*FAQ's & Knowledge-base (Cy... - Question #25
How are speed limits set?
Traffic: Speed Limits
For city streets, there are three basic speed limits set by the California Vehicle Code, (CVC):

     15 mph in an alley, 
     25 mph in a business or residential district, and 
     25 mph in a school zone when children are present. 

When the street does not meet the Vehicle Code definition for these criteria, the City must conduct an engineering and traffic survey to determine the speed limit. Except for certain conditions, the survey must be conducted every five years.

Speed zoning in California is based on the widely accepted principle of setting speed limits as near as practicable to the speed at or below which 85 percent of the drivers are traveling. This speed is subject, of course, to downward revision based upon such factors as: accident experience, roadway geometrics, and adjacent development. 

The survey, which is conducted for each speed limit segment, must consider the following: 

Prevailing speeds as determined by radar speed study, Accident rates, and 
Highway, traffic and roadside conditions not readily apparent to the motorists, such as driveways and curves in the roadway. 

ENGINEERING JUDGMENT 

Probably one of the most important factors in a speed study, but the one most difficult to define, is engineering judgment based on the experience of the traffic engineer. No matter how complete policies and guidelines are, there will always be speed studies with peculiarities requiring engineering judgment. 

Sometimes, the decision to raise or lower a speed limit in a certain area may have to be based on the traffic investigator's own personal judgment. In some areas, where there is insufficient traffic for a valid speed sample, the engineer may have to base his decision on a driving impression of the speed study area. 

In the final analysis, it is the engineering judgment of the investigator that determines which, if any, of the factors in the speed study warrant a downward adjustment to the 85th percentile speeds. 

After all variables are considered and a speed limit is established, traffic should flow at an optimum safe and efficient level.

Sources: Arizona Department of Transportation, City of Santa Ana, ITE, Caltrans
Created on Aug.  4, 2002 at  5:30 PM (PDT). Last updated by CityEngineer on May  4, 2010 at  9:58 AM (PDT). Owned by cmcmahon@ci.cypress.ca.us.
Catherine McMahon
Public Works Director
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When you bring additional fields into a conversion, Quickbase often finds inconsistencies. For example, say you're converting your Companies column into its own table. One company, Acme Corporation, has offices in New York, Dallas and Portland. So, when you add the City column to the conversion, Quickbase finds three different locations for Acme. A single value in the column you're converting can only match one value in any additional field. Quickbase needs you to clean up the extra cities before it can create your new table. To do so, you have one of two choices:

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