced Demand Analysis: A long-term VMT analysis accounts for potential demand increases by using an elasticity-based calculation to estimate the project’s effect on future VMT. This analysis uses the formula: (% increase in lane miles)×(baseline VMT)×(elasticity)=VMT resulting from the project(\% \text{ increase in lane miles}) \times (\text{baseline VMT}) \times (\text{elasticity}) = \text{VMT resulting from the project}(% increase in lane miles)×(baseline VMT)×(elasticity)=VMT resulting from the project Based on current research, an elasticity of 0.75 is recommended for arterial roads in the City of Montebello.
Impact Thresholds for Transportation Projects
The significant impact threshold for transportation projects is based on whether the project leads to a net increase in total citywide VMT. A significant impact is identified if any of the study scenarios show that a transportation project would increase VMT.
Mitigation Measures for Transportation Projects
Mitigation for significant VMT impacts from transportation projects includes measures to discourage solo vehicle travel or encourage alternatives:
- Bicycle and Pedestrian Network Enhancements: Improving cycling and walking infrastructure can reduce car trips.
- Transit Network Expansions: Enhanced transit options may attract potential drivers to public transportation.
- Off-Site TDM Measures: These measures can address VMT impacts on a regional level by promoting alternative transport modes.
Intelligent transportation systems (ITS) can also serve as an alternative to adding vehicle lanes by optimizing traffic flow and reducing VMT without increasing roadway capacity.
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