Posts

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

Specifying RRFBs – The Essentials

/in /by

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!

The Importance of Versatility and Standardization in RRFBs

/in , /by

Have you heard about the importance of versatility and standardization in RRFBs?

In today’s blog, the Availed Technologies team outline why this is so crucial, its many benefits, and a real-life example of versatility and standardization done right.

Let’s dive in.

What Are RRFBs?

RRFBs are a unique traffic control device designed specifically to improve pedestrian safety at uncontrolled marked crosswalks.  Uncontrolled crosswalks come in many different shapes and sizes from one-way or two-way roadways, from two to four lanes, and with or without median islands, curb bulb outs or extensions, etc.

On the other hand, uncontrolled crosswalks can be located at intersections where the major legs are through lanes or at mid-block locations such as school crossings or trail crossings. Other locations include roundabouts and bicycle corridors.

Lastly, crosswalk locations can sometimes have sightline issues due to curves or other features.

What is Versatility and Standardization in RRFB-Related Product Design?

With over 25 years of combined experience in the Solar LED industry (and, more specifically, solar LED for traffic safety), our team has both the knowledge and the skillset to deliver products that out-perform the competition year after year.

How do we achieve this?

By utilizing both versatility and standardization.

Versatility refers to how adept a product is at being used in a range of configurations that stem from the crosswalk and roadway design.

Standardization in this discussion is defined as the extent to which versatility can be accomplished with a single model.

For example, a key requirement for configuring RRFBs at the crosswalk is to have lightbars visible to oncoming vehicles on both the left and right hand side of the roadway.  This requirement, coupled with the wide range of crosswalk configurations results in the need for the RRFB device to be versatile.  Consider these scenarios:

  1. Two way, two lane roadway.  In this common configuration there are two back-to-back lightbars on each side of the crosswalk.
  2. Two way, four lane roadway with median.  In this configuration there are typically single sided lightbar systems on the curb sides and either one back-to-back system or two single sided systems on the median.  The systems on the median may or may not have push buttons.
  3. Crosswalks at a roundabout. In this application each crosswalk is for one-way traffic, therefore single sided lightbars are typically used.

As demonstrated here, RRFBs can include either one or two lightbars and be with or without a push button.  In some cases, such as when sightlines require it, the location of the lightbars will be different than where the push button should be located.  This scenario may utilize a system that consists of only the solar engine and the push button, without any lightbars.

In other cases, such as when RRFBs are installed in advance of the crosswalk with the Ahead sign, the system would consist of one lightbar and no push button.

In all cases with RRFBs, there is a wireless connection between systems so that when a push button is activated on one system the other system(s) at the crosswalk flash.  Ideally the wireless connection between systems is automatic and requires no field configuration.  Regardless of how many systems are used, all will turn on and off in a synchronized manner when the push button on any one of the systems is activated.

In the event that there are multiple crosswalks in proximity to one another there needs to be a means to avoid a push button actuation at one crosswalk activating lightbars at another crosswalk.  This is referred to as crosstalk and can be easily addressed by a field adjustable dial on the solar engine controller for channel selection.

Learn More About Versatility and Standardization for RRFBs Today

FHWA (IA-21) requires that RRFBs be on both the left-hand and right-hand side of the roadway for each approach.  This frames the crosswalk for drivers and is one of the reasons the system is so effective.  As we have seen, it does demand versatility in the system to allow for a range of installation configurations.

To simplify the ordering, inventory, and installation logistics an RRFB system should be able to have two, one, or no lightbars and either be connected to a push button or not.  In other words, it should be both standardized and versatile.

At Availed Technologies, all of our products are created and sold with both versatility and standardization in mind.

By prioritizing these two product design factors, we ensure that our RRFBs fit a wide range of crosswalk configurations and are easy and fast to install.

To learn more about how to utilize our best-in-class RRFBs, or if you have questions about how to implement RRFBs in your particular situation contact our team today.