[Updated: 10/9, 4:37pm]

Chapter 19.90.030 of Portland’s official City Code, defines a bicycle boulevard as “A roadway with low vehicle traffic volumes where the movement of bicycles is given priority.”
Many savvy Portland cyclists know which streets are bike boulevards, but because most of them lack design cues or visible markings, their designation is unknown to most; especially to motorists.
Now, as part of a new Bicycle Boulevard Marking Demonstration Project, PDOT plans to “combine several design elements to communicate to all road users the priority of cyclists.”
PDOT’s bike coordinator Roger Geller is working on the project with the City traffic engineer. The project was discussed at the September meeting of the Portland Bicycle Advisory Committee.
According to the official meeting minutes, three elements will be implemented as part of the project:
Big bicycle symbol. The symbol would likely be the same as the sharrow, but much bigger and placed in the center of the lane.

Step up the use of bike boxes, and improve on their design (more to international standards). There are five components to a bike box: lead in lane, advance stop line, reservoir, marking, and color. The reservoir of the bike box will be deeper, and it will be colored.

(Photo © Jonathan Maus)
Improve bicycle crossing treatments. Currently, PDOT provides a treatment when there are insufficient opportunities to cross (defined as less than one per minute). The crossing treatments would encourage the type of behavior already demonstrated voluntarily by some motorists: stopping for cyclists, even when cyclist has stop sign. Improvements would let motorists know that the intersection is a popular bike crossing.
On a recent trip to Vancouver BC, I found that the addition of bike symbols on their street signs had a huge impact on my perception of safety. I assume they were equally effective for motorists. Here are two examples:
The meeting minutes also note that, in addition to new public art being part of the effort, many committee members felt that an educational component should be done in tandem with design improvements.
The project is expected to be rolled out next spring. Stay tuned for more details.