Variable message signs continue to deliver travel information

Arguably the 'face' of ITS, variable message signs are far from being a passing solution

As the old marketing adage goes, 'sex sells'. Certainly, it is the 'sexier' end of ITS which generates the most interest in the general media. The emergent, consumer-oriented technologies and applications - nomadic devices, cooperative infrastructure and the like - tend to hog the limelight. Meanwhile, much of the technology which already contributes so much to making our roads work better tends to be dismissed or else its performance maligned.

With this in mind, it is perhaps worth starting an article which looks at developments in Variable Message Signs (VMS) or Dynamic Message Signs (DMS) with a quote from Roger Stainforth, Deputy Chairman of UK-based 537 VMS Ltd (VMSL): "Over the next couple of years variable message signs will continue to be the principal means of disseminating information to drivers and managing their behaviour. The alternative methods of getting information to drivers are very individual in nature and depend on vehicles being fitted with appropriate technology. If a road operator wishes to impose a variable speed limit regime they have to know that when the speed limit changes every driver knows the moment the change has occurred. This security of knowledge can be achieved with variable speed limit signs above each lane or at the roadside displaying the information collectively. It is clear and unambiguous. Other means are more disparate and there is no certainty that all driver-received messages have the same weight of importance or, more fundamentally, that the equipment in the car is working.

"Whenever the question comes up about how much longer variable message signs will be deployed I'm reminded of a conference in 1993 in Coventry, England. In the final session the chairman made a prediction that within five to 10 years in-vehicle systems would consign VMS to history. Well, we are still here and going strong. I often wonder how different things might be if a fraction of the research money spent on in-vehicle systems had been spent on encouraging development in display technologies and infrastructure products. Signs and gantries may not be ultra-fashionable but they are very practical." He taps into a theme. Consider the following from 133 Telegra's Robert Ryslavy: "Equipping highways and arterial roads with traffic management systems, of which VMS are an essential part, to convey messages or warn drivers of adverse traffic conditions has become a standard requirement and not an exception - and not only in developed countries but on roads all around the world. As the most democratic way to pass these messages, visible as they are to everybody on the road regardless of the technology in the vehicle itself, VMS will remain a main means of communication for years to come." That robust view is reflected on the other side of the Atlantic by Casey Crabtree, ITS Market Manager with 32 Daktronics. He anticipates sector growth regardless of any government attempts to stimulate the economy by spending more on infrastructure.

"Transportation entities continue to focus on congestion reduction, accident prevention and travel management tactics," he says. "Dynamic message signage is an integral factor in achieving these goals." In short, things are looking good. Not only are network operators looking to deploy technology which will smooth traffic flows and ease congestion but as they gain experience of using VMS/DMS they tend, if anything, to spec up rather than down when purchasing, Ryslavy says.

"With time, end users become more sophisticated, with higher levels of expectation. This usually translates into higher requirements for certification, longevity and quality, design and workmanship. For first-time and inexperienced users, the main criterion is usually price. Experienced users wish to get the maximum for the optimal cost, which usually doesn't mean the cheapest equipment. There's an important educational process here."

Emerging applications

Applications too continue to increase. Although Europe is generally held to lead the US both technically and in terms of deployment, innovation continues on both sides of the Atlantic. In the UK, the Controlled Motorway schemes, such as that on the M25 London Orbital, and the Active Traffic Management hard shoulder-running solution first deployed on the M42 epitomise the European state of the art.

"The UK appears to lead the way in terms of uses and deployment of VMS. Controlled Motorway was first tried here on the M25 over 15 years ago," says Darren Smith, Commercial Director of Techspan. "It is now being rolled out across Europe and in some areas of the United States.

"The above-mentioned schemes are not necessarily novel but very interesting. The use of technology to vary the speed limit or opening the hard shoulder to running traffic during busy periods is a very economic way of increasing a road's capacity. Compared with widening the road, it is also environmentally friendly. It results in a very healthy market for VMS in the UK in the short to medium term." In the US, it is anticipated that a lot of business will arise from the fact that many metropolitan areas are looking to convert their High-Occupancy Vehicle (HOV) lanes to High-Occupancy Toll (HOT) lanes.

Casey Crabtree: "Currently, many HOV lanes are under-used due to the lack of carpooling. When implementing DMS capable of displaying variable toll rates, agencies see an increase in single passenger vehicles willing to pay to use the HOV lane."

Sign technology

In terms of signage deployed, in the US signs are primarily text displays with 7 x 5 or similar layouts and large pixels with large pixel pitch. In Europe, by contrast, the preference is for displays with narrow pixel pitch and control of each pixel. This integrates both graphic and text capabilities - useful in countries using letters with diacritics, as such signs can display any true type font including non-Roman characters. The use of such displays also allows for the display of traffic signs in a form similar to classic static signs.

This is changing, however, and there is a move in the US towards larger, full-colour displays, Crabtree continues: "In a few regions, customers are evolving from low-resolution, 18-inch, text-only signs to full-colour, high-resolution signs. The use of colour and higher resolutions allows messages to display graphics, which increases driver message comprehension; the University of Rhode Island has conducted a study comparing the use of text-only messages with graphical message and found that 94 per cent of drivers prefer the latter.

"The 407 ETR in Toronto, Canada and the New Jersey Turnpike have implemented full-colour signage along their freeways. Portland International Airport has also installed full-colour DMS to inform drivers of available parking facilities. In Florida, we're also seeing a lot of variable speed limit signs in use to better control traffic speeds and reduce 'stop and go' driving on congested freeways.

Brian Nicholson, COO of Imago North America, also picks up on the issue of colour: "Many parts of Europe are still significantly ahead of the market in the USA but we're beginning to see projects in some states, like Minnesota and Washington, for example, where the installations are catching up. These are encouraging from an industry perspective because they fuel growth and innovation. More importantly, they contribute directly and meaningfully to travel efficiency. The Minnesota DOT as a part of the Federal Urban Partnership Agreement is deploying the first and largest full-colour sign project in the USA. It represents a significant technological leap for most domestic DOTs and we're hopeful that this project will encourage other agencies to deploy colour VMS on a wider scale." For VMS/DMS and lane control signals LEDs remain the primary light technology. The improvement in LED candela output and efficiency is leading to more energy-efficient products which enable manufacturers to meet stricter green requirements.

Crashworthiness and passive safety is an area where much debate is taking place. Lattix and VMSL, for example, are together looking at ways of combining passively safe gantry structures and VMS technology to achieve an integrated design.

"In the UK, reliability and weight are the main factors," explains Roger Stainforth. "Reliability is important because of the policy to install signs on non-access gantries. Weight is important because the lighter the weight of the equipment the lighter the weight of the material in the gantry construction.

"There are however limitations to how far weight can be reduced. This is determined by the ability of drivers to read messages. For example, a 400mm-high character is generally accepted to be legible at 300m and suitable for 100km/h highways. Thus if you have a sign with three lines of 18x400mm-high characters with the recommended inter-character, inter-line and backing board spacing, the sign will be around 8m long by 2.7m high."

Standards

Standards are also evolving, although there remain some issues.

In the US, says Nicholson, the NEMA TS-4 standard, which primarily covers environmental and optical requirements, has done a very good job on two fronts: from the perspective of a manufacturer, the standard is very functional in nature so that it doesn't discourage innovation; and from the perspective of an engineer designing a system, it helps create a common basis upon which to build. By contrast, the ITS community has taken a long time to work the bugs out of NTCIP 1203.

"It's a complicated standard and didn't do a very good job of promoting interoperability between signs and central software packages when it was first released," he continues. "Over time, however, the industry has become used to it and the NTCIP working groups have published additional documents to help aid adoption. A second version, which was needed to allow for colour and graphics, has recently been released and we're anticipating a need to repeat a lot of the past pain as agencies make the transition."

Crabtree, meanwhile, is more upbeat about Version 2.

"It will add value by creating a standard that supports graphic images and full-colour support," he says. "This development also enhances the diagnostic reporting capabilities from the display. The specifications define the reporting status of power and climate control systems as well as other hardware devices. The reported values are more detailed and should provide more information to users. In addition, Version 2 will provide rules and guidelines for implementing the standards. These will help eliminate historical interpretation issues." In Europe, EN 12966 is the standard. Although it has done a great deal to harmonise optical and environmental requirements across Europe, Stainforth says that national legislation still has an influence, as do purchasing practices. Another issue, according to Ryslavy, is that many clients and authorities do not take the standard seriously enough. There are particular issues when it comes to optical and some environmental characteristics, he feels.

"We at Telegra believe that the optical standards employed in EN 12966 should be used worldwide and that all signage employed on the road should have third-party certification as an inability to read signs and messages under high external light conditions and high-intensity incident reflection can distract drivers and create dangerous situations in which safety is compromised."

Portable solutions

There is common agreement that moves to make portable signage conform to the same standards as their fixed brethren are both healthy and positive. However, the technology involved has stagnated somewhat, according to Mark Fernandez of National Signal: "Portable signs are becoming more efficient and somewhat more generic from manufacturer to manufacturer so the challenge remains to offer something that the user sees some value in. Finding other improvements that offer other benefits or solve specific needs is where we're currently spending our time."