Comprehensive Traffic Impact Study Report Format for Evaluating Transportation Infrastructure and Mitigation Strategies in the City of Walnut Creek

9.0 Traffic Impact Study - Report Format

The Traffic Impact Study (TIS) report should be submitted in PDF format, including SYNCHRO Level of Service (LOS) files, to the City of Walnut Creek staff. The study should be formatted in a clear and organized manner to facilitate review and decision-making. Below is the required structure of the TIS report:

• Executive Summary

• Introduction

• Existing Conditions

• Project Description

• Trip Generation and Trip Distribution

• Performance Measure Analysis

• Near-Term (Existing Plus Approved and Pending Projects) Conditions

• Near-Term Plus Proposed Project Conditions

• Pedestrians/Bicycles and Transit

• Site Access and Circulation

• Other Analyses

• Cumulative Year 2035 and Cumulative Year 2035 Plus Project Conditions

• Mitigation Measures

• Conclusions

• Appendices

Executive Summary

Each report must contain an executive summary that provides a concise overview of the study. This section should include:

• A brief summary of the Traffic Impact Study (TIS)

• Project location and size

• Intersections analyzed

• Study scenarios considered

• Identified impacts and proposed mitigations

• Key recommendations summarized in both figure and table format

The executive summary should focus on presenting key findings without including a detailed discussion of the methodologies used in the impact analysis.

This section should also document the results of the LOS analysis for intersections and other applicable performance measures for roadway segments. Additionally, it should provide a summary of site access and circulation evaluation. The executive summary should separate findings related to vehicular traffic, pedestrians, bicycles, and transit to highlight their respective impacts and considerations.

The results of the LOS analysis should be presented in a table format similar to the one below for both near-term and cumulative scenarios:

Summary of Intersection Level of Service

Intersection	Existing	Near Term (Existing Plus Approved and Pending)	Near Term Plus Proposed Project
Delay	LOS	Delay	LOS
Delay	LOS	Delay	LOS

Introduction

This section introduces the purpose of the TIS, outlines the scope of work, and identifies the study area. It should summarize the objectives of the analysis, including the evaluation of transportation impacts due to the proposed project and the identification of necessary mitigation measures. Additionally, the introduction should mention any relevant City of Walnut Creek transportation policies and guidelines governing the study.

Existing Conditions

The existing conditions section should provide a comprehensive assessment of the current transportation network within the study area. This includes:

• Roadway classifications and characteristics

• Traffic volumes and LOS for intersections and roadway segments

• Existing pedestrian and bicycle facilities

• Public transit routes and ridership data

• Parking availability and utilization

• Any existing congestion, safety, or operational concerns

This section serves as the baseline for evaluating the impact of the proposed project on transportation infrastructure.

Project Description

A detailed description of the proposed project should be included, outlining:

• Project location and land use

• Proposed site plan

• Development phasing and timeline

• Expected occupancy and operational characteristics

• Any planned transportation improvements associated with the project

Trip Generation and Trip Distribution

This section must estimate the number of trips the project will generate, distribute these trips across the transportation network, and assign them to specific roadways and intersections. Key components include:

• Trip generation rates based on the Institute of Transportation Engineers (ITE) Trip Generation Manual or local data

• Mode share assumptions (automobile, bicycle, pedestrian, transit)

• Trip distribution and assignment methodology

• Peak-hour trip estimates for AM and PM conditions

Performance Measure Analysis

Performance measures should be analyzed using methodologies consistent with the Highway Capacity Manual (HCM) and City of Walnut Creek standards. These include:

• Intersection LOS analysis

• Roadway segment analysis

• Queuing analysis

• Multimodal performance evaluations

Near-Term Conditions (Existing Plus Approved and Pending Projects)

This section analyzes transportation conditions with the addition of approved and pending developments in the study area. It assesses how these projects will impact traffic operations, congestion levels, and multimodal infrastructure.

Near-Term Plus Proposed Project Conditions

This analysis evaluates transportation conditions by incorporating the proposed project into the near-term scenario. The study should identify any degradation in LOS, queuing issues, or multimodal accessibility challenges due to the project.

Pedestrians, Bicycles, and Transit

A detailed assessment of the project’s impact on pedestrian, bicycle, and transit facilities should be included. This analysis should:

• Identify existing deficiencies in pedestrian, bicycle, and transit infrastructure

• Assess project-related changes in pedestrian and bicycle volumes

• Analyze transit stop boardings and passenger load factors

• Evaluate accessibility to transit stops and safety at pedestrian crossings

• Provide recommendations to mitigate potential multimodal impacts

Site Access and Circulation

This section should evaluate the adequacy of site access and internal circulation for vehicles, pedestrians, and bicyclists. Components include:

• Location and design of driveways, curb cuts, and access points

• Internal vehicular circulation patterns

• Pedestrian and bicycle pathways within the site

• Sight distance analysis at access points

• Compliance with City parking and loading space requirements

• Signal warrant analysis (if applicable)

Other Analyses

Any additional studies required by City staff, such as:

• Emergency vehicle access analysis

• Traffic calming assessments

• School transportation impacts

• Special event traffic management plans

Cumulative Year 2035 and Cumulative Year 2035 Plus Project Conditions

This section projects long-term transportation conditions by incorporating regional growth, planned infrastructure improvements, and anticipated development trends. The analysis should consider:

• Future traffic volumes based on regional forecasting models

• Expected changes in LOS and congestion levels

• Long-term pedestrian, bicycle, and transit infrastructure plans

Mitigation Measures

If the project results in significant impacts, appropriate mitigation measures must be proposed. These may include:

• Intersection improvements (signal timing adjustments, turn lane additions)

• Roadway widening or reconfigurations

• Bicycle and pedestrian enhancements

• Transit service improvements

• Transportation Demand Management (TDM) strategies

Each mitigation measure should include an estimate of its effectiveness and feasibility, along with implementation timing and potential funding sources.

Conclusions

This section summarizes the key findings of the TIS, restating:

• Projected transportation impacts

• Recommended mitigation measures

• Any remaining significant impacts that cannot be mitigated

• Compliance with City transportation policies

Appendices

Supporting data, calculations, and supplementary materials should be included in the appendices. This may include:

• Raw traffic count data

• SYNCHRO analysis reports

• Technical documentation of trip generation calculations

• Maps and diagrams of study intersections and proposed site access

By adhering to this structured format, the TIS will provide a comprehensive and systematic evaluation of the transportation impacts associated with the proposed project, ensuring that the City of Walnut Creek has the necessary information to make informed planning and development decisions.

 

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