Rectangular Rapid Flashing Beacons (RRFB) – New Interim Approval 21 (IA-21)

On March 20, 2018, the Federal Highway Administration issued Interim Approval 21 (IA-21) for the use of Rectangular Rapid Flashing Beacons (RRFB).

Here’s what you need to know in the new interim approval:

  • State and local agencies must request and receive permission to use this new Interim Approval, designated IA-21, from the Federal Highway Administration (FHWA) in accordance with the provisions of Section 1A.10 of the MUTCD before they can use the RRFB, even if prior approval had been given for Interim Approval 11 (IA-11), which was terminated. The issuance of this new Interim Approval does not reinstate IA-11 either in whole or in part.
  • States may continue to request Interim Approval for all jurisdictions in that State.
  • The patents on the RRFB have been expressly abandoned.
  • RRFB may be used to supplement the combined bicycle/pedestrian sign (W11-15).
  • To minimize excessive glare during nighttime conditions, an automatic signal dimming device should be used to reduce the brilliance of the RRFB indications.
  • The flashing sequence for existing RRFB units should be reprogrammed to the FHWA defined flashing sequence as part of a systematic upgrading process, such as when the units are serviced or when the existing signs are replaced.

For more information, please contact your local Kimley-Horn partner and visit: