Traffic Impact Study Guidelines for the City of Seal Beach

TRAFFIC IMPACT STUDY GUIDELINES

The City of Seal Beach requires Traffic Impact Studies (TIS) for new development projects and expansions to ensure that they meet the city’s standards for parking, site access, and intersection operations, in line with broader objectives for traffic safety and environmental responsibility. The following guidelines establish the minimum requirements for preparing a TIS for submittal. These requirements are intended to maintain consistency and clarity across various traffic reports, and they must be fulfilled before a report is reviewed or accepted by the City. The City reserves the right to amend these guidelines as necessary.

Determination of Study Requirement: The City Engineer or their designee decides if a Traffic Impact Study is needed for a project. This determination is based on several factors, including projected vehicle volume, project size, proximity to arterial intersections, potential traffic safety issues, environmental or public sensitivity, and nearby sub-standard road conditions. If a TIS is required, the applicant must engage a professional Traffic Engineer to complete the study and prepare the report.

Minimum Study Requirements: The following are the criteria for when a TIS is required:

1. Projects generating at least 50 vehicles per hour during peak hours.
2. Developments within 300 feet of arterial intersections or on sites with multiple street frontages.
3. Sites that could exacerbate traffic safety problems.
4. Projects in environmentally sensitive or controversial areas.
5. Developments near intersections with a “D” level of service or worse.

If a project meets or exceeds these criteria, a TIS is mandatory. However, projects with lower impacts may be required to submit a letter analysis if determined necessary by the City Engineer.

Outline and Elements of the TIS Report: A comprehensive TIS report for the City of Seal Beach must cover multiple elements, including:

1. Executive Summary: A concise summary of the project, traffic generation, potential impacts, and mitigation measures.
2. Introduction: Overview of study procedures, project site, study area, and related road networks.
3. Area Development: Description of surrounding land uses and any deviations from the general plan.
4. Existing Street System: Analysis of the existing transportation network, including roadways, traffic volumes, and pedestrian/bicycle facilities.
5. Project Description and Location: Detailed site layout, traffic circulation, parking provisions, and project phasing.
6. Traffic Generation Forecast: Projections based on ITE standards, with adjustments for specific project characteristics or transit access.
7. Traffic Distribution and Assignment: Estimation of traffic flow patterns in and around the project area.
8. Traffic Impact Analysis: Assessment of the project’s effect on local intersections and street links.
9. On-Site Parking and Circulation: Evaluation of parking adequacy, layout, and circulation for vehicles and bicycles.
10. Truck Service Impacts: Analysis of delivery truck routes and parking provisions.
11. Active Transportation Impacts: Evaluation of bicycle and pedestrian access and safety.
12. Transit Impacts: Description of transit services within a half-mile radius and project site accessibility.
13. Construction Period Impacts: Consideration of lane closures, safety measures, and detours during construction.
14. Mitigation Measures: Proposed actions to address traffic impacts, with LOS tables and intersection modifications as needed.

Detailed Guidelines for Key Elements:

1. Executive Summary: This section should highlight the project’s main features, expected traffic generation, impacts, and the proposed mitigation measures, serving as an overview for readers.

2. Introduction: Provide background information about the study, including boundaries, road networks, and site uses. Include regional and site maps to orient the study area.

3. Area Development: Describe surrounding land use, highlighting any deviations from the general plan and the implications for traffic and transportation.

4. Existing Transportation System: Document local access points and routes, geometric descriptions of roadways, existing traffic volumes, and pedestrian and bicycle infrastructure. Use current traffic counts (within 12 months) to provide an accurate baseline.

5. Project Description and Location: Provide a detailed breakdown of the project’s components, including square footage, density, proposed uses, and internal circulation. Include a site plan and relevant traffic circulation patterns.

6. Traffic Generation Forecast: Use standard trip generation data from the ITE or city-provided sources, with justifications for any modifications. Present forecasts for daily, A.M., and P.M. peak volumes and account for reductions from passer-by or transit trips where applicable.

7. Traffic Distribution and Assignment: Reflect current distribution patterns in the city, adapted for specific land uses. Include exhibits showing projected volumes and turning movements.

8. Traffic Impact Study: Analyze intersections and midblock operations using the Intersection Capacity Utilization (ICU) and Highway Capacity Manual methods, respectively. Study impacts for the existing year, project completion year, and a 20-year horizon to align with the city’s General Plan.

9. On-Site Parking and Circulation: Compare parking provisions with city requirements, and if proposing fewer spaces, include a justification. Describe vehicle and bicycle circulation, access points, and other internal traffic measures.

10. Truck Service Impacts: Detail the routes, access points, and loading areas for delivery trucks. Justify any reductions in loading space if applicable.

11. Active Transportation Impacts: Evaluate how the project will affect pedestrian and bicycle infrastructure and outline any improvements or adjustments to support active transportation.

12. Transit Impacts: Identify nearby transit stops, describe accessibility, and discuss potential impacts on service or infrastructure.

13. Construction Period Impacts: Discuss any planned road or lane closures, safety protocols, and alternate routes during construction. Note that all lanes on arterial roads should remain open during peak travel times unless an exception is granted.

14. Mitigation Measures: Outline measures to address any traffic impacts, focusing on significant effects on Level-of-Service (LOS) or high accident intersections. Include visualizations of proposed intersection modifications and specify any required changes to signal phasing. Improvements due to project impacts may become conditions of approval.

Criteria for Impact Thresholds:

Mitigation may be necessary if the ICU or accident rate exceeds defined thresholds. An increase in ICU beyond certain levels—based on existing ICU—is deemed significant and necessitates mitigation. The ICU thresholds are as follows:

Intersections or road links with five or more reported accidents within 12 months must be analyzed and mitigated as needed.

Approval Conditions:

Any improvements identified as necessary due to project-related impacts will be included as conditions for approval. Roadways adjacent to the project may need upgrades to a half-width configuration. In addition, further off-site traffic improvements could be mandated on a case-by-case basis by the City Engineer.

These guidelines offer a comprehensive approach to assessing and mitigating the transportation impacts of new developments in Seal Beach, helping to support safe, efficient, and sustainable traffic and transportation systems.

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