Shared lane marking

A shared-lane marking or sharrow is a street marking installed at locations in Australia, Canada, Spain, or the United States. This marking is placed in the travel lane to indicate where people should preferably cycle.

The US Manual on Uniform Traffic Control Devices says shared-lane markings may be used to:

B. Assist cyclists with lateral positioning in lanes that are too narrow for a motor vehicle and a bicycle to travel side by side within the same traffic lane;
C. Alert motorists of the lateral location bicyclists are likely to occupy within the traveled way;
D. Encourage safe passing of bicyclists by motorists; and
E. Reduce the incidence of wrong-way bicycling.

These markings are used in the USA, Australia and other countries. In US usage, the wide shape of the arrow, combined with the bike symbol, gave rise to unofficial names such as "bike in a house" or "sharrow". In the UK roughly the same function is served by a bicycle symbol without arrows. However, this tends to be used more as an indication of a formal cycle route rather than as an encouragement to share the road.

The original "bike in a house" or "man jumping barrels at home" marking was developed by James Mackay and included in the 1993 Denver Bicycle Master Plan. While Mackay had considered a "connect the dots" pavement markings approach for bicycle route definition and cyclist lane positioning reinforcement (during his time as the Bicycle Facilities Engineer for the North Carolina Department of Transportation), the City of Denver's unwillingness to commit to bike lane markings meant that shared lane markings were the only pavement marking treatment for bicyclists that the City would implement. The hollow arrow surrounding the cyclist was intended to reinforce the correct direction of travel for bicyclists (who were frequently observed riding the wrong way, against traffic, in Denver).

In 2004, the city of San Francisco, California began experimenting with the shared lane marking, and developed a revised symbol consisting of a bicycle symbol with two chevron markings above the bicycle. In the process, the name was coined by Oliver Gajda, of the City and County of San Francisco Bicycle Program, and is a portmanteau of share and arrow.

In a 2009 paper, Northeastern University researcher Peter G. Furth proposed the "Bicycle Priority Lane", which combines sharrows with dotted lines inside the usual lane markings. This marks a five-foot-wide zone in the center of the lane which bicyclists are encouraged to use. The city of Boston, Massachusetts began experimenting with these markings in 2013.

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Wikipedia