Triggers requiring an impact study guidelines El Dorado County Community Development Agency

Triggers Requiring a Transportation Impact Study (TIS)

A Transportation Impact Study (TIS) is a critical component of the development review process and is required for projects that have the potential to significantly affect traffic conditions. Unless explicitly waived by El Dorado County, a TIS must be conducted when any of the following conditions, as outlined in General Plan Policies TC-Xa and TC-Xe, are met:

1. Increase in Traffic Volumes – If the project is expected to increase traffic during the weekday a.m. peak hour, weekday p.m. peak hour, or over a full day by two percent (2%) or more, a TIS is required. This ensures that even minor increases in traffic are assessed for potential cumulative impacts.

2. Daily Trip Generation – A project that is anticipated to generate 100 or more daily trips necessitates a TIS to evaluate its contribution to overall traffic congestion and transportation network efficiency.

3. Peak Hour Traffic Contribution – Any development that adds 10 or more trips during the weekday a.m. or weekday p.m. peak hour requires a TIS to determine whether these additional vehicle movements impact roadway capacity and safety.

4. Significant Environmental Impact under CEQA – If a project has the potential to create a significant environmental impact as defined under the California Environmental Quality Act (CEQA), a TIS is mandatory to assess transportation-related consequences and propose mitigation strategies.

5. General Plan Amendment – If the project includes a General Plan Amendment that alters the existing land use designation, a TIS must be performed to evaluate how these changes affect current and future traffic conditions.

Applicability of Previous TIS Reports

In cases where a TIS has been previously conducted for a project or a similar development in the vicinity, the report remains applicable as long as traffic conditions have not significantly changed. However, if there has been a two-year period of inactivity, new traffic counts should be collected to determine whether an updated study is necessary. The determination of whether a new TIS is required will be made by Long Range Planning (LRP) staff based on recent traffic trends and changes in local infrastructure.

Master TIS for Large Developments

For larger developments, a master TIS may be prepared to assess transportation impacts over multiple phases of construction. If the master TIS comprehensively evaluates the entire development and includes phased implementation strategies, individual phases or sub-projects may not require additional, separate transportation impact studies. However, each phase must align with the assumptions and findings of the master TIS to be exempt from further review.

On-Site Transportation Review

Regardless of whether a full TIS is required, all projects must undergo an On-Site Transportation Review to ensure site-specific transportation considerations are addressed. This review must be conducted by a registered Traffic Engineer or Civil Engineer and include a detailed evaluation of the following factors:

1. Existing Traffic Conditions – Identification of any known traffic problems in the immediate vicinity of the project, including high-accident locations, non-standard intersections, or intersections that may require a traffic signal.

2. Driveway Placement and Access – Assessment of the proposed site driveway(s) in relation to nearby driveways and intersections to prevent conflicts and ensure safe ingress and egress.

3. Parking Adequacy – Evaluation of parking supply relative to both anticipated demand and compliance with zoning code requirements to prevent parking shortages or excessive overflow onto adjacent streets.

4. Truck Loading and Service Access – Determination of whether the project site can accommodate the anticipated number of daily deliveries and service calls, particularly if these exceed 10 per day.

5. Minimum Required Throat Depth (MRTD) – Analysis of the adequacy of the project site design in providing a minimum required throat depth of 25 feet at all project driveways. This includes the calculation of MRTD to prevent queuing and ensure smooth internal circulation.

6. Accommodation of Various Vehicle Types – Review of the site layout to confirm it can safely and efficiently accommodate all vehicle types expected to access the site, including passenger vehicles, delivery trucks, emergency vehicles, and transit vehicles.

7. Sight Distance Analysis – Verification that the project provides adequate sight distances for safe vehicle movements, particularly at driveways and intersections.

8. Drive-Through Facility Queuing Analysis – For projects with drive-through facilities, a queuing analysis must be conducted to determine whether on-site stacking space is sufficient to prevent queue spillover onto adjacent roadways.

If a TIS is required, the On-Site Transportation Review should be included within the “Other Transportation Related Impacts and Mitigation Considerations” section of the study.

Importance of an Accurate Project Description

A well-defined project description is essential in determining whether a TIS is required. The description should include a clear outline of:

• Proposed land use

• Expected trip generation rates

• Anticipated changes in traffic patterns

• Parking and access design

• Potential transportation improvements

This detailed project description ensures that the TIS accurately assesses the project's potential impacts. If the project undergoes modifications after the initiation of the TIS or during the County’s review process, the study scope and study area may need to be revised accordingly.

A TIS is a fundamental component in evaluating the transportation impacts of proposed development projects. By adhering to the established triggers and conducting a thorough On-Site Transportation Review, project applicants can ensure compliance with El Dorado County’s transportation policies while mitigating potential negative impacts on the road network. Early consultation with County planning and transportation staff is encouraged to confirm study requirements and streamline the approval process.

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