RRFB System Configurations: Single-Sided, Back-to-Back, and Multi-Beacon Systems
RRFB configuration, RRFB light bars, pedestrian crossing beacon
RRFBS
9/6/20269 min read
RRFB System Configurations: Single-Sided, Back-to-Back, and Multi-Station Systems
Rectangular Rapid Flashing Beacon systems can be configured in several ways depending on roadway direction, crossing width, number of lanes, sign visibility, available mounting locations, power supply, and local agency requirements.
Common options include single-sided RRFB light bars, back-to-back light bars, and multi-station systems with two or more synchronized control locations.
Understanding these configurations helps agencies, contractors, engineers, and traffic safety distributors specify the correct number of light bars, controllers, push buttons, signs, poles, batteries, and solar panels for a pedestrian crossing project.
Understanding RRFB System Terminology
Several different components are sometimes informally called an “RRFB.” For accurate planning and quotations, it is important to distinguish between them.
TermMeaningRRFB indicationOne rectangular yellow LED light module.RRFB unit or light barTwo rectangular yellow indications arranged horizontally that flash in the required pattern.Sign assemblyA pedestrian, school, or trail crossing warning sign installed with an RRFB unit and the applicable diagonal downward arrow plaque.RRFB stationA practical configuration term describing one control location, typically consisting of a control box, push button, and either a single-sided or back-to-back light bar configuration.RRFB systemAll RRFB stations, signs, activation devices, controllers, power equipment, and synchronized warning units associated with the crossing.
“Station” is a useful product and project-planning term. The MUTCD primarily describes RRFB units and sign assemblies rather than establishing “station” as the name of a standardized traffic-control-device assembly.
What Is a Single-Sided RRFB Configuration?
A single-sided RRFB configuration has one light bar facing one direction of traffic.
It can be appropriate when an individual support only needs to display a warning toward one traffic approach. Applications may include:
One-way roadways
Advance warning locations
Locations where different supports serve different traffic directions
Installations where pole positions or roadway geometry make separate directional assemblies more practical
Existing systems being expanded with an additional directional warning unit
A single-sided station can typically include:
One control box
One pedestrian push button
One RRFB light bar
Solar or AC power equipment
Mounting hardware
Optional audible push-button features
However, one single-sided light bar does not necessarily constitute a complete RRFB installation.
For post-mounted RRFB applications, the MUTCD generally requires at least two applicable warning sign assemblies for each uncontrolled approach—one on the right side and one on the left side of the roadway. On a divided roadway, the left-side assembly should generally be located in the median where practicable.
The responsible agency or engineer should determine the required number and placement of sign assemblies for the specific roadway.
What Is a Back-to-Back RRFB Configuration?
A back-to-back RRFB configuration installs two light bars on the same support, with the light bars facing opposite traffic directions.
This arrangement is commonly considered for two-way roadways because a single station location can provide an RRFB display toward both directions of traffic.
A typical back-to-back station may include:
One control box
One pedestrian push button
Two RRFB light bars facing opposite directions
Back-to-back warning signs and arrow plaques, when required
A shared solar or AC power system
Mounting brackets and related hardware
Back-to-back systems can reduce the number of separate control locations while still providing warning displays toward opposing traffic approaches.
The light bars are only part of the installation. Sign orientation must also be considered. If motorists approaching from both directions need to see a warning sign at the same location, back-to-back signs and applicable arrow plaques may also be required.
Advantages of a Back-to-Back Configuration
A back-to-back RRFB configuration can provide:
Warning displays for two traffic directions from one support
Fewer separate controller enclosures
Shared power and activation equipment
A cleaner installation where pole locations are limited
Easier synchronization between the two light bars at the same station
Because two light bars consume more energy than one, a back-to-back solar system may require a larger solar panel, battery, or both. The correct power configuration depends on expected activations, flash duration, available sunlight, temperature, system voltage, and other site conditions.
What Is a Multi-Station RRFB System?
A multi-station system uses two or more RRFB control locations operating together at the same crossing.
A typical two-station installation places one station on each side of the roadway. Depending on the required viewing directions, each station can use single-sided or back-to-back light bars.
Three, four, or more stations may be appropriate for:
Wide multilane roadways
Divided highways
Crossings with a raised median or pedestrian refuge island
Locations with restricted sign visibility
Skewed or unusual roadway geometry
Crossings requiring additional warning assemblies
Systems that include advance RRFB assemblies
Projects where additional warning locations are requested by the roadway agency
The number of stations should not be selected only by counting lanes. The design should also consider the number of approaches, which traffic directions need to see each sign, the available sign locations, sight distance, median geometry, and the requirements of the responsible agency.
Common RRFB Configuration Examples
Two Stations with Back-to-Back Light Bars
This is a common configuration for a two-way roadway.
One station is installed on each side of the crossing. Each station has two light bars facing opposite directions, allowing drivers approaching from either direction to see an RRFB assembly on both sides of the roadway.
A typical equipment package may include:
Two control boxes
Two pedestrian push buttons
Four RRFB light bars
Two power systems
Applicable warning signs and arrow plaques
Wireless synchronization between stations
This is only a conceptual example. Final sign placement and equipment quantities should be confirmed for the project.
Two Stations with Single-Sided Light Bars
Two single-sided stations may be used where each station is intended to face a specific traffic approach or where additional assemblies are installed separately.
This arrangement can be suitable for certain one-way roadways, advance warning applications, or site-specific configurations. It should not be assumed to satisfy the assembly requirements for every two-way roadway crossing.
Three- or Four-Station Systems
A divided or unusually wide roadway may need additional stations at the median or other strategic locations.
For example, a four-station design could include two roadside stations and two median stations. Depending on traffic direction and sign placement, some stations might use single-sided light bars while others use back-to-back light bars.
The goal is to provide the required sign assemblies and make the warning displays visible to each applicable traffic approach.
How Wireless RRFB Synchronization Works
Compatible RRFB controllers can communicate wirelessly so that all stations assigned to the same crossing activate together.
A typical activation sequence is:
A pedestrian presses a push button at either side of the crossing.
The local controller initiates the programmed activation cycle.
The controller sends an activation signal to the other paired stations.
All RRFB units assigned to the crossing begin flashing together.
The units continue operating for the configured flash period.
All associated RRFB units stop at the end of the activation cycle.
Under the MUTCD, all RRFB units associated with a crosswalk must begin flashing simultaneously and cease operation simultaneously. Wireless communication is one method of achieving this coordinated operation; the MUTCD does not require wireless communication specifically.
Benefits of Wireless Communication
Wireless synchronization can:
Eliminate the need for a communication cable beneath the roadway
Reduce trenching and pavement disturbance
Simplify installation at existing crossings
Allow activation from either side of the roadway
Support additional compatible stations
Make future system expansion easier
Wireless performance depends on the controller model, antenna position, distance, roadway geometry, physical obstructions, electrical interference, and local site conditions.
Available communication ranges may include approximately 82 feet, 164 feet, or customized distances depending on the selected equipment. The appropriate range should be confirmed before ordering, and wireless operation should be tested after installation.
Can an Existing RRFB System Be Expanded?
Some compatible RRFB systems can be expanded by adding:
Additional controllers
Additional push buttons
Single-sided light bars
Back-to-back light bars
Median stations
Advance warning stations
Before expanding an existing system, confirm:
Controller and firmware compatibility
Wireless frequency and communication protocol
Available communication range
Controller grouping or pairing requirements
Power-system capacity
Mounting and sign compatibility
Flash timing and activation logic
Applicable agency approval requirements
An additional light bar should not simply be connected without checking whether the controller, battery, solar panel, wiring, and protection devices can support the increased electrical load.
Solar and AC Power Considerations
RRFB systems can generally be configured for solar or AC power.
Solar-Powered RRFB Systems
Solar power is often selected where utility power is unavailable or where trenching and electrical service would be costly.
Solar-system sizing should account for:
Number of RRFB light bars
Single-sided or back-to-back configuration
Expected daily activations
Programmed flash duration
Solar exposure at the installation site
Seasonal sunlight conditions
Battery capacity
Low-temperature performance
Wireless controller consumption
Push-button and audible-device loads
A standard solar panel and battery configuration should not automatically be used for every project. Back-to-back and multi-station systems may require different power equipment than a single-light-bar installation.
AC-Powered RRFB Systems
AC power may be appropriate where reliable electrical service is readily available.
An AC-powered system can reduce dependence on solar exposure, but the project may require:
Electrical service coordination
Trenching or conduit
Permits and inspections
Surge protection
Appropriate power conversion
Qualified electrical installation
The most economical choice depends on the availability of existing power and the cost of civil and electrical work at the site.
Selecting the Correct Flash Duration
RRFB flash duration should be based on the time pedestrians need to cross the roadway.
Although controllers may offer standard settings such as 25, 35, or 45 seconds, the correct setting should not be selected only from a product menu.
The MUTCD indicates that the predetermined flash period should be based on pedestrian clearance-time procedures and may include additional time for a pedestrian to detect a gap and for motorists to recognize and respond to the activated warning device.
The responsible agency or engineer should establish the appropriate timing based on:
Crossing distance
Pedestrian walking speed
Median or refuge-island operation
Expected pedestrian population
Roadway geometry
Applicable agency standards
Use of passive or active pedestrian detection
Important MUTCD Configuration Requirements
Chapter 4L of the current MUTCD establishes requirements for RRFB design and operation. Important configuration points include:
Each RRFB unit consists of two rectangular yellow LED indications.
The two indications are arranged horizontally.
An RRFB unit supplements an applicable pedestrian, school, or trail crossing warning sign.
The warning sign assembly includes the applicable diagonal downward arrow plaque at the crosswalk.
RRFBs are normally dark and activate when a pedestrian is detected.
All RRFB units associated with the crossing begin and end their flashing operation simultaneously.
Push-button installations require the applicable pedestrian instruction sign.
Daytime light intensity must meet the specified SAE J595 Class 1 yellow requirements.
Automatic nighttime dimming may be used when full-intensity operation would create excessive glare.
RRFB placement, signs, accessibility features, timing, and operating conditions should be reviewed using the current MUTCD and applicable state or local agency requirements.
Common RRFB Configuration Mistakes
Treating One Light Bar as a Complete System
A light bar does not include all the signs, supports, controllers, activation devices, power components, and synchronized units that may be required for a complete crossing.
Specifying Only the Number of Light Bars
A quotation request should identify which direction each light bar faces. Four single-sided bars and two back-to-back pairs both use four light bars, but their mounting hardware and station layouts are different.
Ignoring Sign Orientation
Back-to-back light bars do not automatically mean that the signs are also back-to-back. The required sign faces and arrow plaques should be shown in the project layout.
Assuming All Controllers Will Communicate
Controllers must use compatible communication equipment and be correctly paired or grouped. Wireless communication range should also be evaluated for the installation site.
Using a Standard Flash Time Without Reviewing the Crossing
Flash duration should be based on the crossing and pedestrian-clearance requirements, not simply on a factory default.
Using the Same Solar System for Every Configuration
Battery and solar-panel requirements can change when additional light bars, audible devices, longer flash periods, or cold-weather conditions are introduced.
Failing to Confirm Included Equipment
Traffic signs, poles, foundations, anchor hardware, push buttons, solar panels, batteries, and mounting brackets may be quoted separately. The final quotation should clearly identify what is and is not included.
Information Needed to Configure an RRFB System
To request an RRFB system recommendation or quotation, provide as much of the following information as possible:
Roadway name and project location
One-way or two-way traffic
Number of lanes
Roadway and crossing width
Presence of a median or refuge island
Posted speed limit
Preferred sign and pole locations
Number of traffic approaches
Required viewing direction at each station
Single-sided or back-to-back preference
Solar or AC power
Push-button or passive activation
Desired wireless communication distance
Required flash duration
Sign sizes and sheeting requirements
Pole and foundation requirements
Applicable state or local agency specifications
Photographs, plans, or a simple site sketch
If the final configuration is not yet known, a roadway plan or marked-up photograph can often help identify the appropriate equipment layout.
Frequently Asked Questions
Is an RRFB station the same as an RRFB light bar?
No. A light bar is the flashing visual warning unit. A station is a practical term for a control location that can include a controller, push button, power system, and one or more light bars.
Can one RRFB station have two light bars?
Yes. A back-to-back station can have two light bars facing opposite directions. Other customized mounting arrangements may also be available depending on the project.
Do wireless RRFB systems need a cable across the road?
Compatible wireless controllers can synchronize stations without a roadway-spanning communication cable. Each station still requires its own power and local wiring.
Do all RRFB light bars at a crossing flash together?
Yes. The MUTCD requires all RRFB units associated with a crosswalk to start and stop their flashing operation simultaneously.
Can a third station be added in a median?
Yes, if compatible equipment is used and the system is designed for the additional station. The roadway agency or engineer should determine whether the median station and its sign assemblies are needed.
Are traffic signs and poles included with every RRFB system?
Not necessarily. Signs, poles, foundations, anchor hardware, and other components should be specifically listed in the quotation. Do not assume they are included unless stated.
Configure an RRFB System for Your Crossing
The appropriate RRFB configuration depends on more than the number of light bars. Traffic direction, sign placement, roadway width, visibility, power availability, wireless communication, activation method, and agency requirements should all be considered.
Zoodico Traffic Solutions offers single-sided, back-to-back, solar-powered, AC-powered, and synchronized multi-station RRFB configurations.
Send us your roadway plan, crossing dimensions, preferred sign locations, and project requirements, and we can help identify a suitable equipment configuration for quotation.
References
This article provides general product and configuration information. Final traffic-control-device selection, placement, timing, accessibility features, and installation should be reviewed by the responsible agency or qualified engineer for the specific project.
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Ann Arbor, Michigan, US