Traffic light cycle deceiving

John Ray of Marysville writes: Can something be done about the sensitivity of the traffic light from westbound 88th Street NE to southbound I-5 in Marysville?

In the morning, the left turn lanes are packed with cars waiting to get on southbound I-5, but the light stays red for no apparent reason. The signal for Quil Ceda Village goes through several cycles for maybe one or two cars while traffic continues to back-up in the turn lanes to I-5. It also seems that the light will not change until there is traffic waiting to turn left from the off-ramp from southbound I-5, and that traffic goes first before the light turns green for the southbound ramp to I-5.

It appears that the lights are synchronized to account for heavy traffic from the shopping center, but in the mornings the heavy traffic is westbound on 88th trying to get on I-5. In the morning the lights don’t need to be synchronized and should be more sensitive to changing on their own when traffic is present. It’s really frustrating to have to sit in the left turn lanes and watch traffic continue to back-up on 88th street while the non-existent traffic from the shopping center continues to have green lights.

Bronlea Mishler, spokeswoman for the state Department of Transportation, responds: We had our engineers take a look at the signal at 88th and I-5 to make sure it’s working properly. They found that the lights and the loops that detect waiting cars are working the way they’re supposed to. However, because the traffic signals go through different cycles in the morning than they do in the afternoon, this can give drivers the impression that the lights aren’t working properly. While the intervals between turn cycles may be long, the system actually results in more turn time for those entering southbound I-5.

As John noticed, the traffic signals at the southbound on- and off-ramps are coordinated between 6 and 9:30 a.m., however they operate with a different sequence than he might be accustomed to.

In the mornings, the left-turn signal from 88th to southbound I-5 is “lagged.” That means rather than serving traffic turning from 88th to southbound I-5 first, then serving through traffic on 88th, the signal clears the through traffic on 88th first, then gives the green light to drivers turning left.

This flip-flop can make it seem that through traffic is getting priority over turning traffic, but it actually allows turning traffic more green time.

Here’s how: Each signal is allotted a maximum amount of “green” time – the time the light stays green. For example, the left-turn lane to southbound I-5 is allowed 35 seconds of green time each cycle in the morning. But if through-traffic on 88th is light, that signal may not use all the green time it’s allotted, and that extra time is then reallocated to traffic turning left onto southbound I-5. In the mornings, traffic turning left typically ends up with an average of 50 seconds of green time – an extra 15 seconds. So even though drivers turning left may have to wait for through-traffic on 88th, if that traffic is light, they’ll actually benefit by having more time to turn.

Lizette Sismaet of Lynnwood writes; My daughter attends the new Lynnwood High School on North Road. There are only two ways to get to the school and that’s from 164th Street SW or Filbert Road.

I frequently drive her to and from school for practices, and wanted to alert road officials to the danger of the intersection of Larch Way and Filbert Road.

While driving eastbound on Filbert Road, I frequently see drivers dangerously make the left turn (eastbound) from Larch Way onto Filbert Road, narrowly missing cars heading both directions on Filbert Road.

I believe because of the new high school just a few blocks away, many of these drivers are inexperienced high school kids.

A possible solution is a traffic light. Something has to be done soon before someone gets hurt or worse.

Bronlea Mishler of the transportation department responds

We share your concerns about safety at this intersection. While we’ve explored several options for improving the intersection, there’s very little we can do in the way of low-cost safety improvements. The road is too narrow to allow us to re-stripe and add a turn pocket, and widening the highway to accommodate improvements would be a sizeable undertaking because it would negatively affect nearby drainage and wetlands. A project to build turn pockets and add a signal at the intersection of Larch Way was included as part of Proposition 1 on the November 2007 ballot, but the measure didn’t pass. While we don’t have funding for a project, we continue to monitor the intersection and pursue additional funding sources so we can improve safety.

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