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Monday, April 26, 2010
ACHD to turn on new traffic signal timing plans

Drivers on two major travel corridors, State Street and Federal Way, will benefit from new signal timing plans that will be put in place by the Ada County Highway District (ACHD) prior to the morning commute on Tuesday April 27, 2010. 

On State Street improved signal timing will better synchronize 14 signalized intersections between 23rd Street and Saxton Drive, which is just west of the Glenwood and State intersection.  The change was made because the existing timing plan on State was more than a decade old.  While ACHD has made adjustments over the years, a large-scale upgrade was needed because of growth and increased traffic through this corridor, which is one of the busiest in the county with as many as 39,000 vehicles each day. ”During the AM commute, it takes drivers up to 12 minutes to travel through this section of State Street," said ACHD Traffic Operations Engineer Mike Boydstun.  "During the evening commute, it can take up to 15 minutes.  After the improved synchronization is in place, that time is expected to be reduced for the majority of drivers." 

Traffic counts provided the information needed to adjust the green times on the traffic signals so each intersection will work better with nearby intersections.  The coordination helps improve traffic flow and minimizes delays for most drivers because there will be less stopping at red traffic signals on State Street, and when there are stops, the waits should be shorter.

The improvements on Federal Way will impact 12 signalized intersections between the Kootenai/Protest/Federal Way intersection and the Tolpmis/Federal Way intersection just south of Gowen Road. In addition, new signal synchronization on Gowen will also be done at the Eisenman Road intersection and the eastbound Interstate 84 off-ramp.

This week, ACHD staff will be at all three locations doing fine-tuning of the new traffic signal timing plans. 

Past Major Signal Coordination Projects and Benefits

ACHD puts coordination plans in place where they will help improve traffic flow, generally where there are overwhelming concentrations of traffic moving in the same direction or if the signals are closely spaced.  Half of the traffic signals in Ada County are coordinated.  Other large-scale timing plans done by ACHD were in downtown Meridian and in downtown Boise.  A signal retiming done in 2006 reduced travel time by up to 36% and saves more than 114,000 gallons of fuel each year.  Another retiming project in downtown Boise in 2005 resulted in up to a 12% reduction in travel time and over 250,000 gallons of fuel saved per year.  ACHD hired DKS Associates to work on the downtown projects as well as the improvements on State Street, Federal Way and Gowen. ACHD hopes to see similar benefits thanks to the latest improvements. Future efforts include the planned coordination of traffic signals on ParkCenter Boulevard in Boise.

As part of its duties as a county-wide highway district, ACHD manages all of the traffic signals within Ada County, including all signals at freeway on/off ramps and roads under the jurisdiction of the Idaho Transportation Department.  For more information visit www.achdidaho.org.

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