You know those symbols showing up on the edges of streets around Seattle -- the ones that look like a small bicycle wearing an oversized pointy hat?

That's a sharrow, and it's not a license to drive in the middle of the street, run down cyclists who aren't riding over the marks, or otherwise cause mayhem on the city's roadways.

Sharrows are a friendly reminder from the Seattle Department of Transportation to drivers: Leave room for those who choose to pedal their way around town.

The symbol, a bicycle underneath a chevron sign, doesn't alter the rules of the road, city transportation spokesman Gregg Hirakawa said.

"The duties and obligations of cyclists and motorists do not change whether there is a sharrow present," he said in an e-mail.

But city officials are anticipating that the behavior of motorists and cyclists will change -- it is hoped for the better.

About 20 streets will be branded with sharrows by the year's end -- part of the city's Bicycle Master Plan. The marks, made from a synthetic thermal material, have already been burned onto a handful of streets, including Stone Way North, 19th Avenue East and Beach Drive Southwest.

Sharrows should also show up soon on Yesler Way, Magnolia Boulevard West and Western Avenue.

"The jury is out on sharrows," said David Hiller, advocacy director for the Cascade Bicycle Club. He's waiting to see if they'll work on Seattle's hilly terrain.

Sharrows have made a relatively uncontroversial debut in Seattle, though the circumstances around the installment of some have more than made up for it.

When city officials decided to install bike lanes on the northern part of Stone Way North but opted for sharrows on the southern part, bike activists organized a protest rally-ride through that neighborhood.

And the decision to delay installing sharrows on California Avenue Southwest had activists once again questioning the city's dedication to the Bicycle Master Plan.

Cities such as Denver (where the marks were first used), San Francisco, Portland, Chicago and Paris have some variation of sharrows on their streets -- and some wonder if they're more than just goodwill gestures to cyclists. After all, critics say, what does it really change?

Michael Ronkin, an Oregon-based consultant who specializes in designing pedestrian- and cyclist-friendly streets, said sharrows do lead to positive results, but it "really doesn't change the nature of the street that much."

He said sharrows are a practical alternative to bike lanes, which require roads to get wider or the number of lanes has to be reduced.

A 2004 study by the San Francisco Department of Parking and Traffic showed sharrows do provoke drivers to leave about two feet more between their car and cyclists when passing. The study also examined which sharrow design was most effective; in the end they -- like Seattle -- chose the chevron symbol pioneered in Chicago and Paris.

One other recommendation of the San Francisco study was for an educational campaign about the purpose of sharrows, since only two out of seven motorists interpreted the markings to mean they should give cyclists more room.

In Seattle, SDOT workers are trying to communicate information about sharrows to those who live along streets earmarked for application, but there's not a campaign aimed at the general public yet. "That doesn't mean we won't in the future, as people see more of these," Hirakawa said.