What is a Rectangular Rapid Flashing Beacon and what does it mean?

RRFB Pedestrian Crosswalk System - Pedestrian Safety

14: Rectangular Rapid-flashing Beacon (RRFBs), Source

Pedestrian Safety: RRFB or Rectangular Rapid Flashing Beacons

Solar-Powered RRFB Side-of-Pole - Traffic Safety Supply Company

TS60-RRFB LED Rectangular Rapid Flashing Beacons - Traffic Safety Corp.

New Rapid-Flashing Beacon Shows Great Promise in Improving Pedestrian Safety — Texas A&M Transportation Institute

These RRFB Crosswalk Packages contain everything you need, except for the signs and poles, to install a RRFB (Rectangular Rapid Flashing Beacon)

RRFB Push-Button Activated Crosswalk Packages

Rectangular Rapid Flashing Beacon By Transportation Solutions And Lighting, Inc.

FHWA Rescission of Interim Approval of Rectangular Rapid Flashing Beacons — Alta Planning + Design