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Speed Limits and Traffic Calming

This page provides an overview of speed limits and traffic calming for local governments in Washington State, including speed limit changes, school and playground zones, design considerations, and examples of local traffic calming programs.


RCW 46.61.400 establishes a maximum speed limit of 25 mph for city/town streets and 50 mph on county roads, or higher as permitted under RCW 46.61.415. For state highways, the statute establishes a maximum speed limit of 60 mph, or up to 75 mph under RCW 46.61.410.

However, under certain situations a city or county (or, for state highways, the state Department of Transportation) may establish lower speed limits as allowed by statute.

Speed limits must be set in multiples of 5 mph – see WAC 468-95-045.

Legal Citations

Below are selected state statutes and regulations pertaining to speed limits and traffic calming. The rest of this page provides more detail about these requirements. The city and county statutes are also adopted by reference as part of the state Model Traffic Ordinance (see WAC 308-330-423).



Speed Limit Changes

RCW 46.61.415 authorizes local authorities to lower the speed limit at intersections, increase the speed limit up to 60 mph, or reduce the speed limit as low as 20 mph. RCW 46.61.405 -.410 provides similar authority for the state Department of Transportation on state highways.

To change a speed limit, the city or county must determine on the basis of an "engineering and traffic investigation" that the maximum speed permitted is greater than or less than is reasonable or safe under the conditions.

However, cities and towns (not counties) may reduce speed limits on nonarterial highways within a residence district or business district without an engineering and traffic investigation, if the city has developed procedures regarding establishing the maximum speed limit in such areas. In such cases, the city or town may also cancel the new speed limit and reestablish the old speed limit within one year without an engineering and traffic investigation.

The term "engineering and traffic investigation" is not defined by statute, but some examples are provided later on this page. According to the bill report for HB 1045 (2013), which established the exception for city residence and business districts:

Generally, [an engineering and traffic] investigation will consider factors such as the speed of the 85th percentile of drivers on the road, road characteristics, parking practices, pedestrian activity, roadside development and environment, a history of crashes, and other factors.

Maximum speed limits may be uniform for all vehicles and times of day, but they may also be varied for different times of day, types of vehicles, weather conditions, or other factors affecting safe speeds (RCW 46.61.415(5)).

New speed limits become effective when the appropriate signage is posted, but any changes to speed limits on a state highway within incorporated cities or towns must first be approved by the state secretary of transportation. No public hearing is required, although one might be politically advisable.

Practice Tip: We have been asked repeatedly whether changes to the speed limit must be adopted by the legislative body (such as the city council or county commission), or whether such decisions can be made administratively (for instance, delegated to the city or county engineer).

Our interpretation is that this authority cannot be delegated. This is because RCW 46.61.415 states that the "local authority" may determine and establish speed limits, and RCW 46.04.280 states that "local authorities includes every county, municipal, or other local public board or body having authority to adopt local police regulations under the Constitution and laws of this state."

As a result, we think the traffic engineer should perform the analysis and issue a recommendation, but that the final action should be taken by the legislative body through ordinance or resolution, as appropriate.

School Zones and Playgrounds

RCW 46.61.440 establishes a maximum speed limit of 20 mph (unless otherwise provided) within 300 feet of any marked school or playground crosswalk, when the crosswalk is fully posted with standard school or playground speed limit signs.

In addition, the same statute authorizes cities, towns, and counties to create a school speed zone or playground speed zone on a road bordering a marked school or playground, in which speeds may not exceed 20 mph. The speed zone may extend up to 300 feet from the border of the school or playground property, but it may only include areas consistent with active school or playground use.

Some jurisdictions have established school zones based on time of day (for instance, 7 AM-4 PM on days when school is in session), while others have installed "when flashing" school zone beacon signs that are activated around the start and end of the school day. Other jurisdictions have opted to use "when children are present" school zone signage. Because "when children are present" is more nebulous (see WAC 468-05-335 for a definition) and can potentially create some confusion, some jurisdictions have begun switching to flashing beacons instead.

To enforce school zone speed limits, local jurisdictions are authorized to install school zone speed cameras under RCW 46.63.170. For more information, see our page Automated Traffic Enforcement Cameras.

Effects of Roadway Design

Changing the speed limit alone or adding additional signage is unlikely to have a significant impact on observed speeds. Roadway design and the surrounding environment also play a very significant role, and drivers often ignore or disregard the posted speed limit signs and drive according to the "feel" of the road.

As Bellevue's Residential Traffic Guidebook states on page 60:

Engineering studies show that speed limit signs are not the most significant factor influencing driver speeds. Research indicates that a reasonable and prudent driver will drive the speed suggested by roadway and traffic conditions, to the extent of disregarding the posted speed limit. A speed limit that is unrealistic invites the majority of drivers to disregard posted speeds.


Lowering the posted speed limit does not significantly lower traffic speed and can lead to unreasonable ticketing for acceptable driving behavior.

Similarly, extra stop signs or "children at play" signs are generally considered to be ineffective at reducing speeds and can create a false sense of security.

However, radar signs that display the speeds of passing motorists have been shown to be more effective at reducing speeds. These radar signs can either be mobile and temporary or stationary and permanent. See a 2009 Bellevue report on the subject.

Design factors that influence observed speeds include, but are not limited to: the number of lanes, lane widths and curve radiuses, pedestrian bulb-outs or islands, on-street parking, two-way traffic versus one-way traffic, speed humps and speed bumps, landscaping, the surrounding environment, and other elements.

For more information on design elements, see the Recommended Resources section below, as well as the examples of local traffic calming programs.

Examples of Local Speed Limit Provisions

Below are selected examples of local speed limit and school zone provisions in Washington State.

Engineering and Traffic Investigation Reports

  • Jefferson County Resolution No. 59-18 (2018) – Reducing the speed limit on a residential county road from 35 mph to 25 mph; includes engineering and traffic investigation report
  • Lewis County Resolution No. 14-64 (2014) – Setting date for (optional) public hearing for reducing speed limit on a county road from 50 mph to 40 mph; includes engineering and traffic investigation report
  • Seattle Ordinance No. 125169 (2016) – Lowering citywide speed limits to 20 mph for non-arterials and 25 mph for arterials unless otherwise provided; includes FAQs and engineering and traffic investigation report.

General City/Town Provisions

General County Provisions

Examples of Local Traffic Calming Programs

Below are selected examples of city and county traffic calming programs and resources in Washington State.



Recommended Resources

Last Modified: February 01, 2023