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Background

Shared roadways make up the majority of most bike route networks. These shared roadways are often composed of curb lanes too narrow for motorists and bicyclists to safely share side by side (defined here as “substandard width”). On these roadways, the following problems often occur:

• Cyclists are pressured into hazards on the edge of the road or lane, such as the �door zone� where motorists leaving parked cars may suddenly open their door in a cyclist's path.
• Motorists attempt to pass cyclists too closely or intimidate cyclists legally in the lane.
• Cyclists decide to ride on the sidewalk illegally.
• Cyclists ride the wrong way on the road.

Though these problems are faced regularly by municipalities, there is no accepted pavement marking standard for shared roadways. Denver attempted to address this issue by developing an arrow with cyclist symbol inside to be placed in shared lanes. San Francisco used this marking on some streets but determined that the marking could be more visible.

Countermeasures

Figure 1. “Bike and Chevron”

Figure 2. “Bike-in-House”

After obtaining permission from the California Traffic Control Device Committee (CTCDC) to experiment, San Francisco hired a consultant to review a number of marking designs and study the best two in the field. The two marking designs (see figures 1 and 2) were placed on six city streets with substandard curb lane widths (5.1 m (16 ft, 10 in) to 6.7 m (22 ft) wide, with parking).

Based on previously recorded observations which showed that car doors open to about 2.9 m (9 ft, 6 in) from the curb face, the markings were placed 11 feet from the curb, giving cyclists with 0.6 m (2 ft) wide handlebars approximately 15.2 cm (6 in) of clearance from opened doors.

Evaluation and Results

“Before” and “after” video was taken at each marking location, and a limited number of surveys were distributed to cyclists and motorists to determine their understanding of the marking designs. Recorded behaviors taken with video included:

• Cyclists' positions on roadway (e.g. distance from parked cars).
• Motorists' positions (e.g. distance from cyclists when passing).
• Cyclist direction (with or against traffic).
• Cyclist location (street or sidewalk).
• Conflicts between cyclists and motorists.

After reviewing videotape of 2400 cyclists and 2400 motorists, the most effective pavement marking design, the “bike and chevron” (figure 1), was shown to:

• Encourage cyclists to ride 20.3 cm (8 in) further away from the door zone.
• Encourage motorists to give 68.6 cm (2 ft, 3 in) more space when passing cyclists.
• Reduce the incidence of wrong way riding by 80 percent.
• Reduce the incidence of sidewalk riding by 35 percent.

There was no statistically significant change in hostile or aggressive behavior by motorists, but this may be attributed to the very small number of observed conflicts in both the “before” and “after” videotapes.

Through the motorist and cyclist surveys, it was determined that the meaning of the markings was not always clearly understood.

Conclusions and Recommendations

 

 

As a result of this study, the bike and chevron design (figure 1) was recommended by the California Traffic Control Device Committee as a pavement marking to be included in the MUTCD 2003 California Supplement. As of October 2004, the CTCDC and Caltrans had developed draft language for inclusion of the marking in the manual. The language discusses the optional use of this marking on roadways used by bicyclists, and gives placement guidance.

San Francisco is developing a set of local warrants to help determine on what streets the markings will be placed. Thus far, the following list of factors to consider has been developed:

• Curb lane width
• Parking turnover
• ADTs
• Dooring, overtaking, midblock bicycle collision history
• Gap in otherwise continuous Class I/II bikeway
• Current demand by cyclists
• Prevailing speeds by motor vehicles and cyclists
• Prevalence of cyclists riding on sidewalk or in wrong direction
• Anticipated addition of Class II bikeway to street

Based on the results of the surveys taken as part of the study, outreach campaigns explaining this new marking are recommended. San Francisco plans to launch a campaign, using bus tail cards for example, and other advertising, to explain the shared lane marking. This will likely be an ongoing effort for the first year or so of implementation as people grow accustomed to the new marking.

Costs and Funding

The $73,000 study was funded by grants generated by local and state initiatives (San Francisco and California) which earmark portions of sales taxes for transportation projects.

A rough cost estimate of labor and materials for markings applied using methyl methacrylate is $100 each.

References

• San Francisco's Shared Lane Pavement Markings: Improving Bicycle Safety, written by Alta Planning + Design for the San Francisco Department of Parking and Traffic, February 2004, http://www.sfgov.org

Contacts

For information about the study:
Mia Birk, Principal
Alta Planning + Design
144 NE 28th Ave
Portland, OR 97232
(503) 230-9862
miabirk@altaplanning.com

For information about the CTCDC approval process or use of the shared lane marking in San Francisco:
Michael Sallaberry
San Francisco Department of Parking and Traffic
(415) 554-2351
mike.sallaberry@sfgov.org

The modification (shared lane markings) that is the subject of this case study is not currently compliant with the Manual on Uniform Traffic Control Devices, but it is being considered for inclusion (the “Bike-in-House” marking in Figure 2 is not being endorsed by the Bicycle Technical Committee of the National Committee on Uniform Traffic Control Devices, however). Accordingly, it is imperative that any jurisdiction wishing to utilize the shared lane markings (or any other non-approved traffic control device) should seek experimental approval from the Federal Highway Administration. For information on how to do so, please visit this Web site: http://mutcd.fhwa.dot.gov/kno-amend.htm.

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