NOMINATION SUMMARY Uninterruptable Power Supply / Battery Backup for Traffic Signals

ABSTRACT OF THE PROGRAM

Montgomery County DOT has recently completed they deployment of uninterruptable power supplies / battery backup units (UPS/BBU) for all County owned traffic signals. There are over 320 of these devices installed in the field. This work was undertaken as part of a larger capital improvement project for modernization of the County’s traffic signal system. The decision to install UPS/BBU at all County owned traffic signals was made to address the following issues; 1) improve public safety by keeping traffic signals on color during temporary short term power outages, 2) keep critical communication hub sites powered so that a power outage won’t disrupt communications to other traffic signals connected to that hub and 3) reduce the need to dispatch police officers and signal technicians for short term power outages. In addition to installing the UPS/BBU at traffic signals, they are equipped with communication ports that permit the County’s Transportation Management Center (TMC) to remotely manage and monitor these devices. When the power is lost at a traffic signal, the UPS/BBU instantaneously switches to an inverter powered by batteries to keep the signal on color. The TMC is notified immediately when the power goes out at any UPS/BBU equipped traffic signal. The County designed these devices to provide a minimum of eight hours of battery backup power which will keep the traffic signals on color for the duration of the vast majority of power outages experienced. In addition, the UPS/BBU will protect the traffic signals from under or over voltage. If utility voltage gets below a set threshold, the UPS/BBU will boost the voltage back by supplementing with the inverter. If the utility voltage goes over a set threshold, the inverter will bring that voltage back down to a safe level to protect the signal control equipment.

THE PROBLEM OR NEED FOR THE PROGRAM

On June 29, 2012, the Baltimore-Washington area was hit by a severe and uncommon weather event known as a “derecho.” A “derecho” is defined by the Wikipedia/NOAA Storm Prediction Center as a “widespread, long lived, straight-line windstorm that is associated with a fast moving band of severe thunderstorms. They travel quickly in the direction of travel of their associated storms, similar to an outflow boundary (gust front), except that the wind is sustained and increases in strength behind the front, generally exceeding hurricane force.” This particular storm resulted in wide spread and sustained power outages throughout the DC/Baltimore Metropolitan area. The resulting power outages left approximately two-thirds of the traffic signals in Montgomery County in a dark condition (i.e. the traffic signal has no power and thus the signal displays are not illuminated). Add to this a new motor vehicle law that went into effect on October 1, 2012 that requires motorists to treat a dark traffic signal as an all-way stop condition. Dark traffic signals increase the potential for accidents to occur, and can have a significant impact on traffic and pedestrian mobility at the affected intersections. Dark signals that now must be legally treated as all way stop intersections has a significant negative impact on traffic operations. The current DOT strategy for managing traffic flow during long term power outages at traffic signals is police control or temporary STOP signs. Managing traffic flow at multiple dark traffic signals over a long term power outage with police control places a significant staffing burden on law enforcement agencies, as many traffic signals require more than one uniformed officer to safely provide point control. In Montgomery County, the larger intersections (e.g. intersections of two or more routes, each with multiple lanes) require four to six officers to safely provide point control. This has a significant impact on police emergency response time and availability, as well as departmental budgets. In order to ensure that limited police resources are deployed at the most-critical intersections, the DOT performed an evaluation of intersections and developed a three-tier ranking system to recommend the type of control, if any during power outages (both short term and long term). This ranking system allowed the County to quickly decide which locations require Police direction, which need temporary stop signs and which would be left dark until power was restored. Police direction and temporary stop sign deployments are labor intensive operations while leaving some signals dark is less efficient for traffic and safety.

DESCRIPTION OF THE PROGRAM

Montgomery County DOT has recently completed they deployment of uninterruptable power supplies / battery backup units (UPS/BBU) for all County owned traffic signals. There are over 320 of these devices installed in the field. This work was undertaken as part of a larger capital improvement project for modernization of the County’s traffic signal system. The decision to install UPS/BBU at all County owned traffic signals was made to address the following issues; 1) improve public safety by keeping traffic signals on color during temporary short term power outages, 2) keep critical communication hub sites powered so that a power outage won’t disrupt communications to other traffic signals connected to that hub and 3) reduce the need to dispatch police officers and signal technicians for short term power outages. In addition to installing the UPS/BBU at traffic signals, they are equipped with communication ports that permit the County’s Transportation Management Center (TMC) to remotely manage and monitor these devices. When the power is lost at a traffic signal, the UPS/BBU instantaneously switches to an inverter powered by batteries to keep the signal on color. The TMC is notified immediately when the power goes out at any UPS/BBU equipped traffic signal. The County designed these devices to provide a minimum of eight hours of battery backup power which will keep the traffic signals on color for the duration of the vast majority of power outages experienced. In addition, the UPS/BBU will protect the traffic signals from under or over voltage. If utility voltage gets below a set threshold, the UPS/BBU will boost the voltage back by supplementing with the inverter. If the utility voltage goes over a set threshold, the inverter will bring that voltage back down to a safe level to protect the signal control equipment.

Montgomery County DOT currently employees 18 traffic signal technicians in the maintenance and operations of the 827 traffic signals within the county. During and after a major storm event these technicians would be responsible for the following: verifying power outages, checking for blow equipment or fuses, re-setting traffic signal equipment, and repairing damaged signal and ITS equipment such as traffic monitoring cameras. The on-off schedules of these technicians is adjusted accordingly to provide efficient coverage and response to traffic signal outages and emergencies, while providing sufficient rest periods during extended emergency operations. Any technologies selected for managing long term power outages had to be given careful consideration to the additional manpower that may be required to implement, operate, and maintain that system. A battery back-up system (BBS) provides an alternate means to power a traffic signal in the event of an electrical power failure through battery power. BBS typically provide between eight to sixteen hours of operation before the batteries are exhausted. The battery back-up systems used by Montgomery County DOT require approximately 18 hours to safely re-charge the batteries. In addition, the County designed a cabinet enclosure that adds a quick connect generator plug which allows the County to place a gasoline powered generator onsite to run the traffic signal while recharging the batteries during power outages that last longer than the typical battery run time would cover.

The BBS utilized by Montgomery County are monitored remotely, and can provide various information including: when the battery back-up system is active, when it has been active for two hours, and when it has been active for six hours. This information is used to detect, assess and plan the necessary response to unexpected power outages across the traffic signal system. The system provides a reasonable estimate of remaining runtime on battery given the load and battery charge level remaining. Knowing this key piece of information allows us to delay the deployment of police and signal technicians in many cases which saves the County money in the long run.

Montgomery County DOT followed systems engineering principles in order to decide what needed to be done to mitigate the short term power outages at traffic signals. This process included a literature review and state of the practice surveys sent to stakeholders and colleagues with relevant expertise. It was important to know what options exist and to determine the feasibility of those different options from a cost and performance perspective. Details from that systems engineering effort follow.

SPR Research Project - The most comprehensive resource on the subject was SPR Research

Project No. C-06-08, Guidelines for Traffic Signal Energy Back-Up Systems, Rensselaer Polytechnic Institute, and Advanced Energy Conversion, LLC. This research effort, which was conducted for the New York State Department of Transportation in 2009, evaluated battery backup systems, solar power technology, generators, fuel cells, future technologies such as ultra-capacitors, pseudo-capacitors, and dedicated standby power lines. The battery backup system was recognized as the most technologically developed and cost effective alternative. The length of time that a typical battery back-up system can power a traffic signal, without being refueled, ranges from two to ten hours. Generators were also recognized as an advancing technology that could maintain backup power for longer periods of time at critical locations. The biggest disadvantage to gasoline generators, both portable and permanent, is the need for storage and maintenance methods to guarantee reliable starting, as well as fuel supply issues.

The technology for fuel cells, ultra-capacitors, and pseudo-capacitors has not advanced to the

point that these technologies should be considered as options for powering traffic signals. They are not competitive or readily available.

Dedicated power lines are an option for locations with closely spaced traffic signals, with an

advantage being one generator could supply multiple locations. The major disadvantage to this option is the need for costly dedicated power lines, and the potential size/location requirements for a generator capable of powering multiple locations.

This research report recommended against using solar power panels in New York, due to the size

of the solar panels needed to ensure sufficient battery charging, and because weather conditions could not guarantee sufficient sun light for proper battery charging. It should be noted that the June 29th storm that caused wide spread power outages in Montgomery County would have most likely caused significant damage to solar power panels had they been in use for traffic signal applications. In addition, many of the traffic signals in Montgomery County are located in heavily shadowed or shaded areas that may result in insufficient battery charging capability. In downtown areas, the poor aesthetic features of the solar panels may also reduce the applicability of this alternative.

As mentioned, State of the Practice Surveys were completed. In addition to the literature search

that was conducted, a questionnaire was circulated via the Institute of Transportation Engineers (ITE), and National Traffic Operations Coalition (NTOC) List Services, and through direct contact with other state and local transportation agencies. The majority of the agencies that responded have established programs for the installation of battery back-up systems, most of which are for short-term power outages. Some jurisdictions have or will be installing battery backup systems at all intersections, while other jurisdictions only install battery backup systems at intersections that meet specific criteria. The criteria may include: volumes, speeds, number of lanes, presence of railroad or emergency vehicle pre-emption, proximity to military installations or hospitals, or locations that are susceptible to frequent power failures. The following is a summary of the main themes that were gathered from the contact with other local and state transportation agencies:

a. Battery Swapping/Charging Stations Several jurisdictions, including Anne Arundel County, Maryland, utilize battery swapping to

provide the power needed to support continuous traffic signal operation during long term power outages. Fully charged batteries are removed from locations that have utility company power, and swapped with the exhausted batteries at locations that do not have utility company power. Some jurisdictions also utilize battery charging stations to keep batteries fully charged and available for swapping. The City of Federal Way, Washington utilizes battery charging stations. They currently have four charging station available to support battery swapping at 77 intersections. The cost to set-up each charging station is approximately $9,000 and each station can accommodate 18 batteries.

b. Permanent Generators The cities of Suffolk, Virginia, and Overland Park, Kansas have permanently installed natural gas

generators. The initial installations in Suffolk were battery back-up systems, which provided 6 hours of battery power to keep the traffic signals running full-color in the event of a power failure. Being the only land evacuation route for the City of Tidewater, Virginia, the City of Suffolk wanted to ensure extended run time for their intersections. The solution was the installation of permanent compressed natural gas generators that could provide unlimited run time. Suffolk currently has approximately 30 locations that have battery back-up systems with a compressed natural gas generator, and installs 6-8 new locations each year. Their standard for all new, or reconstructed traffic signals, includes a battery back-up system with a compressed natural gas generator.

In Overland Park, Kansas, where ice storms, summer thunder storms, and tornados have the

potential to disrupt power, the City’s philosophy has been to install battery back-up systems at major intersections. To supplement the battery back-up systems, permanent compressed natural gas generators are installed at locations that have the highest traffic volumes, or where CCTV cameras are present. A power failure will trigger a battery back-up system to supply power to run the intersection. If utility power is still down after 10 minutes, a permanently installed DC generator powered by natural gas will come on-line to provide continuous charge to the batteries which keep the intersection running full-color. To date, battery back-up systems have been installed at 66 locations, and combination battery back-up system with compressed natural gas generator have been installed at 28 priority locations. Overland Park has a total of 266 traffic signals The cost for these permanent installations ranges from $20,000 to $30,000 and includes the battery back-up system. The units in Suffolk and Overland Park were designed by Alpha Technologies, and Critical Power and Energy Systems, Inc., and utilize a DC generator that charges the batteries in the battery back-up system, which in turn provides power to run the intersection. These units include several safety features such as an “excess flow value” installed below grade to cut off the flow of compressed natural gas in the event the system is damaged, and a “cool touch” enclosure to prevent contact with any hot components. The footprint for these units is slightly smaller than a typical traffic signal cabinet. These units are capable of up to three weeks of consecutive runtime before maintenance is required. A propane version that can provide approximately 96 hours of run time is also available for locations where access to a compressed natural gas line may not be feasible.

Compress natural gas units are also being installed in Blacksburg, Virginia, around Virginia Tech

University to guarantee signals are operational during any evacuation at the college. To date, four units have been installed and 15 additional units are on order.

Beaufort County, Georgia, has nine traffic signals that can be powered from permanently

installed gasoline generators. These generators were originally installed to support communications and ITS equipment. Powering of the traffic signals was considered a secondary benefit.

c. Portable Generators Several of the jurisdictions that responded to the survey indicated that portable generators are an

option for longer term power outages. Most jurisdictions noted a generator supply between two and fifty portable units. In all cases, generator security and refueling was noted as an issue. Many of the jurisdictions also noted that generator connection plugs have been, or will be installed at all intersections.

The Florida DOT has several hundred portable generators stored at operations centers throughout

the State that can be deployed during long term power outages. Florida DOT also commented that they relied on portable generators since they can be moved to where the need is, whereas permanent generators cannot.

In Delaware, all of the traffic signal cabinets have been adapted to readily accept back-up power

from a generator. DelDOT maintains direct contact with utility companies during any events that impact power, and DelDOT forces will respond with a portable generator if it is determined that the outage will

be prolonged. DelDOT has approximately 900 full-color traffic signals, with 35 generators of various models (11 mounted on sign trucks, 23 portable, 1 trailer mounted), and has plans to purchase additional units as budgeting allows.

The City of Bellevue, Washington, has 10 portable generators to support 184 traffic signals.

They were only able to procure 10 units during a major prolonged outage in the region (and thus the reason that they do not own more units). It should be noted that in their policy for wide spread power outages it specifically states that “there may be so many intersections dark that it does not make sense to deploy 10 generators because the overall benefit to traffic is minimal. Once the event stabilizes, generators could be deployed at large intersections near freeway interchanges, or along a corridor.”

Federal Way, Washington considered the use of generators “undesirable” due to security and

refueling issues. Illinois DOT also dismissed the use of generators due to the large number of traffic signals (7,000) they maintain. They rely on available battery back-up systems, and indicated that in some cases they have installed yellow reflective tape around the signal heads to improve their conspicuity. The City of Houston, Texas replied that they did use some portable generators after hurricane Ike, however they typically do not use them, and that it is left up to local police departments to decide whether or not they will deploy point control.

Several of the local jurisdictions in Maryland that have traffic signal maintenance responsibilities,

including Anne Arundel County, Baltimore City, Baltimore County, Howard County, and Prince George’s County, have all indicated that they utilize portable generators at critical county owned intersections during long term power outages.

A recent study conducted by SWA for Falls Church, Virginia (26 traffic signals total), identified

the Generac GP3250 as an acceptable unit for powering a traffic signal. This unit has a 3.5 gallon fuel tank, which is capable of providing up to 9 hours of run time. These units are available for approximately $450 per unit at home improvement supply stores. This unit is also available in a portable propane model. The propane model has a per unit price of $650, with a 20 gallon propane tank capable of providing up to 9 hours of operation.

The portable generator that was frequently mentioned by jurisdictions that responded to the List

Serve questionnaire as well as subject matter experts was the Honda CUB 20. This is a pure sine wave generator with a 3.5 gallon fuel tank capable of providing up to 22 hours of runtime. This unit is also marketed as being “whisper quiet”, with a 60dB audio level. Its low noise level makes it inconspicuous, and less susceptible to theft. In bulk quantities (200 units or greater), these units sell for approximately $5500 per unit. Quantities less than 200 are available at $7000 per unit.

d. Solar and Wind Power Limited information is available on solar, and/or wind power systems. The City of Lincoln,

Nebraska, is in the middle of a three year pilot project to develop a solar/wind hybrid system. The estimated cost to install the solar/wind hybrid at an intersection in Lincoln was $20,000. This included the cost for a new structure to support the wind turbine and solar panels. The City of Houston, Texas, had a feasibility study completed on solar powered traffic signals. This study estimated that material and labor costs for a battery back-up system with solar charging capability would be approximately $12,500 per location. Field implementation and testing of this system was never undertaken. A study was also completed in South Africa on solar powered traffic signals. This study ultimately determined that while feasible to power traffic signals via solar power, the upfront Capital costs were prohibitive and it could take up to 50 years to mitigate the installation costs.

Other options considered and dismissed as not feasible for full scale deployment in the current

environment included the following.

• Portable Gasoline Generators (AC and DC). • Permanent Gasoline Generator • Permanent Natural Gas Generator • Vehicle Supported Power Inverters

RESPONDING TO ECONOMIC DOWNTURN (OPTIONAL)

N/A

USE OF TECHNOLOGY

The UPS/BBU systems deployed provide several types of technology to Montgomery County DOT. The IP communications infrastructure was provided as part of the traffic signal modernization project. Communications are vital for a UPS/BBU system to be used to its full potential. The IP communications network is a good example of a shared resource being leveraged to provide better service. The UPS/BBU units installed are made by Alpha Technologies. The unit used is the Alpha Technologies Alpha FXM 2000 system. This unit is well matched to the typical load (~375 W max load) of a County traffic signal. The FXM 2000 is paired with two automatic transfer switches. One switch automatically switches between utility power and battery/inverter power, the second transfer switch automatically selects the portable generator input when a generator is connected and operating.

The FXM 2000 is configured to communicate over broadband IP networks, so the device is assigned an IP address in the subnet appropriate for its location in the field. Operators and technicians can access this device remotely from anywhere in the TMC network. In addition, the FXM 2000 provides Simple Network Management Protocol (SNMP) traps which alert our internal management systems to changing field conditions related to the UPS/BBU units. These traps include but are not limited to on inverter, on retransfer, back on utility power, alarms for 2 hours and 6 hours on battery and other equipment malfunction faults.

THE COST OF THE PROGRAM

It must be noted that the County had already converted its traffic signals to LED indications which is a requirement for UPS/BBU installation. Capital costs include both the cost of the device including installation and the cost of providing communications to the devices. The costs presented here are related to the purchase, installation and ongoing maintenance of the UPS/BBU devices described in this application. Communication network costs will be variable and highly dependent upon device location including proximity to existing communications infrastructure so that cost is not fully covered in this section. The County’s capital costs to procure and install the Alpha FXM 2000 devices at over 300 traffic signals ended up being approximately $275,000 which works out to about $8,500 per device (as mentioned earlier, this cost is after LED signal indication replacement costs). The County’s ongoing operating cost for periodic maintenance is approximately $1,000 per year per device which includes needed repair and life cycle replacement of batteries. While communications costs will vary significantly depending upon location and therefore not necessarily applicable to other agencies, we can suggest that our experience in using 4G cellular modems for some other remote devices one could expect a cost of approximately $700 per unit to purchase and ongoing costs per device in the $40-50 per month range.

The RESULTS/SUCCESS OF THE PROGRAM

The UPS/BBU deployment program has been very successful and has proven its value on a daily basis. With over 320 traffic signals equipped, we see daily occurrences of short term local power outages. From a public perception and safety perspective, the results are very real even if the general public

doesn’t know they are reaping the benefit as they drive past a traffic signal that is on battery power. From road users’ perspectives, they would not know or care that the power is out at the traffic signal as long as the signal is still operating. This program provides significant safety improvements without requiring any action or decision on the part of pedestrians, bicyclists or motorists. From there perspective everything is working.

In the past these outages would have immediately resulted in a call for Police service and dispatch of a signal technician. Today, we can acknowledge the power outage reported by the UPS/BBU to our remote monitoring systems. Our SOP has been modified such that TMC technicians will monitor the situation for a period of time to see if power comes back on before dispatching a signal technician. We don’t request police assistance until we know that we are getting close to the end of the battery run time. 99% of the time the TMC doesn’t have to request police assistance as utility outages are typically much less than our anticipated battery run-time. All this results in an overall success in that we may conserve our overly accounted for County resources (Police, signal technicians, sign crews) by not deploying them unnecessarily. We wait until they are needed and more strategically those resources only when they are really needed.

The County’s communications infrastructure includes communication hubs that are attached to strategically located traffic signals. These hubs provide communication links to up to 30 traffic signals in the area. Keeping these hubs powered during a local power outage allows the TMC to monitor the status of signals that are otherwise not impacted by a local power outage in their area. We see multiple times a month where these communication hubs are kept up and running during short term power outages by the UPS/BBU on the traffic signal to which they are attached.

WORTHINESS OF AWARD

This program meets several of the program criteria for receiving a NACO Achievement Award. This project greatly improved the operation and maintenance of our traffic signal system. It allows us to provide a much higher level of service than was possible before this project was implemented. Public safety is best served by keeping traffic signals on color as much as possible. Avoiding the temporary short term power outages that make traffic signals go dark provides a significant safety improvement to the road users.

This project also involved significant coordination between agencies and contractors including Montgomery County DOT, Maryland State Highway Administration, City of Rockville, City of Gaithersburg, Baldwin Line Construction, Econolite control systems, Static Power Conversion Services Inc, Electric Advantage, RGA Inc and Alpha Technologies Ltd. This coordination was critical to the success of the project and is a very good reason this project is worthy of a 2017 NACO award.

SUPPLEMENTAL MATERIALS (OPTIONAL)

Supplemental materials such as pictures and charts may be uploaded in separate PDF documents once you complete the check-out process. Supplemental materials are not required but are highly encouraged. Please note that supplemental materials may be published.

Inside a UPS/BBU cabinet

Warning Label installed on signal cabinet to alert first responders that power may be present even if utility power is turned off

Generator connected to a UPS/BBU

Generator Plug connected into UPS/BBU cabinet

Alpha UPS/BBU Main Status Page

Alpha UPS/BBU Events Page

Alpha UPS/BBU Inverter Page

Alpha UPS/BBU Relay Status Page

Equipment Monitoring System EM7 Main screen

Equipment Monitoring System EM7 Events Page

Equipment Monitoring System EM7 Alpha Uptime Performance Page