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Nov
30

S 360th Street at Military Road S Roundabout Project

Project scheduled for construction in 2025

Southbound Military Road S.

Heavy, fast-moving traffic on southbound Military Road S leaves few gaps to safely enter the two-lane road the intersection from S 360th Street.

We will improve safety and traffic flow at this intersection with a single-lane roundabout. The project is scheduled for construction in 2025.

Status update

August 4, 2023

This project was initially scheduled for construction in summer 2024, however it has been postponed to summer 2025.

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Project overview

King County will build a single-lane roundabout at the intersection of Military Road S and S 360th Street, in the Lakeland South neighborhood. Roundabouts are proven to reduce collisions, calm traffic and prevent long wait times. With traffic continuing to grow in the area, especially on Military Road S, a roundabout at this intersection will keep motorized and non-motorized vehicles moving smoothly for the next 20 years.

This project also includes wider shoulders, sidewalks, accessible curb ramps and crosswalks.

Why is a roundabout needed at this intersection?

Military Road S is a heavily traveled main road with no signals or stop signs for four miles. As more people move to the region, this road and others, including S 360th Street, have seen a significant increase in traffic. More traffic at busy intersections brings longer wait times and a higher rate of crashes.

  • Drivers on S 360th Street that need to cross or turn onto Military Road S must wait a long time for a gap in traffic.
  • Most of the reported collisions at this intersection are a result of vehicles colliding into oncoming traffic while attempting to turn or cross Military Road S.

A roundabout at this location will calm speeding traffic in this growing neighborhood and make it easier for vehicles to turn on and off Military Road S.

Vicinity map

S 360th vicinity map.

Larger view, PDF 217KB

Local map

S 360th St. map of the local area.

Larger view, PDF 323KB

Timeline

  • Environmental review: Ongoing
  • Construction begins: Summer 2025
  • Construction complete: Fall 2025

Project budget

The estimated total project budget is $4.6 million. This project is funded through federal and local county funds.

Project documents

Frequently asked questions

King County chose a roundabout because it is the safest, most cost-effective solution for this intersection. A roundabout will slow but not stop the heavy traffic on Military Road S. It also will allow slower traffic from S 360th Street to enter the intersection safely and efficiently.
County traffic engineers looked at several alternative traffic-calming options. Both a traffic light and four-way-stop would require drivers to come to a complete stop at the intersection. On Military Road S, a full stop could increase high-speed rear-end collisions. A roundabout that slows but does not stop traffic is the safest and most cost-effective choice for this growing region of King County.
King County looked at seven alternatives.
  • Make no change
  • Add left-turn lanes to Military Road S and S 360th Street in both directions
  • Install a traffic light and make no other changes to the intersection
  • Install a traffic light and add left-turn lanes just to Military Road S
  • Install a traffic light and add left-turn lanes to both roads
  • Build a single-lane roundabout
  • Build a two-lane roundabout
Yes, we are actively working with local property owners to access the space needed to build the roundabout.
Most buses and trucks can get through a single lane roundabout. King County and the Washington State Department of Transportation have designed and built dozens of roundabouts throughout the state so truck and bus drivers can safely use them.
Construction begins in 2025. Between now and 2025, King County will connect with residents, community members, schools, and other community partners to share information about all aspects of the project.
Construction will likely take place during the summer months when there is less traffic. It will be noisy and disruptive for drivers. To manage the noise, we will work only during the day. To reduce the impact on traffic, we will work in the middle of the day and on Saturdays.

Photos

S 360th Street looking west. This busy road to and from Interstate 5 passes two schools, a Buddhist temple, and several neighborhoods.



Military Road S looking south. This car is turning onto westbound S 360th Street. A stoplight here could lead to rear-end collisions on this busy arterial. Instead, a roundabout smooths and calms traffic so cars like this can safely turn and not worry about southbound traffic.



S 360th Street looking toward northbound Military Road S. This is a tricky intersection because Military Road S curves just to the south and S 360th Street comes in at an angle.



A half-mile to the south is Five Mile Park, a popular park with a playground, lake, and picnic tables. During the summer, Military Road S is extra busy with visitors who come and go to this park.

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