MARCH 2008 HOT TOPICS

How Can We Cost-Effectively Protect Rail Passengers from Terrorist Attacks?

More than 12 million Americans travel on passenger-rail lines each weekday. And because of its relatively lower-security nature, rail transit is considered an attractive terrorist target. While there have been no successful attacks on the U.S. rail system recently, attacks on passenger-rail systems around the world—such as the London Underground in 2005—highlight the vulnerability of rail systems and the importance of rail security for passengers.

RAND Corporation researchers have developed a framework for security planners and policymakers to guide cost-effective rail-security planning, specifically for the risk of terrorism, and demonstrated its use on a composite intracity rail system that characterizes rail systems typically found in the United States.

Drawing on data from the RAND-MIPT Terrorist Incident Database, the study found that bombings are the most prevalent terrorist threat to rail systems, that most such attacks produce few fatalities or injuries, and that attacks in densely packed rail cars and train stations are of particular concern because of the casualties that can result. Not all such attacks come from explosives, and so security measures must address the possibility of other attack modes as well. But given the damage from a relatively small number of large attacks, security measures that prevent only the largest-scale attacks could significantly reduce the associated human costs.

To understand how to protect people from such attacks, researchers examined 11 potential attack locations in a rail system and subjected them to eight potential attack modes. The researchers found that some rail-attack modes and targets are more of a concern than others. For example, the use of small explosives is a high or medium risk for most targets, and the system-operation and power infrastructure is a high or medium risk for seven of the eight attack modes.

In examining how to defend a system against such threats, the study compared the cost-effectiveness of adding different security measures to the composite system's baseline security. Four broad categories of cost-effective security measures emerged: (1) relatively inexpensive solutions with highest effectiveness, such as enhanced security training; (2) additional inexpensive solutions with reasonable levels of effectiveness, such as installing retractable bollards at the entrances and exits of the central operation center and power plant; (3) relatively expensive solutions with highest effectiveness, such as installing fixed barriers at the curbsides of all entrances and passageways leading to train stations; and (4) relatively expensive longer-term solutions, such as rail-vehicle surveillance systems.

READ MORE: A Framework for Planning Cost-Effective Rail Security Against a Terrorist Attack

How Can We Assess Novel Threats to Homeland Security?

When it comes to investing homeland security resources wisely, policymakers must account for both known or likely attack modes and for "novel" ones—previously unknown but plausible attack modes that could appear in the future. Since responding to each possible threat can be costly, planners must decide if a new technology or potential attack justifies changes in homeland security spending or if it is adequately addressed by measures that are already in place.

A RAND Corporation study presents an approach to making that decision by examining a new threat from both the attacker's and the homeland security planner's perspectives and uses it to examine one type of potential novel threat to the homeland: terrorist use of cruise missiles and unmanned aerial vehicles (UAVs). The approach considers these technologies as one option among many attack possibilities available to a potential adversary and compares the consequences of attacks using them to other options terrorists already have available to them.

From an adversary's perspective, the researchers found that such attack modes do not appear to have major advantages over other ways of carrying out operations against similar targets, though they do provide an advantage in some circumstances. Where they did appear preferable, the choice for these systems was driven largely by the actions of the defense or in-place security measures—i.e., were alternative attack modes foreclosed by defenses? However, the price of these advantages was greater complexity, technological uncertainty, and higher cost and risks associated with these platforms. Thus, UAVs and cruise missiles appear to represent a "niche threat"—an attack mode that terrorists might choose—but in most cases, there are simpler alternatives that provide similar, or even superior, capabilities.

As a result, the researchers recommend a measured approach to responding to possible terrorist use of these weapons built on a foundation of investments in broader counterterrorism and law enforcement capabilities. While the approach is applied to this particular novel threat, it is equally relevant to examining other novel threats and informing policy and resource-allocation decisions.

READ THE REPORT: Evaluating Novel Threats to the Homeland: Unmanned Aerial Vehicles and Cruise Missiles

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For over 30 years, RAND has been a world leader in terrorism research and analysis. To view RAND's terrorism and homeland security research, go to www.rand.org/research_areas/terrorism/.

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