Last year, I took a tour of Portland’s Greenways with Seattle Greenways. I learned a great deal about traffic safety, calming and diversion from the Portland’s traffic engineers, although most of it was more relevant to creating good bike infrastructure, rather than transit. There was, however, one idea which struck me as having immediate applicability to transit at certain places in Seattle, namely an experimental variant of a curb bulb using a concrete pillow, as shown above.
SDOT’s website defines a curb bulb as “a radial extension of a sidewalk at a corner or mid-block location used to shorten the crossing distance for pedestrians, provide access to transit, and expand the landscape/furniture and walkable zone … The restricted street width provides a visual cue to motorists, encouraging them to travel more slowly at intersections or midblock locations with curb extensions. Turning speeds at intersections can be reduced with curb extensions” by forcing cars to make sharper turns.
There are some situations, though, where the standard style of curb bulb won’t work, or the existing curb arrangement is not working, because the intersection’s angle is acute or the approaching roads are narrow, and it is frequented by long-wheel-base vehicles like semi-trucks or transit buses. For those vehicles, it may be difficult or impossible for the driver to consistently arrange to make the turn without swinging into oncoming traffic or riding over the curb.
The photo above shows a traffic-calming measure on a pedestrian- and bike-oriented Greenway street which is also used by semi-trucks to access property to the left of the photo. With a normal bulb, these vehicles would routinely be driving all over the curb. The solution PBOT is experimenting with is to fully extend only the straight part of the curb, then install a concrete “pillow” that’s shaped like a speed bump in the radial part of the curb. While drivers of smaller vehicles receive similar cues to slow down as with a normal curb bulb, drivers of longer vehicles can make the turn with only a small bump under the rear axle.
More after the jump.
There are some places in Seattle where buses have similar problems due to the awkward geometry of the street, and a similar treatment might make sense, to improve rider comfort and avoid damage to the curb.
- MLK & Madison. Buses on southbound Route 8 often ride over the southwest curb at this narrow and acute-angled intersection.
- 80th St & Wallingford Ave N. This weird intersection has quite a lot of foot traffic, lots of fast car traffic, and the northeast curb has been cut back to only a few feet wide. A pillow-type bulb here might make pedestrians safer, which still allowing the northbound 16 to make the turn.
- Valley St & 5th Ave N. The southeast corner of this intersection is currently “bulbed out” with paint and an offset stop sign. A full bulb probably wouldn’t work, because of the difficult jog the northbound Routes 3 & 4 must make from 5th to Taylor, but a pillow-type bulb could work.
I know we have lots of bus drivers and riders out in the audience who must know of other places where buses often end up on the curb, or there’s a neighborhood arterial that needs traffic calming, but transit or freight turns might pose a problem. What intersections would you like to see receive this treatment?