FHWA issues interim approval of Rectangular Rapid-Flashing Beacons at crosswalks
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FHWA issues interim approval of Rectangular Rapid-Flashing Beacons at crosswalks

In a memorandum released on March 20, the Federal Highway Administration (FHWA) issued “Interim Approval (IA)-21 – Rectangular Rapid-Flashing Beacons (RRFBs) at Crosswalks.” The new IA-21 allows for the optional use of RRFBs as pedestrian-activated visibility enhancements for pedestrian and school crossing warning signs under limited conditions.

The temporary approval to use RRFBs comes after IA-11, which originally allowed for the optional use of RRFB as warning beacons, was rescinded in an FHWA memorandum on Dec. 21, 2017 because of patents issued and pending on the device. The memorandum prohibited new installations of RRFBs, however, the flashing devices that were already installed were allowed to remain in service until they were no longer functional.

Most recently, the FHWA has been informed and has confirmed that the patents are no longer being pursued and RRFB devices are once again eligible for temporary use under IA-21. It is important to note this is a new IA with updated research and information regarding RRFBs. Agencies that want to install RRFBs must apply for permission of use from the FHWA under IA-21, even if they were previously granted permission of use under IA-11. IA-21 does not reinstate IA-11.

In general, IAs allow for the temporary use of a new traffic control device, revisions of the application or manner of use of an existing traffic control device, or adherence to a provision not addressed in the Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD). These permissions are subject to change pending the establishment of official guidelines.

For more information about IA-21, visit and click on “FHWA issues interim approval.” For any additional questions about IA-11 or IA-21, email Duane Thomas at

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