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1 CHAPTER 1 Introduction It is estimated that there are 337 highway tunnels and 211 The traveling public relies on the security and safety of trans- transit tunnels in the United States [Ref. 1]. These tunnels portation tunnels on a daily basis. It is essential that steps be move thousands of people and tons of cargo daily. Many of taken to protect these important assets. these tunnel facilities are located at key "choke points" in the From a policy perspective, tunnel managers have two sig- nation's transportation network. As with other components nificant concerns. First, tunnels serve important day-to-day of the transportation infrastructure, tunnels are susceptible transportation functions, often providing nonredundant net- to a range of hazards and threats. work connections. Second, owners must plan for effective use Tunnels can face disruption from either the occurrence of of the tunnels to transport people and goods as emergency hazards (i.e., unintentional, accidental events) or the success- relief in the event of severe emergencies occurring elsewhere. ful conduct of threats (i.e., intentional acts). Hazards can be For example, an approaching hurricane in a coastal area may human- or equipment-related (e.g., motor vehicle collisions necessitate use of a highway tunnel for mass evacuation if it is and resulting fire) or natural (e.g., flooding and earthquakes). deemed safe to do so. Alternatively, as on September 11, the Relatively new tunnels have allowances for natural disasters initial closing of the transit and highway tunnels leading out incorporated into their design and construction. The of Manhattan required thousands of people to walk across allowances are based on the best engineering practices. outbound bridges. Even less catastrophic events, such as traf- Although older tunnels may lack some features that are com- fic accidents or train derailments, may have rippling effects in monplace in modern design and construction, the older tun- other parts of the transportation system. Moreover, extreme nels may still be quite serviceable. Whether old or new, some events will invariably impact multiple modes and other local, tunnels may be impregnable to natural disaster because of state, or national resources. their location, but still vulnerable to incidents. Because tunnels are expensive to build and operate, the Threats resulting in intentional disruption can include ter- existence of a tunnel usually indicates that no feasible alter- rorist attacks such as those that occurred on September 11, natives existed; thus, no alternate routing or means of trans- 2001. While tunnels and transportation facilities were not the port in the event of disrupted operation is likely to exist. In primary targets of those attacks, there were certainly numer- recognition of tunnels' vital roles and their exposure to harm- ous secondary effects on the transportation system. Tunnels ful disruption, transportation tunnel security and safety make tempting targets because (a) they are important to the issues have become part of the national security dialogue. economic viability of surrounding communities, especially This report provides tunnel owners and operators with when they are used to transport goods; (b) many people are guidelines for protecting their tunnels to minimize the damage present at predictable times; and (c) the enclosed environ- potential from extreme events so that, if damaged, the tunnels ment further compounds the potential for casualties from the may be returned to full functionality in relatively short periods. effects of confined blast events, collapse, and flooding. Tran- The report focuses on three kinds of transportation tun- sit tunnels, in particular, are easily reached from open, acces- nels: highway, rail, and transit. Rail (which includes both pas- sible environments (i.e., stations); as a result, these tunnels are senger and freight) and transit tunnels are separate categories. viewed as high-risk, high-damage potential targets. Examples Rail tunnels are typically larger and can carry greater loads of intentional, harmful aggression against transit tunnel envi- than transit tunnels. Transit lines are typically in urban areas, ronments and users are the 1995 sarin gas attack in Tokyo, the with smaller and shorter cars, slower speeds, shorter dis- 2003 arson fire in Daegu, and the 2004 bombing in Moscow. tances, and higher occupancies than passenger rail lines.