Thursday, July 8, 2010

The Curious Divisadero Islands: DPW Explains the Design and MTA Questions Their Usefulness

At Turk Street the median juts into the crosswalk

The curious case of the Divisadero pedestrian islands has been resolved. The odd placement of the several islands meant to give a mid-point refuge to people crossing the street is not so peculiar after all, according to the city's design team. Each of the Divisadero crosswalks was designed to meet the different conditions of the particular intersection. But a few of the islands, or "raised pedestrian refuges," do not work well and often fail to provide safe passage to people crossing the street.

Christine Falvey, spokesperson for the Department of Public Works, provided BIKE NOPA with the explanation from the interdepartmental design team (including DPW and the Municipal Transportation Agency) for the recent makeover of Divisadero from Waller to Geary Streets.

"Thumbnails and pass-throughs were designed consistently. Medians were to end at the property line, start a five foot wide pass through, then have the raised thumbnail. The apparent variations out there are actually due to the width of the crosswalks, which vary according to the width of the sidewalk leading up to them. In some cases, the crosswalk was not striped the exact width of the sidewalk which gives the impression of another variation of thumbnail design where there is not."

A little complicated? Consider this: if the Hayes Street sidewalk is several feet wider than the Grove Street sidewalk, then the crosswalk crossing Divisadero at Hayes will also be several feet wider than the crosswalk at Grove. Since the islands begin five feet from the end of the median for each intersection, the Hayes island will appear to be floating in the middle of the crosswalk while the Grove island will be closer to the outer line of the crossing. The fact that the city chose to not always follow the width of the sidewalk, of course, makes it more confusing or from the team's perspective, appears more variable that it is.

The intent of this inquiry into the Divisadero island design has never been a "gotcha" attempt to catch traffic engineers making mistakes. On May 4th BIKE NOPA guest contributor, Jeff Gibson, first described the variations at several intersections.* While he found them odd, his concern was for the safety of pedestrians, especially people with mobility limitations, who would likely find their passage either blocked by the islands or too limited by the five- foot width of the pass-throughs.

Motorists block Divisadero crosswalk -- and the pass-through -- way too often

In one ten-minute period, the crosswalk was blocked four times;
An advance stop line could be very helpful here

Gibson's observation especially holds for the situation at Fell Street, as seen in the photos. Drivers at this intersection often intrude into the crosswalk and block the pass-through when they stop at the signal. People crossing the street must walk around the vehicle and step onto the island, if they are able, to proceed. Anyone in a wheelchair or whose difficulty accessing the islands must get around the island and be exposed to the westbound traffic, including motorists making left turns onto Divisadero. The five-foot wide pass-throughs between the end of the median and the start of the island are the standard width. They were designed specifically for people in wheelchairs and those with strollers as well as for pedestrians. At several Divisadero intersections they fail to serve their purpose well. Jeff Gibson appreciates the explanation from the city, but he still thinks "most of the thumbnails on Divisadero are so poorly placed that they act like barriers."

Mike Sallaberry, traffic engineer for the MTA, told BIKE NOPA that one outcome of this discussion and the difficulty placing thumbnails along Divisadero was a reconsideration of whether thumbnails were worth it. "Maybe we don't need them at all," he concluded.


* When BIKE NOPA published a follow-up article in late May, it seemed odd that no one from DPW had responded to Gibson's inquiries -- or our own -- for so many weeks. We were left to wonder about the seeming lack of response and transparancy. As it turns out, the explanatory memo that Falvey passed on to us was written on May 17th. All the parties involved thought someone else had forwarded the message to Gibson and to me. These things happen.


  1. It's nice that they provided the methodology that they are using, but this doesn't explain *why* they are using this design when the Better Streets Plan calls for the median to end at the beginning of the crosswalk, not at the property line, and for the thumbnail to be completely outside the crosswalk, not five feet from the median

  2. @ Steve Smart: True, the design team did not explain why they chose the property line rather than the crosswalk beginning for the end of the median.

    Regarding the thumbnails not being placed outside the crosswalks: The design team provided this explanation: "When designing thumbnails, we must consider the space needed by turning vehicles such as emergency vehicles, buses, and trucks. This affects the size and placement of the thumbnails. On a street like Divisadero with trucks delivering goods to a variety of locations, it was not possible to place the thumbnails outside the crosswalk without them being constantly hit and potentially damaged."