Drivers on I-5 through South King County are already seeing the benefit of this where 8 new ramp meters were installed and activated along with 3 existing ones at nearby locations.
A ramp meters is an on-ramp traffic light that spaces vehicles entering the roadway at a more uniformed and even pace that reflects the real-time travel conditions. This invaluable traffic management tool has proven to decrease highway travel times and reduce collisions.
Before this project began, travel speeds on I-5 in South King County had steadily dropped over the years, with average speeds for the morning commute north bound averaging 37 mph, and 40 mph during the evening for southbound drivers.
Ramp meters for this project at the following locations were activated on July, 29:
- South 188th Street to northbound I-5
- South 188th Street to southbound I-5
- South 200th Street to southbound I-5
- State Route 516 westbound to northbound I-5
- SR 516 eastbound to northbound I-5
- SR 516 to southbound I-5
- South 272nd Street to northbound I-5
- South 272nd Street to southbound I-5
Additional meters installed under previous contracts were also activated at that time:
- South 320th Street eastbound to northbound I-5
- South 320th Street westbound to northbound I-5
- South 320th Street to southbound I-5
All ramp meters are monitored by Traffic Management Center engineering staff to ensure optimal use.
Drivers will most likely see the ramp meters active between 6 and 8 a.m. for northbound traffic and 3:30 to 5:30 p.m. for southbound traffic.
In addition to the ramp meter installations, the northbound and southbound single-lane on-ramps at South 188th Street were revised to double-lane ramps. Traffic sensors were installed on both the ramps and freeway lanes to enable real-time monitoring of the metering operation and automatic adjustments to reflect current conditions. Warning lights, and additional signing were installed along with new lane striping as part of the overall ramp metering system.
Studies have shown that ramp meters can reduce collisions system-wide by as much as 30%.
Ramp meters are a proven and cost-effective method of reducing congestion by allowing cars to enter a highway in controlled intervals, decreasing disruption to traffic on the freeway.
Partnerships & Cooperation
In 2009, the Washington State Legislature identified ramp meters as congestion-relief project for this area and authorized project funding.
Funding for this $1,435,000 project came from pre-existing funds allocated by the Legislature.
WSDOT Traffic Engineer
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