TECHBRIEF Evaluation of Shared 

Lane Markings

FHWA Publication No.: FHWA-HRT-10-044

FHWA Contact: Ann Do, HRDS-07, (202) 493-3319, 

ann.do@dot.gov

This document is a technical summary of the Federal Highway Administration report, Evaluation of Shared Lane 

Markings, FHWA-HRT-10-041.

Objective

Shared lane markings help convey to motorists and 

bicyclists that they must share the roads on which they 

operate. The markings create improved conditions by

clarifying where bicyclists are expected to ride and by 

notifying motorists to expect bicyclists on the road. 

Figure 1 illustrates a generic sharrow as it appears in the 

2009 version of the Manual on Uniform Traffic Control 

Devices (MUTCD).(1) The present study was sponsored by 

the Federal Highway Administration (FHWA), and its purpose was to evaluate the impact of several uses of shared 

lane pavement markings, specifically the sharrow design, 

on operational and safety measures for bicyclists and 

motorists. Experiments were conducted in Cambridge, MA; 

Chapel Hill, NC; and Seattle, WA. This TechBrief provides 

a summary of the findings from the research, and the 

corresponding main technical report (FHWA-HRT-10-041) 

provides additional details.(2)

Background

In 2008, the National Committee on Uniform Traffic Control 

Devices recommended the inclusion of shared lane markings in the next version of the MUTCD.(3,1) That recommendation was made with limited research conducted only on 

an 11-ft spacing from the center of the shared lane marking 

to the curb to prevent a bicyclist from striking an opening 

door of a parked motor vehicle (i.e., a dooring crash).(4) The 

2009 edition of the MUTCD includes a provision for shared 

lane markings with guidance that the markings should be 

placed at least 11 ft from the curb face or the edge of the 

pavement on a street with parallel parking. On streets with 

Research, Development, and 

Technology

Turner-Fairbank Highway 

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

www.tfhrc.gov
2

no parking and an outside lane less than 14 ft 

wide, the centers of the shared lane markings 

should be placed at least 4 ft from the curb 

or edge of the pavement.(1)

Many cities and States have started implementing shared lane markings to encourage the safe coexistence of bicyclists and 

motorists. However, few localities have formally evaluated the impact of these markings 

on safety or operations. Given the opportunity to study shared lane markings, the 

Highway Safety Research Center (HSRC) 

decided to conduct a broad-based study. 

The following hypotheses were explored 

for sharrows by HSRC:

• The markings may help indicate a 

preferred path of travel and thereby 

improve bicyclist positioning relative 

to parked motor vehicles when riding 

in shared lanes with on-street parking.

• The markings may help improve spacing or operations when motorists pass 

bicyclists on streets both with and 

without parking.

• The markings may help improve bicyclist positioning relative to the curb 

or other hazards along the roadway 

edge, including unsafe drain grates or 

uneven pavement.

• The markings could be used where 

bicyclists need to take control of the 

lane, such as on a section of steep 

downgrade where they need more 

operating space and where there is 

inadequate width to provide a sufficiently wide bicycle lane. They could 

also be used in a shared lane situation 

or in a narrow lane situation where 

bicyclists need to move away from the 

door zone or other hazards.

• The markings may reduce bicyclist 

wrong-way and sidewalk riding, which 

can cause collisions.

• The markings may increase the distance

from motor vehicles in the travel lane 

to parked motor vehicles or to the curb 

in the absence of bicyclists, providing 

more operating space for bicyclists.

Separate evaluations were conducted in 

three U.S. cities. In Cambridge, MA, there 

was interest in experimenting with the 

placement of sharrows 10 ft from the curb 

to prevent dooring from parked motor 

vehicles. In Chapel Hill, NC, sharrows were 

placed on a busy five-lane corridor with 

wide outside lanes and no street parking. 

In Seattle, WA, sharrows were placed in the 

center of the lane on a downhill portion of 

a busy bicycle commuting street. Prior to 

Figure 1. Generic version of a sharrow.
3

the sharrows, a 5-ft bicycle lane was added 

to the uphill portion of the street, and the 

center line of the street was shifted. 

Methodology

The experimental design was to collect data 

of bicycles and motor vehicles operating 

in the traffic stream before and after 

installation of the shared lane markings. 

While it would have been desirable to have 

used an experimental design with comparison data, no adequate comparison sites 

were available. This is often the case in 

bicycle safety studies where slight differences in traffic flow, grade, pavement surface, 

or some other variable can greatly influence 

outcomes related to the bicyclists. One way 

to possibly obtain a comparison site is to 

install a treatment on part of a route and to 

use the remainder as a comparison. However, when a community is installing a treatment, almost invariably, the intention is to 

install the treatment along the entire route 

where the cross section is continuous.

Local staff collected videotape data before 

and after sharrow placement. The bicycle 

was the basic unit of analysis. A number 

of measures of effectiveness and other 

attributes were examined. Videotape coding 

was performed to obtain information about 

the bicyclist and to examine the operations of bicycles and motor vehicles when 

a motorist was following or passing a bicyclist. In Cambridge, MA, and Seattle, WA, 

events related to the presence of parked 

motor vehicles were also examined, such 

as existing open doors and near dooring 

events, as well as motorists pulling into or 

out of parking spaces.

The following spacing data were also 

obtained from images extracted from the 

videotapes:

• Distance between bicycles and parked 

motor vehicles (tire to tire).

• Distance between bicycles and the curb 

at the edge of the road (tire to curb) 

where there was no parking.

• Distance between bicycles and passing 

motor vehicles (tire to tire).

• Distance between motor vehicles in the 

travel lane and parked motor vehicles 

(tire to tire) or the curb (tire to curb) 

when no bicycles were present.

Chi-square tests were used to examine the 

distributions of variables before and after 

placement of the shared lane markings. 

Analysis of variance models were used to 

study the effect of shared lane markings on 

spacing and other performance measures. 

In these models, the independent variables 

included site characteristics, type of treatment, and a dummy variable indicating 

whether it was a before or after condition. 

The sign and significance of the coefficient 

of this dummy variable were used to assess 

the effectiveness of the markings. None 

of the data were combined across sites 

because of differences in the uses of the 

shared lane markings in each city.

Cambridge, MA, Experiment

Cambridge, MA, has many street cross 

sections where the recommended 11-ft 

spacing from the curb would not be feasible.

The sharrows were placed 10 ft from the 

curb for about 2,500 ft on Massachusetts 

Avenue, which is a 4-lane divided street 

with approximately 29,000 vehicles per day, 

parallel parking on both sides, and a speed 

limit of 30 mi/h. Figure 2 shows a view of 

Massachusetts Avenue before sharrows 

were placed on the street. The intent was 

to determine whether the sharrows would 

improve spacing of bicycles and motor 

vehicles and also help prevent dooring. 
4

Results pertaining to the interaction of 

bicycles and motor vehicles included the 

following changes from before to after:

• A total of 94 percent of the bicyclists 

rode over the shared lane marking.

• The percentage of bicyclists who took 

the lane decreased from 13 to 8 percent. 

• The percentage of avoidance maneuvers 

(i.e., changing speed or direction to avoid

another party) decreased from 76 to 

37 percent. 

• The percentage of bicyclists who yielded 

(i.e., gave way to a motorist) decreased 

from 23 to 7 percent. 

• The percentage of motorists who yielded 

(i.e., gave way to a bicyclist) increased 

from 5 to 9.5 percent. 

• The percentage of motorists who made 

no change while following a bicyclist 

increased from 44 to 65 percent.

Results pertaining to the spacing of bicycles and motor vehicles in the presence of a 

following motor vehicle in the after period 

included the following:

• The distance from a bicyclist riding 

beside a parked motor vehicle increased 

from 40.1 to 42.3 inches when both directions were combined and increased 

from 37.4 to 41.5 inches for the inbound 

direction. 

• Outbound spacing was 42.7 inches in 

the before period and 43.1 inches in the 

after period. 

• The percentage of bicyclists who rode 

within 40 inches (i.e., near the door zone) 

of parked motor vehicles decreased. 

Most of the effect was in the inbound 

direction with a decrease from 58 to 

41 percent. Comparable outbound values 

were 44 percent in the before period 

and 38 percent in the after period. 

• The percentage of bicyclists who rode 

within 30 inches (i.e., within the door 

zone) remained unchanged at 13 percent.

Results pertaining to the spacing of bicycles and motor vehicles in the absence of a 

following motor vehicle in the after period 

included the following:

• The change in distance between a 

bicyclist and a parked motor vehicle 

was negligible (approximately 45 inches 

before and after). 

• The percentage of bicyclists who rode 

within 40 inches of parked motor vehicles increased from 37.5 to 45 percent, 

although this may reflect the high 

percentage of bicyclists who rode over 

the sharrows.

• When motorists drove past parked 

motor vehicles in the absence of bicycles 

in the after period, the spacing increased 

16 inches (from 77.4 to 93.6 inches) in 

the inbound direction, 12 inches (from 

84.5 to 96.5 inches) in the outbound 

direction, and 14 inches (from 80.9 to 

95.0 inches) combined. 

Overall results from Cambridge, MA, indicate 

the following:

• A total of 94 percent of bicyclists rode 

over the sharrows.

Figure 2. Massachusetts Avenue condition in the before 

period.
5

• There was more operating space for 

bicycles as motor vehicle spacing from 

parked motor vehicles increased.

• A number of variables related to the 

operations of bicycles and motor vehicles 

showed positive effects.

• Placement of the sharrows 10 ft from 

the curb (instead of 11 ft) was not a 

problem.

Chapel Hill, NC, Experiment

The sharrows were placed 43.5 inches from 

the curb along Martin Luther King, Jr. Boulevard (MLK) for 1.25 mi. MLK has a 5-lane 

cross section (4 travel lanes and a center 

two-way left turn lane) with no parking, 

27,000 vehicles per day, a speed limit of 

35 mi/h, and periodic sunken drain grates 

next to the curb. There was a 3 to 4 percent 

grade where the videotape data were 

collected. The street had previously been 

resurfaced, and the outside lanes were 

marked nominally as 15-ft-wide lanes. The 

spacing of bicycles and motor vehicles from 

the curb and in situations where motorists 

passed bicyclists was of primary interest. 

Figure 3 shows MLK in the before period.

Results pertaining to the interaction of bicycles and motor vehicles included the following changes from the before period to the 

after period:

• A total of 91 percent of the bicyclists 

rode over the sharrows—97 percent in 

the downhill direction and 88 percent 

in the uphill direction. Bicyclists riding 

uphill traveled slower and tended to 

ride closer to the curb.

• The percentage of motorists who made 

no movement to change lanes when 

overtaking a bicyclist increased from 

24 to 32 percent. 

• There was no difference in the proportion of bicyclists riding near the curb 

(approximately 98 percent) or taking the 

lane (approximately 2 percent). 

• The percentage of avoidance maneuvers 

decreased from 81 to 71 percent.

• The percentage of motorists staying in 

the lane when following bicyclists 

increased from 20 to 29 percent.

• There was no change in the percentage 

of bicyclists or motorists who yielded. 

Results pertaining to the spacing of bicycles 

and motor vehicles included the following:

• In the presence of a following motor 

vehicle in the after period, bicyclists rode 

closer to the curb after the sharrows by 

about 2.5 inches (40.1 to 37.7 inches). 

The effect was more pronounced downhill (4.6 inches closer) versus uphill 

(2.9 inches closer). Similar to Cambridge, 

MA, this was likely a reflection of bicyclists tracking over the sharrows. 

• There were slight increases in the 

percentages of bicyclists who rode 

within 30 and 40 inches of the curb. The 

percentage within 30 inches increased 

from 12.5 to 15 percent downhill and 

47.3 to 50.5 percent uphill. 

• When motorists passed bicyclists in the 

after period, there was a small decrease 

Figure 3. MLK in the before period.
6

in the passing distance overall from 

82 to 79 inches. In the downhill direction, motorists passed 7 inches closer 

to bicycles (from 84.7 to 77.7 inches). 

There was no change in the uphill 

direction (from 80.0 to 81.1 inches). 

• The percentage of passing motor vehicles within 50 inches showed only 

small and insignificant differences (from 

2.0 to 2.6 percent).

• When the distance of the right front 

tires of motor vehicles from the curb in 

the absence of bicycles was examined 

in the after period, the spacing increased

8.3 inches in the uphill direction 

(from 64.4 to 72.7 inches), 4.7 inches 

in the downhill direction (from 76.6 to 

81.3 inches), and 7 inches overall (from 

70.5 to 77.0 inches). 

• The percentages of motor vehicles 

within 50 and 60 inches of the curb were 

also significantly lower in the after 

period. The effect was most pronounced in the uphill direction (from 16 to 

4 percent within 50 inches and from 

46 to 17 percent within 60 inches).

• Bicyclist sidewalk riding significantly 

decreased from 43 percent in the before 

period to 23 percent in the after period. 

In the downhill direction, sidewalk riding 

decreased from 39 to 10 percent, with 

no significant change in the uphill 

direction.

• Wrong-way riding by bicyclists was 

11 percent in the before period and 

8 percent in the after period (nonsignificant change).

Overall results from Chapel Hill, NC, indicate 

the following:

• A total of 91 percent of bicyclists tracked 

over the sharrows and rode at a safe 

distance from the edge of curb with more 

of an effect in the downhill direction.

• Motorists moved away from the sharrows, providing more operating space 

for bicyclists.

• A number of variables related to the 

operations of bicycles and motor vehicles showed positive effects.

• Bicyclist sidewalk riding decreased in 

the downhill direction.

• There was no change in the percentage 

of bicyclist wrong-way riding.

Seattle, WA, Experiment

Sharrows were placed in the center of the 

lane 12.25 ft from the curb on a downhill 

section of Fremont Street, which is a 2-lane 

street that has a speed limit of 30 mi/h, 

10,000 vehicles per day, 3.6 percent grade, 

and parking on both sides of the street. 

The placement was meant to encourage 

bicyclists to take the lane while traveling 

downhill. Data were collected in two additional periods following the before period. 

The centerline of the street was repositioned 

to allow a 5-ft bicycle lane and parking 

line to be installed on the uphill section of 

the street (after period 1). Sharrows were 

then added in the downhill direction (after 

period 2) since there was not enough width 

for bicycle lanes on both sides of the streets. 

Figure 4 shows a section of Fremont Street 

in the before period.

Results pertaining to the interaction of 

bicycles and motor vehicles included the 

following changes from the before period to 

the after period:

• There was no difference in the safety 

of the manner in which motorists were 

following and passing bicyclists. Overall, 

97 percent of these maneuvers were 

considered to be performed safely.
7

• A total of 15 percent of the bicyclists 

rode over the sharrow during the after 

period 2.

• A significantly higher percentage (51 

versus 28 percent) of bicyclists shifted 

toward the center of the lane and took 

the lane during after period 1 when 

the lane was narrowed to accommodate the addition of the bicycle lane in 

the uphill direction.

• The percentage of bicyclists who yielded 

(i.e., changed direction or speed to 

give way to a motor vehicle) decreased 

from 3.3 percent in the before period 

to 2.8 percent in after period 1 and 

0.7 percent in after period 2.

• The percentage of motorists who 

yielded (i.e., changed direction or speed 

to give way to a bicycle) decreased 

from 13 percent in the before period to 

6.5 percent in after period 1 and 5 percent 

in after period 2.

Results pertaining to the spacing of bicycles 

and motor vehicles included the following:

• In the absence of following motor vehicles, the average spacing between 

bicycles and parked motor vehicles did 

not significantly change across periods 

(45.8 inches in the before period, 

47.5 inches in after period 1, and 

44.5 inches in after period 2). 

• The percentage of bicyclist spacing 

values within 30 inches (i.e., within 

the door zone) increased from about 

6 percent in the before period to about 

12 percent in the two after periods. 

• The percentage of bicyclist spacing 

values within 40 inches increased 

from 36 percent in the before period to 

39 percent in after period 1 and 44 percent 

in after period 2 (nonsignificant change). 

• When motorists drove past parked motor 

vehicles in the absence of bicycles in 

both after periods, the average spacing 

decreased about 18 inches due to the 

change in the roadway configuration 

(the lane had been narrowed by 2.5 ft).

Overall results from Seattle, WA, indicate the 

following:

• Sharrow placement alone did not seem 

to result in an increase in the percentage 

of bicyclists taking the lane.

• Bicyclists were already riding out of the 

door zone in the before period and stayed 

in this location in both after periods. 

Sharrows had previously been installed 

11 ft from the curb next to parked cars 

over a 2,000-ft, four-lane section of 

Fremont Street leading into the section 

studied in the current project.

• It is possible that narrowing the travel 

lanes and adding the uphill bike lane 

had more of an effect on operations and 

spacing than the addition of sharrows.

• The bicyclists riding in the street 

seemed experienced and showed that it 

was not necessary to ride in the middle 

of the lane to control the lane.

Figure 4. Fremont Street in the before period.
8

Researchers—This study was performed by William Hunter, Libby Thomas, Raghavan Srinivasan, 

and Carol Martell of the Highway Safety Research Center of the University of North Carolina.

Distribution—This TechBrief is being distributed according to a standard distribution. Direct 

distribution is being made to the Divisions and Resource Center.

Availability—This TechBrief may be obtained from the FHWA Product Distribution Center by 

e-mail to report.center@dot.gov, fax to (814) 239-2156, phone to (814) 239-1160, or online at 

http://www.tfhrc.gov/safety.

Key Words—Shared lane markings, Sharrows, and Bicycles.

Notice—This document is disseminated under the sponsorship of the U.S. Department of 

Transportation in the interest of information exchange. The U.S. Government assumes no liability 

for the use of the information contained in this document. The U.S. Government does not endorse 

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october 2010 FHWA-HRT-10-044

HRDS-07/10-10(2M)E

Conclusions

Sharrows can be used in a variety of situations, and increased use should enhance 

motorist awareness of bicyclists or the possibility of bicyclists in the traffic stream. 

Results indicate that sharrows increased 

operating space for bicyclists. Sharrows 

have reduced sidewalk riding not only in the 

current study but also in a previous study 

in Gainesville, FL.(5) As communities continue

to experiment with various uses of sharrows,

it is recommended that researchers continue

to create similar trials in other locations and

traffic settings and then evaluate and report

those experiments so that more data can be

examined and guidance to users improved.

References

1. Federal Highway Administration. (2009). 

Manual on Uniform Traffic Control 

Devices, Federal Highway Administration, 

Washington, DC.

2. Hunter, W.W., Thomas, L., Srinivasan, 

R., and Martell, C.A. (2010). Evaluation 

of Shared Lane Markings, Report No. 

FHWA-HRT-10-041, Federal Highway 

Administration, Washington, DC.

3. NCUTCD Bicycle Technical Committee. 

(2007).Proposed Shared Lane Marking 

Part 9 of the MUTCD, National Committee 

on Uniform Traffic Control Devices. 

Obtained from: http://members.cox.net/

ncutcdbtc/sls/slmtoncjan07.pdf. Site last 

accessed August 3, 2010.

4. Alta Planning + Design. (2004). San 

Francisco’s Shared Lane Pavement 

Markings: Improving Bicycle Safety, San 

Francisco Department of Parking and 

Traffic, San Francisco, CA.

5. Pein, W.E., Hunter, W.W., and Stewart, 

J.R. (1999). Evaluation of the SharedUse Arrow, Florida Department of Transportation, Tallahassee, FL.