May Valley Road rumble strips — they’re coming back

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May Valley Road is one of my favorite rides in King County. It links the populated Newcastle suburbs with routes to Issaquah and Hobart via a rural road that’s reminiscent of country byways I used to ride back East.

Rumble strips temporarily covered

Rumble strips temporarily covered

That’s why I rejoiced when I discovered recently that the rumble strips that had been milled into the two-lane road last year had been covered with narrow strips of asphalt.

I called the county road department to find out why they rumble strips had been removed. Was the county abandoning the rumble strip program after the controversy on Vashon Island?


Speaking with safety management engineer Henry Perrin, I learned that the rumble-strip cover-up is a temporary situation and that new rumble strips will be milled into the same locations as soon as the road is resurfaced this fall. Apparently the asphalt in a repaving job doesn’t properly adhere to rumble-strips.

Rumble strips in 2012

Rumble strips in 2012

The rumble strips were first installed in the spring of 2012. One runs down the center of  May Valley Road between Renton-Issaquah Road (State Route 900) and Hobart-Issaquah Road. In addition, rumble strips were milled onto a 1.2-mile stretch of shoulder between Southeast 135th Street Southeast (roughly the entrance to Squak Mountain State Park ) and the bridge over Issaquah Creek.

Those rumble strips on the shoulder are the ones that can cause problems for bicyclists. They either force cyclists to ride way to the right of the shoulder, where road debris accumulates, or ride to the left of the white fog lane in the traffic lane.

An even more dicey situation occurs on a downhill portion of May Valley Road as bicyclists pick up speed and can hit the rumble strips.

Map created by Paul Byrnes. See full route.

Take another look

Perrin said he’d take another look at the shoulder rumble strips on the downhill section. There are lots of criteria regarding where rumble strips can and cannot be located due to bicycle traffic, and “downhill grade” is one of those limiting issues.

Specifically, the design practices dictate that “shoulder rumble strips should not be installed on downgrades exceeding four percent for more than 500 feet.”

Perrin said that because of the amount of bike traffic on May Valley Road, crews are going to install warnings about the shoulder rumble strips. Signs either will be posted at the beginning of the rumble strip section, or white markings will be painted inside the first grooves.

The county has adopted guidelines regarding rumble strip practices that “apply to roadways with frequent bicycle usage, defined as at least 15 cyclists per hour during any measured period:

  1. Warning signs will be installed at the start and end of shoulder rumble strip sections.
  2. Transverse thermoplastic markings will be used to delineate rumble strips at 200-foot intervals.
  3. Discontinuing centerline rumble strips will be considered at locations with less than 14 feet between the centerline and edge of pavement.”

Clarifying the downhill rumble strips, the King County guidelines say:

The WSDOT Design Manual indicates that shoulder rumble strips should not be installed where downhill grades exceed 4 percent for more than 500 feet. According to the WSDOT design office, the purpose of this guideline is to avoid situations where cyclists travel downhill at a high rate of speed beside shoulder rumble strips. According to WSDOT, shoulder rumble strips can be present on the right side of a road heading uphill.

The installation of rumble strips on May Valley Road is part of King County’s High Risk Rural Road Program. In addition of May Valley Road, rural roads chosen for the program include Preston-Fall City Road Southeast, Southeast 400th Street, Southeast North Bend Way, Southeast Petrovitsky Road and Vashon Highway Southwest.

King County back-pedaled on extensive rumble strips on Vashon Highway in 2012 after opposition from local bicyclists. A group actually showed up in front of the road crew one morning to stop them from proceeding.

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