What the MUTCD says about RRFBs

3 min. read
January 18, 2023
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If you have so much as a passing interest in traffic safety, you’ve no doubt come across the MUTCD, the Manual on Uniform Traffic Control Devices, often described as the bible of American road design. Issued by the Federal Highway Administration (FHWA), it essentially dictates what’s acceptable—and what isn’t—when it comes to things like signs, signals, markings, and other devices used to control, warn, and guide traffic.

While rectangular rapid flashing beacons (RRFBs) clearly fit into this category and have consistently been shown to increase driver awareness and pedestrian safety at unsignalized crossings, you won’t find them in the MUTCD. But municipalities can still use them. Here’s why.

A bit of background

RRFBs initially received interim approval (IA-11) from the FHWA in 2008. Transportation departments could request to install them as a warning beacon to supplement a pedestrian (W11-2) or school (S1-1) warning sign located at or adjacent to a marked crosswalk.

For about 10 years, this is exactly what they did, adding much-needed conspicuity to crossings, particularly in areas with high pedestrian volumes, or a history of pedestrian crashes. This ended in 2017 when the FHWA rescinded its approval due to the RRFB being a patented device (which the FHWA prohibits to avoid endorsing one particular product or manufacturer over another).

Reinstating the RRFB

For RRFBs to be used again, and potentially someday included in the MUTCD, the patents needed to be disclaimed. Carmanah did this in 2018, purchasing the patents from their owner and returning them to the public domain. Any manufacturer can now produce RRFBs without worrying about licensing or patent infringement.

With this hurdle cleared, the FHWA issued its second interim approval (IA-21) of the RRFB in March 2018. Though still not included in the MUTCD, IA-21 once again authorized departments to install and utilize RRFBs—this time in an expanded range of scenarios, including at trail crossings and roundabouts.

Allowable uses under IA-21

IA-21 clarified that RRFBs are to be used for “pedestrian-actuated conspicuity enhancement,” rather than general “warning beacons” (as written in IA-11). They can be used to supplement the following post- and overhead-mounted signage:

Three yellow warning signs that are appropriate for use with RRFBs, including pedestrian crossing, school zone crossing, and bicycle/pedestrian crossing.

RRFBs are NOT permitted at controlled crosswalks, meaning where traffic signals or regulatory signs (stop and yield) are present. A notable exception is roundabouts, where RRFBs may be used alongside these signs.

At locations where the sight distance is deemed inadequate (see here), IA-21 provides that an additional RRFB may be installed in advance of the crosswalk, along with a crossing warning sign with an “AHEAD” or distance plaque.

IA-21 also lays out additional specifications, including beacon dimensions, flash pattern, duration, mounting height, and accessibility features (which are optional). Details for all of these can be found in the the Notice of Interim Approval.

Looking forward

The FHWA is currently in the process of updating the MUTCD for the first time since 2009, and there is good reason to believe RRFBs will finally be added. In December 2020, it released a “proposed rule” for public comment, which includes adding RRFBs to the section on Enhanced Conspicuity for Standard Signs, as well as a new chapter with provisions for their application, design, and operation.

As a requirement of the new Infrastructure Investment and Jobs Act (IIJA), the next version of the MUTCD (the 11th) is due to be released no later than May 15, 2023. We look forward to the RRFB’s official introduction to this much-used resource, and to seeing more cities deploying them to keep people safe.

>>> Learn more about RRFBs

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