RRFB Flashing Requirements and MUTCD Considerations
MUTCD considerations
RRFBS
9/6/20264 min read
Where Can an RRFB Be Used?
Under the current MUTCD, an RRFB may supplement certain crossing warning signs at a marked crosswalk across an uncontrolled roadway approach.
Applicable signs include:
W11-2 Pedestrian Crossing
S1-1 School
W11-15 Trail Crossing
For post-mounted installations, the crossing warning sign is normally accompanied by a W16-7P diagonal downward arrow plaque identifying the crosswalk.
An RRFB generally should not be installed at a crosswalk across an approach already controlled by a STOP sign, YIELD sign, traffic control signal, or pedestrian hybrid beacon. The MUTCD provides limited exceptions for certain roundabout crossings and free-flow turn lanes separated by a channelizing island.
The responsible roadway agency should determine whether an RRFB is appropriate for the location.
RRFB Indication Size and Arrangement
Each RRFB unit must contain two rectangular yellow indications using LED-array-based pulsing light sources.
Important physical requirements include:
Each indication must be at least 5 inches wide and 2 inches high.
The longer dimension must be horizontal.
The two indications must be horizontally aligned.
At least 7 inches must separate the nearest edges of the two indications.
The complete RRFB housing must remain within the outside edges of the warning sign it supplements.
These dimensions apply to the visible indications and their arrangement, not simply to the overall enclosure.
The Required Flashing Pattern
RRFBs use a distinctive rapid flash pattern rather than a conventional alternating beacon pattern.
The current MUTCD requires:
75 complete flashing sequences per minute
An 800-millisecond sequence
Alternating left and right pulses
Two simultaneous pulses near the end of each sequence
A final dark interval before the sequence repeats
This pattern is commonly described as a wig-wag plus simultaneous, or WW+S, flash pattern.
The flash rate of each individual indication, measured across the complete sequence, must not exceed five flashes per second. A controller should therefore be tested for the complete timing sequence—not only for a general description such as “rapid flashing.”
All RRFB units serving the same crosswalk must start flashing together and stop flashing together. Wireless systems should maintain this coordination between all stations.
Yellow Color and Daytime Intensity
RRFB indications must be yellow. However, LED wavelength alone does not establish compliance.
For example, a manufacturer may state that its LEDs have a wavelength of 587–590 nanometers. That information can help identify the general color range, but it does not confirm the color and optical performance of the completed RRFB indication.
The assembled light bar should be evaluated for:
Effective yellow color
Complete optical output through the lens
Light distribution at required viewing angles
Daytime peak luminous intensity
Performance at different voltages and temperatures
The current MUTCD requires the daytime intensity of the yellow indications to meet the minimum SAE J595 Class 1 yellow peak luminous intensity specifications referenced by the MUTCD.
When reviewing a product, request a test report for the complete RRFB indication—not only a specification for the individual LED chips.
Nighttime Dimming
An RRFB must be bright enough to attract attention during daylight, but excessive nighttime brightness can create glare and reduce visibility.
The MUTCD permits an automatic dimming device when the indications would otherwise cause excessive nighttime glare. Many roadway agencies include automatic nighttime dimming in their own RRFB specifications.
A photocell or other ambient-light sensor can adjust output automatically as lighting conditions change. The nighttime level should maintain adequate visibility without applying the full daytime intensity after dark.
Pedestrian or Bicyclist Activation
An RRFB must normally remain dark and begin flashing only after pedestrian or bicyclist actuation.
Activation may be provided by:
A pedestrian push button
A bicyclist push button
Approved passive detection
A combination of push-button and passive detection
If a pedestrian push button is used, the MUTCD requires an R10-25 instruction sign explaining the purpose and use of the button.
The location and accessibility of the push button should also be reviewed. The current MUTCD includes provisions concerning push-button placement, locator tones, bicyclist push buttons, and audible information for pedestrians with vision disabilities.
Flash Duration and Re-Activation
An RRFB should not use an arbitrary flashing duration for every project.
The minimum operating period should be based on pedestrian clearance-time procedures, including the crossing distance and applicable walking-speed considerations. Additional time may be considered to allow a pedestrian to confirm that approaching vehicles are yielding before entering the roadway.
Each new actuation must immediately initiate the complete predetermined flash period. This also applies when another pedestrian activates the system while the RRFBs are already flashing or immediately after they stop.
For systems with passive detection, operation may cease after the pedestrian clears the crosswalk when the system is designed and approved for that function.
Sign and Light-Bar Placement
An RRFB cannot be installed as a stand-alone flashing device. It must supplement the appropriate pedestrian, school, or trail crossing warning sign.
For a typical post-mounted installation, at least two sign-and-RRFB assemblies are required for each roadway approach:
One on the right side of the roadway
One on the left side of the roadway
On a divided highway, the left-side assembly should be installed on the median when practicable.
The RRFB may be positioned between the crossing warning sign and downward arrow plaque or within the permitted area above the warning sign. Final placement must follow the MUTCD configuration and project plans.
Final Considerations
RRFB requirements involve the complete installation—not only the light bar. The crossing signs, plaques, light intensity, flash pattern, activation method, operating duration, placement, synchronization, accessibility features, and power system should all be evaluated together.
The current federal requirements are available in Chapter 4L of the FHWA MUTCD, 11th Edition with Revision 1. FHWA also provides a practical RRFB countermeasure overview.
Zoodico offers configurable solar- and AC-powered RRFB systems with push-button activation, multiple station configurations, wireless synchronization, automatic brightness control, and project-specific power options.
Contact Zoodico Traffic Solutions to discuss your crosswalk layout, sign configuration, activation method, power requirements, and applicable agency specifications.
This article provides general MUTCD considerations and is not a complete compliance determination. Final selection, placement, timing, accessibility features, and installation should be reviewed under the current MUTCD, applicable state requirements, agency specifications, and project plans.
Title: RRFB Flashing Requirements and MUTCD Considerations
Focus Keyword: RRFB flashing requirements
Secondary Keywords: RRFB MUTCD requirements, RRFB flash pattern, rectangular rapid flashing beacon requirements
Meta Description: Review key RRFB flashing requirements and MUTCD considerations, including light-bar size, flash pattern, intensity, activation, timing, and placement.
RRFB Flashing Requirements and MUTCD Considerations
Rectangular Rapid Flashing Beacons are pedestrian- and bicyclist-activated warning devices used to increase driver awareness at marked crosswalks.
An RRFB is more than two amber lights mounted below a pedestrian sign. Its indication size, spacing, color, brightness, flash pattern, activation method, operating time, and placement must work together as a complete system.
The following overview summarizes several important MUTCD considerations for selecting and configuring an RRFB system. It is not a substitute for a project-specific engineering review.
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Ann Arbor, Michigan, US