Traffic Study Requirements
The Measure C Growth Management Program (GMP) guidelines require local jurisdictions to prepare traffic studies for any project that generates 100 or more peak hour vehicle trips. Similarly, general plan amendments that generate more than 500 peak hour vehicle trips also require analysis of traffic impacts under the Measure C GMP. Many local jurisdictions have voluntarily adopted a lower threshold for triggering this requirement. For example, Lamorinda uses a 50 vehicle trip threshold for projects, and most Contra Costa County jurisdictions currently use a 100 vehicle trip threshold for general plan amendments.
How big does a new development project have to be to require a study? As a general rule, a detached Single Family Dwelling Unit (SFDU) generates one peak hour vehicle trip. So any new development project that contains more that 100 SFDUs will generally trigger the need for a study. Examples of other types of projects that could trigger the traffic study requirement are apartment complexes of greater than 150 units, hotels that are more than 145 rooms, most fast food restaurants, shopping centers greater than 14,000 square feet, and general office facilities with more than 150 employees.
In all cases, a traffic analysis must be completed and circulated prior to action on the proposed project. In general, preparation of the traffic impact analysis is included as part of the environmental review process. Failure on the part of a local jurisdiction to prepare a traffic study in accordance with the Authority's Technical Procedures could result in a findings of noncompliance with the Authority's GMP.
The Authority's Technical Procedures were developed to help local staff and consultants prepare traffic studies using a uniform set of policies, procedures, and tools. The Procedures include a methodology for determining traffic Level of Service at signalized intersections, guidelines for applying the Authority's travel demand forecasting model, and a step-by-step procedure for preparing the traffic study itself.
To review the Technical Procedures, and to see examples of historic and current traffic studies prepared for Measure C compliance purposes, please click here [PDF - 4 MB].