Traffic Engineering

The Public Works Division performs traffic counts and speed zone surveys on County roadways and maintains a traffic accident database. Staff evaluates road safety to help ensure County road conditions are safe and meet standards identified in the California Manual of Uniform Traffic Control Devices (CA-MUTCD).

If you have a traffic safety concern related to a County road that you would like to report, please do so through the following link: Road Maintenance Request Form

FAQs about speed limits

Yolo County's List of Reduced Speed Limits

What's the speed limit?

Safety and common sense should determine your driving speed, even if it means driving more slowly than the posted speed limit. Engineers study streets and intersections to set safe speed limits that reflect the speeds of prudent motorists. When determining your driving speed, it is important to remember the California Vehicle Code (CVC) Basic Speed Law: No person shall drive a vehicle...at a speed greater than is reasonable or prudent...and in no event at a speed which endangers the safety of person or property.

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How are speed limits set?

Some speed limits are established by federal or state law while others are set by local authorities and posted on the street. Some general guidelines set by California state law are:

55mph is the speed limit on any 2-lane county road not otherwise posted.
25mph is the speed limit in any business district or residential street.
25mph is the speed limit in school zones when children are present.
15mph is the speed limit in alleys, intersections, and railroad crossings (where visibility is limited).

These limits are generally presumed to be reasonable and may not always be posted on the street.

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What about local speed limits?

The CVC allows jurisdictions to set specific speed limits for portions of roads called "speed limit zones" within their boundaries, under strict guidelines established by the state. Yolo County has established speed limit zones between 25 and 55mph, based on engineering traffic surveys. For each speed limit zone's survey, engineers study these factors:

Street collision history
Pedestrian and bicycle traffic
Speed of traffic
Number, visibility, and type of driveways
Type of area (residential, commercial, offices, recreational, etc.)

After considering these factors, traffic engineers set the speed limit either at or 5mph below the speed driven by 85 percent of vehicles surveyed.

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Do speed limit signs reduce collisions?

People frequently ask to lower the speed limit on residential streets to make their streets safer and more livable. It is a common misconception that speed limit signs reduce collisions. Studies indicate that no significant change in average vehicle speed has occurred after the posting of new or revised speed limit signs. Research also shows no direct relationship between posting speed limits and collision frequency.

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