The in basket: Merry McAllister of Valley Road on Bainbridge Island has renewed her campaign to make the road safer for pedestrians with a proposal for speed bumps. She learned via a previous Road Warrior column in November that there’s no likelihood of the road’s narrow to non-existent shoulders being widened for six years or longer.
“Could we get two or three LOW profile speed bumps on Valley, especially going downhill?” she asked in a new e-mail. “One could be at Parkhill, one at Kallgren, and another at Hyla. Any of these would be appreciated. Maybe just start with one at Hyla, so folks get used to it and don’t start aeroplaning going down the hill.
“A sign saying ‘speed bump ahead’ always gets some attention, too,” she said. “Shouldn’t be too expensive.”
The out basket: I told Merry that most jurisdictions won’t approve speed bumps for arterials, and Valley looks like it would fall within that prohibition. But I asked the city about the idea.
K. Chris Hammer, the city’s engineering manager, replied, “Valley Road is classified as a secondary arterial street. (It) is traveled by nearly 3,000 vehicles each day, serving the Rolling Bay Town Center and connecting to many neighborhoods.
“The city has not placed speed bumps on secondary arterials and collector streets,” he said. “There are reasons for this. The primary one is that speed bumps themselves can present a hazard to the traveling public. Another issue is that emergency responders may have a good reason to travel at or higher than the posted speed limit. Maintaining response times to under 5 minutes for paramedics can be the difference between life and death and the severity of a fire can double every two minutes. Ambulances transporting the injured/ critically ill must slow to a crawl over speed bumps.”
Valley Road comes closer than many others to meeting a key measure of how appropriate the posted speed limit is, the so-called 85th percentile, according to the most recent speed study there.
“Designers must consider what speeds most drivers are comfortable driving on a segment of roadway and design the roadway to safely accommodate that speed,” Chris said. “This speed is known as the 85% speed (15% traveling faster, 85% at or lower) which in this location is 35mph, coincidentally the same as the posted speed.”
The 85th percentile is often slightly higher than the posted speed on other roads and highways.
“The city is looking to scoping a speed limit study of its 35mph streets and both Valley and Sunrise (the cross street in Rolling Bay) may be good candidates,” he said. “In 2013 we studied the 40-mph-posted speed streets and the speed zones approaching the Island’s town centers. One result was extending the speed controlled zone (lower speed) for the Rolling Bay Town Center further north on Sunrise.”