How Are Speed Limits Set?
For major streets, speed limits are set through an engineering and traffic survey. For streets that carry local traffic only, the speed limit is set at 25 mph and is not posted. The purpose of this web page is to publish the engineering and traffic surveys for major streets, prepared and reviewed regularly by the City of San Carlos in accordance with the California Vehicle Code.
Engineering and traffic surveys measure the actual speeds that drivers travel on a given street. Certified radar guns are used to ensure that the measurements are accurate. To the extent possible, the speed measurements are taken on days with fair weather, dry pavement, and clear visibility and are taken at a location not affected by stop signs, parks, schools, curves or other features that would affect speed. An effort is made to ensure that the presence of radar survey equipment did not affect the speed of the traffic being surveyed. After the data on actual speeds has been analyzed, the speed limit is normally set at or below the speed at which 85 percent of drivers are driving. Speed limits cannot be set arbitrarily low, as this would create violators of the majority of drives and would not command the respect of the public.
An engineering and traffic survey is to be reviewed five years after it has been completed. If, at the five year point, the City Engineer finds that conditions have not changed, it does not need to be reviewed for another two years. If, when the engineering and traffic survey is reviewed seven years after it has been completed, it does not need to be reviewed for another three years. A new engineering and traffic survey must be completed at the ten year mark. The table below provides the status of engineering and traffic surveys for all of the major streets in San Carlos. Follow the links to download the latest engineering and traffic survey and the 5-year or 7-year review.
For background information on the history, rationale and limitations of setting speed limits, please refer to Special Report 254 from the Transportation Research Board, Managing Speed.