Photonic Solutions for Transportation

Breck Hitz, Senior Technical Editor

The US transportation infrastructure, already dependent in many ways on optics and photonics, will become even more so in the future, according to attendees of a workshop held last month in Washington. From monitoring exhaust emissions to assuring the integrity of shipping containers arriving from foreign ports, these technologies can provide solutions to many transportation problems. The purpose of the workshop was to provide a comprehensive overview of the future role of optics and photonics in transportation and to make transportation planners aware of the usefulness of these technologies.

The issues facing the US are not trivial. “Air-travel delays cost the country more than $9 billion a year,” Maj. Gen. William W. Hoover, chairman of the Aeronautics and Space Engineering Board, told the assembled government officials, engineers and business leaders. “More than 40,000 Americans lose their lives in highway accidents every year,” reported Jeffrey N. Shane, undersecretary of transportation for policy. The workshop, which was jointly sponsored by the US Departments of Transportation and Commerce, OSA and SPIE, sought to address the role that optics and photonics can play in solving these and other problems.

The two-day conference began with presentations by authorities from government and industry describing the challenges facing the national transportation infrastructure. Stephen J. McHale, deputy administrator of the Transportation Security Administration, predicted that airport security will change drastically in the next five years. “The existing technologies are near their limits in terms of throughput and sensitivity,” he said. But they aren’t working well enough, he noted, pointing to the long lines of waiting passengers at security checkpoints at virtually every major US airport.

McHale’s concern extends beyond passenger inconvenience: Lines just inside the airports’ doors offer an enticing target for terrorists. “How can we provide security without generating a target?” he asked. Answering his own question, he described his vision of standoff security systems that would unobtrusively scan passengers and their baggage as they walk into the airport, so that any lines and crowds would be inside the security perimeter. The challenge is determining which technologies can provide that capability, and the question is how optics and photonics may contribute to these next-generation security systems.

Of course, air travel is not the only transportation mode. Motor vehicles traveled more than 1 trillion miles on the nation’s roads in 1970, according to John Horsley, executive director of the American Association of State Highway and Transportation Officials. By 1990, the figure had grown to 2.2 trillion miles, and it will exceed 3.5 trillion by 2010, he predicts. The problem is that highway construction cannot keep pace with this increasing level of traffic. The only alternative is to increase the capacity of existing highways.

Photonic solutions already have been applied to many highway and traffic issues, Horsley observed. Fiber optic temperature sensors embedded in roadways indicate when to apply salt to frozen surfaces. Optical interference can measure the deflection of metal plates when a truck drives over them, providing a much faster method of weighing them than conventional scales. And tens of thousands of LEDs have found use in taillights and in traffic signals.

After the transportation experts had outlined their perspectives of the infrastructure’s future needs, the workshop participants separated to discuss how photonics technology might address these needs. “Ballast water could be analyzed spectroscopically,” suggested Duncan T. Moore of the University of Rochester, chairman of the session on maritime transportation, who gave one example of the conclusions reached. Harmful organisms can be transported around the globe and introduced into new environments in a ship’s ballast water, which is discharged when the ship takes on fresh cargo in a foreign port. Another potential use of photonics that Moore cited is in fiber optic hydrophone arrays around a ship to enhance security. Such arrays can detect the approach of unauthorized vessels on or beneath the surface.

Security was the issue in many of the breakout sessions. The thousands of shipping containers that arrive daily in US ports are a major concern. The group led by Robert P. Breault, president of Breault Research Organization Inc., suggested sealing containers at their overseas source, using a seal whose spectral characteristics would be altered if it were broken en route. Widespread acceptance of the technique could result in a market for millions of seals annually, in addition to the hundreds of units that would be required to interrogate the seals.

Synthetic vision was one of many photonics technologies listed as contributing to the expansion of air-transport efficiency and safety in the coming decade. In synthetic vision, an accurate image of a runway, for example, is projected in front of the pilot, even when exterior conditions render the runway completely invisible to the eye. These systems not only would reduce the financial loss caused by air-traffic delays, but also would improve the airlines’ safety records.

In February, the workshop’s sponsors will release a final report and a road map describing how optics and photonics may be integrated into the nation’s transportation infrastructure.