Introduction
These guidelines outline the transportation analysis requirements for land development, roadway projects, and specific plans in the City of Diamond Bar, focusing on evaluating environmental transportation impacts and their effects on the local transportation system. The aim is to provide clear guidance for preparing transportation studies in accordance with relevant City and State regulations.
Background Information
Senate Bill 743, enacted in 2013, changed the approach to identifying transportation impacts under the California Environmental Quality Act (CEQA). This legislation directed the Office of Planning and Research (OPR) to establish new metrics, leading to the adoption of Vehicle Miles Traveled (VMT) as the primary metric for assessing transportation impacts, with all lead agencies required to implement VMT analysis by July 2020.
To facilitate this transition, the San Gabriel Valley Council of Governments (SGVCOG) conducted the SB 743 Implementation Study, addressing methodology, thresholds, and mitigation strategies for VMT analysis. Key components of the study include the identification of significance thresholds for VMT assessments, potential mitigation strategies, and a web-based VMT assessment tool for screening and recommendations.
The City of Diamond Bar adopted the methodologies and significance thresholds outlined in the Implementation Study, as encouraged by CEQA Guidelines Section 15064.7(b). This section emphasizes the importance of public agencies establishing and publishing their significance thresholds, which must be adopted through a public review process and supported by substantial evidence.
These Transportation Study (TS) Guidelines have been developed to detail the steps for complying with the updated CEQA expectations for VMT analysis while addressing general plan consistency related to Level of Service (LOS) standards.
As CEQA requirements evolve through updates and legal interpretations, the City will continuously review these guidelines to ensure their relevance, and consultants are advised to verify they are utilizing the most current guidelines for project impact assessments.
CEQA Changes
Since the previous update of the TS Guidelines, SB 743 has been enacted, eliminating measures such as auto delay and LOS from the criteria for determining significant environmental impacts. This change aims to balance congestion management with statewide goals for infill development, active transportation promotion, and greenhouse gas emission reduction.
SB 743 also allows cities and counties to opt out of LOS standards in areas where Congestion Management Plans (CMPs) apply, and it mandates OPR to update the CEQA Guidelines to establish criteria for transportation impact significance. In December 2018, OPR recommended VMT as the most suitable measure for assessing transportation impacts from land use projects, while allowing lead agencies to choose metrics for transportation projects as long as they are backed by substantial evidence. However, cities and counties can still analyze delay or LOS outside of CEQA for other planning purposes.
Level of Service Policy
The City maintains vehicle LOS standards to guide local infrastructure development and is applicable to discretionary approvals of new land use and transportation projects. Consequently, these TS Guidelines incorporate instructions for conducting vehicle LOS analysis in alignment with City requirements.
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