Patent Publication Number: US-6666148-B1

Title: Vehicle carrying rail road car structure

Description:
FIELD OF THE INVENTION 
     This invention relates to the field of rail road cars for carrying wheeled vehicles. 
     BACKGROUND OF THE INVENTION 
     Railroad flat cars are used to transport highway trailers from one place to another in what is referred to as intermodal Trailer-on-Flat-Car (TOFC) service. TOFC service competes with intermodal container service known as Container-on-Flat-Car (COFC), and with truck trailers driven on the highway. TOFC service has been in relative decline for some years due to a number of disadvantages. 
     First, for distances of less than about 500 miles (800 km), TOFC service is thought to be slower and less flexible than highway operation. Second, in terms of lading per rail car, TOFC tends to be less efficient than Container-on-Flat-Car (COFC) service, and tends also to be less efficient than double-stack COFC service in which containers are carried on top of each other. Third, TOFC (and COFC) terminals tend to require significant capital outlays. Fourth, TOFC loading tends to take a relatively long time to permit rail road cars to be shunted to the right tracks, for trailers to be unloaded from incoming cars, for other trailers to be loaded, and for the rail road cars to be shunted again to make up a new train consist. Fifth, shock and other dynamic loads imparted during shunting and train operation may tend to damage the lading. It would be advantageous to improve rail road car equipment to reduce or eliminate some of these disadvantages. 
     As highways have become more crowded, demand for a fast TOFC service has increased. Recently, there has been an effort to reduce the loading and unloading time in TOFC service, and an effort to increase the length of TOFC trains. There are two methods for loading highway trailers on flat cars. First, they can be side-loaded with an overhead crane or side-lifting fork-lift crane. Loading with overhead cranes, or with specialized fork-lift equipment tends to occur at large yards, and tends to be capital intensive. 
     The second method of loading highway trailers, or other wheeled vehicles, onto rail road cars having decks for carrying vehicles, is by end-loading. End-loading, or circus loading as it is called, has two main variations. First, a string of cars can be backed up to a permanently fixed loading dock, typically a concrete structure having a deck level with the deck of the rail cars. Alternatively, a movable ramp can be placed at one end of a string of rail car units. In either case, the vehicles are driven onto the rail road cars from one end. Each vehicle can be loaded in sequence by driving (in the case of highway trailers, by driving the trailers backward) along the decks of the rail road car units. The gaps between successive rail car units are spanned by bridge plates that permit vehicles to be driven from one rail car unit to the next. Although circus loading is common for a string of cars, end-loading can be used for individual rail car units, or multiple rail car units as may be convenient. 
     One way to reduce shunting time, and to run a more cost effective service, is to operate a dedicated unit train of TOFC cars whose cars are only rarely uncoupled. However, as the number of units in the train increases, circus loading becomes less attractive, since a greater proportion of loading time is spent running a towing rig back and forth along an empty string of cars. It is therefore advantageous to break the unit train in several places when loading and unloading. Although multiple fixed platforms have been used, each fixed platform requires a corresponding dedicated dead-end siding to which a separate portion of train can be shunted. It is not advantageous to require a large number of dedicated parallel sidings with a relatively large fixed investment in concrete platforms. 
     To avoid shunting to different tracks, as required if a plurality of fixed platforms is used, it is advantageous to break a unit train of TOFC rail road cars on a single siding, so that the train can be re-assembled without switching from one track to another. For example, using a 5000 or 6000 ft siding, a train having 60 rail car units in sections of 15 units made up of three coupled five-pack articulated cars, can be split at two places, namely fifteen units from each end, permitting the sequential loading of fifteen units per section to either side of each split. Once loaded, the gaps between the splits can be closed, without shunting cars from one siding to another. Use of a single siding is made possible by moving the ramps to the split location, rather than switching strings of cars to fixed platforms. 
     In using movable ramps for loading, the highway trailers are typically backed onto the railcars using a special rail yard truck, called a hostler truck. Railcars can be equipped with a collapsible highway trailer kingpin stand. When the highway trailer is in the right position, the hostler truck hooks onto the collapsible stand (or hitch) and pulls it forward, thereby lifting it to a deployed (i.e., raised) and locked position. The hostler truck is then used to push the trailer back to engage the kingpin of the hitch. The landing gear of the highway trailer is lowered, and, in addition, it is cranked downward firmly against the rail road car deck as a safety measure in the event of a hitch failure or the king pin of the trailer is sheared off. Once one trailer has been loaded, the towing rig, namely the hostler truck, drives back to the end of the string, another trailer is backed into place, and the process is repeated until all of the trailers have been loaded in the successive positions on the string of railcars. Unloading involves the same process, in reverse. In some circumstances, circus loaded flat cars can be loaded with trucks, tractors, farm machinery, construction equipment or automobiles, in a similar manner, except that it is not always necessary to use a towing rig. 
     From time to time, the train consist may be broken up, with various highway-trailer-carrying rail road cars being disconnected, and others being joined. Bridge plates have been the source of some difficulties at the rail car ends where adjacent railroad cars are connected, given the nomenclature “the coupler ends”. Traditionally, a pair of cars to be joined at a coupler would each be equipped with one bridge plate permanently mounted on a hinged connection on one side of the car, typically the left hand side. In this arrangement the axis of the hinge is horizontal and transverse to the longitudinal centerline of the rail car. 
     Conventionally, for loading and unloading operations, the bridge plate of each car at the respective coupled end is lowered, like a draw bridge, into a generally horizontal arrangement to mate with the adjoining car, each plate providing one side of the path so that the co-operative effect of the two plates is to provide a pair of tracks along which a vehicle can roll. When loading is complete, the bridge plates are pivoted about their hinges to a generally vertical, or raised, position, and locked in place so that they cannot fall back down accidentally. 
     Conventionally, bridge plates at the coupler ends are returned to the raised, or vertical, position before the train can move, to avoid the tendency to become jammed or damaged during travel. That is, as the train travels through a curve, the bridge plates would tend to break off if left in the spanning position between the coupler ends of two rail road cars. Since bridge plates carry multi-ton loads, they tend to have significant structure and weight. Consequently, the requirement to raise and lower the bridge plates into position is a time consuming manual task contributing to the relatively long time required for loading and unloading. Raising and lowering bridge plates may tend to expose rail-yard personnel to both accidents and repetitive strain injuries caused by lifting. 
     It would be advantageous to have (a) a bridge plate that can be moved to a storage, or stowed, position, with less lifting; (b) a bridge plate system that does not require the bridge plate to be moved by hand as often, such as by permitting the bridge plate to remain in place during train operation, rather than having to be lowered every time the train is loaded and unloaded, and raised again before the train can move. 
     Further, a rail road car may sometimes be an internal car, with its bridge plates extended to neighbouring cars, and at other times the rail road car may be an “end” car at which the unit train is either (a) split for loading and unloading, (b) coupled to the locomotive; or (c) coupled to another type of rail road car. In each case, the bridge plate at the split does not need to be in an extended “drive-over” position, and should be in a stowed position. Therefore it is advantageous to have a rail car with bridge plates that can remain in position during operation as an internal car in a unit train, and that can also be stowed as necessary when the car is placed in an end or split position. 
     Loading and unloading of highway trailers, or other vehicles in the manner described above, can also be a relatively tedious and time consuming chore, particularly as the number of railroad cars in the string increases. Persons engaged in such activity may, after some time, perhaps late at night, tend to become less fastidious in their conduct. They may tend to become overconfident in their abilities, and may tend to try to back the highway trailers on to the rail cars rather more quickly than may be prudent. It has been suggested that speeds in the order of 20 km/h have been attempted. In the past, it has been difficult to form bridge plates that lie roughly flush with the deck. Due to their strength requirement, they tend to be about 2 inches thick or more. As a result there is often a significant bump at the bridge plate. Aggressive loading and unloading of the trailers may cause an undesirable impact at the bump, and loss of control of the load. In that regard, it would be advantageous to reduce the height or severity of the bump. It is also advantageous to employ side sills that have a portion, such as the side sill top chord, that extends above the height of the deck and acts as a curb bounding the trackway, or roadway, defined between the side sills. It is also helpful to have flared sill, or curb, ends that may tend to aid in urging highway trailers toward the center of the trackway along the rail cars. 
     It is sometimes desirable to keep the load in the highway trailer level, to avoid damage to the lading. Movable ramps tend to be relatively steep compared to road grades and fixed loading platforms. Some hostler trucks are able to raise the front end of the highway trailer while backing up the ramp, in an effort to maintain the trailer in a more nearly level orientation. This facilitates the use of the ramp loading method on a siding with relatively little permanent capital investment in loading facilities, and increasing the attractiveness of TOFC operation. However, when highway trailers are parked on the railcar deck, if the railcar deck adjacent to the trailer is too high, the hostler truck at the receiving end may have difficulty picking up the trailer. It is desirable to keep the deck adjacent to the hitch flush. 
     As noted above, when highway trailers are circus-loaded on a string of railroad flat car units, the landing gear of each highway trailer is cranked down to bear firmly on the deck of the flat car in the event of a collapsible hitch or kingpin failure. The flat car units are not always located next to a convenient platform, and there is not always a generous amount of space available for loading or unloading crew to work on the deck around the trailers to perform the cranking operation. It is not necessarily prudent to stand on the deck of a flat car while highway trailers are being backed into place. It may also take some time to ascend the deck after the highway trailer has stopped moving, to edge along from the ladder to the landing gear, and then to lower (or raise) the landing gear, and then to descend from the car, particularly in bad weather, such as freezing rain. 
     It would be advantageous to have a ladder abreast of the position of the landing gear, (that is, at a location corresponding to the longitudinal location of the landing gear). Therefore, it would be advantageous to have foot supports, and corresponding handholds, mounted to the body of the railcar abreast of the collapsible hitch and landing gear area to facilitate loading and unloading of the highway trailers. 
     It would also be advantageous to mount running boards longitudinally inboard of the hitch centerline, abreast of the landing gear position, i.e., the location of the landing gear feet of the highway trailers. It may be advantageous to mount the running boards slightly below the level of the main deck, as this may tend to allow a person operating the landing gear crank not to have to bend over as far. 
     It has been noted that the feet of collapsible hitches, such as are mounted to rail cars used in TOFC trailer operation, sometimes extend into the path of the trailer wheels, and may tend to damage the highway trailer truck tires. It would be advantageous to have a collapsible hitch, such as can be mounted above a center sill, that has a narrower footprint to stay clear of the tires. 
     Demand for transport by TOFC or by container may fluctuate over time. Therefore, it would be advantageous to be able to convert a rail road car from one type of service to the other. To that end it would be advantageous to have a rail road car that has structure for either service, and that permits subsequent conversion as may be desired according to market conditions. 
     Reference is made herein to shipping containers and various sizes of highway trailers. Shipping containers come in International Standards Association (ISO) sizes, or domestic sizes. The ISO containers are 8′-0″ wide, 8′-6″ high, and come in a 20′-0″ length weighing up to 52,900 lbs., or a 40′-0″ length weighing up to 67,200 lbs., fully loaded. Domestic containers are 8′-6″ wide and 9′-6″ high. Their standard lengths are 45′, 48′, and 53′. All domestic containers have a maximum fully loaded weight of 67,200 lbs. Some common sizes of highway trailers are, the 28′ pup trailer weighing up to 40,000 lbs., and the 45′ to 53′ trailer weighing up to 65,000 lbs. for a two axle trailer and up to 90,000 lbs. for a three axle trailer. 
     SUMMARY OF THE INVENTION 
     In an aspect of the invention, there is a rail road car for carrying wheeled vehicles. The rail road car includes a rail car body having a first end, a second end, and a vehicle deck running between the first and second ends. The first end of the rail car body has a releasable coupler mounted thereto. Curbs extend along the deck to define a roadway therebetween along which wheeled vehicles can be conducted between the first and second ends. At least one bridge plate is mounted to the rail car body adjacent to the first end of the deck. The bridge plate is mounted to yaw relative to the rail car body when the rail road car is travelling. At least one of the curbs is flared laterally outward adjacent to the bridge plate to accommodate yawing of the bridge plate when the rail road car is in motion. 
     In another feature of that aspect of the invention, the body includes first and second side sills. Each of the curbs is defined by a respective portion of the first and second side sills. That portion extends to a height greater than the deck relative to top of rail, and is located to border the deck. In a further additional feature, the side sills have end portions adjacent the first end of the body, and the ends of the side sills broaden out adjacent to the first end of the body. In still another feature, the side sills have end portions adjacent the first end of the body, and the end portions are chamfered outwardly adjacent to the first end of the body. In another additional feature, the curbs are flared laterally outwardly at both ends of the body. In a still further feature, the body includes side sills extending along either side of the deck between the first and second ends, Each of the side sills has a top chord member, and at least a portion of each of the curbs is defined by a respective one of the top chord members. 
     In another aspect of the invention, there is a rail road car for carrying wheeled vehicles. It comprises a rail road car body supported for rolling motion in a longitudinal direction on rail car trucks. The body has a first end, a second end, and an end-loadable deck extending between the first and second ends of the body. The body has curbs mounted thereto. The curbs extend along the deck to define a roadway therebetween along which wheeled vehicles can be conducted. A hitch for engaging highway trailer king pins is mounted to the deck between the curbs. The hitch is movable to a lowered position to allow the running gear of highway trailers to pass thereover, and to a raised position for engaging a king pin of a highway trailer. The highway trailers have a minimum allowable outside tire width, WTO (min) , and a minimum allowable inside tire clearance width, WTI (min) . The curbs having parallel portions spaced apart a road width distance, W D , and the hitch has a width W H  at least as small as the value W obtained in the equation: 
     
       
         W=WTO (min) +WTI (min) −W D . 
       
     
     In another feature of that aspect of the invention, WH is less than or equal to 37½ inches. In still another feature, W D  is 104 inches. In a further feature, the car body includes a center sill extending between the first and second ends thereof. The center sill has a top flange forming a portion of the deck. The hitch is mounted to the top flange. The top flange is at least as wide as the hitch. In still another feature, the decking includes deck plates mounted to either side of the center sill. In a further feature, the deck plates are mounted flush with the top flange of the center sill. 
     In another aspect of the invention, there is an articulated, vehicle-carrying rail road car comprising a first rail road car unit and a second rail road car unit, the first and second rail road car units being supported by rail car trucks for travel in a longitudinal rolling direction, and being joined together at an articulated connector. The first rail car unit has a first deck along which wheeled vehicles can be conducted. The second rail car unit has a second deck along which vehicles can be conducted, the second deck being separated longitudinally at the articulated connector. A set of bridge plates extends between the first and second decks to permit wheeled vehicles to be conducted between the first and second decks. At least a portion of the bridge plates being mounted flush with the first deck. 
     In another feature of that aspect of the invention, the first deck has a first articulated connector end facing toward the articulated connector, and the bridge plate has a second portion overlapping the first deck. In another feature of the invention, the first deck has a first articulated connector end facing the articulated connector. The second deck has a second articulated connector end facing the articulated connector. A support member extends from the second articulated connector end at a level below the second deck, and the first portion of the bridge plate bears upon the support member. 
     In a further feature, the second deck has a second articulated connector end facing the articulated connector. A support member extends from the second articulated connector end at a level below the second deck. The first portion of the bridge plate bears upon the support member. In a still further feature, the bridge plate is maintained in place relative to the second deck by a retainer, the retainer permitting the bridge plate to be lifted relative to the second deck. In another feature, the retainer includes at least one hook member. The second deck has a fitting engaged by the hook. 
     In yet another feature, the first deck has a wear plate mounted thereto. The overlapping portion of the bridge plate is located to bear upon the wear plate. The overlapping portion of the bridge plate can slide across the wear plate during curving motion of the rail road car during travel. In an additional feature, the wear plate is a stainless steel wear plate. In a still further feature, the second deck has a hitch mounted thereto for engaging highway trailers, and, in the longitudinal direction, the hitch is mounted within ten feet of the bridge plate. In yet another feature, the first portion of the bridge plate has traction enhancement members mounted thereon. In still another feature, the second rail car body has side bearing arms extending therefrom next to the articulated connector. The bridge plate is mounted over one of the side bearing arms. 
     In a further aspect of the invention, there is a rail road car comprising a rail road car body supported by rail cars trucks for rolling operation in a longitudinal direction. The body has a first end, a second end, and a center sill extending between the first and second ends. The center sill is supported by the trucks. The rail road car having a pair of side sills spaced to either side of the center sill and a set of cross-bearers extending between the center sill and the side sills. A deck is mounted between the side sills and above the cross-bearers, the deck permitting the loading of vehicles thereupon. The rail road car has first and second pairs of laterally extending beams mounted to the center sill. The first pair of laterally extending beams and the second pair of laterally extending beams are mounted below the deck and are longitudinally spaced a distance corresponding to a 40 foot container pedestal separation distance. The first and second pairs of beams are capable of supporting a fully laden 40 foot ISO shipping container. 
     In a further feature of that aspect of the invention, the laterally extending beams are mounted to support the deck. In another feature, at least a portion of the deck over each of the pairs of laterally extending beams is removable to permit a container support pedestal to be mounted to each of the beams. In yet another feature, each of the laterally extending beams has a first portion proximate to the center sill, and a second portion distant from the center sill. The first portion has a greater depth of section than the second portion. In a further feature, the rail road car has side sheets depending from the side sills. At least one of the pairs of beams has distal portions extending beyond the side sheets. In a further additional feature, the distal portions having jacking fittings by which an end of the rail car body can be lifted. 
     In further aspect of the invention, there is a rail road car having a rail car body including an end-loading deck for wheeled vehicles. The rail car body being supported by rail car trucks for rolling in a longitudinal direction. A set of container support beams is mounted to the body beneath the deck. At least a portion of the deck being removable to permit container support pedestals to be mounted to the container support beams. 
     In an additional feature of that aspect of the invention, the support beams support portions of the deck. In a further feature, at least a pair of the container support beams have laterally outboard portions, and jacking fittings mounted thereto by which an end of the rail road car can be lifted. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 a  shows a conceptual side view of a train having several articulated vehicle carrying rail road cars, in an unloaded condition; 
     FIG. 1 b  shows portions of the train of FIG. 1 a  as split for loading, 
     FIG. 1 c  shows the train portions of FIG. 1 a  in a split configuration ready for loading, 
     FIG. 1 d  shows the train portions of FIG. 1 a  in a partially loaded condition; 
     FIG. 1 e  shows the train portions of FIG. 1 a  in a fully loaded condition; 
     FIG. 1 f  shows portions of the train of FIG. 1 a  in an assembled condition; 
     FIG. 2 a  shows a side view of a five-pack articulated railroad car for carrying highway trailers as loaded; 
     FIG. 2 b  shows a top view of the five pack articulated rail road car of FIG. 2 a  in an unloaded condition; 
     FIG. 2 c  shows a side view of the rail road car of FIG. 2 a  in an unloaded condition; 
     FIG. 3 a  shows an isometric view of a “B-End” unit of an articulated rail road car such as shown in either FIG. 1 a  or FIG. 2 a , with middle floor deck plates removed for clarity; 
     FIG. 3 b  shows a top view of the articulated rail road unit car of FIG. 3 a;    
     FIG. 3 c  shows a side view of the articulated rail car unit of FIG. 3 a;    
     FIG. 3 d  shows an underside view of the rail road car unit of FIG. 3 a;    
     FIG. 3 e  shows an end view of the articulated rail road car unit of FIG. 3 a;    
     FIG. 3 f  shows a mid-span cross-section of the rail road car unit of FIG. 3 a;    
     FIG. 3 g  shows an enlarged side detail of the rail car unit of FIG. 3 a  at the coupler end of the car; 
     FIG. 3 h  shows an enlarged top detail of the rail car unit of FIG. 3 a;    
     FIG. 4 a  shows a top view of a bridge plate for the rail car unit of FIG. 3 a;    
     FIG. 4 b  shows a side view of the bridge plate of FIG. 4 a;    
     FIG. 4 c  shows an end view of the bridge plate of FIG. 4 a;    
     FIG. 4 d  shows a section of the bridge plate of FIG. 4 a  taken on ‘ 4   d — 4   d’;    
     FIG. 4 e  shows a section of the bridge plate of FIG. 4 a  taken on ‘ 4   e — 4   e’;    
     FIG. 5 a  is a partial isometric view of the bridge plate of FIG. 4 a  in an extended position relative to the rail car unit of FIG. 3 a;    
     FIG. 5 b  is a partial isometric view of the bridge plate of FIG. 4 a  in a stored position relative to the rail car unit of FIG. 3 a;    
     FIG. 5 c  is a top view of the bridge plate of FIG. 5 a  showing in service deflection; 
     FIG. 6 a  is an isometric view of a transition bridge plate for the rail car unit of FIG. 3 a;    
     FIG. 6 b  is a top view of the transition bridge plate of FIG. 6 a;    
     FIG. 6 c  is a side view of the transition bridge plate of FIG. 6 a;    
     FIG. 7 a  is an isometric view of a cam crank of the rail car unit of FIG. 3 a;    
     FIG. 7 b  is a side view of the cam crank of FIG. 7 a;    
     FIG. 7 c  is an end view of the cam crank of FIG. 7 a;    
     FIG. 7 d  is a cross-section of the cam crank of FIG. 7 a  taken on ‘ 7   d — 7   d’;    
     FIG. 7 e  is a view of the cam crank of FIG. 7 a  taken on arrow ‘ 7   e’;    
     FIG. 7 f  shows a partial cross-section of the rail car unit of FIG. 3 a  taken on ‘ 7   f — 7   f ’ showing the cam crank of FIG. 7 a  installed; 
     FIG. 7 g  shows a partial sectional view across the rail car unit of FIG. 3 a  with the cam crank of FIG. 7 a  installed; 
     FIG. 8 a  shows a partial side sectional view of two rail road cars having bridge plates, as shown in FIG. 7 a , in a separated position, 
     FIG. 8 b  shows the rail road cars of FIG. 8 a  in an approach position; 
     FIG. 8 c  shows the rail cars of FIG. 8 a  as one bridge plate meets a cam crank; 
     FIG. 8 d  shows the rail cars of FIG. 8 a  in a coupled relationship; 
     FIG. 8 e  shows the rail road cars of FIG. 8 a  in an alternate approach position to that of FIG. 8 b;    
     FIG. 8 f  shows the rail cars of FIG. 8 e  as one bridge plate meets a cam crank; 
     FIG. 9 a  shows a top view of an articulated connector end of the rail car unit of FIG. 3 a  and another adjoining rail car unit; 
     FIG. 9 b  shows an isometric view of an articulation connection end bridge plate for the rail road car of FIG. 9 a;    
     FIG. 9 c  shows a top view of the bridge plate of FIG. 9 b;    
     FIG. 9 d  shows a side view of the rail road car of FIG. 9 b;    
     FIG. 10 a  shows an isometric view of a ‘A-End” unit of the articulated rail road car of FIG. 1 a  with middle floor deck plates removed for clarity; 
     FIG. 10 b  shows a top view of the articulated rail road unit car of FIG. 10 a;    
     FIG. 10 c  shows a side view of the articulated rail car unit of FIG. 10 a;    
     FIG. 10 d  shows an underside view of the rail road car unit of FIG. 10 a;    
     FIG. 11 a  shows an isometric view of an intermediate “C” unit of the articulated rail road car of FIG. 1 a  with middle floor deck plates removed for clarity; 
     FIG. 11 b  shows a top view of the articulated rail road unit car of FIG. 11 a;    
     FIG. 11 c  shows a side view of the articulated rail car unit of FIG. 11 a;    
     FIG. 11 d  shows an underside view of the rail road car unit of FIG. 11 a;    
     FIG. 12 a  shows a top view of the draft gear at the coupler end of the articulated rail road car of FIG. 3 a;    
     FIG. 12 b  shows a sectional view of the draft gear of FIG. 12 a  taken on ‘ 12   b — 12   b’;    
     FIG. 13 shows an alternate side sill assembly for a rail car unit such as shown in FIG. 3 a;    
     FIG. 14 a  shows an end view of a hitch assembly such as shown in FIG. 3 a , in a raised position; 
     FIG. 14 b  shows the end view of FIG. 14 a  with the hitch in a lowered position and a highway trailer rolling thereover; and 
     FIG. 14 c  shows the end view of FIG. 14 a  with the hitch in a lowered position and a highway trailer rolling eccentrically thereby; 
     FIG. 15 a  shows an isometric view of a dual purpose cross-beam of the articulated rail car unit of FIG. 3 a;    
     FIG. 15 b  shows a top view of the dual purpose cross-beam of FIG. 15 a;    
     FIG. 15 c  shows an end view of the dual purpose cross-beam of FIG. 15 a ; and 
     FIG. 15 d  shows the cross-beam of FIG. 15 b  viewed on section ‘ 15   d — 15   d’   
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The description that follows, and the embodiments described therein, are provided by way of illustration of an example, or examples of particular embodiments of the principles of the present invention. These examples are provided for the purposes of explanation, and not of limitation, of those principles and of the invention. In the description, like parts are marked throughout the specification and the drawings with the same respective reference numerals. The drawings are not necessarily to scale and in some instances proportions may have been exaggerated in order more clearly to depict certain features of the invention. 
     In terms of general orientation and directional nomenclature, for each of the rail road cars described herein, the longitudinal direction is defined as being coincident with the rolling direction of the car, or car unit, when located on tangent (that is, straight) track. In the case of a car having a center sill, whether a through center sill or stub sill, the longitudinal direction is parallel to the center sill, and parallel to the side sills, if any. Unless otherwise noted, vertical, or upward and downward, are terms that use top of rail, TOR, as a datum. The term lateral, or laterally outboard, refers to a distance or orientation relative to the longitudinal centerline of the railroad car, or car unit, indicated as CL—Rail Car. The term “longitudinally inboard”, or “longitudinally outboard” is a distance taken relative to a mid-span lateral section of the car, or car unit. Pitching motion is angular motion of a rail car unit about a horizontal axis perpendicular to the longitudinal direction. Yawing is angular motion about a vertical axis. Roll is angular motion about the longitudinal axis. 
     By way of general overview, FIG. 1 a  to If illustrate the process of loading wheeled vehicles onto a train of multi-unit articulated railroad cars. In this example, an assembled train of articulated rail road cars, indicted generally as  20 , includes a string of three-pack articulated railroad cars  21 ,  22 ,  23  and  24  joined together with a two rail car unit articulated rail road car  25 , drawn by a locomotive indicated as  38 . Train  20  travels in a longitudinal direction toward its destination. While train  20  is travelling, bridge plates  150  (described more fully below) remain extended in a length-wise (i.e., longitudinal) “drive-over” orientation, such as shown in FIG. 5 a  below, to span the gap at the releasable coupling between the decks of the adjacent rail car units of rail road car  21  and rail road car  22 , as well as between rail road cars  23  and  24 ,  24  and  25 . At the coupled connection between rail road cars  22  and  23 , bridge plates  150  do not extend lengthwise but are disposed in a stowed, cross-wise orientation, transverse to the longitudinal centerlines of the rail road cars, as shown in FIG. 5 b  below. Likewise, at the ends of the string of vehicle carrying rail road cars, such as adjacent locomotive  38 , at the end of train location, (or, in another context, at a car coupled to a different type of freight car), bridge plates  150  are also placed in their stowed position, as in FIG. 5 b . It is preferred that train  20  be a unit train composed of vehicle carrying rail road cars, and not coupled to any other type of car. 
     In the second, enlarged, partial view of FIG. 1 b , train  20  has arrived at its destination, and a rear portion  27  of train  20  has been spotted at a first location, while another, more forward portion  29  has been spotted further along the track. The two portions are separated by a few hundred feet. Train  20  has been split at the releasable coupling between the rear end unit of rail road car  22  and the forward end unit of rail road car  23 . In the separated position of FIGS. 1 b ,  1   c ,  1   d , and  1   e , the cross-wise stowed orientation of the bridge plates at the opposing ends of rail road cars  22  and  23  facilitates use of movable ramps  59  for loading, or unloading, of train  20 . As shown in the succession of views of FIGS. 1 c ,  1   d ,  1   e  and  1   f , hostler trucks  40  are used to move ramps  59  into place adjacent the split, (i.e., uncoupled), ends of rail road cars  22  and  23 , and are then used to back wheeled vehicles, in this instance highway trailers  42 , into place, each highway trailer  42  facing the split, with its king pin engaging the hitch plate of a collapsible hitch  112  or  114  (see below), and its landing gear cranked firmly down. (Other types of wheeled vehicles, whether automobiles, trucks, farm machinery, or buses could be loaded in a similar manner, with or without a towing tractor, as may be suitable). At the internal ends of rail road cars  21 ,  22 ,  23 ,  24 , and  25 , the length-wise extended bridge plates make those ends “drive-over” ends that permit highway trailers to be conducted along a continuous path between cars. 
     When all of the rail car units have been loaded, train  20  is ready. The split, (or splits, as the case may be) can be closed by gently shunting the forward and rearward portions  29  and  27  together. Train  20  is then ready to depart for its next destination. In the example train  20  arrives empty. However, it would be customary for the loading procedure described to have been preceded by an unloading procedure for highway trailer units arriving from the previous depot, as by reversing the steps of FIGS. 1 e ,  1   d ,  1   c  and  1   b.    
     Describing elements of train  20  in greater detail, coupled units  22  and  23  have respective first, or “drive over” end units  26 , and  28 , intermediate articulated units  30  and  32 , and coupled end units  34  and  36 . For the purposes of this description, it can be taken that units  26  and  28  are the same, units  30  and  32  are the same, and units  34  and  36  are the same, but facing in opposite directions. Each of the rail car units having a coupler end, namely units  26  and  28 ,  34  and  36 , has an end truck,  35 , mounted under a main bolster at the coupler end, whichever end it may be. Rail car units  26  and  30 ,  30  and  34 ,  36  and  32 , and  32  and  28  are joined together by articulated connectors indicated generally as  37 , mounted over respective shared articulated connection trucks  39 . Rail car units  34  and  36  are connected by releasable couplers  44  and  46 . Articulated connector bridge plates  300  (whether left or right handed, as described below) span the gaps between rail car units  26  and  30 ,  30  and  34 ,  36  and  32 , and  32  and  28 . With the aid of articulated connector bridge plates  300 , and movable bridge plates  150 , to one side of the split between rail road cars  22  and  23 , decks  47 ,  48 ,  49 ,  50 ,  51 , and  52 , (and to the other side,  47 ,  48 ,  49 ,  50 ,  51 ,  52 ,  53  and  54 ) form continuous pathways, or roadways, upon which vehicles can be conducted in either forward, driving, direction or a reverse, backward direction. If additional railroad cars are joined at the opposite ends of railroad cars  22  and  23 , further bridge plates can be employed to extend the length of the pathway. 
     For the purposes of this description, although FIGS. 1 a ,  1   b ,  1   c ,  1   d ,  1   e , and  1   f  show a locomotive and three-pack or two-pack articulated cars, other combinations of articulated cars having any reasonable number of articulation units can be employed. 2-unit, 3-unit, and 5-unit articulated packs are relatively common. It will be understood that the example of FIGS. 1 a - 1   f  is meant symbolically to represent a train of any suitable length. Typically, a unit train would include a much larger number of cars units, such as 60 or 80 rail car units composed of a multiplicity of 2, 3, 5 or 6 (or more) unit articulated cars strung together. Such a train can be directed onto a siding, with successive portions of the string spotted at different locations along the siding, leaving gaps of, typically, 200 or 300 feet between sections to permit the placement of ramps as may be suitable. When the cars are loaded, the ramps are removed. The locomotive can then reverse, closing each successive gap and permitting the rail road cars to be reconnected at their respective coupler ends. 
     In the example shown, end rail car units  26  of rail road car  21 , and  28  of rail road car  25 , each have a movable bridge plate  150  carried at their uncoupled ends (in the case of rail car unit  26 , the “uncoupled end” is actually coupled to locomotive  38 , the context of “uncoupled” meaning an end that is not coupled to another similar rail car for carrying vehicles to which a bridge plate would be extended). If a larger train were assembled, the uncoupled ends of car units  26  and  28  would be coupled to mating ends of other articulated cars. When additional cars are joined, the collapsible hitches are oriented in the same direction, namely, all facing toward the location of the split. Thus, away from the split, a car unit  26  would mate with a car unit like car unit  34 , and so on. In a long train there would tend to be more than one split. 
     For the purposes of illustration, rail road car  22 , which includes rail car units  26 ,  30 , and  34  will be described in greater detail. It will be appreciated that a two-unit articulated rail road car, such as rail road car  25 , can be assembled by joining units  26  and  34  directly together, and that, in general, articulated rail cars of varying lengths can be assembled from a pair of ends units, such as units  26  and  34 , and any chosen number of intermediate units (i.e., cars not having coupler ends) such as unit  30 . A five-pack assembled in this way is shown loaded in FIG. 2 a , and unloaded in FIGS. 2 b  and  2   c . For the purposes of this description, unit  26  is arbitrarily designated as the “A-End” unit, unit  34  is the “B-End” unit, and unit  30  is the “C”, or intermediate unit. In rail road terminology the “B” end of a rail road car is the handbrake end, or predominant hand brake end. When several “C” units are employed in a multi-unit articulated rail road car, as in the five pack of FIGS. 2 a ,  2   b  and  2   c , each may be referred to as the “C”, “D”, or “E” unit (and so on if more units are used). There are minor structural differences between the intermediate units, such as whether one hitch is provided or two, and corresponding cross-bearer and deck web reinforcements. For the purposes of this structural description any intermediate car unit will be referred to as a “C” unit, and unit  30  will be taken as representative of intermediate units in general, whatever their hitch layout may be. 
     The second end unit (the “B” unit)  34  is shown in FIGS. 3 a , (isometric, with decking partially removed to reveal deck supporting structure),  3   b  (side)  3   c  (top view, with decking partially removed to reveal structure)  3   d  (underframe) and  3   e  (coupler end view). Car unit  34  has a main longitudinal structural member in the nature of a main center sill  60  having a draft pocket  62  at one end (i.e., the “coupler end” portion,  64  of unit  34 ), and an articulated connector socket in the nature of a rectangular fabricated steel box  66  into which one half of an articulated connector  68  is mounted at the other end (i.e., the articulated connection end portion,  70  of car unit  34 ). In between the coupler end portion  66  and the articulated end portion  70  is a central portion,  72 , being the mid-span portion of the car between its trucks. 
     As shown in the offset section of FIG. 3 f , over the central portion  72 , of unit  34  center sill  60  has the form of a hollow beam having a top flange  74 , a bottom flange  76 , and a pair of spaced apart vertical webs  78 ,  80 . A set of cross-bearers  82  extend outwardly from roots at the side webs of center sill  60  to laterally outboard ends that meet in lap welded joints with vertical gussets  83  of meet side sills  84  and  86 . Each of side sills  84  and  86  has a hollow rectangular top chord member  90 , an outer cowling sheet, or web  92 , a bottom chord in the form of an angle  94 , and a cross-bearer flange extension  96  in the form of a bent member welded to the inner face of top chord member  90  in a downwardly hanging position, the upward portion, or leg of extension  96  lying on the same slope as the top chord web, the inwardly extending portion, or leg, of extension  96  lying roughly horizontally to provide a lip that is welded to the top flange of the cross-bearer. 
     Floor panels  100  span the pitches between cross-bearers  82 , to provide a continuous pathway from one end of the car to the other. Each floor panel  100  is formed from a series of spaced apart, longitudinally extending channels  102 ,  103 ,  104  surmounted by a top sheet, or flange  106  whose upper surface  108  forms a path for the wheels of vehicles loaded on the car unit. Upper surface  108  is roughly flush with top flange  74  of center sill  60 , and floor panels  100  and top flange  74  co-operate to form deck  47  of rail car unit  34 . Side sills  84  and  86 , run along the sides of deck  47 . Top chord member  90  of each of side sills  84  and  86  extends well above the level of top surface  108 , and serves as a curb to encourage trailers to stay on the trackway, or roadway, defined on deck  47  between top chord members  90 , as they are backed along the rail car unit. 
     Each of side sills  84  and  86  is canted inwardly, such that its lower extremity, or toe, is nearer to the rail car longitudinal centerline than the top chord. The inward cant of top chord member  90  of side sills  84  and  86  gives this curb an angle or chamfer, as shown in FIG. 3 f , such that a truck tire must ride up the slope before it can escape, the chamfer yielding a self-centering effect as the tires try to ride along it. Although only a few floor panels  100  are shown, it will be appreciated that floor panels  100  are located continuously to permit vehicles to be driven over the car units, as in FIG. 2 b.    
     At either end of the central portion of car unit  34 , there are dual purpose cross-beams  109 ,  110  located at longitudinal stations corresponding to the 40 ft container pedestal locations of a container carrying rail car. Cross-beam  10  is shown in greater detail in FIGS. 15 a  to  15   d . These dual purpose cross-bearers have a rectangular box section, having fore and aft webs  105 ,  107 , a top flange  115 , and an inclined bottom flange  117 . Cross-beams  109 ,  110  perform as cross-bearers generally, but also permit lifting of one end or the other of car unit  34  during maintenance (such as truck replacement). Cross beams  109  and  110  also permit the removal of floor panels  100  and installation of container support pedestals if it is desired to convert car unit  34  to container carrying service rather than TOFC service, and as such are capable of supporting a fully loaded  40 ′ ISO or  45 ′,  48 ′ or  53 ′ domestic container. Cross-bearers  82 , and dual purpose cross-beams  109 ,  110  have respective intermediate webs  111 ,  113  to discourage deflection of the upper cross-bearer flange at the location of application of the floor panel loads, or, additionally, in the case of cross-bearers  110 , container pedestal loads. Cross-bearers  109 ,  110  have upwardly and downwardly extending gussets  99 ,  101  that mate with web  92  or side sill  84  (or  86 ), and a distal tip  97  that extends proud of side sills  84  (or  86 ) to provide a jacking point fitting  98  at these locations. This facilitates lifting of end portion  70  during, for example, repair, maintenance or replacement of shared truck  39 . Web  92  has a V-shaped external reinforcement doubler plate  119  at this location. 
     A first collapsible hitch  112  is also mounted to top flange  74  of center sill  60  in a mid span position for engaging a  28 ′ pup-trailer, if required. A second collapsible hitch  114  is mounted roughly 4 inches inboard from the truck center, CL Truck, at coupler end, end portion  64 . The cross-bearer flanges are reinforced under the hitch locations, as shown at  116 . 
     At the coupler end, end portion  64 , main center sill  60  of rail car unit  34  becomes shallower, the bottom flange being stepped upwardly to a height suitable for being supported on truck  35 . Side sills  84  and  86  also become shallower as the bottom flange curves upward to clear truck  35 . Rail car unit  34  has a laterally extending main bolster  120  at the longitudinal station of the truck center (CL Truck), and a parallel, laterally extending end sill  122  having left and right hand arms  121 ,  123  extending laterally between the coupler pocket and the side sills. In their distal, or outboard regions, arms  121  and  123  have ramp engagement sockets  125  in the nature of rectangular apertures, with which prongs  127  of ramp  59  can be engaged to align ramp  59  with car unit  34  for loading. 
     As shown in FIG. 7 g , top flange  74  of center sill  60  has a downwardly sloping transition  124  longitudinally outboard of main bolster  120 , and a level, horizontally extending portion  126  lying outboard thereof, such that the end portion of center sill  60  is stepped downward relative to the main portion of top flange  74  inboard of bolster  120 . A bridge plate support member, in the nature of an outboard horizontal shelf portion  134 , includes left and right hand plates  128 ,  130  that form upper flanges for, and extend longitudinally inboard of, arms  121  and  123  of end sill  122  to define bridge plate support members. 
     A laterally extending structural member, in the nature of a fabricated closed beam  136  is welded to horizontal portion  126  of center sill  60  between side sills  84  and  86 . Beam  136  has vertical legs  138  extending upwardly of portion  126  and a horizontal back  140 , lying flush with the level of top flange  74  at the longitudinal location of main bolster  120 . Left and right hand deck plates  141  are welded to back  140  and extend above tapered portion  132  to terminate at main bolster  120 . 
     Plates  128  and  130  are flush with downwardly stepped horizontal portion  126  of top flange  74 , and co-operate with portion  126  to define a continuous shelf across (i.e., extending cross-wise relative to) the end of rail car unit  34 , outboard of the end of deck  47  defined by the longitudinally outboard edge of beam  136 . In this way a step, depression, shelf, or rebate, or recess  142  for accommodating (or for receiving) a bridge plate, is formed in the end of rail car unit  34  adjacent to the coupler  144 , upon which bridge plate  150  can rest, as described below. 
     When seen from above, as in FIG. 3 h , the outboard end portions  146  and  148  of side sills  84  and  86 , respectively, are splayed laterally outward to give a flared end to the pathway, trackway, or roadway, defined between the curbs of their respective top chord members  90 . The flare is achieved with a mitre, or chamfer, but could also be achieved with a smooth curve, and serves to provide a lead-in for truck wheels to the straight curb portions of top chord members  90  and to allow motion of the bridge plates during operation, as indicated in FIG. 5 c . The angle of the flare is sufficient to tolerate yawing of bridge plate  150  as the train travels, the edge of bridge plate  150  lying next to the flare on the minimum design track radius. 
     A gap spanning structural member, or beam, namely bridge plate  150 , is indicated in FIGS. 4 a ,  4   b ,  4   c , and  4   d . Bridge plate  150  is preferably of steel construction, but could be of aluminum, or suitable reinforced engineered plastics, to reduce the weight to be manipulated by railyard crews. Bridge plate  150  has the construction of a rigid flanged beam, having a top flange, or sheet  152 , upon whose upper surface  154  vehicles can be conducted. Sheet  152  is backed by a pair of spaced apart, longitudinally extending channel members  155  and  156 , welded with toes against sheet  152 . A pair of formed angles  158  and  160  are welded laterally outboard of channel members  155  and  156 , and a plate  162  is welded to span the gap between the backs of channel members  155  and  156 . In this way plate  162 , the backs of channel members  155  and  156 , and the horizontal legs  164  and  166  of formed angles  158  and  160  act as a bottom flange in opposition to the top flange, sheet  152 , with the other legs and toes acting as vertical shear transfer webs. A traction enhancement means is provided to give bridge plate  150  a non-smooth, or roughened track, in the nature of laterally extending, parallel, spaced tread bars  168  welded to the mid-span portion of sheet  152 . 
     At one end, defined as the proximal, or inboard end,  170 , bridge plate  150  has a pivot fitting, in the nature of a pair of aligned holes  172 ,  173  formed in sheet  152  and plate  162  to define a hinge pin passage. The axis  174  of the passage formed through hole  172  is normal (i.e., perpendicular) to upper surface  154  of sheet  152 , and, in use, is ideally vertical, or predominantly vertical given tolerance and allowance for yaw, pitch and roll between the rail road cars. Proximal end  170  is chamfered as shown at  176 ,  178  and is boxed in with web members  180 ,  182 . Although a mitre is preferred for simplicity of manufacture, either end of bridge plate  150  could have a rounded shape, rather than a mitre. 
     At the other end, defined to be the distal, or outboard end,  184 , bridge plate  150  is bifurcated, having a linear expansion member in the nature of a longitudinally extending guideway, or slot,  186 , defined between a pair of tines, or toes  188 ,  190 , each having an external chamfer as shown at  192 ,  194 . The distal ends of channel members  154 ,  156  are also boxed in at distal end  184  as shown at  196 . A web member, in the nature of a gusset  198  is welded between the facing walls of channels  155  and  156 , adjacent to the groin of slot  186 , to encourage toes  188  and  190  to maintain their planar orientation relative to each other. 
     As shown in FIG. 5 a , bridge plate  150  can be mounted in an employed, drive-over, or length-wise extended position, in which distal end  184  is located longitudinally outboard of end sill  122 , and in which the longitudinal axis of bridge plate  150  is parallel to the longitudinal centerline axis of car unit  34  (on straight track, but otherwise depending on pitch and yaw between cars) to permit vehicles to be conducted between cars. Bridge plate  150  can also be mounted in a stowed, lateral, transverse or cross-wise position, as shown in FIG. 5 b , in which the centerline of bridge plate  150  is perpendicular to the longitudinal centerline of car unit  34 . 
     Shelf portion  134  has a first bore formed therein to one side of longitudinal centerline of unit  34 . A pivot fitting, or mounting fitting, in the nature of a collar  200  is mounted flush with, or slightly shy of the upper surface of shelf portion  134 , at a first location, indicated as bore  202 , for alignment with through hole  172 . As discussed below in the context of FIGS. 8 a - 8   c  the toe of bridge plate  150  can be tipped up slightly. To do this, the rear, or longitudinally inboard edge of shelf portion  134  acts as a fulcrum. A retaining member, in the nature of a hinge pin  204 , is fabricated from a section of pipe  206  of a size permitting a loose fit within collar  200  to allow for roll, pitch and yaw between cars. Pipe  206  has a flange  208  mounted at one end, the proximal or upper end. Flange  208  bears on sheet  152  to prevent pipe  206  from falling though collar  200 . Pin  204  also has a lifting fitting in the nature of a internal cross bar  209  mounted at the flanged end. Bar  209  is grasped to withdraw pin  204  (or  205 , below). The distal or lower end of pipe  206  is slotted to accept a transverse pin  210 , itself held in place by a locking member in the nature of a cotter pin, that prevents hinge pin  204  from unintentionally lifting out or collar  200 . Shelf portion  134  also has an abutment, or stop, not shown, welded to the upper surface of plate  130  to prevent bridge plate  150  from being pivoted past the stowed position, and so preventing the side of bridge plate  150  from hitting cam crank  241  (described below) inadvertently if transition plates  232  is in the raised position (also described below). 
     When hinge pin  204  is in place, bridge plate  150  is restricted, or constrained, within the limits of a loose fit, to a single degree of freedom relative to rail car unit  34 , namely pivotal motion about a vertical axis. The sloppy, or loose, fit of hinge pin  204  within collar  200  gives a limited amount of play to permit tipping the bridge plate upward during coupling, and to permit sufficient roll, pitch and yaw for normal railroad operation. In the preferred embodiment, a nylon (t.m) pad  211  is mounted to the underside of bridge plate  150  to provide a bearing surface for riding against shelf portion  134 . In alternative embodiments other types of relatively slippery, high density, or UHMW, polymer materials could be used. 
     Shelf portion  134  of shear plate  130  has a second bore formed therein offset to the other side of longitudinal underside of car unit  34 . As shown in FIG. 7 g , another collar  200  is mounted to the underside of, and flush with (or, shy of) plate  128  of shelf portion  134  at a second location, indicated as bore  214 , at the same longitudinal station as bore  202  for alignment with slot  186  when bridge plate  150  is in the lateral, or storage, position resting fully on shelf portion  134 . Another hinge pin  205 , of the same construction as pin  204  described above, is provided to secure bridge plate  150  in the stowed position, the distal end of pin  205  locating in bore  202  and the proximal end locating in slot  186  defined between toes  188 ,  190  where hinge pin  205  is removed, bridge plate  150  is able to pivot about the hinge formed by the co-operation of hinge pin  204 , collar  200  and through hole  172 . 
     When a bridge plate such as bridge plate  150  is in the extended (i.e., lengthwise, or longitudinal) position, and its distal end (or tip) engages the adjacent car, pin  205  is again used, this time to provide a positive, securing, retaining, indexing, or alignment member to the engaging fitting, namely slot  186 . Slot  186  is then constrained, within the confines of a loose fit, to permit motion along a first linear degree of freedom, namely to slide as the gap between cars shortens and lengthens as adjacent rail car units yaw, or translate transversely, relative to each other, and a rotational degree of freedom relative to the locating pin, i.e., pin  205 , of the adjacent car. As above, the loose fit of pin  205  in slot  186  allows for normal pitch and roll motion of the cars. As shown in FIG. 5 c , the combination of a rotational degree of freedom at pin  204  of one rail road car, and both rotational and linear displacement at pin  205  of the other rail road car, accommodates both curving and transverse displacement of the coupler ends relative to each other. That is, the interaction of slot  186  with pin  205  provides both a pivot fitting for accommodating yawing motion of the adjacent rail road car, but also provides a linear expansion member for accommodating variation in distance between the respective vertical axes of pin  204  (and, collar  200 ) of one rail road car, e.g., car  22 , and pin  205  (and its collar  200 ) of the adjacently coupled rail road car, e.g., car  21 . 
     When viewed in FIG. 4 a  it can be seen that bridge plate  150  has cut-outs  216 ,  218  formed in its distal end to accommodate cam crank  241  (described below) when bridge plate  150  is in the stowed position, and a pair of hand hold rungs  220 ,  222  mounted to the chamfer of toes  188 ,  190  to facilitate pulling of bridge plate  150  from the stowed position, and to facilitate tipping the distal end, or toe, of bridge plate  150  upward, preparatory to coupling two rail car unit coupler ends together. 
     Left and right hand transition plates are shown in FIGS. 6 a ,  6   b , and  6   c  as  230 ,  232 . Each has pivot fittings in the nature of arcuate hinge tangs  234 ,  236  extending from proximal edge  235 . Hinge tangs  234 ,  236  locate in corresponding apertures, namely rectangular slots  238 ,  240  (FIG. 7 g ) formed in back  140  of formed channel  136 . Hinge tangs  234 ,  236  and slots  238 ,  240  co-operate to permit upward lifting of their distal tips by pivotal motion of each of transition plates  230 ,  232  about a horizontal pivot axis lying perpendicular to the longitudinal centerline of rail car unit  34 . As above, there is tolerance in the fit of tangs  234 ,  236  and slots  238 ,  240  to allow for normal railcar motion. Transition plates  230  and  232  cover the gap that could otherwise exist between the inboard, or proximal end of bridge plate  150  (on one side, i.e.,  230 ) or the toes of the bridge plate of the adjoining rail car (on the other side, i.e.,  232 ) and the end of deck  47  of rail car unit  34 . Since transition plates  230  and  232  are relatively thin (⅝ inch) they do not present a large bump when highway trailer wheels encounter them. Transition plates  230 ,  232  each have a U-shaped central relief  237  formed in distal portion  239  to avoid fouling pin  204  (or  205 ). 
     In the preferred embodiment, the upper surface of bridge plate  150  is roughly flush with the level of the adjacent end of deck  47 , as taken at the height of the upper surface of the top flange fabricated cross-beam  136 , such that a generally level roadway is formed. It is possible to conduct highway trailers from bridge plates  150  to deck  47  without the use of transition plates  230 ,  232 , but is more advantageous to use transition plates. It is also not necessary that the depth of shelf portion  134  relative to the end of the deck, (i.e., the height of the step) indicated as D 1 , be the same as the depth of bridge plate  150 , indicated as D 2 . It is advantageous that the height differential between the top of bridge plate  150  and the end of deck  47  be small, such as less than 1½ inches, and better still, less than ½ inch to reduce the potential bump. The severity of the bump is also reduced by the use of transition plates  230 ,  232 , that permit a mismatch in height to be taken up over a modest longitudinal distance, rather than suddenly. 
     It is also possible to use a bridge plate support member other than shelf portion  134 . For example, a cross-beam or cantilevered beam could be used, whether mounted to end sill  122 , center sill  60 , side sills  84 ,  86  or some combination thereof Alternatively a pedestal could be employed having an upwardly protruding pin in place of pin  204 , and an alternative form of second retainer in place of pin  205 , such as one or more retractable abutments, whether spring loaded or otherwise in the manner of spring loaded detents, or a releasable hook or latch, could be used to similar effect. The use of a bridge plate kit including bridge plate  150  and pins  204  and  205  is advantageous since pins  204  and  205  are interchangeable, are used to provide motion tolerant retention of the proximal end (by pin  204 ) and distal end (by pin  205 ) of bridge plate  150  in either lengthwise or cross-wise positions, are relatively robust, and are of relatively simple fabrication. 
     Left and right hand cam cranks are indicated in FIGS. 3 h  and  7   a  to  7   g , as  241 ,  242 . Each cam crank is formed from a bent steel bar. Each cam crank has an inboard hinge portion  244  and an outboard hinge portion  246  that lie on a common hinge axis,  248 . As shown in FIGS. 7 f ,  7   g , inboard hinge portion  244  seats in an aperture or socket  245  mounted to the underside of, and at the laterally outboard edge of, top flange  72 , longitudinally outboard of main bolster  120 . Outboard hinge portion  246  seats in an aperture  247  formed through side sill  84  (or  86 , as the case may be). Socket  245  and aperture  247  act as hinge fittings within which the shaft portions of cam cranks  241  and  242  are constrained to turn. The laterally outboard, or distal, end of hinge portion  246  has a torque input fitting, in the nature of an obliquely angled transverse bore indicated as slot  249 . This angle, α, is greater than the outward cant of the side sill web and, in the preferred embodiment illustrated is about 25 degrees. Slot  249  admits entry of a lever member in the nature of a turning handle, or pry bar, by which means railroad personnel can impose a turning torque on cam crank  241 ,  242 . As shown, oblique slots  249  are formed in both ends of cam crank  241 ,  242  permitting the same part to be used as either  241  or  242  rather than requiring fabrication of different left hand and right hand parts. The obliqueness of slot  249  permits a straight bar to be inserted with less tendency, when rotated, to foul side sill  84  or  86  as the case may be. Although slot  249  is preferred, other types of torque input fitting, such as a bent arm (to act as a lever), a lateral pin of shaft, a keyway, a spline or splines, a hexagonal or square head to be engaged by a wrench or socket, an allen head and so on could be used. Slot  249  conveniently does not require the use of a special socket or key of a particular size. 
     A first radially extending member, in the nature of an M-shaped cam throw portion  250  extends between inboard and outboard hinge portions  244  and  246 , and will be forced through an arcuate path when a sufficiently large torque is applied though the crank. In so moving, the flattened peaks of the M-shape, indicated as  254 ,  255 , act as cams that work to raise distal portion  239  of bridge plate transition plate  230 , (or  232 ), forcing plate  230  (or  232 ) to pivot, the proximal end of plate  230  being held down by hinge tangs  234 ,  236  so that the tip, i.e., distal portion  239  of plate  230  (FIGS. 6 a ,  6   b ,  6   c ) is lifted clear of bridge plate  150 . Flattened peaks  254  and  255  (FIGS. 7 a ,  7   b ,  7   c ) are provided with bushings, or rollers  257 , that bear against the underside of bridge plate transition plate  230  (or  232 ). 
     If bridge plate  150  is in an employed, i.e., extended, position when transition plate  230  is lifted, it may tend to want to droop downward since it is cantilevered out over end sill  122  without sufficient reaction force, or weight, at the proximal end to keep the distal end up. A downward droop may tend not to be advantageous when pushing cars together to be coupled, since the distal tip would then have a tendency to jam into the end sill of the adjacent car. It is also not desirable to require railroad employees to have to hold the bridge plate tips up as railcars come together. To that end the middle portion of the M-shape, indicated as  258  has a retainer, in the nature of a protruding catch, pawl, tooth, stop or abutment  260 , fabricated in the form of a bent, t-shaped tang  261  with arms welded to either side of portion  258  and the tongue of tang  261  extending above and beyond portion  258 . When cam crank  241  is rotated to lift plate  230 , abutment  260  is placed in a position to intercept the most inboard edge  262  of sheet  152 . When thus engaged, abutment  260  discourages bridge plate  150  from drooping as adjacent cars are brought together. 
     Further, cam crank  242  can be moved to a fully engaged position to lift transition plate  232  whether or not a bridgeplate is present. When the tip, or distal, portion  239  of plate  232  is thus lifted, the distal tip of a bridge plate  150  of an adjoining car can then be introduced, as shown in FIGS. 8 a  and  8   b . As the tip of the other bridge plate moves into position, it engages the M-shape of cam crank  242  and pushes it backward (i.e., counterclockwise from the viewpoint of a person standing beside car unit  34  facing side sill  86  on the handle side of cam crank  242 ) to a disengaged position. As this happens, transition plate  232  falls down to engage the upper surface of the incoming bridge plate in an overlapping position. Once the tip of the other bridge plate is on shelf portion  134  (FIG. 8 d ) it can be nudged (if required) into position to permit pin  205  to be inserted. 
     The sequence of operation for uncoupling two rail road cars such as cars  21  and  22  to permit conversion from “drive-over” ends to a “ramp end” is as follows: Remove the cross-pin from the lower slot of pin  205 . Lift pin  205  and place on deck  100 . Support the distal tip of bridge plate  150  (can be manually lifted, or alternatively, propped in place). Engage a pry bar or similar bar as a lever in the outboard oblique slot in cam crank  241 , and apply a force to the bar to generate a torque to twist cam crank  241  counter-clockwise (as viewed facing the side sill by a person standing beside the car applying force to the lever). This causes the distal edge of transition plate  230  to lift, thereby disengaging plate  230  from bridge plate  150 . Engage abutment  260  to edge  262  of bridge plate  150 . (The distal tip of bridge plate  150  can be released once abutment  260  is engaged). Engage a pry bar as a lever in the outboard oblique slot in cam crank  242  and twist in a clockwise direction to lift transition plate  232  to a position for receiving another plate. (This step can either precede or follow the step of lifting transition plate  230 ). Operate the uncoupling rod to unlock the coupler and close the angle cocks (standard steps for uncoupling railcars generally). Pull the rail road cars apart. Rotate (i.e., pivot) bridge plate  150  clockwise (as viewed from above) on pin  204  until toes  88  and  90  rest on shelf portion  134  beneath the overhang of plate  232 . Adjust as needed to permit pin  205  to enter collar  200 , and install pin  205  to secure the distal end of the bridge plate in place in the stored position. Lower plate  232  to engage, i.e., sit on, bridge plate  150 . 
     To reverse the process: Unlock, and remove pin  205 . Use a pry bar as a lever in the outboard oblique bores (i.e., slot  249 ) of cam cranks  241 ,  242  to raise intermediate transition bridge plates  230 ,  232 , disengaging them from bridge plate  150 . Haul bridge plate  150  out of its storage position by rotating (i.e., pivoting) it counter-clockwise about pin  204  to the extended position, with edge  262  restrained under abutment  260 . This is the position shown in FIG. 8 a . Advance the rail cars towards each other to cause the respective bridge plates  150  to be received under respective intermediate transition plates  232 , each bridge plate advancing to encounter cam crank  242  of the opposing railcar, knocking it down as the couplers connect. (See FIGS. 8 b , and  8   c ). Replace pins  205  of each respective car, nudging or adjusting the bridge plates as required, partially raising bridge plate  232  if necessary to facilitate this nudging, and locking pins  205  in place when seated satisfactorily, thus securing bridge plate  150 . Lower plate  230  onto bridge plate  150 . Re-establish the coupling between the two cars, including brake lines. The train is again ready to be moved along the rail line. 
     Alternatively, following the sequence of FIGS. 8 a ,  8   e ,  8   f  and  8   d , when moving the rail road cars together, once the toe of bridge plate  150  (of, for example, car unit  34  of car  22 ) overhangs shelf portion  134  of the adjacent car (e.g., car unit  36  of car  24 ), locomotive  38  can be stopped. Bridge plate  150  can be lowered to lie on the receiving portion of the adjacent car, namely shelf  134 , by twisting cam crank  242  to release the heel edge, edge  262 , of bridge plate  150 . The locomotive can continue to urge the cars together, with bridge plate  150  sliding across shelf  134  to meet cam crank  241 . The procedure may then continue as before, with re-insertion of pin  205 , and so on. 
     In either sequence, the process includes the steps of positioning the respective bridge plates of the rail road cars in a length-wise orientation and advancing the rail road cars toward each other to cause their respective couplers to mate. The step of advancing includes the step of engaging an extended portion, the distal tip, of each of the bridge plates with a receiving member, shelf portion  134 , of the other rail car. The step of positioning each of the bridge plates includes securing the distal tip in a raised attitude relative to the proximal portion, as described above. The step of engaging includes a step of securing each the bridge plate to the other of the rail road cars by re-inserting hinge pin  205  to link slot  186  of each bridge plate with the socket formed by the respective collars,  200 . 
     The step of advancing the cars together is preceded by the step of moving (i.e., raising) transition plates  232  to the raised position to facilitate engagement of bridge plate  150  with the receiving member, namely shelf portion  134 . The step of engaging is followed by the step of placing, (i.e., lowering) transition plate  232  to an overlapping position between the received distal tip of bridge plate  150  and vehicle carrying deck  47 . The step of raising transition plate  232  includes the step of employing a prop, namely cam crank  241  to maintain transition plate  232  in the raised position. The step of engaging includes advancing the bridge plate to disengage the prop, thus causing transition plate  232  to move to the overlapping position. 
     On level track, the swinging of bridge plate  150  between length-wise and cross-wise positions occurs in the plane of shelf portion  134 , that plane being a horizontal plane, such that rail yard personnel do not need to raise (or lower) the bridge plate to (or from) a vertical, or nearly vertical, position as was formerly common. Further still, since the arrangement of bridge plate  150  can accommodate train motion, whether due to pitch, yaw, roll or uneven spring compression between, for example, car units  34  and  36 , bridge plate  150  may remain in its extended, bridging position spanning the gap between units  34  and  36  when rail road cars  22  and  24  are in motion, and does not need to be moved each time the train is loaded or unloaded. Bridge plate  150  may tend not to need to be moved to or from its stowed position except when rail road cars  22  and  23  (or such others as may be joined together) are split apart from their neighbours, or joined together again. This may occur only relatively infrequently to permit the train consist to be changed. This may tend to reduce the number of times rail yard personnel are required to handle the bridge plates, and may tend to reduce the length of time required for loading and unloading. 
     The process for changing bridge plate  150  from the length-wise position to the cross-wise position is relatively simple. the rail car is established in an uncoupled position by uncoupling the rail road cars and moving them apart, thus disengaging the distal tip of bridge plate  150  from the adjacent car, and establishing bridge plate  150  in the extended position. Pin  205  is removed, transition plate  230  is disengaged from bridge plate  150  by raising its distal portions clear of bridge plate  150 . Plate  232  is also raised. Then bridge plate  150  is moved from the length-wise position to the cross-wise position. As noted, the step of moving includes swinging bridge plate  150  in the horizontal plane of portion  134  about the pivot mounting provided by the interaction of pin  204  in collar  200 . This is followed by securing bridge plate  150  in place by reinserting pin  205  as a retainer, and by re-engaging transition plates  230 ,  232 , as by lowering them to the overlapping position. The step of disengaging the transition plate from the bridge plate includes the step of operating cam cranks  241 ,  242  to lift the distal portions of transition plates  230 ,  232 . The step of operating the cam cranks includes the step of turning them to bear against the transition plates. 
     The process of converting and re-coupling cars can be followed by a series of steps for unloading, and then loading (or re-loading) that include placing ramps at the rail road car ends, as described above and shown in FIGS. 1 a - 1   e . In the loading and unloading processes the hostler truck and the highway trailers will cross bridge plate  150  in its stored, or laterally transverse, position. 
     Considering now the far end of car unit  34 , namely the articulated connection end  70 , shown in FIG. 9 a , the main vertical shear load is carried though main center sill  60  to articulated connector  37  and into shared truck  39 . A male pair of left and right hand dog-legged side bearing arms  270  and  272  are rooted to main center sill  60  longitudinally outboard of end body bolster  268 . The male pair of side bearing arms of the ‘B’ unit, namely side bearing arms  270  and  272  of car unit  26 , nest within the corresponding left and right hand female side bearing arms  274 ,  276  of the adjoining car unit, intermediate “C” car unit  30 . In each case the side bearing arms,  270 ,  272 ,  274 , and  276  are mounted above side bearing reaction seats, or pads, mounted to the truck bolster of shared truck  37 . Left and right hand end sills portions  278 ,  280  extend between side bearing arms  270 ,  272  and side sills  84 ,  86 . In the case of car unit  30 , left and right hand end sill portions  282 ,  284  extend between side bearing arms  274 ,  276  and side sills  283 ,  285 . In each case, side sills  84 ,  86  and side sills  282 ,  284  have chamfered ends as indicated at  286 ,  287 , to give a flared opening analogous to that described above at the coupler end of car unit  34 . 
     The decking of car unit  34  is indicated generally as  47 , and includes left and right hand deck plates  288 ,  290  mounted generally flush with, and to either side of, the top flange of center sill  60 . Similarly, the decking of car unit  30  is indicated generally as  48 , and includes left and right hand deck plates  292 ,  294  mounted to either side of, and generally flush with, the top flange of center sill  296 . 
     Articulated connection end bridge plates  300  include left and right hand plate assemblies. Although FIG. 9 a  and the detail drawings of FIGS. 9 b ,  9   c  and  9   d  show only a left hand plate assembly  300 , the corresponding right hand plate is of the same design and construction, and is a mirror image of the assembly shown. Hence a description of the left hand plate serves also to describe the right hand plate. Assembly  300  includes a plate member  302  with a peripheral profile  304  as seen in FIG. 9 c . The outer portion  306  of profile  304  forms a circular arc having a center of curvature at the pivot center of articulated connector  37  (as seen from above in FIG. 9 a ). The arc of outer portion  306  falls within the profile of flared ends  284 ,  286 . Working in a counter-clockwise direction in FIGS. 9 a  and  9   c , adjacent to arc  306 , profile  304  has a straight portion  308  cut on a mitre to correspond to the mitred edge  309  of deck plate  292  (or  294 , if opposite handed). The plates are mitred to conform to the taper of the end of deck  48 . At the laterally inboard end of mitred edge, portion  308 , is an inward tab,  312 , and an inboard edge  314  following, generally, the profile of the male side bearing arm  270  (or  272 , as may be). An outwardly extending edge  316  runs obliquely outward from inboard edge  314  to terminate at a generally arcuate horn, or protruding wing  318  whose outer edge is defined by circular arc. The underside of wing  318  bears on a stainless steel wear pad  320  (or  321 , opposite hand) welded to the upper surface of deck plate  292  (or  294 ) in the region of the flare of side sill  84  (or  86 ) over end sill portions  278 ,  280 . A stainless steel wear plate may tend to be less prone to rust than mild steel, and, like assembly  300 , can be replaced as a consumable if needed. 
     An array of deck engagement fittings is indicated generally as  322  and includes plate retainers in the nature of three parallel bars bent into ‘Z’ shaped hooks. The first, upper leg  323  of the ‘Z’ is longer than the lower leg, and is welded in position lying along the top of plate  302  and, when installed, extends parallel to the rail car longitudinal centerline of unit  30 , as shown in FIG. 9 a . Deck plates  292  and  294  of car unit  30  have deck extension portions  324 ,  326  that extend past respective end sill portions  282  and  284  and that are welded on inboard and outboard edges to female side bearing arms  274 ,  276  and corresponding flared side sill end portions, namely chamfers  286 ,  287 . 
     Extension portions  324 ,  326  have members for supporting the adjacent edge portion  308 , namely a backing bar, or shelf  327  welded to extend past the lip of the mitred edge of deck  48 . Extension portions  324 ,  326  also have mating fittings for engaging the hooked ends of fittings  322 , namely a set of corresponding holes  328  and are cut on a mitred angle to match the mitre of edge  308 . The short end legs  330  of fittings  322  can be inserted into holes  328 , and then assembly  300  can be pivoted and the vertical riser portions  332  slid through the holes, such that assembly  300  is placed in its installed position. As such, assembly  300  can be raised relatively easily by hand to permit replacement or to permit separation of rail car units  26  and  30 , as may be required to permit replacement of the shared truck during a maintenance overhaul. As additional features, assembly is stepped downward at oblique fold lines, indicated at  334 ,  336 , and has traction bars  338  to encourage better grip as vehicles are moved thereover. Traction bars  340  are also provided on deck  52 . 
     As illustrated, the “B-end” unit, rail car unit  34 , has two collapsible hitches  112 ,  114  as indicated above. The “A-end” unit, rail car unit  26  has a single collapsible hitch, mounted over the main bolster, and the intermediate “C” unit, rail car unit  30 , has a collapsible hitch mounted roughly 6 feet longitudinally inboard of the nearest point of articulation. The choice of hitch number, and location may vary depending on the anticipated population of trailer sizes to be carried. As such, any of the “A”, “B”, “C” or other units may have a single collapsible hitch, or two collapsible hitches, at the option of the rail car buyer. The proximity of hitch  114  to the articulated connector end of rail car unit  30  is such that hostler truck  40  is supported by plate assemblies  300  when picking up a trailer from hitch  114 . It is advantageous to maintain a flush deck, as at the portion of assembly  300  immediately adjacent to deck  48 , to give the hostler truck more vertical clearance under the nose of the highway trailer than if the assembly  300  were raised to overlap deck  48 . 
     As shown in FIGS. 3 f ,  3   g  and  3   h , deck access fittings, in the nature of steps  350 ,  352  and hand grabs  354 ,  356  are located inboard of the king-pin mounting centerline of hitch  112  (or  114 , as the case may be) a distance ‘δ’ generally corresponding to the distance between the king pin and the crank for the landing gear of the highway trailer. These deck access fittings may tend to permit rail yard personnel to mount the rail car units (whichever they may be) more closely adjacent to the position of the landing gear cranks of the highway trailers, reducing the distance to walk along the car, and reducing the need to edge past the nose of the highway trailer to reach the landing gear crank. 
     The preferred distance ‘δ’ from the center of the hitch kingpin fitting to the center of the ladder rungs (or steps  350 ,  352 , as may be the case) is about 88 inches, the rung width is about 18 inches and the opening between the hand grabs  354 ,  356  is about 24 inches, the height of the hand grabs being about 8 inches above the top of the top chord, and the top of the top chord being about 8 inches above the deck on which the highway trailer wheels roll. While the optimal distance will vary depending on the size and strength of the person operating the landing gear crank of the highway trailers, a range of distances would be suitable from 5 to 10 feet inboard (i.e., rearward relative to a highway trailer mounted to the hitch plate) of the hitch king-pin centerline, and preferably 7 to 8 feet inboard. 
     Running-boards  358 ,  360  are mounted to side sill web  92  longitudinally to either side of steps  350 ,  352  and extend along web  92  adjacent to hand grabs  354 ,  356 . In the preferred embodiment, the length of each running board is 41 inches, and the width is 6 inches. A running board size in the range of 30 to 60 inches, or preferably in the range of 3 to 4 feet, allows for different sizes and strengths of operators, and may permit operation of the crank either predominantly with the right hand or predominantly with the left hand as may suit the user. Running boards  358 ,  360  are provided with deformed metal perforated non-skid grating sheets  362 . Running boards  358 ,  360  are mounted slightly below (roughly 2″) the adjacent deck level such that personnel operating highway trailer landing gear cranks may stand somewhat more upright, and may tend to have a better posture while operating the loading gear crank than if standing at the same level as the rail car deck. 
     Although ladder rungs are shown mounted to side sills  84 ,  86 , other types of climbing foothold can be used. For example, in the alternative embodiment of FIG. 13, a rail road car side sill assembly  370  is provided with square sided foot holds  372  formed in the web  374  of the side sill. 
     Returning to hitches  112  and  114 , and FIGS. 14 a  (hitch raised),  14   b , and  14   c  (hitch lowered), the width of deck  47  between side sills  84  and  86  is indicated as W D . In the preferred embodiment, this width is 104 inches. The W D  deck width is chosen to accommodate the maximum highway trailer bogie tire width, nominally 102 inches. Hitch  112  (or  114 , as the case may be) is a retractable, tractor operated hitch that can be raised an lowered by hostler truck  40 . It has a front pivot mount  375  and a rear pivot mount  376 , each falling within a hitch width designated as W H . Inasmuch as not all highway trailers have bogies of the same width, if the outside tire sidewall on one side is bearing against the chamfered inside face of either side sill  84  or  86 , the inside tire sidewall will be closer to hitch  112  (or  114 ) than the corresponding inside face of the opposite inside tire. Hitch width W H  is chosen such that it is less than, or equal to, the dimension obtained by adding the minimum overall outside highway trailer bogie tire width WTO (MIN) , nominally 96 inches, and the minimum inside highway trailer bogie tire width WTI (MIN) , 47 inches; and subtracting deck width W D , 104 inches and an amount of at least 1½ inches to account for the bulge of the side walls of the tires. This value is 37½ inches. It is preferred that W H  be 37¼″ or less. 
     The foregoing description has been generally directed to elements related to deck  47  and operational features associated with deck  47 . FIGS. 12 a  and  12   b  show the draft gear at the coupler end of rail car unit  34 , being representative of the coupler end draft gear of rail road cars  21 ,  22 ,  23 ,  24  and  25  more generally. Coupler pocket  62  houses a coupler indicated as  44 . It is mounted to a coupler yoke  378 , joined together by a pin  380 . Yoke  378  houses a coupler follower  382 , a Mini-BuffGear  384  such as manufactured by the Keystone Railway Equipment Company, of 3420 Simpson Ferry Road, Camp Hill, Pa., held in place by a shim (or shims, as required)  386 , a wedge  388  and a filler block  390 . Fore and aft draft gear stops  392 ,  394  are welded inside coupler pocket  62  to retain Mini-BuffGear  384 , and to transfer the longitudinal buff and draft loads through Mini-BuffGear  384  and on to coupler  44 . In the preferred embodiment, coupler  44  is an AAR Type F70DE coupler, used in conjunction with an AAR Y45AE coupler yoke and an AAR Y47 pin. As taken together, this draft gear and coupler assembly yields a reduced slack, or low slack, short travel, coupling as compared to a Type E coupler with standard draft gear or an hydraulic EOCC device. As such it may tend to reduce overall train slack, and may tend to reduce the range of travel to be accommodated by bridge plates  150 . In addition to mounting the Mini-BuffGear directly to the draft pocket, that is, coupler pocket  62 , and hence to the structure of the rail car body of car unit  34 , the construction described and illustrated is free of other long travel draft gear, sliding sills and EOCC devices, and the fittings associated with them. 
     Other than brake and minor fittings, the basic structure of center sill, cross-bearer and decking structure of intermediate car unit  30  is substantially the same as car units  26  and  34 . Car unit  26 , shown in FIGS. 10 a  (isometric),  10   b  (top),  10   c  (side view) and  10   d  (underframe) differs from car unit  34  primarily in having a female set of side bearing arms, like those of car unit  30  adjacent to car unit  34 . The hitch arrangement will be different, with the hitches on all of car units  26 ,  30  and  34  being arranged such that trailers mounted thereon will have their forward ends (i.e, the end with the king pin) facing toward end portion  64  of car unit  34 . Car units  26 ,  30  and  34  may also vary in their brake arrangements, and other fittings, but share the same basic structural features. However, as intermediate unit  30 , shown in FIGS. 11 a  (isometric),  11   b  (top),  11   c  (side view) and  11   d  (underframe) has no coupler end, its construction can be conceptualized as having the articulation connection end of car unit  34  taken from a mid span section, with a set of male side bearing arms, and the articulation connection end of car unit  26  with female side bearing arms, also taken from mid-span section, and joining them together in one car, with the pair of female side bearing arms facing car unit  34  and the pair of male side bearing arms facing car unit  30 . 
     Various embodiments of the invention have now been described in detail. Since changes in and or additions to the above-described best mode may be made without departing from the nature, spirit or scope of the invention, the invention is not to be limited to those details.