FHWA Interim Approval Allows Optional Use of Rectangular Rapid Flashing Beacons

Wednesday, April 11, 2018

On March 20, the U.S. Federal Highway Administration (FHWA) issued interim approval of optional use of Rectangular Rapid Flashing Beacons (RRFBs) in the United States.

Patents associated with RRFBs have been expressly abandoned, making this device eligible for use on a provisional basis. State and local agencies wishing to use RRFBs must now submit a written request to the FHWA, including jurisdictions that requested and obtained the FHWA's permission under the previous interim approval, which ended in December 2017.

The FHWA's reintroduction of RRFBs gives practitioners more options, in addition to those already allowed by the U.S. Manual of Uniform Traffic Control Devices (MUTCD). Reference to patented devices is prohibited in the MUTCD.

The latest developments regarding the use of RRFBs in the U.S. MUTCD will be discussed at the Transportation Association of Canada (TAC) Traffic Operations and Management Standing Committee meeting in Ottawa, April 18-23, 2018.

Responses to frequently asked questions about the new interim approval are available on the FHWA website.


The FHWA has issued interim approval to allow the use of RRFBs to supplement standard pedestrian and school crossing warning signs at uncontrolled marked crosswalks. RRFBs do not meet the current standards for flashing warning beacons as contained in the 2009 edition of the MUTCD, Chapter 4L, which requires a warning beacon to be circular in shape and either 8 or 12 inches in diameter, to flash at a rate of approximately once per second, and to be located no less than 12 inches outside the nearest edge of the warning sign it supplements. RRFBs use rectangular-shaped high-intensity light-emitting-diode (LED)-based indications, flash rapidly in a combination wig-wag and simultaneous flash pattern, and may be mounted immediately adjacent to the crossing sign.