Sharrow: A road marking indicating that the road is to be shared by cars and bicycles. A portmanteau of share and arrow.
The original sharrows were sometimes called “bike in a house” because of their design:
They were included in the 1993 Denver Bicycle Master Plan but not widely implemented in that city until 2010. In 2004, the city of San Francisco, where incidents of “dooring” were increasingly common, commissioned a study of the effectiveness of sharrows. According to One Less Car: Denver:
The goal of the study was to determine which markings were most effective, and how they should be used. The really neat part of this study is how it was conducted. The group used before-and-after video footage to determine the effectiveness of the sharrow. They tested two versions of the sharrow; the 'Chevron style' … and the 'Bike-In-House' version … They looked for cyclist positions relative to the curb or a parked car, as well as passing motorist traffic positions relative to the cyclist. In short, what they determined is that ANY sharrow improves cyclist and motorist positioning. Sharrows created a buffer between cyclists and parked cars, as well as between the passing cars and cyclists. They did a good job of evaluating variables, and in the end concluded that sharrows can be an effective solution to improve cyclist safety and both cyclist and motorist behavior.
David Darlington writes about sharrows and other features of urban bicycling in “Critical Mass,” in the November issue of San Francisco magazine:
Polk [Street] is an officially designated bike route, but the part we were riding has no formal bike lanes. We were following “sharrows”—stenciled images of bikes with arrows, indicating where cyclists should ride, especially to avoid car doors. To make room for these, 11 years ago two southbound lanes on Polk were reduced to one, following the example of Valencia Street, ground zero for the bike explosion now engulfing the city.
Darlington reports that San Francisco has 2,800 sharrows.
At least 27 other US cities have introduced sharrows to their roadways, according to a Wikipedia entry.
Photo credit: Bikehugger.