A Guide to Bike Sharrows
West Allis just installed some. You find them all over. How do they differ from bike lanes and how should they be used?
There seems to be an explosion of sharrows, also called shared lane pavement markings, being installed in communities around Wisconsin since they were approved a few years ago by the Federal Highway Administration and now appear in the Manual of Uniform Traffic Control Devices, the bible for traffic engineers.
West Allis recently painted the bike and chevrons on 3.2 miles of streets. They were placed on S. 60th St., S. 76th St., S. 116th St., W. Greenfield Ave. and W. National Ave.
Up north, Wausau added a the shared lane markings to a number of streets in July, including Merrill Avenue (from Highway U to Union Avenue), Third Avenue (Union Avenue to Thomas Street), First Avenue (Union Avenue to Thomas Street), Bridge Street (Third Avenue to Sixth Street), Fifth Street (Bridge Street to Forest Street) and Sixth Street (Forest Street to Bridge Street).
As with any new traffic control device, there is going to be some initial confusion about what sharrows mean and how to use them. What exactly are sharrows and are they just a poor substitute for bike lanes? Here’s a guide to help you better understand them.
Lets begin with the standard traffic engineering guidance for parking lanes, bike lanes and motor vehicle travel lanes. Engineers can use their judgement and change these widths one way or the other by a foot or so, but standard widths are recommended:
- Parking Lane: 7-8ft, 8ft standard
- Bike Lane: 4ft (next to a curb) or 5-6ft next to parking, 5ft standard
- Motor vehicle travel lane: 10-12ft, 11ft standard
The image below illustrates a typical cross section for a 48ft wide street. I made this image on Streetmix.net, a cool interactive site that allows you to change the cross section of any street.
Sharrows are used when a road is an important bike connection but doesn’t have the width required to to add a bike lane. Among other benefits, shared lane markings reinforce the legitimacy of bicycle traffic on the street and can be used to suggest where bicyclists should ride, encouraging people to stay out of the door zone or even take the lane.
The bible (or at least the Old Testament) of traffic engineering is the Federal Manual of Uniform Traffic Control Devices. It offers the following standards and guidance on shared lane pavement markings:
- Assist bicyclists with lateral positioning in a shared lane with on-street parallel parking in order to reduce the chance of a bicyclist’s colliding with the open door of a parked vehicle;
- Assist bicyclists 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;
- Alert road users of the lateral location bicyclists are likely to occupy within the traveled way;
- Encourage safe passing of bicyclists by motorists; and
- Reduce the incidence of wrong-way bicycling.
- Shared Lane Marking should not be placed on roadways that have a speed limit above 35 mph.
- Shared Lane Markings shall not be used on shoulders or in designated bicycle lanes.
- If used in a shared lane with on-street parallel parking, Shared Lane Markings should be placed so that the centers of the markings are at least 11 feet from the face of the curb, or from the edge of the pavement where there is no curb.
- If used on a street without on-street parking that has an outside travel lane that is less than 14 feet wide, the centers of the Shared Lane Markings should be at least 4 feet from the face of the curb, or from the edge of the pavement where there is no curb.
- If used, the Shared Lane Marking should be placed immediately after an intersection and spaced at intervals not greater than 250 feet thereafter.
- Option: Section 9B.06 describes a Bicycles May Use Full Lane sign that may be used in addition to or instead of the Shared Lane Marking to inform road users that bicyclists might occupy the travel lane.
So sharrows should not be used instead of bike lanes; rather they are used where bike lanes just won’t fit. They can also be used in mixing zones and through intersections to help guide bicycle traffic and remind people in motor vehicle traffic to look for bicycles. And just like any other poorly designed road, if you put sharrows in the wrong place, it can be worse than no bicycle markings at all.
This story was originally published by the Bicycle Federation of Wisconsin.