How traffic cabinets are preparing us for a world of connected vehicles and driverless cars, by Mike Shea.
Communities around the world are experiencing the benefits of more efficient roadways, lower vehicle emissions and increased safety through the deployment and implementation of Intelligent Transportation System (ITS) programs. While the industry marvels at the sophistication of the software systems and leading-edge hardware that power ITS, one critical component is often taken for granted – the traffic control cabinet. As with most large systems, the components at the granular level can sometimes make or break the operability of the system, and traffic cabinets certainly fall into that category.
You’ve seen them. The sturdy box with a locking door mounted near a signalized intersection. While they don’t draw attention to themselves (they’re designed that way), the traffic control cabinet is arguably the most important ITS component at the signalized intersection, and will be increasingly important in the near future as more multi-modal ITS – adaptive signal, transit priority, connected vehicle, driverless cars, etc. systems – are adopted and deployed.
Often referred to as the heart and brain of the signalized intersection, today’s traffic signal cabinet is called upon more and more to function as a small independent computer server room and communications hub. In fact, without the traffic control cabinet, coordinated signals and ITS would likely not be a possibility, and intersections would merely be four-way stops. As you shutter from the thought of that scenario on your next commute, let’s take a closer look at how strategically important a traffic cabinet is to an intersection and ITS.
The Traffic Control Cabinet and ITS
As more and more ITS and related components are leveraged on the roadways as part of a networked system, for each piece of field equipment installed on the roadway, corresponding components are installed in the traffic cabinet. So, in addition to the typical power supplies, load switches and relays for signal and street lighting, cabling and street/intersection-level communications, the traffic cabinet also houses the controller and all of the decoders, encoders and amplifiers for various detectors and sensors (vehicles, bicycles and pedestrians). The cabinet also houses the conflict or malfunction management unit (depending on the type of cabinet), CCTV, and an uninterruptible power supply (UPS) that an agency may specify for use.
In Figure 1, the hybrid ITS cabinet houses the components via a standardized computer rackmount system, taking advantage of electronic component hardware standardization, while efficiently using as much available space as possible. This modular configuration neatly and securely mounts the equipment and provides a modular platform for future upgrades and equipment. In addition, components such as the bus interface unit (BIU), not only provide centralized high speed interface capabilities for the cabinet and the components, it can also provide an efficient means to incorporate additional types of detection (advance and midblock video and radar detection) and vehicle tracking necessary for adaptive signal control and connected vehicle programs – Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I).
As an example, the State of Maryland began installing a newly designed traffic control cabinet in 2011. This new cabinet has helped the State save money and support new ITS capabilities that were being deployed throughout the State. One such ITS program that would impact the size and functionality of the cabinet was the integration of a UPS is to ensure traffic signal operation during periods of power outage. This requires a UPS installed at certain critical or regionally important traffic signal locations to maintain power to the intersection and signal system operability.
As a result, additional costs were being incurred from purchasing a secondary cabinet and constructing an additional cabinet foundation just to install the UPS system. Another program goal with safety in mind, Maryland continues to increase the percentage of intersections equipped with audible accessible pedestrian signals (APS), while ensuring sidewalks are American Disabilities Act (ADA) compliant. With many of the intersections representing the junctions of historic roadways, real estate and configuration of the traffic control cabinets are critical to a new cabinet solution. Equally important in the roadway safety upgrade program is the safety of the State’s field technicians, which is impacted by how accessible the components inside the cabinet are to the technician – as you can imagine, doors only opening toward traffic on narrow sidewalks is quite hazardous for the technician.
A need for something bespoke
So, a traffic control cabinet that supports traditional intersection control as well as ITS, while accommodating the needs of historic locations was needed. How does a transportation agency get a custom cabinet designed and built? Maryland is a current and long-time user of National Electrical Manufacturers Association (NEMA) TS2 Type 2, size 6 traffic control cabinets, but facing the need to add an audible pedestrian system, as well as a UPS system at each intersection as part of its ongoing transportation upgrade program, the State turned to a long-time traffic control solutions provider – Econolite. Through a collaborative effort between Econolite and Maryland, a new traffic cabinet design was developed. Based on an existing cabinet offering – a Hybrid Rackmount cabinet design currently offered by Safetran, an Econolite Group company – the new Hybrid “S” cabinet was developed to fit Maryland’s needs and requirements to house all components into a single modular unit while providing flexibility for future ITS upgrades.
Addressing the limited sidewalk space and accessibility of the equipment, the cabinet was designed with dual front and dual rear doors for easy and flexible access to all components in a myriad of locations and sidewalk configurations – even historical sites. With the ability to mount equipment on cabinet racks on the front and back, the cabinet provides total flexibility for virtually all intersection and ITS applications. The Hybrid “S” cabinet provides the best of both NEMA TS2 and 33X Series cabinet worlds by using the full functionality of a TS2 Type 1 controller in a rack mount cabinet assembly. Additionally, the Hybrid “S” cabinet provides Maryland the ability to maintain or enhance the current level of intersection control while also being able to incorporate the UPS assembly eliminating the need for additional cabinets and cabinet foundations, keeping the footprint the same as the NEMA cabinet the agency was using prior.
Just a couple of years later, on the opposite side of the country, a Californian city was facing a similar situation with its traffic system upgrade and traffic control cabinets. Part of this City’s ongoing traffic system and safety upgrade included ensuring signal operation during power outages (due to earthquakes, wild fires, or black outs), it incorporated a UPS at each intersection, as well as upgraded its network communications to fiber optic. However, the City sought a solution that would avoid having to purchase and install separate cabinets. The City wanted a single traffic cabinet that housed the UPS while providing flexibility for future ITS capabilities.With the success in Maryland, the City and its transportation department turned to Econolite to collaborate on a traffic cabinet solution. As a result, the City is now receiving a Hybrid Rack Mount cabinet that incorporates two standard Electronic Industries Alliance (EIA) 19″ racks. It houses the entire UPS, accommodates the fiber optic communications, and provides additional space and flexibility for future ITS components.
The Near Future
As automakers, ITS companies, and network/communications providers continue to work ever more closely to bring the driving populous crash avoidance through vehicle tracking, autonomous vehicle, adaptive signal control technologies, just to name a few, the equipment powering all of these technologies will likely be housed in the traffic control cabinets. In addition to the components and equipment, a large portion of the technologies will be driven by wireless communications (eg, Bluetooth, microwave, etc), increasing the use of routers, antennas, and other wireless communications devices. All of this will need to be packaged into the traffic control cabinet. As the traffic control cabinet is called upon to be more of a computer server room and communications hub, it will become even more critical in the world of connected vehicles, robotaxis, and driverless cars.