Rectangular Rapid-Flashing Beacons (RRFBs) - New Interim Approval (IA-21) Issued
Edited by: Airton Kohls & Frank Brewer (Source: FHWA & MUTCD)
A NEW Interim Approval (IA-21) was issued for the use of Rectangular Rapid-Flashing Beacons (RRFBs) on March 20, 2018. The Federal Highway Administration (FHWA) has been informed and has confirmed that the patents issued and pending (that trigger IA-11 being rescinded in December 2017) have been expressly abandoned, and that the RRFB is once again eligible for provisional use through an Interim Approval. This Interim Approval (IA-21) has been updated to reflect more recent research and experience with the device. Agencies that previously had been approved to use RRFBs under IA-11 are not covered by this new Interim Approval to install new RRFBs. If agencies that had approval under IA-11 wish to continue to install new RRFBs, then they must submit a new request to the FHWA and agree to comply with the terms and conditions of IA-21.
Some of the changes on IA-21 is that a RRFB shall only be installed to function as a pedestrian-actuated conspicuity enhancement. Before, IA-11 stated that RRFB's shall only be installed to function as a warning beacon. Furthermore, the beacon flashing requirements for the RFRFB have been detailed on IA-21:
- When actuated, the two yellow indications in each RRFB unit shall flash in a rapidly flashing sequence.
- As a specific exception to the requirements for the flash rate of beacons provided in Paragraph 3 of
Section 4L.01, RRFBs shall use a much faster flash rate and shall provide 75 flashing sequences per
minute. Except as provided in Condition 5f below, during each 800-millisecond flashing sequence, the
left and right RRFB indications shall operate using the following sequence:
The RRFB indication on the left-hand side shall be illuminated for approximately 50 milliseconds.
Both RRFB indications shall be dark for approximately 50 milliseconds.
The RRFB indication on the right-hand side shall be illuminated for approximately 50 milliseconds.
Both RRFB indications shall be dark for approximately 50 milliseconds.
The RRFB indication on the left-hand side shall be illuminated for approximately 50 milliseconds.
Both RRFB indications shall be dark for approximately 50 milliseconds.
The RRFB indication on the right-hand side shall be illuminated for approximately 50 milliseconds.
Both RRFB indications shall be dark for approximately 50 milliseconds.
Both RRFB indications shall be illuminated for approximately 50 milliseconds.
Both RRFB indications shall be dark for approximately 50 milliseconds.
Both RRFB indications shall be illuminated for approximately 50 milliseconds.
Both RRFB indications shall be dark for approximately 250 milliseconds. - The flash rate of each individual RRFB indication, as applied over the full flashing sequence, shall not be between 5 and 30 flashes per second to avoid frequencies that might cause seizures.
- The light intensity of the yellow indications during daytime conditions shall meet the minimum specifications for Class 1 yellow peak luminous intensity in the Society of Automotive Engineers (SAE) Standard J595 (Directional Flashing Optical Warning Devices for Authorized Emergency, Maintenance, and Service Vehicles) dated January 2005.
- To minimize excessive glare during nighttime conditions, an automatic signal dimming device should be used to reduce the brilliance of the RRFB indications during nighttime conditions.
- Existing RRFB units that use the flashing sequence that was specified in the Interim Approval 11 memorandum and a subsequent interpretation (the RRFB indication on the left-hand side emits two slow pulses of light after which the RRFB indication on the right-hand side emits four rapid pulses of light followed by one long pulse of light) should be reprogrammed to the flash pattern specified above in Condition 5b as part of a systematic upgrading process, such as when the units are serviced or when the existing signs are replaced.
IA-21 also details the allowable uses of RRFBs: An RRFB shall only be installed to function as a pedestrian-actuated conspicuity enhancement.
- An RRFB shall only be used to supplement a post-mounted W11-2 (Pedestrian), S1-1 (School), or W11-15 (Trail) crossing warning sign with a diagonal downward arrow (W16-7P) plaque, or an overhead-mounted W11-2, S1-1, or W11-15 crossing warning sign, located at or immediately adjacent to an uncontrolled marked crosswalk.
- Except for crosswalks across the approach to or egress from a roundabout, an RRFB shall not be used for crosswalks across approaches controlled by YIELD signs, STOP signs, traffic control signals, or pedestrian hybrid beacons.
- In the event sight distance approaching the crosswalk at which RRFBs are used is less than deemed necessary by the engineer, an additional RRFB may be installed on that approach in advance of the crosswalk, as a pedestrian-actuated conspicuity enhancement to supplement a W11-2 (Pedestrian), S1-1 (School), or W11-15 (Trail) crossing warning sign with an AHEAD (W16-9P) or distance (W16-2P or W16-2aP) plaque. If an additional RRFB is installed on the approach in advance of the crosswalk, it shall be supplemental to and not a replacement for the RRFBs at the crosswalk itself.
In addition to the conditions of the Interim Approval, IA-21 details the general conditions, sign/beacon assembly locations, beacon dimensions and placement in the assembly, beacon flashing requirements, beacon operation and accessible pedestrian features. IA-21 can be accessed at the following link: https://mutcd.fhwa.dot.gov/resources/interim_approval/ia21/ index.htm
The RRFB, while popular and effective, is not the only treatment available for uncontrolled crosswalks. Every crosswalk should be evaluated to determine the most appropriate treatment(s) based on the specifics of each location. To assist agencies and practitioners, the FHWA has prepared a four-page informational brief on effective treatments that comply with the MUTCD and can be used individually or in combination at uncontrolled marked crosswalks. The informational brief can be found at: https://mutcd.fhwa.dot.gov/resources/interim_approval/ ia11/informationalbrief/index.htm
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