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Traffic Impact Study Guidelines

Download TIS Guidelines

Traffic impact studies must be conducted in accordance with County standards, as detailed in the Guidelines for Traffic Impact Studies PDF Document.

Download Guidelines for Traffic Impact Studies (PDF, 1.69 MB)

Download June 2019 Queuing Language Update


Roads are a critical public resource and constitute a major investment of the public’s money. Traffic impacts caused by new development – reduction in the traffic carrying capacity of the highways, increased collisions, and traffic congestion – can be very costly for state and local governments, as well as the broader community.

The impact of any proposed development on transportation system performance, whether it is small or large, depends on the number of trips generated by the proposed development, the location of the connection(s) to the transportation system, and the routes taken to and from the site. This impact is quantified by preparing a traffic impact study (TIS).


The Permit and Resource Management Department (PRMD) and the Department of Transportation and Public Works (TPW) are both responsible for the review and conditioning of private development projects.

For questions regarding the traffic impact study guidelines, please contact the Department of Transportation and Public Works (TPW).

Traffic Engineering Home Page

Contact Information

Business Hours
Monday – Friday
8:00 AM – 2:00 PM

Lobby Hours temporarily reduced as of 8/30/21 until further notice

Contact us by Phone
Office Location
La Plaza B
2300 County Center Drive
Suite B 100
Santa Rosa, CA 95403
38.462023, -122.725381

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Permit & Resource Management Department

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Customer-focused process for the orderly development of real property.