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Can ‘Michigan Lefts’ solve Federal Way's traffic pains?
The Federal Way City Council has approved the use of median U-turns as a tool to keep signaled intersections safe and friendly for future drivers and pedestrians.
Senior traffic engineer Rick Perez presented a bleak traffic analysis to the city council March 2. If preventative measures are not taken, by the year 2035, 42 of Federal Way's intersections are predicted to be operating at or over capacity, Perez said. This takes into consideration the presence of link light rail in the city and the completion of the Interstate 5/State Route 18 interchange, known as the Triangle project. Traffic at busy intersections could back up for a half mile during peak hours, he said.
Median U-turns, also known as "Michigan Lefts" or indirect lefts, could address the problem. A pilot project will likely be tested before any decision to adopt the design citywide.
The introduction of the Michigan Left was the result of a traffic analysis that came at the request of the city council. The council is concerned with the impact of Federal Way's several multiple-lane intersections on pedestrians, drivers and the environment. In the future and where appropriate, city officials wish to avoid adding more traffic lanes at established intersections. However, the city also wants to keep traffic flowing safely and at a reasonable speed.
Creative traffic tool
With the council’s goals in mind, city staff recommended the use of Michigan Lefts. They are not common practice in road design, but they are expected to accommodate Federal Way's future levels of traffic. As implied by the name, the design was first used in Michigan. Federal Way could be the first Washington city to adopt the design.
“It probably would be a little trend setting to try them here," senior traffic engineer Maryanne Zukowski said.
Here's how a Michigan Left works. Instead of adding a standard left-turn lane at an intersection, a Michigan Left is installed approximately 600 feet up-road of where a driver wants to turn, Perez said. A standard left-turn lane requires road widening at an intersection. However, Michigan Lefts avoid the additional lane by instead using part of the median as a U-turn lane, he said.
Take this example at one of the city’s busiest intersections. Drivers traveling east on South 320th Street and wishing to turn left at First Avenue South will pass straight through the intersection where they would otherwise have turned left. They will then use the Michigan Left to traverse the median and switch directions of travel. Now traveling west on South 320th, drivers will need to get in the right-most lane to turn right onto First Avenue South.
Some Michigan Lefts constructed in Federal Way could require signalization to allow drivers exiting the U-turn to flow safely into traffic traveling the opposite direction, Perez said. The signalization would help drivers safely cross several lanes to prepare to turn right, Zukowski said.
Level of Service
Michigan Lefts will take some getting used to, but will permit the city to maintain its current Level of Service (LOS). LOS is defined as a quantifiable means of grading the experience of an individual using the city's transportation system. Transportation systems are graded "A" through "F." On urban streets, LOS predominantly takes into consideration delays and the volume of traffic compared to the capacity the street is able to handle. The city council set Federal Way's LOS at a grade of "E." The volume to capacity ratio is 1.00.
This means the city's intersections must operate within capacity. It also means signalized intersections are evaluated using a 120-second, or less, cycle length, according to a memorandum from Perez to the city council. This is equivalent to an 80 second, or less, delay per vehicle, according to the memo.
Roundabouts were another top contender, but the Michigan Left design rose to the top. A roundabout would require the city to purchase surrounding properties at some of the intersections, Zukowski said.
To test the effectiveness of Michigan Lefts in Federal Way, staff plans to recommend a pilot project, Perez said. The intersection of 21st Avenue Southwest and Southwest Campus Drive/South 336th Street is a good candidate, he said. Drivers will need to be eased into the new road design, Zukowski said.
"People don't like change," she said.
A Michigan Left at this intersection is estimated to cost the city $3.8 million in 2010 figures, opposed to the $4.2 million it would cost add a double left-turn lane at the intersection, Zukowski said. There are no estimates for when the pilot project may be launched.
Check it out
To view a simulation of traffic flow in a Michigan Left set-up, visit click here or visit www.bqaz.org/parkways_popUp-1.html.