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34 CHAPTER 3 EMERGENCY RESPONSE PLANS, OPTIONS, AND STRUCTURE This chapter presents a summary of the different U.S. System (NHS) was developed by the Department of Trans- transportation modes. The summary includes functional, op- portation (DOT) in cooperation with the states, local offi- erational, and control characteristics of these modes, which cials, and metropolitan planning organizations (MPO). The will assist in meeting the ultimate objective of this research, NHS includes several subsystems of roadways that overlap: which is to develop a guide that will help state and local arterials and other road classifications (that are part of the transportation officials to develop their transportation re- national road network, but of which only a small part of the sponse options in the case of an extreme event. mileage falls within the NHS). The U.S. transportation system carries both freight and people, transported using the following modes: Arterials Highway, Maritime, These roadways provide the highest level of mobility, at Rail, the highest speed, for long and uninterrupted travel. Arteri- Air, and als typically have higher design standards than other roads. Mass transit. They often include multiple lanes and have some degree of access control. The rural arterial network provides inter- The last category is unique in that it uses the former modes state and inter-county service so that all developed areas are of transportation, but is limited to the transport of people. The within a reasonable distance of an arterial highway. FHWA operations of the mass transit system are quite different from subclassifications for arterials in the NHS include the freight or personal transportation, thus, the options for use of this following: system in the case of extreme events is considered separately. Each of the five transportation mode summaries is divided Interstate. The Eisenhower Interstate System, as origi- into the following subsections: nally established by the Federal-Aid Highway Act of 1956, retains a separate identity within the NHS. The In- Definitions used to describe the system; terstate System connects, as directly as practicable, prin- National system size and characteristics; cipal metropolitan areas, cities, and industrial centers; System use under normal operations; serves the national defense; and connects at suitable bor- System financing as it relates to security funds and der points with routes of continental importance. emergency options; Other Principal Arterials. These are highways in rural General organization from a management perspective; and urban areas that provide access between an arterial General operations under normal conditions; and a major port, airport, public transportation facility, Emergency plans in the system and organization during or other intermodal transportation facility. Almost all emergency events; urban areas with more than 50,000 people, and most Historical emergency actions; and urban areas with more than 25,000 people, are con- Summary matrixes of operations and traffic, and emer- nected by principal arterial highways that may or may gency options, limits, and authority. not be part of the Interstate System. Strategic Highway Network (STRAHNET). This net- 3.1 THE HIGHWAY SYSTEM work of highways is important to U.S. strategic defense policy; it provides defense access and continuity and 3.1.1 Definitions emergency capabilities for defense purposes. Major Strategic Highway Network Connectors. These The U.S. highway system is approximately 160,000 miles are highways that provide access between major mili- (256,000 kilometers) of roadway important to the nation's tary installations and highways that are part of the economy, defense, and mobility. The National Highway Strategic Highway Network.