Countering terrorism in transportation

Issues in Science and Technology, Summer 2002 by Downey, Mortimer L, Menzies, Thomas R

Our failed piecemeal approach to security must be replaced with a layered, wellintegrated system.

Americans now face almost weekly warnings about potential terrorist targets, from banks and apartment buildings to dams and nuclear power plants. This threat of terrorism is not new to transportation. From jet airliners to mass transit buses and rail terminals, vehicles and transport facilities are all-toofamiliar targets of terrorist attacks in this country and abroad. Although new attacks could occur, we cannot simply accept a recurrence as inevitable. Terrorist attacks on the transportation system can be derailed, and they can also be deterred.

Successful transportation counterterrorism, however, will require a new strategy. There is no point in trying to protect against or weed out every possible opening for terrorists. That is a traditional approach to transportation security, but it is expensive and demonstrably ineffective. The new strategy should rely instead on layering and interleaving various defensive measures. With layering, each safeguard, even though it may be inadequate by itself, reinforces the others. A layering strategy will not only protect against vulnerabilities in transportation security, it will also deter terrorists by creating uncertainties about the chances of being caught. Developing a better transportation security strategy should be the job of the newly created federal Transportation Security Administration (TSA). We present some recommendations for how the TSA should proceed.

Transport vehicles are ubiquitous, moving virtually unnoticed within industrial locations and major population centers; across borders; and (in the case of mail and express package services) to nearly every household, business, and government office in the country. This is how our transportation system works and must continue to work.

Using four jet airliners as cruise missiles, however, the September 11 th attackers showed how the omnipresent air transportation system could be turned into a weapon far deadlier than ever envisioned by those charged with aviation security. Only a few weeks later, the mailer of anthrax spores, capitalizing on the anonymity and reach of the postal system, showed how a seemingly innocuous transportation mode could be turned into a weapons delivery system.

The question now facing the federal government and the many state, local, and private entities that own and operate the nation's air, land, and water transportation systems is how best to secure these systems to keep them from being exploited again to such tragic effect.

The solutions are not obvious. The very nature of the transportation enterprise is to be open, efficient, and accessible. Security that restricts access and impedes transportation can send costly ripple effects throughout the national economy and society. Moreover, the vast scale and scope of the transportation system means that efforts to protect its many potential vulnerabilities through traditional means-guards, guns, and gates-may do little more than disperse and dilute the nation's security resources. Determined attackers can find ways to defeat such single-tiered perimeter defenses; that is the lesson from the Trojan horse's penetration of the walls of Troy as well as from modern-day experience with computer hackers.

We contend that setting out to eliminate or defend every vulnerability in the transportation system, one by one, is the wrong approach to countering terrorism. Attempts are likely to prove futile and costly. How, for instance, does one go about even identifying, much less defending, every possible target in the 300,000-mile rail and 45,000-mile interstate highway networks? Even civil aviation comprises some 14,000 airports and 200,000 airplanes scattered across the country. Deploying one protection at a time, matched to a specific vulnerability, is likely to yield little more than a thinned-out patchwork of unconnected defenses. We now know that an attacker who can find a way to breach a single imperfect protection, as the September I th hijackers did in defeating the airport screeners, can overcome an entire security regime. Little else is in the way.

A more sensible approach is to layer security measures so that each element, however imperfect, provides backup and redundancy to another. No single protection is likely to be foolproof or impermeable. When protections are layered, if one fails, others can compensate. A layered system, therefore, does not require a sustained high-level performance from each protection, just a reasonable expectation of success. Long used to secure communications and information systems, the collective layering of protections provides deep, dynamic defenses.

This is not to say that key facilities should be left unguarded. We must identify those elements of the transportation system that require a dedication of security resources because their destruction or impairment would cause considerable harm to people and to the transportation system. Such facilities-key bridges, underwater tunnels, command-and-control centers, and the like-should be guarded, but as part of a layered system of defenses. The hardened cockpit door is not the only defense against an armed hijacker; it is the last in a series of layered defenses.