TECHBRIEF Comparison of Driver Yielding 

for Three Rapid-Flashing 

Patterns Used With

Pedestrian Crossing Signs

FHWA Publication No.: FHWA-HRT-15-041

FHWA Contact: Ann Do, HRDS-30, (202) 493-3319, 

ann.do@dot.gov

Introduction

Flashing traffic control devices can help draw drivers’ 

attention to the traffic control device and to the area 

around the device. An example of a device that has 

resulted in significant improvements in increasing driver 

yielding to crossing pedestrians is the rectangular rapidflashing beacon (RRFB). Studies have been conducted 

in several locations, including Florida, Texas, Oregon, 

Michigan, Arizona, Wisconsin, and Calgary, AB. (See references 1 through 10.) These studies show a large range in 

the number of driver yielding responses for the RRFBs, 

extending from a low of 22 percent to a high of 98 percent.

This wide range in yielding indicates that device, site, 

or roadway characteristics are potentially affecting the 

driver’s decision to yield. Even with this wide range, the 

use of RRFBs has resulted in more drivers yielding to 

crossing pedestrians. 

Although the RRFB is allowed under interim approval 

from the Federal Highway Administration (FHWA), there 

is growing interest in adding it to the Manual on Uniform Traffic Control Devices (MUTCD).(11,12) The Signals 

Technical Committee (STC) of the National Committee on 

Uniform Traffic Control Devices (NCUTCD), which assists 

in developing language for chapter 4 of the MUTCD, is 

interested in research and/or assistance in developing 

materials on the design, application, and effectiveness 

of the RRFB. The initial research studies did not address 

certain issues that the STC believes are important in 

crafting language suitable for the MUTCD. For example, 

Research, Development, and 

Technology

Turner-Fairbank Highway 

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

www.fhwa.dot.gov/research
2

will other flash patterns be just as effective 

as the initial flash pattern that was evaluated and approved by FHWA? 

This TechBrief describes the methodology and results from an open-road study 

sponsored by FHWA that examined driver 

yielding behavior at crosswalks with three 

different flash patterns used with yellow, 

rapid-flashing beacons. 

FHWA Interim Approval of RRFB

On July 16, 2008, FHWA issued Interim 

Approval 11 (IA-11) for the optional use of 

the RRFB at uncontrolled pedestrian and 

school crosswalks.(11) As defined in IA-11, 

the RRFB should consist of two rapidly 

and alternately flashing rectangular yellow 

indicators with light-emitting diode arraybased pulsing light sources.(11) When IA-11 

was issued, the only flash pattern that had 

been tested was a pattern commonly called 

the 2-5 pattern as part of the initial evaluations conducted in Florida.(1) The name of 

the 2-5 pattern was developed based on the 

flash cycle of the beacon, which pulses two 

times on one side followed by five faster 

pulses on the other side. Because the 2-5 

pattern appears to the human eye to be a 2-3 

flash pattern, the IA-11 contained language 

describing a 2-3 pattern. Therefore, several 

devices were installed with the 2-3 pattern 

rather than the 2-5 pattern. Only after 

looking at the flash pattern using an oscilloscope were university researchers able 

to determine that the original devices had 

a 2-5 pattern, which led to FHWA changing 

the flash pattern from a 2-3 pattern to a 2-5 

pattern in Official Interpretation 4(09)-21.(13)

Study Objective

An inability to accurately determine the 

number of pulses within the 2-5 RRFB 

pattern was later confirmed in a closedcourse study.(14) The same study found that 

certain flash patterns—those that could be 

characterized as having limited or no dark 

periods within the flash pattern—negatively 

influenced the amount of time participants 

needed to identify a pedestrian’s direction 

of travel at night. Participants needed more 

time to identify the pedestrian walking 

direction when a pattern had limited or 

no dark periods. Before developing the 

proposed provisions for incorporating a 

rapid-flashing beacon traffic control device 

into the MUTCD, it is important to determine which flash patterns are acceptable 

from the perspectives of driver yielding 

and flash pattern simplicity.(12) This study 

sought to determine whether less complicated flash patterns and flash patterns 

with different proportions of dark and light 

periods can be equally or more effective 

than the 2-5 pattern during daytime 

conditions. A reason for investigating 

patterns with increased dark periods is to 

study the effect that increased dark periods 

would have on driver yielding compliance. 

Study Development

Study Sites

Based on a statistical analysis of past driver 

yielding data at RRFB locations in Texas, 

the research team estimated that it would 

take between 7 and 13 sites to obtain a sufficient sample of data to permit detection 

of at least a 5-percent difference in driver 

yielding.(5) Given available resources for the 

study, a total of eight sites were selected for 

testing. 

The Texas cities of College Station and 

Garland, along with Texas A&M University, 

agreed to participate in the study by 
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providing locations where the research 

team could install temporary equipment. 

Table 1 lists the sites included in this study. 

A goal was to try to match the distribution 

of site characteristics used in the original 

FHWA study on RRFBs.(1) For example, 

the research team preferred locations on 

multilane roads so that yielding behavior associated with the “multiple threats” 

issue could be observed. Because of 

limited ability to mount temporary 

beacons on overhead mast arms, the 

research team did not consider locations 

where the existing RRFBs are located on 

mast arms over the roadway.

Temporary Light Bar

To conduct an in-field evaluation of multiple 

flash patterns, the research team needed 

to be able to set the flash pattern and 

brightness of the beacons at the study sites 

in a quick, reliable, and consistent manner. 

Because of the difficulties with working 

with different equipment in different cities 

and unknown characteristics of the beacons 

at these locations (such as brightness), 

the research team designed temporary 

controllers for use with temporary light 

bars. In the field, the temporary light bars 

were mounted in front of existing RRFB 

light bars. 

The temporary light bar setup was designed 

so that it was not obvious that the beacons 

being observed during the staged pedestrian crossings were any different from 

the permanent RRFB equipment. Figure 1 

shows an example of the installed light bar 

being used by a staged pedestrian. Findings 

from a closed-course study indicate that 

brightness of the beacons can influence 

how quickly a participant can detect a 

pedestrian within a crosswalk.(14) Findings 

from another open-road study revealed 

that brightness affects driver yielding 

decisions.(7) Therefore, the same brightness level was used for all three flash 

patterns tested.

Flash Patterns

The study budget and parameters made it 

possible to test three different flash patterns 

Site ID Posted Speed Limit (mi/h) Number of Lanes Median Crossing Distance (ft)

CS-02 40 4 TWLTL 56

CS-03 30 2 TWLTL 37

GA-02 40 4 LTL 58

GA-06 40 4 Raised 80

GA-07 45 4 Raised 82

GA-10 40 4 Raised 62

GA-11 40 4 Raised 62

GA-13 40 4 Raised 55

Table 1. List of sites for rapid-flash pattern study.

LTL = Left-turn lane.

TWLTL = Two-way, left-turn lane.
4

at each study site with one of the patterns 

reserved for the baseline 2-5 flash pattern. To determine flash patterns for the 

other two conditions, a flash pattern workshop was held consisting of a selection 

of licensed transportation engineering professionals, representatives of FHWA, and 

Texas A&M Transportation Institute research 

staff. Several predeveloped patterns were 

shown to the participants. Based on participant comments, new patterns were developed. For example, some flash patterns 

were changed to have longer dark periods 

within the cycle, and some were changed to 

have periods where both beacons were on. 

Based on the meeting participants’ comments, two potential patterns in addition 

to the 2-5 pattern were selected. These two 

patterns were demonstrated to FHWA representatives, and final approval was given. 

Figure 2 shows the three patterns selected 

for testing in the field using the temporary 

light bars. The three conditions considered 

in this study include the following:

• Pattern using a combination of long and 

short flashes (called Blocks).

• Pattern using a combination of wigwag and simultaneous flashes (called 

WW+S).

• The 2-5 pattern (called 2-5).

The order in which treatments are presented 

could have an effect on results; therefore, flash pattern order for the sites was 

randomized. 

Figure 1. CS-02 study site with installed temporary light bars and staged pedestrian crossing.(15)

Source: Fitzpatrick.
5

Figure 2. Flash patterns studied.(15)

Source: Adapted from Fitzpatrick.
6

Data Collection

The data were collected during daytime 

conditions in February and March 2014. The 

research team used a staged pedestrian 

protocol to collect driver-yielding data to 

present oncoming drivers with a consistent presentation of approaching pedestrians. Under this protocol, a member of the 

research team acted as a pedestrian using 

the crosswalk. Each staged pedestrian wore 

similar clothing (gray T-shirt, blue jeans, 

and gray tennis shoes) and followed specific instructions in crossing the roadway. A 

second researcher accompanied the staged 

pedestrian and was responsible for observing and recording the yielding data on datasheets. Additional details regarding the protocol are available elsewhere.(6)

The protocol specified the completion of a 

minimum of 20 staged crossing maneuvers 

in each direction of travel for each condition, 

which is a minimum of 40 total crossings for 

each condition and 120 total crossings at 

each study site. Observation periods were 

chosen so that vehicle traffic was heavy 

enough to create frequent yielding situations but not heavy enough for congestion 

to affect vehicle speeds. Researchers only 

collected data during daylight and in good 

weather, with a focus on avoiding rain, wet 

pavement following rain, dusk or dawn, or 

other conditions that affect a driver’s ability to see and react to a waiting, staged 

pedestrian. In situations where a nonstaged 

pedestrian approached the crosswalk, data 

collection would stop momentarily, and the 

researcher would activate the temporary 

beacons for the pedestrian crossing.

Results

After completing the data collection, researchers returned to the office and entered 

the crossing data and the site characteristics 

data from the field worksheets into an 

electronic database. The average yielding 

rate for each flash pattern was calculated; 

however, data for individual crossings 

were used in the statistical evaluation. The 

average driver yielding rates for each flash 

pattern were as follows: 

• Blocks: 80 percent.

• WW+S: 80 percent.

• 2-5: 78 percent.

When a driver approaches a crossing, the 

driver either yields and stops the vehicle or 

does not yield to the waiting staged pedestrian. This binary behavior (yield or no yield) 

can be modeled using logistic regression. 

A significant advantage of using logistic 

regression is that it permits consideration of 

individual crossing data rather than reducing all the data at a site to only one value. 

From the preliminary review of the results 

above, it appears that there are only minor, 

if any, differences between the tested 

flash patterns. Because a previous study 

on RRFBs found that posted speed limit, 

crossing distance, and city influenced driver 

yielding, this analysis also considered those 

variables.(5)

The statistical analyses conducted using 

individual crossing data found that there 

are no significant differences between the 

tested flash patterns. 

Conclusions

This study investigated whether different 

flash patterns used with an RRFB are associated with different driver yielding. For the 

three patterns tested (see figure 2), no statistically significant differences were found. 

A closed-course study found that drivers 
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are better at judging pedestrian direction 

when there are more or longer dark periods 

within a flash pattern, suggesting an advantage in using a flash pattern with more 

or longer dark period(s).(14) The findings of 

this study indicated that the advantages of 

longer or more dark periods are not offset 

by a reduction in driver yielding (at least 

during the daytime conditions because 

data were only collected during daytime for 

this study). These findings suggest that the 

profession should consider using a flash 

pattern with increased dark periods when 

specifiying the pattern for RRFBs. 

The findings from these research efforts 

were presented to the NCUTCD STC during 

its June 2014 meeting. STC recommended 

that the WW+S pattern be used with future 

rapid-flashing pedestrian treatments. Based 

on the findings from this research, FHWA 

issued an official interpretation on July 25, 

2014, to permit agencies to use either the 

previously approved 2-5 flash pattern or the 

optional WW+S flash pattern.(16)

Although both flash patterns are available 

for use, the official interpretation mentions 

that FHWA favors the WW+S flash pattern 

because it has a greater percentage of dark 

time when both beacons of the RRFB are 

off and because the beacons are on for less 

total time. The greater percentage of dark 

time is important because drivers will be 

able to read the sign and to see the waiting 

pedestrian more easily, especially under 

nighttime conditions. The lesser total on 

time will make the RRFB more energy efficient, which is important because they are 

usually powered by solar energy.

References

1. Shurbutt, J., and Van Houten, R. (2010), 

Effects of Yellow Rectangular RapidFlashing Beacons on Yielding at Multilane Uncontrolled Crosswalks, FHWAHRT-10-043, FHWA, Washington, DC.

2. Pécheux, K., Bauer, J., and McLeod, P. 

(2009), Pedestrian Safety Engineering 

and ITS-Based Countermeasures 

Program for Reducing Pedestrian 

Fatalities, Injury Conflicts, and Other 

Surrogate Measures Final System 

Impact Report, FHWA, U.S. Department 

of Transportation, Washington, DC.

3. Hunter, W.W., Srinivasan, R., and 

Martell, C.A. (2009), Evaluation of the 

Rectangular Rapid Flash Beacon at a 

Pinellas Trail Crossing in St. Petersburg, 

Florida, Florida Department of 

Transportation, Tallahassee, FL.

4. Brewer, M.A., Fitzpatrick, K., Larson, 

G.W., and Minter, H. (2011), Beforeand-After Study of the Effectiveness of 

Rectangular Rapid-Flashing Beacons 

Used With School Sign in Garland, 

Texas, Technical Memorandum to City of 

Garland Department of Transportation, 

TTI, College Station, TX.

5. Fitzpatrick, K. et al. (2014), Characteristics 

of Texas Pedestrian Crashes and 

Evaluation of Driver Yielding at 

Pedestrian Treatments, FHWA/TX-14/0-

6702-1, TTI, College Station, TX.

6. Fitzpatrick, K., Brewer, M., and Avelar, 

R. “Driver Yielding to Traffic Control 

Signals, Pedestrian Hybrid Beacons, and 

Rectangular Rapid Flashing Beacons in 

Texas,” Journal of the Transportation 

Research Board, 2463, October 2013.

7. Fitzpatrick, K. et al. (2014), Investigating 

Improvements to Pedestrian Crossings 

with an Emphasis on the Rectangular 

Rapid-Flashing Beacon, Draft, FHWAHRT-15-043, FHWA, Washington, DC.

8. Ross, J., Serpico, D., and Lewis, R. 

(2011), Assessment of Driver Yielding 

Rates Pre- and Post-RRFB Installation, 

Bend, Oregon, Oregon Department of 

Transportation, Salem, OR.
8

9. Bennett, M.K., Manal, H., Van Houten, R., 

“A Comparison of Gateway In-Street Sign 

Configuration to Other Driver Prompts 

to Increase Yielding to Pedestrians at 

Crosswalks,” Journal of Applied Behavior 

Analysis, 47(1), Spring 2014.

10. Domarad, J., Grisak, P., and Bolger, J. 

(2013), “Improving Crosswalk Safety: 

Rectangular Rapid-Flashing Beacons 

(RRFB) Trial in Calgary,” Canada Institute 

of Transportation Compendium, 

http://www.cite7.org/conferences/

compendium/2013_Pedestrian_

ImprovingCrosswalkSafety.pdf.

11. Furst, A. (2008), MUTCD—Interim 

Approval for Optional Use of Rectangular Rapid Flashing Beacons

(IA-11), U.S. Department of Transportation, FHWA Memorandum, July 16, 

Washington, DC.

12. Federal Highway Administration (2009), 

Manual on Uniform Traffic Control Devices,

last accessed January 5, 2011, http://mutcd.

fhwa.dot.gov/kno_2009.htm.

13. Kehrili, M. (2012), 4(09)-21 (I)—

Clarification of RRFB Flashing Pattern, 

U.S. Department of Transportation, 

FHWA Memorandum, June 13, 

Washington, DC.

14. Fitzpatrick, K. Avelar, R., and Robertson, 

J. (2014), Rapid-Flash Yellow LEDs 

Impact on Detecting Pedestrians in 

a Closed-Course Setting, Technical 

Memorandum to FHWA.

15. Fitzpatrick, K., Avelar, R., Robertson, J., 

Miles, J. (2014), Driver Yielding Results 

for Three Rectangular Rapid-Flash 

Patterns, Executive Summary, Texas 

A&M Transportation Institute website, 

last accessed on October 7, 2014, http://

d2dtl5nnlpfr0r.cloudfront.net/tti.tamu.

edu/documents/TTI-2014-5.pdf.

16. Kehrili, M. (2014). 4(09)-41 (I)—Additional 

Flash Pattern for RRFBs, U.S. Department 

of Transportation, FHWA Memorandum, 

July 25, Washington, DC.

MAY 2015 FHWA-HRT-15-041

HRDS-30/05-15(WEB)E

Researchers—This study was performed by Principal Investigator Kay Fitzpatrick along with Raul 

Avelar, James Robertson, and Jeff Miles. For more information about this research, contact Dr. Kay 

Fitzpatrick, Texas A&M Transportation Institute, 2935 Research Parkway, College Station, TX 77845-3135, 

k-fitzpatrick@tamu.edu. 

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.fhwa.dot.gov/research.

Key Words—Rectangular rapid-flashing beacon, flash patterns, pedestrian crossing, driver yielding 

to pedestrians.

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