Look at any of the great bicycle-friendly cities of world (Copenhagen, Amsterdam, Portland, to name a few). In a quick glance one thing stands out: the existence of clearly demarcated lanes for bicycle travel. Whether separate from auto traffic or adjacent to it, when demarcated bike lanes appear, people tend to use them. A real-world case of "if you build it, they will come."
In Seattle, however something quite different has also appeared: "Sharrows" or "shared-lane markings." No doubt you've seen them. They amount to a bicycle graphic slapped into car lanes and are inconsistently spaced and placed on streets all throughout the city. For the city transportation department, they are quick and easy to apply. From a public relations point of view, the introduction of sharrows allows a rapid ramp-up of statistics on how many miles of bike facilities the city has and plans for the future.
The problem with sharrows is that they are a poor solution. Their meaning is not intuitive. Is the space they mark intended for a bike or a car — or both? Why is this one set out in the lane and that one over on the side? Who has priority?
They are easy to implement but a confusing waste of paint compared to a proper bike lane. Other than serving as a way for politicans to attempt to spray-paint their way to reelection, sharrows don't really work very well.
Local cyclists seem to agree. In the Cascade Bicycling Club's Report Card on Bicycling, Seattle 2009, the number one response to the survey question, "What would make Seattle better for bicycling?" comes the answer "separate bike paths." The top answer to the question, "What is the main issue with bicycling in Seattle?" is "disconnected bicycle routes." Of all the categories rated in the group's Report Card, the Network/Satisfaction with Routes category earned Seattle the lowest grade of the report: a mere C+.
A better approach would be to standardize Seattle's bike lane design by slightly narrowing car lanes where possible and creating separated lanes for bikes. Define a reasonable but narrower car lane standard, then spray-paint away. Every street with a certain width could have a standard format bike lane applied and the bicycling free-market would sort out which routes become the most popular.
This approach would provide space for bikes and also offer a natural traffic-calming effect without the expense (and perennial neighborhood funding squabbles) of traffic circles or ad hoc speed bumps that create an unpleasant ride for everyone. (What's more, traffic circles have the nasty side-effect of diverting the cars driving around them directly into paths of sidestreet-crossing pedestrians.) Multi-lane streets can likely withstand a reduction in each car lane width to provide an adequate bike lane or two. And if there isn't room for a proper bike lane, don't put one there. If there's not room for the lane, there's probably not room for safe cycling.
Perhaps the ultimate word on sharrows comes from the City of Seattle's own website, which today answers the question "What do sharrows mean for motorists and bicyclists?" with this damning bit of faint praise: "Motorists: Follow the rules of the road as if there were no sharrows... Bicyclists: Follow the rules of the road as if there were no sharrows."
Exactly the point — so why waste the paint?