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The use of such LED electronic signage has evolved into several types of highway sign systems including overhead electronic sign cabinets which are placed on a suspended scaffold across major highway routes. These units are generally known as walk-in sign cabinets which allow on-site maintenance without the need to shut down highway lanes to service the sign. Another type of electronic signage is available for arterial (secondary) roads which feed traffic to and from the major highway routes. These signs are generally installed (but not always) on single post stanchions with the same message capabilities as the overhead highway signs. Access to these signs is provided by lifting up each front sign face section.

Additional roadside LED units includes towed, mobile trailers with electronic LED sign systems attached to them. These trailers are used for temporary road incident situations, in most cases for road construction. Finally there is toll booth signage that creates messages about collection fees and lane direction which manage traffic funnel points near bridge and tunnel toll collection points.

Good intentions
The intention of roadside LED text messages is to communicate ongoing traffic conditions to drivers in as close to real-time updates as possible. Known as 'roadside incidents' the sign systems report on any number of traffic incidents including slow downs, accidents, construction, lane closures, weather concerns, amber alerts and travel time alerts. The LED sign network is dedicated to keeping drivers aware of these situations and providing safe traffic conditions. In the event of any deviation of these "safe driving conditions" drivers are immediately alerted via updated messages with a status alert and if necessary, an alternate route to by-pass the incident. Typical message alerts can vary from global messages that cover the entire network (from amber alerts to posted speed limits) to messages dedicated to a road incident along a specific highway route.

The integration of LED message centers into highway traffic management is part of a more complex information gathering network know as the Intelligent Transportation System (ITS) program. ITS is an initiative of the United States DOT to add information technology as a traffic management component to each state-wide transportation infrastructure. ITS does this with the goal of improving safety and reducing vehicle wear, negative transportation times and fuel costs. The central component of maintaining real-time roadside communications with LED message centers in the ITS world it is known as Dynamic Message Signs (DMS), though some state-wide DOTs describe them as Variable or Changeable Message Signs (VMS or CMS).

In building a DMS highway network, a subset of its ITS requirement is that different sign manufacturers who provide LED sign systems are able to properly communicate with the DOTs command center's sign network software program. This is known as interoperability and defined by the National Transportation Communications for Intelligent Transportation Systems (NTCIP) protocols. The outcome of this protocol establishes a traffic control standard that allows DOTs to "mix and match" different kinds of LED sign equipment allowing them to operate in a common sign network, despite any unique manufacturing or operating characteristic they may have.

Understanding the DMS roadside environment is a study of how the various DOTs maintain and acquire electronic signage for their highways. One side being how the DOTs use VMS and the other side referring to a select group of LED sign manufacturers who supply VMS to the various state DOTs. To understand the DOTs needs both Georgia and Washington state DOT command centers were interviewed on the importance of VMS for traffic management. This is followed with an overview of several LED sign manufacturers who supply VMS signage to the state-wide DOTs as needed.

Georgia Department of Transportation has developed their ITS with a complete electronic traffic management operation that includes television monitoring of highway traffic, on-site observers who deal with incident management and motorist assistance, ramp meters and weather monitoring. All the traffic data is summerized by NaviGAtor, GDOT's web site with real-time local and regional 24/7 traffic information. photo credit: GDOT

Georgia DOT
The Georgia DOT, which maintains an extensive and on-going DMS network, was noted by their public relations spokesperson, Monica Luck, "Georgia has one of the most comprehensive ITS installations in the United States. Our state had already begun to see significant traffic increases starting in the late 1980s and early 1990s and this was further amplified by the forthcoming 1996 Summer Olympic Games. We knew from sponsoring the Olympics that traffic operation was going to be even more intense, with the vehicular concerns of moving the anticipated Olympic audiences, plus the daily movements of local residents through the metro Atlanta area."

To manage our expanding traffic flows, we developed our ITS with a complete electronic traffic management operation that included television monitoring of highway traffic, on-site observers who deal with incident management and motorist assistance, ramp meters, weather monitoring and NaviGAtor, our web site with real-time local and regional 24/7 traffic information. Finally, all that information is synthesized on our LED signs to alert drivers of approaching travel incidents and if it's serious enough, to suggest an alternate route. To date, we have about 97 permanent CMS units installed on our highways throughout the state"

"As our metro-Atlanta population has grown (100,000 new residents yearly), we have found it's not a question of building more roads to accommodate expanding traffic, as much as it is to improve our ability to manage existing roads with better information deployment systems," noted Luck. "A critical part of this is placing individual CMS LED sign units where we think they'll do the most good. The importance of our metro Atlanta area is such that we are the central hub for most of the highways in Georgia. This is emphasized by at least two major interstate routes, I-75 and I-85, that feed mid-west and eastern seaboard traffic right through the Atlanta downtown area."

"Not only do we manage the traffic flow within our state, but our highway activities are even influenced by incidents that happen in other nearby states. Although we're not directly affected by hurricane weather, we are affected from a by product of that weather. Our state is a destination of much of the mass evacuations from the Florida panhandle. To deal with that, we have placed some of our CMS units in southeast and southwest Georgia to keep in assisting Floridian evacuees to give them up-to-date traffic and evacuation information as they travel north towards through Georgia."

From "behind the curtain", a camera eye's view of the Washington DOT traffic management center. Washington's VMS network is defined in some instances by how traffic activity rearranges itself with new travel patterns or because of certain road conditions such as construction, or locations like mountain passes where weather can go through very quick extreme changes. photo credit: Washington Department of Transportation

Washington DOT
In Washington State, DOT operations engineer Bill Legg noted that his state began its involvement in improving its ITS starting in 1992 when they began to retrofit existing sign cabinets by removing the old sign face equipment and replacing it with early LED VMS systems. "As for having enough electronic signage on the road, we find that 'enough' is really a tricky word. How we place our VMS network is defined in some instances by how traffic activity rearranges itself with new travel patterns or because of certain road conditions (construction, or locations like mountain passes where weather can go through very quick extreme changes), all this activity influences the design and operation of our VMS network "We know first hand the effectiveness of this electronic sign system because when we post travel time alerts (time to travel between locations) or amber alerts (child abductions) we get a lot of responses, so we know that people are paying attention to our electronic messag es as we communicate to them."

In terms of getting new VMS units for Washington's roads as Legg observed, "what we do is put an electronic sign specification together that details exactly the kinds of signs we need as well as to define their performance capabilities and operability to work with our existing electronic sign central control system. We then put this out to the appropriate LED sign manufacturers and they bid on it. We select a vendor and having done that, any one of Washington's six operational regions that needs to add new VMS units can buy off the selected vendor list to fulfill their specific VMS needs."

Daktronics offers a dedicated LED display transportation product line known as Vanguard and offers an entire family of ITS-based LED sign systems including the overhead walk-in sign cabinets as seen above along the Cumberland Gap highway system. photo credit: Daktronics

Daktronics, an LED sign manufacturer with a strong commercial and sports LED sign product line, has also been a major provider of LED signs to the DOT community since 1988. The company provides a dedicated transportation product line known as Vanguard and offers an entire family of ITS-based LED sign systems including the overhead walk-in sign cabinets, the arterial secondary roadside signs and a mobile trailer used for road construction and lane closure alerts. In a secondary traffic management situation, Daktronics also offers toll booth lane control signage and parking lot price and parking lot status indicator signage.

In line with its Vanguard, ITS-based signage, Daktronics also offers to the DOTs an NTCIP-compliant software management system that controls all VMS signage dispersed roadside within a state highway system. Among its many features, the software has a message scheduling function, allows traffic management users to edit and change sign messages in real time, provides self -diagnostics of the entire LED sign network it monitors and simultaneously interfaces with various roadside communication systems including telephone, cellular, fiber optic and radio communication set-ups.

Because of the critical importance of the VMS network to the DOTs, LED outdoor sign manufacturing processes have much more rigorous fabricating demands than typical commercial signs. Tom Becker, Daktronics ITS Market Manager noted a few of the more robust demands DOTs require to have their VMS signs operate in an ITS, NTCIP environment:

• Has special welding standards, based on the American Welding Standards guidelines
• Structural standards for wind loading, ice loading and hurricane gust level are more demanding than commercial level requirements.
• Requires redundant power supply support
• High level of self-diagnostics
• Must demonstrate performance capabilities to prove its interoperability compliance with NTCIP requirements.
• Provide sign brightness levels of 9000 nits that far exceed typical outdoor commercial (usually 5000 nits) brightness levels.

Perhaps the biggest difference Becker noted is purchasing time, "In the commercial world, the decision making process moves pretty quickly in regard to sign purchases. In the DOTs world, there is more of a bureaucratic acquisition process in place that requires a longer lead time for the DOTs in getting their VMS signs for interstate use."

Another VMS supplier is Adaptive Micro Systems, an LED sign manufacturer that designs develops and fabricates indoor and outdoor LED signs. Transportation is one of Adaptive's market applications as noted by vice president Ron Levac, who described the company's beginning involvement with the VMS marketplace. "We saw that outdoor LED signs were the perfect technology for the DOTs ITS market, in terms of replacing the older, electro-mechanical Flip Disk technology As an electronic LED sign provider, we introduced our AlphaXpress signs as a highway sign system to the DOTs throughout the United States. We provide the two critical types of VMS signs, both the overhead walk-in cabinets and the smaller, arterial roadside signs."

As for the DOTs stringent manufacturing and operating standards we apply these requirements to all our VMS manufactured signage. Under this policy we provide among their many requirements redundant power supplies, pixel failure diagnostics and a ventilation system to manage the sign's ambient operating temperatures. All our AlphaXpress signage is compliant with NTCIP standards (the DOTs protocol for controlling all LED signs) allowing our signs to fit within all DOT interoperability standards. In 2006, at ITS America in Philadelphia, we introduced an innovative browser interface allowing service personal to diagnose and service a VMS with any browser enabled device. We've been successful in installing AlphaExpress in DOTs through out most of the United States."

Dashboard signage possibilities
As the DOTs discover more of the potential of VMS and its effectiveness for both traffic managers and drivers, so will its operation of electronic signage be enhanced. While most electronic signs are networked via landlines, there is the potential of WiFi becoming a new standard of connectivity between LED signs and the various DOTs traffic command centers. Color and graphics are also being added to enhance driver/traffic management communications.

Here Daktronics has taken the lead by offering its VMS signs with full color and graphic symbol capabilities. Icons such as merging traffic lane symbols or using the disability graphic (blue background with white wheelchair symbol) can now be viewed on certain electronic LED signs when appropriate. With a little crystal ball gazing, Washington State DOT administrator Bill Legg noted, vehicles already have electronic navigation systems with on board maps, but in the future, drivers may find new vehicles with dedicated display panels that will pick up electronic ITS sign messages and replay them on the dash board. This of course would never replace LED highway signage, but certainly give a new twist to CMS from Changeable Message Systems' to Car Message Systems.

Louis M. Brill is a journalist and consultant for high-tech entertainment and media communications. He can be reached at (415) 664-0694 or louisbrill@sbcglobal.net