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J Route: See Jet Route.

J-T-W: Journey To Work (FHWA13)

Jack Staff: A vertical pole erected on the lead barge of a tow used by the pilot for aligning the heading of the tow. (TNDOT1)

Jacking It Around: Backing a semitrailer around a very sharp curve. (ATA1)

Jackknife: (See also Accident, Rollover) Jackknife can occur at any time during the crash sequence. In this report, jackknifing is restricted to truck tractors pulling a trailing unit in which the trailing unit and the pulling vehicle rotate with respect to each other. (NHTSA3)

Jacob's Ladder: A rope ladder suspended from the side of a vessel and used for boarding. (MARAD2)

Jamming: Electronic or mechanical interference which may disrupt the display of aircraft on radar or the transmission/reception of radio communications/navigation. (FAA4)

JAR: Joint Aviation Requirement (FAA7)

JAX: Jacksonville International Airport (FAA11)

Jeep-Like Vehicle: See Sport-Utility Vehicle.

Jet Blast: Jet engine exhaust (thrust stream turbulence). (FAA4)

Jet Down: To sink an object, generally a buoy sinker, deep into the mud below the river bottom by the use of high pressure water jet. (TNDOT1)

Jet Fuel: The term includes kerosene-type jet fuel and naphtha-type jet fuel. Kerosene-type jet fuel is a kerosene quality product used primarily for commercial turbojet and turboprop aircraft engines. Naphtha-type jet fuel is a fuel in the heavy naphtha boiling range used primarily for military turbojet and turboprop aircraft engines. (DOE3) (DOE5) (DOE6)

Jet Route: A route designed to serve aircraft operations from 18,000 feet mean sea level (MSL) up to and including flight level 450. The routes are referred to as "J" routes with numbering to identify the designated route; e.g. J105. (FAA2) (FAA4)

Jet Stream: A migrating stream of high-speed winds present at high altitudes. (FAA4)

Jettisoning of External Stores: (See also Fuel Dumping) Airborne release of external stores; (e.g., tiptanks, ordnance). (FAA4)

JFAST: Joint Flow and Analysis System for Transportation (MTMC1)

JFK: John F Kennedy International Airport (FAA11)

JIT: Just-In-Time (BTS2)

Jitney: Privately-owned, small or medium-sized vehicle usually operated on a fixed route but not on a fixed schedule. (APTA1)

Jitney: Passenger cars or vans operating on fixed routes (sometimes with minor deviations) as demand warrants without fixed schedules or fixed stops. (FTA1)

Jockey Line: Lashing used to prevent lateral movement between barges connected in tandem. (TNDOT1)

Johnboat: Flat bottomed skiff type boat with square bow and stern. (TNDOT1)

Joint Operations: Rail operations conducted on a track used jointly or in common by two or more railroads subject to 49 CFR 225 or operation of a train, locomotive, car or other on-track equipment by one railroad over the track of another railroad. (49CFR225) (FRA2)

Joint-Use Airport: A military installation at which the Department of Defense permits some degree of civil aviation use. Degrees of civil aviation use include: 1) Open to all civil aviation under a joint-use agreement 2) Joint-use agreement for limited use. Strictly military airports do not qualify for primary or commercial service status. (FAA11)

Joule: Unit of measurement of energy consumption. (TNDOT1)

JPL: Jet Propulsion Laboratory (FHWAII)

JTB: Joint Transportation Board (MTMC1)

JTIC: Joint Transportation Intelligence Center (MTMC1)

Jumbo Barge: A barge 35 feet wide by 195 or 200 feet long that may be either a hopper or cover-type barge. (TNDOT1)

Jumped the Pin: Missing the fifth wheel pin on the trailer when coupling tractor to trailer. (ATA1)

Junction: Area formed by the connection of two roadways, including intersections, interchange areas and entrance/exit ramps. (NHTSA3)

Just In Time: In this method of inventory control, warehousing is minimal or non-existent; the container is the movable warehouse and must arrive "just in time", that is not too early nor too late. (MARAD2)