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Crosswalk with two Availed RRFB poles on a sunny day. A castle-like house stands majestically in the background.

Specifying RRFBs – The Essentials

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This article provides the essential Performance Requirements to include when specifying Rectangular Rapid Flashing Beacons (RRFBs).

Here at Availed Technologies, we work with municipalities and engineering firms across North America everyday who are in the process of specifying RRFBs. We focus on the following three points: Array to Load Ratio, Autonomy, and Shading.

Before we get into the performance requirements it should be noted that the operational requirements of an RRFB are important to specify and these are clearly defined in the MUTCD IA-21. One other point that is discussed at the end of this article is the option to use standard sign posts for RRFBs.

#1: RRFBs and Array to Load Ratio

The Array to Load Ratio is the power coming into the system divided by the power consumed by the system. It is the single most important metric to pay attention to when specifying Solar RRFBs. The ALR Ratio must be greater than 1:1, and a minimum of 1.2:1 is recommended. Regardless of the size of the solar panel or size of the battery, a system with an ALR of less than one means there is a power deficit and the system will run out of power eventually.

For Solar RRFBs, the ALR must be calculated using worst case conditions to ensure reliable year-round operation. This is typically in December when the solar energy available is at a minimum. The Solar insolation for a particular location is available through a comprehensive database from NREL that is based on historical information which accounts for prevailing weather conditions and latitude.

Factoring in the site-specific solar data, the daily power generated by the RRFB is determined by how the device converts the available solar energy into electrical energy that runs the system and is stored in the battery. This calculation is manufacturer-specific and varies significantly from one brand to another.

Power Consumed By RRFBs

The power consumed by the RRFB is also very manufacturer-specific and will vary even more from brand to brand than the power generation side of the equation. Power is consumed by the RRFB lightbars when they flash and also by the wireless connection between the systems which manages the activation of all systems at the crosswalk, so that when any one push button is pressed all the RRFBs start flashing immediately and stop flashing at the same time.

The wireless connection must always be ‘on’ and therefore this function is a significant portion of the power consumed. Advances in both LED and wireless technology have enabled dramatic improvements in power efficiency, the result of which is the ability to achieve a high ALR with a compact and lightweight system.

#2: RRFBs and Autonomy

The autonomy of an RRFB is defined as the number of days it can operate without any charging. It is a function of the daily power consumption and the battery capacity of the system. In an actual installation autonomy is hypothetical because the system will charge in the day even during cloudy conditions. Cold temperatures will decrease the battery capacity and this should be factored into an autonomy calculation.

Autonomy should never be the sole metric used in specifying a solar RRFB because it does not take into account the ‘power in’ of the system. Nevertheless, it is an important consideration as energy storage is essential for the system to function during nighttime and low light conditions. An autonomy of 5-10 days is recommended.

#3: RRFBs and Shading

Shading from trees and buildings is site specific and is often overlooked. At Availed Technologies, we can review the location with google street view and we will incorporate this information when producing the solar performance report.

Key takeaways:

  • Always use ALR and Autonomy when specifying RRFBs
  • Use a solar performance report that factors in site specific shading to ensure system reliability
  • Never specify the solar panel size or battery capacity alone as these metrics do not factor in the power generation and power consumption of the system.

For further information on ALR, Autonomy, and RRFB efficiency see the article The Power of Solar RRFB Systems.

A final consideration when specifying RRFBs is the pole type. A positive benefit of an efficient system is that the product is compact and lightweight which makes it feasible to use standard sign posts. Using 2” Telespar square perforated tubing or standard 2” round sign posts will significantly reduce the installed cost of the system and will simplify the installation process. Standard sign posts can also be helpful for placement of RRFBs in locations where space is limited.

One feature worth mentioning regarding the Availed AV-400 RRFB is that it comes with a Universal mounting system that is compatible with all pole types, from the traditional 4 ½” diameter pedestal poles to 2” square and round posts, and everything in between.

Have any further questions about the essentials of RRFBs? Reach out to our team today!

Highlighter yellow Availed RRFB school crossing sign with arrow, with a tree and blue sky in background.

Availed Technologies Has Been Approved by Oregon DOT

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We are happy to announce that the Availed AV-400 Rectangular Rapid Flashing Beacon is now listed as a qualified product on the Oregon DOT Green Sheets.

What is the Green Sheet Qualification Process?

Maintained by the Traffic-Roadway Section of the Oregon Department of Transportation, the Green Sheet Qualification process has a comprehensive evaluation process for a wide range of Traffic Signal, Illumination, and ITS equipment that includes physical, operational, and environmental testing.  For RRFBs in particular, the device is evaluated to ensure it is compliant with the requirements of the FHWA interim approval and the MUTCD and that it meets the requirements for mounting as shown in TM493.  Only prequalified RRFBs already listed on the green sheets will be approved for use for Oregon DOT projects under contract

The Importance of Energy Efficiency for RRFBs

As is very typical in the Pacific Northwest, many parts of Oregon have very low solar insolation during the winter months which presents a challenging environment for solar products such as the Availed AV-400 RRFB.  Key to ensuring reliable operation is energy efficiency, and this is where the AV-400 stands out.  All aspects of the product, from the wireless connectivity between units to the optical design of the LED lightbars has been designed to minimize power consumption.

 

For more about energy efficiency with RRFBs and how to specify products to ensure reliable operation see this article.

 

RRFBs in the Next MUTCD

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RRFBs were first introduced under an interim approval with the Federal Highway Administration (FHWA) in 2008.  Since that time, and due to the high effectiveness of the device, the use of  RRFBs as a crosswalk enhancement has become widespread.

Today, we here at Availed Technologies are going to outline RRFBs proposed role in the next MUTCD– including the most significant proposed changes to it to enhance pedestrian safety.

Let’s jump right in:

The Absence of an Updated MUTCD

In the absence of an updated version of the Manual on Uniform Traffic Control Devices (MUTCD),  the RRFB has remained under an interim approval for well over a decade.  On March 4th, 2022 FHWA Issued a Status of Rulemaking for the Eleventh Edition of the MUTCD.

According to this update, The Infrastructure Investment and Jobs Act directs USDOT to update the MUTCD by no later than May 15, 2023.

As one would expect, RRFBs are a key feature of the recommended changes as noted in the FWHA, U.S. Department of Transportation (DOT) notice of proposed amendments (NPA). These recommended changes orbit around the incorporation of provisional traffic control devices.

The Incorporation of Provisional Traffic Control Devices

The incorporation of provisional traffic control devices currently under Interim Approval, including pedestrian-actuated rectangular rapid-flashing beacons at uncontrolled marked crosswalks, green-colored pavement for bicycle lanes, red-colored pavement for transit lanes, and a new traffic signal warrant based on crash experience.

It is also noteworthy that several other key proposed changes to the MUTCD focus on pedestrians and bicyclists, mainly:

  • Improvements to safety and accessibility for pedestrians, including the location of pushbuttons at signalized crosswalks, crosswalk marking patterns, and accommodations in work zones
  • Expanded traffic control devices to improve safety and operation for bicyclists, including intersection bicycle boxes,two-stage turn boxes, bicycle traffic signal faces, and a new design for the U.S. Bicycle Route sign

The National Committee on Uniform Traffic Control Devices (NCUTCD) recommended changes to the MUTCD are very similar to the Interim Approval (IA-21).  One significant addition is guidance on the use of RRFBs at intersections with two crosswalks on an uncontrolled approach.  Additional guidance is provided for the use of RRFBs with overhead-mounted signs.

The Role of RRFBs in the Future of Pedestrian Safety

Here at Availed Technologies, we have over 25 years of experience in the Solar LED industry. We understand that providing a best-in-class product demands the support of industry-leading partners, and we are very proud to be represented by some of the most trusted companies in the business.

We strongly encourage you to read more about the MUTCD proposed changes today– and, if you have any questions, to reach out to our team!