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Keyword Definition
Maintenance Area Maintenance area is any geographic region of the United States previously designated nonattainment pursuant to the CAA Amendments of 1990 and subsequently redesignated to attainment subject to the requirement to develop a maintenance plan under section 175A of the CAA, as amended.
Majors (Air) Air carrier groups with annual operating revenues exceeding $1 billion.
Management Systems (1) Systems to improve identification of problems and opportunities throughout the entire surface transportation network, and to evaluate and prioritize alternative strategies, actions and solutions. (2) A systematic process, designed to assist decisionmakers in selecting cost-effective strategies/actions to improve the efficiency and safety of, and protect the investment in, the nation's transportation infrastructure.
Maritime Business pertaining to commerce or navigation transacted upon the sea or in seaports in such matters as the court of admiralty has jurisdiction. (MARAD2)
Maritime Administration (MARAD) The Maritime Administration was established by Reorganization Plan No. 21 of 1950 (5 U.S.C. app.) effective May 24, 1950. The Maritime Act of 1981 (46 U.S.C. 1601) transferred the Maritime Administration to the Department of Transportation, effective Aug
Mass Transportation Another name for public transportation. (APTA1)
Mass Transportation Agency An agency authorized to transport people by bus, rail, or other conveyance, either publicly or privately owned, and providing to the public general or special service (but not including school, charter or sightseeing service) on a regular basis. (FTA1)
Measures of Effectiveness Measures or tests which reflect the degree of attainment of particular objectives.
Memorandum of Understanding (MOU) A document providing a general description of the responsibilities that are to be assumed by two or more parties in their pursuit of some goal(s). More specific information may be provided in an associated SOW.
Methanol A light, volatile alcohol produced commercially by the catalyzed reaction of hydrogen and carbon monoxide. Methanol is blended with gasoline to improve its operational efficiency.
Methyl-Tertiary-Butyl-Ether (MTBE) A colorless, flammable, liquid oxygenated hydrocarbon that contains 18.15 percent oxygen. It is a fuel oxygenate produced by reacting methanol with isobutylene.
Metropolitan Planning Area The geographic area in which the metropolitan transportation planning process required by 23 U.S.C. 134 and section 8 of the Federal Transit Act (49 U.S.C. app. 1607) must be carried out. (23CFR420)
Metropolitan Planning Organization (MPO) 1) Regional policy body, required in urbanized areas with populations over 50,000, and designated by local officials and the governor of the state. Responsible in cooperation with the state and other transportation providers for carrying out the metropolitan transportation planning requirements of federal highway and transit legislation. 2) Formed in cooperation with the state, develops transportation plans and programs for the metropolitan area. For each urbanized area, a Metropolitan Planning Organization (MPO) must be designated by agreement between the Governor and local units of government representing 75% of the affected population (in the metropolitan area), including the central cities or cities as defined by the Bureau of the Census, or in accordance with procedures established by applicable State or local law (23 U.S.C. 134(b)(1)/Federal Transit Act of 1991 Sec. 8(b)(1)). (FHWA2)
Metropolitan Statistical Area (MSA) Areas defined by the U.S. Office of Management and Budget. A Metropolitan Statistical Area (MSA) is 1) A county or a group of contiguous counties that contain at least one city of 50,000 inhabitants or more, or 2) An urbanized area of at least 50,000 inhabitants and a total MSA population of at least 100,000 (75,000 in New England). The contiguous counties are included in an MSA if, according to certain criteria, they are essentially metropolitan in character and are socially and economically integrated with the central city. In New England, MSAs consist of towns and cities rather than counties. (DOE4) (DOE5) (FHWA3)
Metropolitan Status A building classification referring to the location of the building either located within a Metropolitan Statistical Area (MSA) or outside a MSA. (DOE5)
Metropolitan Transportation Plan (MTP) The official intermodal transportation plan that is developed and adopted through the metropolitan transportation planning process for the metropolitan planning area, in accordance with 23 U.S.C. 134, 23 USC 135 and 49 U.S.C. 5303.
Mile A statute mile (5,280 feet). All mileage computations are based on statute miles. (BTS5) (BTS6)
Miles Per Gallon (MPG) A measure of vehicle fuel efficiency. Miles Per Gallon (MPG) represents "Fleet Miles per Gallon". For each subgroup or "table cell", MPG is computed as the ratio of the total number of miles traveled by all vehicles in the subgroup to the total number of gallons consumed. MPGs are assigned to each vehicle using the Environmental Protection Agency (EPA) certification files and adjusted for on-road driving. (DOE4) (DOE5)
Milestone The meaning given in CAA sections 182(g)(1) and 189(c) for serious and above ozone nonattainment areas and PM10 nonattainment areas, respectively. For all other nonattainment areas, a milestone consists of an emissions level and the date on which that level is to be achieved as required by the applicable CAA provision for reasonable further progress towards attainment.
Minor Arterials (Highway) Roads linking cities and larger towns in rural areas. In urban areas, roads that link but do not penetrate neighborhoods within a community.
Mobile Source 1) The mobile source-related pollutants are carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM-10 and PM 2.5). 2) Mobile sources include motor vehicles, aircraft, seagoing vessels, and other transportation modes. The mobile source related pollutants are carbon monoxide (CO), hydrocarbons (HC) or volatile organic compounds (VOCs), nitrogen oxides (NOx), and small particulate matter (PM-10).
Mobile Source Air Toxics (MSATS) Identified by the EPA, MSATs are the 21 hazardous air pollutants generated in large part by transportation sources.
Mobility The ability to move or be moved from place to place.
Mode A specific form of transportation, such as automobile, subway, bus, rail, or air.
Motor Carrier Safety Administration (FMCS) The Federal Motor Carrier Safety Administration (FMCSA) was established as a separate administration within the U.S. Department of Transportation on January 1, 2000, pursuant to the Motor Carrier Safety Improvement Act of 1999. The primary mission of FMCS is to reduce crashes, injuries, and fatalities involving large trucks and buses . FMCSA is headquartered in Washington, DC. We employ more than 1,000 individuals, in all 50 States and the District of Columbia, dedicated to improving bus and truck safety and saving lives.
Motor Vehicle Emissions Budget The portion of the total allowable emissions defined in the submitted or approved control strategy implementation plan revision or maintenance plan for a certain date for the purpose of meeting reasonable further progress milestones or demonstrating attainment or maintenance of the NAAQS, for any criteria pollutant or its precursors, allocated to highway and transit vehicle use and emissions.
Motorbus (Transit) A rubber-tired, self-propelled, manually steered bus with a fuel supply onboard the vehicle. Motorbus types include intercity, school, and transit.
Motorcycle A two- or three-wheeled motor vehicle designed to transport one or two people, including motor scooters, minibikes, and mopeds.
Motorized Vehicle Includes all vehicles that are licensed for highway driving. Specifically excluded are snow mobiles and minibikes. (FHWA3)
Multimodal The availability of transportation options using different modes within a system or corridor.
Multimodal Transportation Often used as a synonym for intermodalism. Congress and others frequently use the term intermodalism in its broadest interpretation as a synonym for multimodal transportation. Most precisely, multimodal transportation covers all modes without necessarily including a holistic or integrated approach. (BTS2)

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