Section 3.2 - CEQA Transportation Impact Analysis (TIA) for Transportation Projects
Transportation projects that expand roadway capacity can result in additional vehicle travel, often referred to as "induced travel." This phenomenon occurs when increased highway capacity leads to higher speeds, more efficient travel, or stimulates growth, which in turn raises the total vehicle miles traveled (VMT) on the network. "Induced" VMT refers specifically to the extra vehicle travel generated by the enhanced road capacity. To ensure consistency in the assessment of transportation impacts and to align with sustainability goals, the screening criteria for evaluating such impacts are based on the following key question:
- Does the project conflict with or fail to align with CEQA Guidelines Section 15064.3, subdivision (b)(2)? This section presumes that transportation projects which either reduce or have no impact on VMT will have a less-than-significant environmental impact. Additionally, it excludes projects that are already addressed within a regional transportation plan Environmental Impact Report (EIR). For roadway capacity projects, public agencies have the flexibility to determine their own methods for measuring transportation impacts, provided that they remain consistent with CEQA. In this case, the City of Manhattan Beach follows the methodology adopted by the County.
The primary aim of the transportation impact assessment (TIA) is to evaluate whether a proposed project will induce a substantial increase in VMT. The following sections outline the screening and impact criteria used to determine whether a project is likely to generate a significant transportation impact and whether a full TIA is required. The City Traffic Engineer will review these criteria on a case-by-case basis for each project.
Section 3.2.1 - Screening Criteria
To quickly determine whether a detailed analysis is needed, the following screening criterion is applied. If the answer to the question below is NO, then no further analysis is required, and the project can be considered to have a less-than-significant impact regarding transportation:
- Does the project involve adding through traffic lanes on existing or new highways, including general purpose lanes, HOV lanes, peak period lanes, auxiliary lanes, or lanes through grade-separated interchanges (excluding managed lanes, transit lanes, and auxiliary lanes under one mile designed to enhance safety)?
Projects focused on transit, active transportation, or reducing roadway capacity generally result in reduced VMT and are therefore presumed to have a less-than-significant transportation impact. Below is a list of project types that are unlikely to generate a substantial increase in vehicle travel and are thus exempt from conducting a full induced travel analysis:
- Maintenance, rehabilitation, or repair projects aimed at improving the condition of existing transportation infrastructure (e.g., highways, roadways, bridges, tunnels, transit systems, or pedestrian and bicycle facilities) that do not add motor vehicle capacity.
- Safety projects that involve the installation of roadside safety devices (e.g., median barriers, guardrails).
- Shoulder enhancements designed to improve safety but not used as vehicle travel lanes.
- Auxiliary lanes under one mile intended to improve roadway safety.
- Reconfiguration of traffic lanes not intended for through traffic (e.g., left, right, U-turn pockets, two-way left turn lanes).
- Capacity improvements on local or collector streets, provided the project also improves conditions for pedestrians, cyclists, and, where applicable, transit users.
- Conversion of existing lanes to managed or transit lanes without a significant increase in vehicle travel.
- Reduction in the number of through lanes or the addition of transit-only lanes.
- Traffic control modifications such as installing or removing traffic signals, roundabouts, metering systems, or traffic calming devices.
- Toll lane projects where toll rates are set to mitigate VMT increases.
- New transit services or infrastructure to support non-motorized travel (e.g., bike paths, pedestrian facilities).
- Installation of alternative fuel/charging infrastructure.
Section 3.2.2 – Impact Criteria
A project will have a potentially significant VMT impact if it meets the following criterion, which serves as a guideline for determining whether further analysis is needed:
- The project increases VMT within the project area, as measured by the SCAG RTP/SCS (Southern California Association of Governments Regional Transportation Plan/Sustainable Communities Strategy) base year Travel Demand Forecasting Model, plus an induced travel elasticity factor per lane mile.
Section 3.2.3 - Methodology
Section 3.2.3.1 - Project Impacts Determination
The City of Manhattan Beach uses the SCAG RTP/SCS Travel Demand Forecasting Model to assess the change in VMT resulting from proposed transportation projects. This model calculates changes in VMT based on factors such as trip length, mode split, and route choices but does not account for induced travel due to latent demand or land use changes. Therefore, an induced travel elasticity factor must be applied based on established academic research.
The process for assessing a project’s VMT impact includes the following steps:
- Run the SCAG RTP/SCS model with and without the proposed project to isolate direct changes in network VMT.
- Determine the total lane miles affected by the project, capturing any changes in driving behavior.
- Calculate the percentage change in lane miles due to the project.
- Determine existing VMT over the affected area using the SCAG model.
- Apply the induced travel elasticity factor to estimate the increase in VMT due to the added lane miles.
- Sum the induced VMT with the direct VMT changes from trip length, mode split, and route choice to determine the project's total VMT impact.
Section 3.2.3.2 - Cumulative Impacts Determination
Both short- and long-term impacts of a project on VMT must be considered. Short-term effects are captured through the project-specific VMT analysis described above. Long-term, cumulative impacts are evaluated based on the project's consistency with the SCAG RTP/SCS. Projects that are consistent with this regional plan, which aligns with air quality and GHG reduction goals, are considered to have a less-than-significant cumulative impact on VMT. Conversely, projects that are inconsistent with the plan may have significant cumulative VMT impacts, which would require further evaluation through the SCAG RTP/SCS model to assess the induced demand.
Section 3.2.4 - Mitigation
To mitigate potential VMT increases induced by roadway capacity projects, several strategies can be employed. These include, but are not limited to:
- Converting general-purpose lanes to HOV, HOT, toll, or bus lanes, which encourage carpooling and support transit.
- Funding or implementing off-site mobility improvements, such as transportation management organizations (TMOs).
- Deploying intelligent transportation systems (ITS) to optimize the existing road network and enhance vehicle throughput.
- Any additional mitigation measures must be backed by substantial evidence to demonstrate their effectiveness in reducing VMT.
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