Rectangular Rapid Flash Beacon 

(RRFB)

Purpose

According to the National Highway Traffic Safety Administration, there were a total of 

14,340 pedestrian fatalities and 193,000 pedestrian injuries resulting from pedestrianvehicle crashes nationwide during the 2004-2006 period. Rectangular Rapid Flash 

Beacons (RRFB) can enhance safety by reducing crashes between vehicles and 

pedestrians at unsignalized intersections and mid-block pedestrian crossings by 

increasing driver awareness of potential pedestrian conflicts. 

Alternative Names

Light Emitting Diode (LED) Rapid-Flash System, Stutter Flash or LED Beacons.

Operation

• RRFBs are user-actuated amber LEDs that supplement warning signs at unsignalized 

intersections or mid-block crosswalks. They can be activated by pedestrians manually by 

a push button or passively by a pedestrian detection system.

• RRFBs use an irregular flash pattern that is similar to emergency flashers on police vehicles. 

• RRFBs may be installed on either two-lane or multi-lane roadways.

Potential Benefits

• RRFBs are a lower cost alternative to traffic signals and hybrid signals that are shown to 

increase driver yielding behavior at crosswalks significantly when supplementing standard 

pedestrian crossing warning signs and markings. 

• An official FHWA-sponsored experimental implementation and evaluation conducted in 

St. Petersburg, Florida found that RRFBs at pedestrian crosswalks are dramatically more 

effective at increasing driver yielding rates to pedestrians than traditional overhead beacons. 

• The novelty and unique nature of the stutter flash may elicit a greater response from drivers 

than traditional methods.

• The addition of RRFB may also increase the safety effectiveness of other treatments, such as 

the use of advance yield markings with YIELD (or STOP) HERE FOR PEDESTRIANS signs. These 

signs and markings are used to reduce the incidence of multiple-threat crashes at crosswalks 

on multi-lane roads (i.e., crashes where a vehicle in one lane stops to allow a pedestrian to 

cross the street while a vehicle in an adjacent lane, traveling in the same direction, strikes the 

pedestrian), but alone they only have a small effect on overall driver yielding rates. 

This summary is one in a series 

describing Innovative Intersection 

Safety Treatments. The summaries 

identify new technologies and 

techniques to improve intersection 

safety developed since NCHRP 

Report 500, Volumes 5 and 12, 

were published in 2003 and 2004, 

respectively. These treatments 

show promise for improving safety 

but comprehensive effectiveness 

evaluations are not yet available.

May 2009

FHWA-SA-09-009
Agency Experience

“An Analysis of the Effects of Stutter Flash LED Beacons to Increase Yielding to Pedestrians 

Using Multilane Crosswalks,” along with “The Use of Stutter Flash LED Beacons to Increase 

Yielding to Pedestrians at Crosswalks,” presented at the Transportation Research Board 

Annual Meeting in 2008, summarized the results of two studies on the effects of RRFBs 

when used to supplement standard pedestrian crossing warning signs at crosswalks1.

The former found that going from a no-beacon arrangement to a two-beacon system, 

mounted on the supplementary warning sign on the right side of the crossing, increased 

yielding from 18 percent to 81 percent. There was a further increase in yielding behavior, 

with a four-beacon system (with two beacons on both the right and left side of the 

crossing) to 88 percent. “An Analysis of the Effects of Stutter Flash LED Beacons to Increase 

Yielding to Pedestrians Using Multilane Crosswalks” also evaluated the sites over a 1-year 

period, and found that there was little to no decrease in yielding behavior over time.

Implementation Considerations

• Including RRFBs on the roadside increases driver yielding behavior significantly. Including RRFBs 

on a center island or median as well can further increase driver yielding behavior, although with 

a lower marginal benefit than roadside beacons.

• RRFBs can use manual push-buttons or automated passive (e.g., video or infrared) pedestrian 

detection, and should be unlit when not activated.

• RRFBs typically receive power by standalone solar panel units, but may also be wired to a 

traditional power source.

Manual on Uniform Traffic Control Devices (MUTCD) Specifications

• The MUTCD gave interim approval to RRFBs for optional use in limited circumstances in July 

2008. The interim approval allows for usage as a warning beacon to supplement standard 

pedestrian crossing warning signs and markings at either a pedestrian or school crossing; where 

the crosswalk approach is not controlled by a yield sign, stop sign, or traffic-control signal; or at 

a crosswalk at a roundabout.

• The MUTCD interim approval memo also contains other provisions for the implementation of 

the device and should be reviewed (http://mutcd.fhwa.dot.gov/resources/interim_approval/ia11/

fhwamemo.htm).

Costs

• Cost is approximately $10,000 to $15,000 for purchase and installation of two units (one on 

either side of a street). This includes solar panels for powering the units, pad lighting, indication 

units (for both sides of street) with RRFBs in the back and front of each unit, signage on 

both approaches, all posts, and either passive infrared detection or push buttons with audio 

instructions. 

• Costs would be proportionately higher for additional units placed on a median island, etc.

Figure 1: Activated, solar-powered RRFB on 

a center island at an unsignalized intersection– 

beacons flash using an irregular flash pattern that 

is similar to emergency flashers on police vehicles

Figure 2: Activated, solar-powered, roadside RRFB 

at a mid-block crosswalk

Figure 3: Combined roadside and median system 

of solar-powered RRFB

Learn More

Michael Frederick, St. Petersburg Neighborhood 

Transportation Manager

727.893.7843

michael.frederick@stpete.org

Ed Rice, Intersection Safety Team Leader 

FHWA Office of Safety

202.366.9064 

ed.rice@dot.gov

See Also: 

http://mutcd.fhwa.dot.gov/resources/

interim_approval/ia11/stpetersburgrpt/intro.htm 

http://www.stpete.org/pdf/ite_paper_07.pdf

Solar Panel

1

The two known studies of stutter flash were both conducted in Florida—one in Miami Beach and one in St. Petersburg. They are:

Sherbutt, J., R. Van Houten, and S. Turner. “An Analysis of the Effects of Stutter Flash LED Beacons to Increase Yielding to Pedestrians Using 

Multilane Crosswalks.” Presented at the Transportation Research Board Annual Meeting, Washington, DC, 2008.

Van Houten, R., R. Ellis, and E. Marmolejo. “The Use of Stutter Flash LED Beacons to Increase Yielding to Pedestrians at Crosswalks.” Presented at 

the Transportation Research Board Annual Meeting, Washington, DC, 2008.