DN Staff

October 7, 1996

11 Min Read
The intelligent highway

No machine is at once as liberating and dangerous as the automobile. So liberating, in fact, that there is no debate over the appropriateness of private ownership. So dangerous that annual U.S. car crash fatalities are nearly equal to the number of American lives lost in the entire Vietnam War.

Last January, Transportation Secretary Federico Pena announced what he termed, Operation TimeSaver: "A new initiative designed to cut the daily travel time of Americans living in congested metropolitan areas by 15 percent over the next ten years." Potential time savings--rather than lives--is what Pena used to sell intelligent highways to the public. However, Operation TimeSaver also offers a safer, more responsive, and even a cleaner national highway system.

These goals are to be achieved through the erection of an Intelligent Transportation Infrastructure (ITI), a massive undertaking involving federal, state, and local government agencies in addition to universities and private enterprise. A concept more than a program, ITI is bringing many existing projects under its aegis and giving the nod to others currently outside its scope.

ITI and its kin are deploying thousands of sensors, transponders, and information systems in highways, along roadsides, and in cars and trucks across America. These systems are generating unprecedented amounts of traveler data that can be put to a wide variety of traffic control purposes. Highway intelligence promises to support--and compensate for--intelligence behind the wheel.

The challenge for municipalities is to design informtion systems using available technology in innovative ways so as to minimize the cost to the taxpayer. Another challenge is coming up with enough useful information to put on the system so it actually does enhance highway efficiency and safety. Since drivers themselves are major components of any highway system, designers are working to make real-time data readily available without the need for special equipment, such as in-car terminals and CRTs.

A prime example of this principle in action is Washington State's pioneering efforts to construct a comprehensive driver information system using changeable message signs, a common method for communicating information from roadside. The DOT in Spokane is experimenting with AT&T sonic detectors as well as lasers to supplement ramp metering data in order to accurately determine traffic levels. In addition, the information system receives input from a half-dozen weather stations around the state to provide real-time weather reports.

The system is designed to provide targeted, local data: a must in a state where temperate coastal rain forest conspires with arid interior conditions to defy long-term forecasters. The focused approach also helps improve driver safety in some of the challenging terrain traversed by Washington's highways. For example, weather sensors near Snoqualmie Pass are used to support changeable speed limit displays in that alpine region.

Washington State also maintains its Strategic Highway Research Program Database for the purpose of collecting and disseminating information related to the implementation of a statewide intelligent highway infrastructure. The information is available via the World Wide Web to vendors, researchers, and the public.

Weighing in. Getting vehicles to cooperate by providing data about them-selves makes a traffic administrator's job that much easier. This is the idea behind Advantage I-75, a system of automated weigh stations running from Florida to Michigan and into Ontario on Highway 401. Under the project, 29 stations (22 in the U.S., seven in Canada) have been fitted out with equipment and networked so registered truckers can bypass them, saving time and easing the enforce-ment burden.

Although not conceived as an ITI project, Advantage I-75 is now being lauded by the U.S. DOT as an ITI success story. Secretary Pena was present for the ribbon-cutting ceremonies last December, a month before he announced Operation TimeSaver.

An automatic vehicle identification (AVI) system is instrumental to the success of Advantage I-75. The system works this way: a participating truck carries a Delco transponder encoded with carrier, vehicle, and trip data. An advance AVI reader mounted on a light-pole a half-mile up the road from a weigh station automatically sends periodic queries in the 915 MHz band. When the approaching truck's transponder receives a query message, it broadcasts its stored data.

These are received by the reader, which enters them into the system-wide Advantage I-75 database. If the truck's credentials are satisfactory, the reader updates the truck's electronic tag and clears the driver to bypass the station. Every transaction between a transponder and a weigh station is a read/write transaction. If something is amiss, or if the truck is not on the network, it is pulled in for a manual inspection. Pass and pull-in signals are communicated to the driver by lights and tones.

"The AVI is similar to an identify friend/foe (IFF) system used by the military," says Joe Crabtree, an adjunct professor of civil engineering at the University of Kentucky, Lexington, and director of Advantage I-75 operations. "The system is quite simple from a component technology standpoint. Sophistication and features can be added by doing neat things with database management."

Every state and province participating in the program has access to the same data, which is centrally maintained at U. Kentucky's Transportation Center. Local authorities have the opportunity to do what they like with that data and can enforce laws according to local statutes. The system offers application flexibility without the need for specialized hardware.

Crabtree says Advantage I-75 makes life easier for truckers and enforcement personnel alike. First off, carriers are able to deliver goods faster. Secondly, automatically passing trucks with good credentials enables enforcement personnel to concentrate on more troublesome carriers. Since every transaction updatesthe database, authorities all over the network have access to the most current information on trucks moving through their jurisdictions.

The Advantage I-75 operational test program is funded through 1997 and will provide 4,500 transponders at no cost to users who fill out an application and qualify. Crabtree says questions of funding beyond 1997 and who pays for transponders over and above the initial offering are still being discussed. "I expect this test to lead to a permanent system that will spread to other highways and corridors," Crabtree says.

Such a goal is obscured by system compatibility and integration problems. Advantage I-75's Delco transponders use an AVI protocol developed by Hughes Transportation Systems. Other weigh-in-motion systems elsewhere, such as on Kentucky's I-65 and Illinois' I-55, have readers and transponders from Amtech Corp., Dallas, TX, that do not use the Hughes AVI and are incompatible with systems that do.

Amtech was among the first to apply transponder/reader technology to intelligent highway systems. Amtech's tags use a backscatter technology where energy from a transceiver's query broadcast is used by the transponder tags to power on-board circuitry. The tags reflect the updated signal back to the reader and can be used for read/write applications.

Said Majdi, research engineer at Amtech, says an advantage of backscatter technology is that it is frequency agile within an assigned band. While the FCC has set aside the 915 MHz frequency for dedicated short-range communications (DSRC) broadcasts (which intelligent highway applications typically use), there is latitude for local variation within this band. "Backscatter tags, because they reflect transmissions, operate in a more generous frequency range and can usually handle local frequency variations," Majdi says.

For whom the tag tolls. Although they may use incompatible systems, many successful intelligent highway applications have this in common: they save the sponsoring municipalities money. Material benefits provide the incentive for building the system, which collects data that can be used to create a driver information system later. A number of intelligent information applications are developing along these lines.

Electronic toll collection is one of the more popular intelligent highway applications (with state and local governments at least). Governments favor them because they provide for more efficient revenue flow in addition to improving the flow of traffic. The largest in the U.S. is the E-ZPass system, involving eight agencies in New York, New Jersey, and Pennsylvania.

This Interagency Group, headed by the NYS Thruway Authority, is unclogging some of the most congested roads in America by hurrying cars through its bevy of bridge, tunnel, and highway toll booths. In 1994, the group settled on a common automated collection architecture and selected Mark IV Industries of Mississauga, ON, Canada to supply transponder tags and readers. E-ZPass already had been implemented throughout the New York Thruway and at most of the region's toll river crossings.

Approved E-ZPass customers receive a Mark IV transponder tag which they affix to the interior of the windshield behind the rear-view mirror. These customers pay a sum into their E-ZPass accounts by check or credit card.

The Interagency Group has designated some lanes of its toll booths E-ZPass-only lanes. These are equipped with readers that broadcast 915 MHz query signals. When a customer's car approaches a designated lane, the tag replies to the query with an identification signal. The reader receives the signal and automatically deducts the toll from the customer's account. On ticket-toll routes, such as the Thruway, the appropriate amount is deducted when the car exits.

Driver information signs at E-ZPass lanes indicate when accounts are running low. If a car without an E-ZPass tag or with an insufficient account balance runs a reader-equipped lane, a video camera is on hand to capture an image of the offender's rear license plate. The image is used to support a violations notice.

Paul Manuel, marketing manager at Mark IV's intelligent vehicle highway systems division, said the E-ZPass read/write system grew out of technology developed for railroad companies to keep track of rolling stock. Very few changes were required to adapt the transponders/readers to the purpose of metaphysically lightening drivers' wallets.

According to the NYS Thruway Authority's 1995 annual report, some 125,000 E-ZPass tags were in circulation statewide. Approximately 50 percent of all weekday travelers who crossed the Hudson River via the Tappan Zee Bridge north of New York did so with E-ZPass tags. While staffed lanes are able to process a peak of 450 cars per hour, E-ZPass lanes are able to process more than 900 vehicles per hour. In addition to reducing congestion, the Authority claims a reduction in the amount of air pollution from cars stuck in toll plazas.

E-ZPass may yet yield other benefits. John Cardillo, senior public information specialist at the NYS Thruway Authority, says some E-ZPass data is being used to monitor traffic flow in a test program, dubbed Transmit, with the goal of developing a new-generation driver information system for the Empire State. Albany is expanding its traffic operations center, planning a fiber optic network along its rights-of-way, and testing variable message signs, highway advisory radio, and other technologies for delivering traveler information.

Technology dialects. One of the main barriers to an integrated, nationwide ITI system is that regional requirements tend to produce regional solutions. Kentucky's Transportation Cabinet (as that state refers to its DOT) did not consider New York's toll collection requirements when it asked the Transportation Center at U. Kentucky to research a weigh-in-motion system. Even though Advantage I-75 and E-ZPass both are read/write, transponder/reader architectures, the hardware used in each are incompat-ible. Thus, instead of an overall ITI architecture, the country might see its highways carved up by region andby application.

Vendors and standards bodies are working to prevent this from happening. Mark IV is developing a dual protocol reader that recognizes both its own and Hughes' protocols. Also in the works is a transponder that will broadcast in both protocols as well. Mark IV's Manuel says this solution will enable municipalities using E-ZPass or systems based on the Hughes protocol, such as Delco, to be integrated until a standard is accepted by the American Society for Testing & Materials. Amtech is developing multi-frequency tags that will be able to operate with readers used in any country.

Despite the admirable goals of Operation TimeSaver, the concept is not without its critics who think the DOT's time could be better spent. Some of this criticism comes from surprising source. "Forget about ITI; Secretary Pena should be doing more to promote a first-class mass transit infrastructure in this country," said a senior engineer at one of the Big Three who, for obvious reasons, wishes to remain anonymous.

The U.S. DOT says ITI will serve as a framework for highway automation, at least domestically. Secretary Pena promises a national architecture will be finalized this year, along with published guidelines for state and local officials.

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