question: Why do things on the back of flatbed trucks not fly off into my car while going down the road?
comment: According to DOT regulations: [it's tied down]( URL_0 ). This is a safety precaution that flatbeds are required to observe.
passages: Airbus are investigating a novel approach to reducing FOD. By developing, in conjunction with Israel Aerospace Industries, the Taxibot, a tractor controlled by the pilot, aircraft will not need to use jet engines while taxiing, so will not be vulnerable to FOD on aprons or taxiways.
  
  Section::::FOD damage examples.
  
  Section::::FOD damage examples.:Runway debris.
   Because the fairing is attached to the vehicle via the front axle, it is prone to clunky vibrations at low speeds and on turbulent surfaces. The nature and position of the motor produce a constant, loud mechanical sound much like a motorcycle. The weight limit for the vehicle, including the driver and all carried cargo, is 200 pounds.
  
  Section::::Design.:Kits.
   These usually smaller units have no motive drive and require external force to move them. Dependent on size and whether they are wheeled or otherwise supported, this may be possible by hand, or may require a vehicle for towing or transport. Small non-powered AWPs can be light enough to be transported in a pickup truck bed, and can usually be moved through a standard doorway.
  
  Section::::Motive mechanisms.:Self-propelled.
   Boeing 737 aircraft have been shipped throughout the United States on special trains, including the fuselage.
  
  Section::::Specialized types.:Bulkhead flatcars.
   Some designs use a demountable axle, where the axle detaches from the bed of the trailer. Access to the load bed is now through low ramps, without needing to climb over the height of the wheels. Again, the intention is to keep centre of gravity low.
  
  Section::::Loading.:Power for loading.
   Section::::Engine and airframe designs which avoid FOD.
   It is also common in North America to transport semi-trailers on railway flatcars or spine cars, an arrangement called "piggyback" or TOFC "(trailer on flatcar)" to distinguish it from "container on flatcar" (COFC). Some flatcars are designed with collapsible trailer hitches so they can be used for trailer or container service. Such designs allow trailers to be rolled on from one end, though lifting trailers on and off flatcars by specialized loaders is more common. TOFC terminals typically have large areas for storing trailers pending loading or pickup.
   An Iowa statute restricted most truck combinations to 55 feet in length. The statute did provide for some exceptions: doubles, mobile homes, and trucks that carried livestock or certain types of farm equipment were permitted to be 60 feet, and cities which abutted the state line were permitted to adopt the length limitations of the adjacent State. Deliverers of trucks or oversized mobile homes were required by law to obtain a permit before shipping the items into or out of the state.
   The term "ATA case" is frequently used to describe cases that resemble those that comply with ATA Specification 300 category I or II, but have not been certified by the independent testing defined in ATA Specification 300. Category I and II cases are required to be tested both as a pre-production prototype and as a sample selected from the first production lot. Tests include stackability, drop or impact, water resistance, vibration (category I only), and penetration (category I only). Of these, the drop test, stackability, and vibration tests are probably the most severe. For cases under gross (loaded) the drop test requires 160 face drops from , 80 edge drops from , and 40 corner drops from 36 inches. The face drop distance is reduced to up to , , or more. Category II cases are dropped one-tenth as many times from and at 50 pounds, and proportionally for heavier cases. The stackability test requires every case face over to support centered on of the face for 24 hours. The vibration test searches for the four strongest resonances between 5 and 50 Hz, and then tests each at for 2 hours on each principal axis. The penetration test is a 6-kilogram steel bar 3.2 centimeters in diameter with a hemispherical end dropped 0.5 meters on the weakest point. For all tests no degradation or functional damage is allowed.
   Liquids, such as fuel, readily flow within their containers, causing changes in the vehicle's CoM. As fuel is consumed, not only does the position of the CoM change, but the total weight of the vehicle is also reduced.
   Bulkhead flatcars are designed with sturdy end-walls (bulkheads) to prevent loads from shifting past the ends of the car. Loads typically carried are pipe, steel slabs, utility poles and lumber, though lumber and utility poles are increasingly being hauled by skeleton cars. Bulkheads are typically lightweight when empty. An empty bulkhead on a train puts it at a speed restriction to go no more than 50 MPH. Since bulkheads are lightweight when empty, hunting can occur when the car is above 50 MPH. Hunting is the wobbling movement of the trucks on a freight car or a locomotive. If the wheels hunt against the rails for a period of time, there is a high risk of a derailment.
   Section::::Road trucks.:Tow trucks.
   Roll-offs are characterized by a rectangular footprint, utilizing wheels to facilitate rolling the dumpster in place. The container is designed to be transported by special roll-off trucks. They are relatively efficient for bulk loads of waste or extremely heavy loads of construction or demolition debris.
  
  Section::::Bin tipper.
   The simplest semi-trailer is "half of a trailer", having wheels at the rear only and an articulated connection to the tractor unit. A strong metal post or kingpin on the trailer fits into a socket or fifth wheel on the tractor.
  
  Semi-trailers cannot be moved on their own, or pushed and pulled by ballast tractors. They are only mobile when connected to the correct tractor unit, which can limit their use in recovery.
   BULLET::::- In an inclined plane, a load can be pulled up the plane by a sideways input force, but if the plane is not too steep and there is enough friction between load and plane, when the input force is removed the load will remain motionless and will not slide down the plane, regardless of its weight.
   Idler flatcars are also used in oversize freight service, as loads such as pipe often overhang the ends of most standard-sized flatcars. Empty flatcars will be placed on both ends of the loaded car. This protects the cargo ends from damage and ensures that the loaded cars don't bind and damage the ends of adjacent cars.
  
  Often a flat car is placed directly in front of a crane ("big hook") in order to:
  
  BULLET::::- provide a way to remove a wrecked car from a crash site.
  
  BULLET::::- provide a way to store new or removed rail from a work site.
   In this way, the central office knows where its trucks are. The company tracks individual loads by using barcoded containers and pallets to track loads combined into a larger container. To minimize handling-expense, damage and waste of vehicle capacity, optimal-sized pallets are often constructed at distribution points to go to particular destinations.
   Since off-road versions do not have to drive on roads at highway speeds, a typical top speed is just . It is rare for these vehicles to be on highways, so it was very unusual when a pedestrian was accidentally struck and dragged by a yard truck at an intersection in Bellevue, Washington, in February 2014.
   BULLET::::- Drop-bed, wherein the platform is lowered to the ground in a substantially horizontally fashion and the motorcycle has only to be rolled or ridden over the lip of the platform and secured to it, whereupon the entire platform and load are raised and secured for towing. Such designs only require the machine be raised by the thickness of the platform, which is typically less than 10 cm (4 in). Numerous mechanical designs have been devised by trailer fabricators to achieve this goal.
  
  Section::::Trailers pulled behind motorcycles.
   The preferred way to travel any distance. Usually the vehicles are purpose-built low-loading 'Transporters' although trailers are still used, especially for the movement of coaches and buses. Some transporter designs are very sophisticated, with bodies that 'demount' to give a low loading angle. This is especially useful for sports cars, etc., with low ground clearance. There are also transporters with totally enclosed bodies, used for example for the transportation of prestige vehicles, or vehicles involved in crime that are going for forensic analyses. In the sites it often common to see 'city loaders,' a type of transporter fitted with a cradle to totally suspend a vehicle for loading. These are often used to move illegally parked vehicles.
   Direct extrusion, also known as forward extrusion, is the most common extrusion process. It works by placing the billet in a heavy walled container. The billet is pushed through the die by a ram or screw. There is a reusable dummy block between the ram and the billet to keep them separated. The major disadvantage of this process is that the force required to extrude the billet is greater than that needed in the indirect extrusion process because of the frictional forces introduced by the need for the billet to travel the entire length of the container. Because of this the greatest force required is at the beginning of process and slowly decreases as the billet is used up. At the end of the billet the force greatly increases because the billet is thin and the material must flow radially to exit the die. The end of the billet (called the butt end) is not used for this reason.
   BULLET::::- Tilt-bed, wherein the platform teeters on the axle, bringing the tail of the trailer to ground level. The motorcycle is pushed or ridden onto the trailer bed, which in some designs automatically tilts back to the horizontal and locks in place when the load moves forward of the bed pivot point. Such designs still require the machine be pushed up an inclined plane.
   Aircraft parts were hauled via conventional freight cars beginning in World War II. However, given the ever-increasing size of aircraft assemblies, the "Sky Box" method of shipping parts was developed in the late 1960s specifically to transport parts for the Boeing 747 and other "jumbo" jets of the time. The "Sky Box" consists of a two-piece metal shell that is placed atop a standard flatcar to support and protect wing and tail assemblies and fuselage sections in transit (originally, depressed-center or "fish belly" cars were utilized).
   Rule based analysis of extrusion process
  
  Extrusion is a plastic deformation process in which raw material (billet) is forced to flow by compression through the die opening of a smaller cross-section area. The extrusion process is divided in two basic types: direct extrusion and indirect extrusion. In direct extrusion the billet is pushed through the die with ram pressure, whereas in indirect extrusion die moves relative to the container.
   It was noticed early on in the development of the hovercraft that the energy needed to lift a vehicle was directly related to the smoothness of the surface on which it travelled. This was not entirely surprising; the air trapped under the hovercraft will remain there except where it leaks out where the lifting surface contacts the ground — if this interface is smooth, the amount of leaked air will be low. This is the purpose of the "skirt" found on most hovercraft; it allows the fuselage to be some distance from the ground while keeping the air gap as small as possible.
  