There’s been a lot of back-and-forth in recent weeks about rumble strips and their potential to keep drivers safe. Some say they help. Others don’t. Many have wondered about the statistics King County engineers used to inform the Vashon project.

A new page on the county’s transportation department’s website answers some of these questions. (Google “King County rumble strips” and you’ll find the FAQ about Vashon’s project.) Indeed, to read it is to get a window into the department’s rationale.

According to the county, there were 92 accidents between 2003 and 2008 that involved a car veering out of its lane — two instances where a driver crossed the center lane and 90 times when a car ran off the road. In 42 of those instances, there was an injury; once, according to the county, someone was killed.

The county then examined the factors that contributed to each accident: 39 percent of the time excessive speed played a role; 11 percent of the time a driver was attempting to avoid an animal or another object; 14 percent of the time drugs or alcohol were involved; and another 14 percent of the time the driver was drowsy, inattentive or distracted.

Rumble strips might have helped in about half of the instances, the county maintains. Indeed, it was this analysis that made Vashon one of the county’s six “high-risk rural roads.”

But those statistics don’t tell the whole story. The reason is that they only took into account motorized vehicles. Cyclists weren’t part of the equation.

Last week, a cyclist named Dan Brenner came into The Beachcomber’s office to tell his story. He was near the Episcopal church, riding south on the highway with his girlfriend’s 8-year-old daughter on a bike behind him. They were headed to a softball game at McMurray Middle School. He glanced behind him to see if a car was coming — and, as is so often the case, his bike veered slightly in the direction of his turning head.

The next thing he knew, he hit the milled pavement, lost control and landed in the traffic lane. Fortunately, no cars were coming, but he still got hurt. When he stopped by our office on Friday, he had a bandage on his chin, covering the eight stitches he needed from the fall.

One bad fall doesn’t counter the weight of the county’s five years’ worth of numbers. But it does raise important questions: What is the impact of these strips on cyclists? And in light of how vulnerable a cyclist is, do the risks cyclists face outweigh the potential protection they provide a driver?

Children ride bikes on Vashon Island. A growing number of Islanders are cycling — some of whom are inexperienced. What kind of safety are we providing them?

The county has some compelling stats, numbers that led them to believe rumble strips made sense. But as is so often the case, the answer one gets depends on the questions one asks. And in this instance, the county failed to ask some critical questions.

If they’re going to convince an increasingly dubious Island population of the rightness of their position, county engineers are going to need to do some more research. The picture, at this point, seems incomplete.