Traffic Impact Analysis Requirements

Effective July 1, 2020, the County of San Mateo has transitioned to using Vehicle Miles Traveled (VMT) instead of Level of Service (LOS) as the metric for determining transportation-related impacts under CEQA. 

In the past, CEQA transportation-related impacts from a proposed project have been evaluated based on LOS, which measures delay at signalized intersections surrounding the proposed project. Projects determined to have significant impacts based on LOS are required to mitigate these impacts by road widenings, signal improvements, or similar measures to maintain operational efficiency and capacity.

With the passage of SB 743, beginning July 1, 2020, the County of San Mateo, along with other public agencies (Cities of San Francisco, San Mateo, etc.), are required to use VMT to address CEQA transportation-related impacts. Projects determined to generate VMT above our defined thresholds will be required to mitigate their impacts through measures such as car-sharing services, unbundled parking, improved transit, and enhanced pedestrian and bicycle infrastructures.

However, as noted in SB 743, local agencies may still use LOS to determine local impacts and the County of San Mateo will still require projects to determine local impacts based on LOS. Therefore, Both LOS and VMT analyses must be completed prior to project approval. The requirements for a Traffic Impact Analysis based on LOS and criteria for a VMT analysis are provided on the bottom of the page.