Shared Lane Marking

A shared lane marking, also known as a sharrow is a lane marking depicting a bicycle intended to inform road users where bicycles are supposed to ride within the lane.

Common reasons for their use include

Communicating to drivers that cyclists have a right to use the road
Encouraging cyclists to use a specific part of the lane, such as the edge or center (taking the lane).

Recommended Use and Limitations

Shared lane markings can be helpful as part of a Bike Boulevard or a shared space by assisting in communicating how bicycles are meant to use the infrastructure. Simply painting sharrows does not address the fundamental bike safety and comfort issues that plague most roadways. Meeting the needs of cyclists of all ages & abilities requires reducing the number and severity of conflicts between bicycles and motor vehicles.

Shared lane markings can be used as part of a low speed, low AADT roadway, such as a bike boulevard or shared space, to mark where bicycles are supposed to ride within the lane^[1]. Even in these situations, however, a dedicated vertically separated bikeway or constrained bike lane is preferable if space allows^[2].

Shared lane markings have historically been used on roadways with high traffic volumes or high speeds as a form of compromise bikeway. This is no longer recommended, because these facilities are not accessible to all ages and abilities. Design manuals differ slightly on when shared bicycle-motor vehicle lanes are appropriate, but the advice is largely the same. According to the 2025 NACTO Urban Bikeway Design Manual, roadways where bikes and motor vehicles share a lane should have less than 2000 vehicles/day and a target speed of 20 mph or lower. In this case, sharrows should be applied in the center of the lane, to encourage cyclists to take the lane^[3]. The 2024 AASHTO Guide for the Development of Bicycle Facilities confirms this by stating that sharrows should only be used as part of a bicycle boulevard or shared space {citation needed}.

↑ National Association of City Transportation Officials. Urban Bikeway Design Guide(3rd ed.). Island Press, §3.2.1 Shared Spaces, "Design Guidance: Markings", p. 100. ISBN 978-1-64283-384-3.
↑ National Association of City Transportation Officials. Urban Bikeway Design Guide(3rd ed.). Island Press, §3.2.3 Constrained Bike Lanes, "Designing for All Ages & Abilities", p. 129. ISBN 978-1-64283-384-3.
↑ National Association of City Transportation Officials. Urban Bikeway Design Guide(3rd ed.). Island Press, §3.2.2 Bike Boulevards, "Design Guidance: Markings", p. 109. ISBN 978-1-64283-384-3.

[1] National Association of City Transportation Officials. Urban Bikeway Design Guide(3rd ed.). Island Press, §3.2.1 Shared Spaces, "Design Guidance: Markings", p. 100. ISBN 978-1-64283-384-3.

[2] National Association of City Transportation Officials. Urban Bikeway Design Guide(3rd ed.). Island Press, §3.2.3 Constrained Bike Lanes, "Designing for All Ages & Abilities", p. 129. ISBN 978-1-64283-384-3.

[3] National Association of City Transportation Officials. Urban Bikeway Design Guide(3rd ed.). Island Press, §3.2.2 Bike Boulevards, "Design Guidance: Markings", p. 109. ISBN 978-1-64283-384-3.

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