Speed Limit Assessment Projects

Want to request a speed limit or speed zone change?

Call the 24/7 Road Helpline at 206-477-8100 or email maint.roads@kingcounty.gov. 

Program overview

Reducing speed limits can make roads safer for everyone. When vehicles go slower, drivers have more time to react to sudden changes, like a child running into the street or another car stopping quickly. Slower speeds also reduce the force of crashes, which means fewer serious injuries. It helps pedestrians and cyclists feel safer too, encouraging more people to walk or bike. By lowering the speed limit, we create safer and more pleasant neighborhoods for everyone.

Community involvement

For each speed limit reduction proposal, Road Services opens a 14-day public comment period. We use the comments provided to help our decision making and better understand how a reduction may impact the community and the people who use the road. This is not a simple yes or no vote. Sometimes community members make alternative suggestions that are very useful and can be incorporated into road improvements. 

Safety benefits of speed limit reduction 

Reducing the posted speed limit has many safety benefits. Here are some key advantages: 

• Reduced traffic collisions and severity: Slower speeds provide drivers with more time to react to potential hazards, reducing the likelihood of collisions. 
• Improved pedestrian safety: Gives drivers more time to notice and react to pedestrians at crosswalks or along the road. Reduced speeds can also decrease the severity of injuries in case of accidents involving pedestrians. 
• Shorter stopping distances: Slower speeds mean shorter stopping distances. This can be critical in situations where a driver needs to stop suddenly, such as when a vehicle ahead brakes unexpectedly or when approaching an intersection. 
• Less severe crashes: Lower speeds often result in less severe crashes. This can lead to fewer fatalities and reduced injury severity among occupants of vehicles involved in accidents. 
• Encourages walking, biking (active transportation): Lower speed limits can make roads more comfortable for pedestrians and cyclists. This can have positive effects on public health and reduce traffic congestion. 

What is the process for getting a speed limit reduced in my community?

The process to consider a speed limit reduction on a road in unincorporated King County has several steps:

1. Concern is identified: A concern about the speed limit on a road can be brought from a community member or internal member of the Road Services team.
2. Data collection and review: The Road Services staff visit the area and use tools to count vehicles and measure speeds. We also look at the road itself to better understand how it is used and if the speed limit is appropriate for the real-world conditions. This part of the process often takes six to eight weeks. Next, the county reviews the data and determines if a speed reduction proposal is warranted. 
3. Outreach period: If the speed limit outreach period is approved, then we share the proposal with the community and conduct a 14-day public comment period. Community members are welcome to share their comments via online form or send a letter in the mail. The comments are tabulated and summarized.  It is important to note that comments received do help us better understand the community’s perspective, however comments are not counted as votes.
4. Review comments: The team meets and discusses the results and reviews comments.
5. Decision on speed limit proposal is made: Once a decision is made, we will post it on this website and send an email to those who shared their email address on the feedback form. 
6. If approved, new speed limit signs are installed: If approved, a work order to change signs is submitted. It usually takes 4-6 weeks for the new signs to be installed once the order is put in.  

What is King County’s procedure for evaluating speed limits?

King County uses rules from Washington State and a federal guide to decide speed limits.

In 2018, a new rule allowed the Director of Local Services to change speed limits by up to 10 mph based on certain factors including:

• Road conditions and visibility
• How fast most people drive
• Nearby buildings and activities
• Safe speeds for curves and tricky spots
• Parking and pedestrian activity
• Recent accident history

If a short piece of road (less than 1 mile) has a different speed limit than the roads around it, the County can change the speed limit by up to 5 mph without a detailed review. This often happens when a city takes over part of a road and changes the speed limit, leaving a small part with a different limit.

For other changes, the County first looks at the road and then asks for public comments for two-weeks. These comments are reviewed by the County Traffic Engineer and County Road Engineer. They then recommend the change to the Director of Local Services, who sends it to the King County Council to make it official. 

2024 Speed Assessment Projects 

East of Maple Valley

Road Services proposes to reduce the speed limit on 276th Avenue SE, north of Landsburg, WA. The existing speed limit is 50 mph, and we propose extending a 0.4 mile stretch of road to 40 mph until SE 236th St. 276th Ave SE is a busy arterial and more than 8,300 vehicles drive on this road every day. This road has steep hills that you can’t see over, and drivers don’t see stopped vehicles and school buses until it is too late. 

Lowering the speed limit here allows motorists enough time to slow down and stop on this hilly section. This could help prevent collisions in the future. From 2019 to 2024, there were 13 collisions within the study area. These included two head-on, seven single vehicle, two left turn, and two rear end crashes.

• Location: 140th Avenue SE between Renton city limits and SE 192nd Street.  
  • Proposed: reduce speed limit from 40 mph to 35 mph
  • Result and action: The County is reducing the speed limit from 40 mph to 35 mph on 140th Ave SE, from SE 192 St. to the Renton City Limits. Approximately 25 percent of the public comments received supported the lower speed limit, however more than half felt lowering the speed limit would not do enough to calm traffic. In addition to lowering the speed limit, the county will make additional traffic calming improvements later in fall 2024. A full list of these improvements can be found on the Traffic Safety in Fairwood website. Highlights include installing pylons in the center turn lane along 140th Ave SE to prevent drivers from using the center lane to pass slower traffic in the main travel lanes, adding additional speed radar, and new speed limit signs.

Near Black Diamond

• Location: SE Lake Holm Road between SE Lake Moneysmith Road and SE Black Diamond Road
  • Proposed: reduce speed limit from 40 mph to 35 mph
  • Result and action: public comment was open from July 23rd to August 6th. Road Services is evaluating public comment feedback and will decide about the proposed speed limit reduction this fall. Any change will be shared on this website and will also be emailed to those who shared their email address on the feedback form.

Vashon Island

• Location 1: Vashon Highway SW between SW 182nd St and SW Cemetery Road
  • Proposed: reduce speed limit from 40 mph to 35 mph
  • Result and action: Following public comment, the speed limit was reduced to 35 mph. The new speed limit signs were installed in August 2024.
• Location 2: Vashon Highway SW between SW 127th St and SW 153rd St
  • Proposed: reduce speed limit from 50 mph to 45 mph
  • Result and action: Following public comment, the speed limit was reduced to 45 mph. The new speed limit signs were installed in August 2024.

2022 Speed Assessment Projects

Vashon Island 

• Location 1: Vashon Highway SW between Burma Road SW and SW 127th
  • Proposed: reduce speed limit from 50 mph to 35 mph at this location
  • Result and action: Following public comment, the speed limit was reduced to 35 mph. The new speed limit signs were installed in early 2023.
• Location 2: 91st Avenue SW between SW 167the Street and SW Dilworth Road
  • Proposed: reduce speed limit from 35 mph to 25 mph at this location
  • Result and action: following public comment, the speed limit was reduced to 25 mph. The new speed limit signs were installed in early 2023.
• Location 3: SW Bank St from 96th Place SW to 95th Lane SW
  • Proposed: reduce speed limit from 35 mph to 25 mph
  • Result and action: following public comment, the speed limit was reduced to 25 mph. The new speed limit signs were installed in early 2023.

White Center

• Location 1: Myers Way S/1st Ave S between S 99th St to S 116th St 
  • Proposed: reduce speed limit from 40 mph to 35 mph 
  • Result and action: following public comment, the speed limit was reduced to 35 mph. The new speed limit signs were installed on Myers Way S in October 2022. 

2021 Speed Assessment Projects

In 2021, Road Services proposed speed limits in two locations on Vashon Island: 

• Location 1: Vashon Highway SW, just south of SW Burton Drive to midway along the waterfront northeast of 115th Avenue SW.
  • Proposed: Reduce speed limit from 45 mph to 25 mph.
    King County proposed to lower the speed limit from 45 mph to 25 mph at this location.
  • Result and action: Speed limit was reduced to 35 mph.
    Based on a second review of the area and public comment, King County will NOT lower the speed limit to 25 mph.
• Location 2: Vashon Highway SW between 115th Avenue SW and Inspiration Point
  • Proposed: Reduce speed limit from 45 mph to 35 mph.
    King County proposed to lower the speed limit from 45 mph to 35 mph in this location. This area has limited sight distance and sub-standard shoulders.
  • Result and action: Speed limit has been reduced to 35 mph.
    The lower speed limit will be safer for pedestrians and bicyclists. The new speed limit signs were installed on Vashon Highway SW in late June 2021.