TECHBRIEF Effects of Yellow Rectangular

Rapid-Flashing Beacons 

on Yielding at Multilane 

Uncontrolled Crosswalks

FHWA Publication No.: FHWA-HRT-10-046

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, Effects of Yellow Rectangular Rapid-Flashing Beacons 

on Yielding at Multilane Uncontrolled Crosswalks (FHWA-HRT-10-043).

Objective

This study examined the effects of side-mounted yellow light-emitting 

diode (LED) rectangular rapid-flashing beacons (RRFBs) at uncontrolled 

marked crosswalks in a series of experiments. Many methods have 

been examined to increase driver yielding behavior to pedestrians at 

multilane crosswalks at uncontrolled sites with relatively high average 

daily traffic (ADT). Only treatments that employ a red phase have consistently produced sustained high levels of yielding in previous studies.(1) A series of five experiments examined the efficacy of RRFBs to 

increase driver yielding behavior. These studies examined the effects of 

RRFBs at 22 sites in 3 cities in the United States (St. Petersburg, FL; 

Washington, DC; and Mundelein, IL). Data were also collected over a 

2-year follow-up period at 18 of these sites to determine the long-term 

effects of the RRFB treatments. Another objective of the study was to 

compare the RRFB with a traditional overhead yellow flashing beacon 

and a side-mounted traditional yellow flashing beacon. A final objective 

of the study was to attempt to identify ways to further increase the 

effectiveness of the treatment. Variants subjected to evaluation included 

mounting additional units on a median or pedestrian refuge island 

and aiming the RRFB system to maximize brightness at a target site. 

Introduction

Drivers generally fail to yield right-of-way to pedestrians in marked crosswalks at uncontrolled sites. From the beginning of 2004 to the end of 

2006, there were a total of 14,351 pedestrian fatalities and 212,786 pedestrian injuries resulting from pedestrian-vehicle accidents nationwide.(2)

Decreasing the occurrence of these crashes would increase the safety 

and overall walking experience for pedestrians. One alternative to 

in-roadway signs and yellow flashing beacons is to add yellow LED 

RRFBs to pedestrian warning signs, which are similar in operation to 

emergency flashers on police vehicles. Figure 1 shows an example of an 

RRFB mounted below a W11-2 pedestrian warning sign at a crosswalk. 

This system is solar powered and is linked to the unit on the other side 

of the street by radio frequency transmitters and receivers. Each LED 

flasher is 6 inches wide and 2.5 inches high and placed 9 inches apart. 

In addition, each unit is dual indicated, with LEDs on the front and 

Research, Development, and 

Technology

Turner-Fairbank Highway 

Research Center

6300 Georgetown Pike

McLean, VA 22101-2296

www.tfhrc.gov
2

back. Each side of the LED flasher illuminates in a

wig-wag sequence (left and then right). The left LED 

flashes two times in a slow volley each time it is 

energized (124 ms on and 76 ms off per flash). This 

is followed by the right LED, which flashes four times 

in a rapid volley when energized (25 ms on and 

25 ms off per flash) and then has a longer flash for 

200 ms. The effect has been described as a “stutter 

flash effect.”(3) Advance yield markings were installed 

before all installations during the baseline measurement phase to reduce the risk of multiple threat 

crashes.

Methodology

The general methodology followed for all of the experiments included measuring driver yielding behavior 

and vehicle/pedestrian evasive conflicts. Observers 

scored the percentage of drivers yielding and not 

yielding to pedestrians. Drivers were scored as yielding 

if they stopped or slowed and allowed the pedestrian 

to cross. Conversely, drivers were scored as not 

yielding if they passed in front of the pedestrian but 

would have been able to stop when the pedestrian 

arrived at the crosswalk. 

The Institute of Transportation Engineers signal formula applied to calculate the duration of the yellow

signal phase was used to determine whether a driver 

could stop safely.(4) A landmark associated with 

this distance was identified for each approach to the 

crosswalk. Drivers who passed this landmark before 

the pedestrian started to cross could be scored as 

yielding to pedestrians but not as failing to yield 

because they might not have sufficient distance to 

stop safely. Drivers beyond the landmark when the 

pedestrian entered the crosswalk could be scored as 

yielding or not yielding because they had sufficient 

distance to stop safely. When the pedestrian first 

started to cross, only drivers in the first half of the 

roadway were scored for yielding. Once the pedestrian 

approached the painted median, the yielding behaviors 

of drivers in the remaining two lanes were scored. 

This procedure was followed because it conformed 

to the obligation of drivers specified in the statutes 

of each of the three cities that were studied.

Results

Geographic Sustainability 

Yielding during the baseline period before the introduction of the RRFB ranged between zero and 26 percent.

The introduction of the RRFB was associated with 

yielding that ranged between 72 and 96 percent at the

2-year follow-up. Table 1 shows the percentage yielding

at each of the 22 sites. 

The general statistical methodology used in this 

study and presented in table 2 was based on the 

general time-series intervention regression modeling 

approach described in Huitema and McKean and 

McKnight et al. (See references 5–8.)

The five main parameter estimates are shown in 

table 2. There is an immediate and large level change 

from the baseline to day 7, a small but statistically 

significant additional increase from day 7 to day 30, a 

minor and not statistically significant level decrease 

at day 60, and a general trend after day 60 that has 

little slope across the remaining observation days. 

Therefore, the evidence for change is overwhelming 

and is maintained for the duration of the study. In 

the table, there are 166 degrees of freedom for all tests.

Two-Beacon Versus Four-Beacon Systems

This experiment evaluated the effectiveness of the installation of only two RRFBs (one for each direction of 

approach mounted at the right-hand side of the approach) compared to the installation of four RRFBs (two

per approach with one on the roadway median and

one on the right-hand side). The average yielding during

baseline conditions across four sites was 18.2 percent. 

Installation and activation of the two RRFB systems

increased the average yielding to 81.2 percent. The

addition of the median beacons produced a further

increase in yielding to 87.8 percent. Yielding for the

four-beacon system continued to improve over time 

during follow-up data collection. 

Figure 1. RRFB with two forward-facing LED flashers and 

a side-mounted LED flasher.
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Aimed Versus Unaimed Beacons

This experiment evaluated the effectiveness of RRFBs 

with LEDs aimed parallel to the approach roadway 

compared to RRFBs with LEDs specifically aimed 

toward the eyes of approaching drivers at a given distance in advance of the crossing using a system that

allowed the engineer to aim the LEDs. The percentage

of drivers yielding to pedestrians during the baseline condition was zero percent. The average yielding 

compliance 7 days after RRFB installation increased 

to 33.4 percent. There was an additional increase to 

72 percent 30 days after installation. The change 

from parallel LEDs to the LEDs that could be aimed 

produced an increased average of 89 percent. 

Night Versus Day Operations

Night data were collected at one site where data 

had been collected during the daytime. During daytime collection, the site had a baseline average of 

18.3 percent. The initiation of the two- and four-RRFB 

systems increased yielding to 86.7 and 89.6 percent, 

respectively. When the site was evaluated during nighttime hours, baseline yielding was only 4.8 percent.

Introduction of the two- and four-RRFB systems 

showed increases in yielding to 84.6 and 99.5 percent, 

respectively. 

Standard Beacons Versus RRFBs

Two sites were selected for this experiment. The 

first site had an above roadway standard yellow

flashing beacon, while the second site was equipped

with a side-mounted standard yellow flashing beacon

attached to the pedestrian warning sign. The average 

baseline yielding when the standard beacons were not 

activated was 12 percent for the above roadway beacon and zero percent for the side-mounted beacon. 

Table 1. Baseline and follow-up yielding data at sites in Florida, Illinois, and Washington, DC.

Site

Baseline 

(Percent)

Day (Percent)

7 30 60 90 180 270 365 730

Florida

31st Street south of 54th Avenue S 0 54 76 N/A 59 N/A 91 75 83

4th Street at 18th Avenue S 0 63 72 N/A 69 N/A 69 80 80

22d Avenue N and 7th Street 0 97 96 91 93 92 91 98 96

9th Avenue N and 26th Street 0 80 82 85 95 81 88 77 78

22d Avenue N and 5th Street 8 87 89 92 92 87 96 92 95

Martin Luther King Street and 15th Ave S 1 86 84 85 82 N/A 89 88 88

Martin Luther King Street and 17th Ave N 0 96 94 80 82 83 88 82 83

1st Avenue N and 13th Street 2 85 87 75 78 N/A 91 88 N/A

9th Avenue N and 25th Street 0 86 90 83 90 N/A 88 81 79

1st Street and 37th Avenue N 0 79 87 85 87 N/A 90 97 95

58th Street and 3d Avenue N 0 85 84 85 85 79 92 82 88

Central Avenue and 61st Street 0 94 95 77 73 72 79 67 72

1st Avenue S and 61st Street 5 68 72 73 75 72 90 72 78

1st Avenue N and 61st Street 0 75 75 68 82 42 76 79 83

83d Avenue N and Macoma Drive 0 86 93 91 73 88 84 80 90

9th Avenue N and 45th Street 0 54 91 89 90 80 83 77 78

22d Avenue S west of 23d Street 0 89 86 78 77 60 75 81 82

62d Avenue S and 21st Street 0 77 76 77 53 78 81 84 80

9th Avenue N and 31st Street 16 93 95 89 88 82 82 89 N/A

Average 2 81 86 82 80 76 86 83 84

Illinois

Midlothian Road and Kilarny Pass Road 7 62 62 N/A N/A N/A N/A N/A N/A

Hawley Street and Atwater Drive 19 71 68 N/A N/A N/A N/A N/A N/A

Average 13 67 65 N/A N/A N/A N/A N/A N/A

Washington, DC

Brentwood Road and 13th Street 26 62 74 N/A N/A 80 N/A N/A N/A

Average Yield (All Sites) 4 78 82 83 80 77 85 83 84

N/A indicates that the measure was missed or has not yet been scheduled.

Table 2. Florida data estimates of treatment effect 

parameters and associated t-ratios and p-values.

Treatment Effect 

Parameter

Estimate 

Parameter t-Ratio p-Value

Baseline level 1.79

Level change day 7 77.25 29.22 0.001

Level change day 30 6.03 2.38 0.02

Level change day 60 −4.26 −1.75 0.08

Follow-up slope 0.0059 1.62 0.11

Note: Certain cells were left blank because only t-ratios and 

p-values that show change from the baseline were included.
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Researchers—This study was performed by Principal Investigators Jim Shurbutt and Ron Van Houten. For more information about 

this research, contact Dr. Ron Van Houten, Psychology Department, Western Michigan University, 3700 Wood Hall, Kalamazoo, MI 

49008, ron.vanhouten@wmich.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.tfhrc.gov/safety.

Key Words—LED rectangular rapid-flashing beacon, RRFB, LED beacon, Stutter-flash beacon, Yielding at uncontrolled locations, and 

Advance yield markings.

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 products or manufacturers. Trademarks or manufacturers’ names appear in this report only 

because they are considered essential to the objective of the document.

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august 2010 FHWA-HRT-10-046

HRDS-07/08-10(2M)E

The activation of the overhead standard beacon produced an average yielding compliance of 15.5 percent. 

The introduction of a two-beacon RRFB system at this 

site produced an increase in yielding to 78.3 percent. 

The introduction of the four-beacon RRFB system was 

associated with 88 percent yielding compliance. At 

the second site, activating the side-mounted standard 

beacon produced 12 percent yielding compliance. The 

two-beacon rectangular rapid-flashing system produced 72 percent yielding compliance. A four-beacon 

RRFB system was not available for this second site. 

Conclusion

The results show that the rectangular LED yellow 

RRFBs appear to be an effective tool for producing 

large numbers of drivers yielding right-of-way to pedestrians in crosswalks at sites where drivers rarely 

yielded to pedestrians. The results seem to be maintained over time. Because 19 systems were introduced 

in St. Petersburg, FL, it is clear that the effects do not 

diminish when a modest number of systems are installed. However, it is not clear whether the effect of the 

device would diminish if it were installed at hundreds 

of sites. The findings of the present study suggest that 

the RRFB used in conjunction with advance yield 

marking can increase yielding and may increase safety 

at uncontrolled crosswalks at high ADT multilane sites. 

Future research should examine crash data using timeseries or empirical Bayes methodology to determine 

the safety benefits of the RRFB.

References

1. Fitzpatrick, K., Turner, S., Brewer, M., Carlson, 

P., Lalani, N., Ullman, B., Trout, N., Park, E.S., Lord, 

D., and Whitacre, J. (2006). Improving Pedestrian 

Safety at Unsignalized Crossings, TCRP/NCHRP 

Report 112/562, Transportation Research Board, 

Washington, DC.

2. National Highway Transportation Safety Administration. (2008). National Pedestrian Crash Report, 

Report No. DOT HS 810 968, United States Department of Transportation, Washington, DC.

3. Van Houten, R., Ellis, R., and Marmolejo, E. (2008). 

“The Use of Stutter Flash LED Beacons to Increase 

Yielding to Pedestrians at Crosswalks,” Transportation 

Research Record 2073, 69–78, Transportation 

Research Board, Washington, DC. 

4. Institute of Transportation Engineers Technical 

Council Committee 4A-16. (1985). Determining 

Vehicle Change Intervals: A Proposed Recommended Practice, Institute of Transportation Engineers, 

Washington, DC.

5. Huitema, B.E. and McKean, J.W. (1998). “Irrelevant 

Autocorrelation in Least-Squares Intervention 

Models,” Psychological Methods, 3, 104–116.

6. Huitema, B.E. and McKean, J.W. (2000). “A Simple 

and Powerful Test for Autocorrelated Errors in OLS 

Intervention Models,” Psychological Reports, 87, 

3–20.

7. Huitema, B.E. and McKean, J.W. (2000). “Design 

Specification Issues in Time-Series Intervention 

Models,” Educational and Psychological Measurement, 60, 38–58.

8. McKnight, S.D., McKean, J.W., and Huitema, B.E. 

(2000). “A Double Bootstrap Method to Analyze 

Linear Models with Autoregressive Error Terms,” 

Psychological Methods, 5, 87–101.