AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Innovation Patent Applicant(s): KRUEGER TRANSPORT EQUIPMENT PTY LTD Invention Title: Cargo trailer sets and trailers therefor The following statement is a full description of this invention, including the best method for performing it known to me/us: - 2 Cargo trailer sets and trailers therefor Field of the invention This invention relates generally to cargo transport 5 trailers of the kind that provide an enclosure for cargo that is typically loaded into the enclosure on pallets. A typical such cargo trailer is a curtain-sider: the invention will be primarily described herein with reference to curtain-sider trailers but it is to be io understood the invention is more broadly applicable to cargo trailers in which an enclosure for the cargo is defined by any suitable sub-structure of the trailer. Background of the invention is The standard curtain-sider trailer has a chassis, a floor fixed to the chassis for carrying palletised cargo, a roof atop a frame defining a generally longitudinal box-like space, and retractable side curtains. Each curtain is typically suspended from an overhead track at a respective 20 edge of the roof, and is slidable along the track to selectively open and close the side of the trailer and thereby to provide an opening through which cargo may be loaded into and unloaded from the trailer. 25 In this standard trailer, the floor is substantially straight (as in step-free) and slopes front to rear. The front is about 150mm higher than the rear. The principal components of the chassis are a pair of full length steel beams, typically I-beams, of a given depth (e.g. 400mm) 30 for most of the length of the trailer but reduced to, say, 150mm, towards the front end where the trailer is in articulated engagement with a prime mover or lead trailer. This reduction of the chassis depth towards the front end of the trailer is necessary to allow the chassis to clear 35 the wheels and mudguards of the prime mover or lead trailer during turning manoeuvres into driveways with uneven road surfaces. 3167583_1 (GHMatters) P89639.AU 22/02/12 -3 This standard trailer can be the sole trailer in a semi trailer configuration with a prime mover, the rear trailer in a B-double set, or the rearmost trailer in a road 5 train. In a B-double set, the rear trailer is commonly referred to as the B trailer, and the lead trailer, the A trailer, has a special configuration in that it has a front section designed to be coupled to a prime mover and a trailing wheeled section behind its curtained enclosure io that has a coupling above the wheels for articulated engagement with a B trailer king pin. In this specification, the terminology "A trailer" and "B trailer" is adopted to generally refer to the leading and following trailers of any pair of cargo trailers. 15 Given that the maximum height of enclosed cargo trailers is generally set by road regulations and/or indirectly arises from regulations governing the height of the centre of gravity, there are limited options for improving the 20 internal cargo holding volume available in such trailers. An existing modification is the drop deck trailer, in which the chassis and floor are stepped down behind a front portion (which must still clear the wheels and mudguards of the prime mover or lead trailer when 25 turning), and the wheels are of smaller diameter than those of the prime mover or lead trailer. In a B-double trailer set, the A trailer can be provided with a drop deck between its wheel set and the prime mover wheel set. These modifications do gain a significant increase in 30 cargo carrying volume but the presence of the step and the two different deck heights at the open side of the trailer can be inconvenient for some logistics providers and their customers. 35 It is an object of this invention to further improve the available cargo carrying volume in cargo trailers, cargo trailer sets and road trains made up of enclosed trailers 31675831 (GHMatters) P89639.AU 22/02/12 -4 such as curtain-sider trailers; or at least to provide an alternative for those concerned with cargo trailers. It is not admitted that any of the information in this 5 specification is common general knowledge, or that the person skilled in the art could reasonably be expected to have ascertained, understood, regarded it as relevant or combined it in anyway at the priority date. 10 Summary of the invention Various aspects of the present invention entail a realisation that a practical approach to addressing the object of the invention lies in the adoption of a special thin chassis design in the front portion of the A trailer is and/or the B trailer. In other aspects, an A trailer accommodates 'standard' prime mover ground wheels at its front coupling section but provides relatively smaller ground wheels at its rear coupling section. 20 In a first aspect, therefore, the invention provides a cargo trailer set comprising: respective A and B trailers each having a chassis including a front chassis section, a floor for carrying 25 palletised cargo, and an enclosure for the cargo, the A trailer further including a trailing chassis section that is at least partly behind the cargo enclosure thereof and has a first group of ground wheels for the trailer set, and the B trailer further having a second group of ground 30 wheels for the trailer set at or towards its rear; wherein the trailing chassis section of the A trailer and the front chassis section of the B trailer have cooperable coupling elements engageable for 35 articulated coupling of the trailers with the cargo enclosure of the B trailer partly overlying the first group of ground wheels; 3167583_1 (GHMatters) P89639.AU 22/02/12 - 5 and wherein the floor of the B trailer above its front chassis section is lower than the floor of the A trailer above its front chassis section whereby the latter s can accommodate wheels of larger diameter than the wheels of said first group of ground wheels, and the front chassis section of the B trailer is a structural unit that includes multiple beam sections inked by one or more structural plates whereby to minimise the vertical extent 10 of that front chassis section and thereby said deck height above ground of the floor of the B trailer. The first aspect of the invention also provides an A trailer for a cargo trailer set. The A trailer includes: 15 a chassis including a front chassis section, a floor for carrying palletised cargo, an enclosure for the cargo, and a trailing chassis section that is at least partly behind the cargo enclosure thereof and has a first 20 group of ground wheels for the trailer set; wherein the trailing chassis section of the A trailer has a coupling element engageable with a coupling element of a B trailer for articulated coupling of the 25 trailers; wherein the A trailer front chassis section accommodates prime mover wheels of larger diameter than the wheels of said first group of ground wheels. 30 Preferably the front chassis section of the A trailer is a structural unit that includes multiple beam sections linked by one or more structural plates whereby to minimise the vertical extent of that front chassis section 35 and thereby the deck height above ground of the floor of the front chassis section. 3167583_1 (GHMatters) P89639.AU 22/02/12 - 6 In a second aspect, the invention provides a cargo trailer set and A and B trailers therefor. The set comprising: respective A and B trailers each having a chassis s including a front chassis section, a floor for carrying palletised cargo, and an enclosure for the cargo, the A trailer further including a trailing chassis section that is at least partly behind the cargo enclosure thereof and has a first group of ground wheels for the trailer set, 10 and the B trailer further having a second group of ground wheels for the trailer set at or towards its rear; wherein the trailing chassis section of the A trailer and the front chassis section of the B trailer is have cooperable coupling elements engageable for articulated coupling of 15 the trailers with the cargo enclosure of the B trailer partly overlying the first group of ground wheels; 20 and wherein the front chassis section of each trailer is a structural unit that includes multiple beam sections linked by one or more structural plates whereby to minimise the vertical extent of the respective front chassis section and to maximise the vertical extent of the 25 cargo enclosure at the respective front chassis sections. In a third aspect the invention provides a cargo trailer for a cargo trailer set, the trailer having a chassis, a floor for carrying palletised cargo, and an enclosure for 30 the cargo, the chassis including a front chassis section having a coupling element engageable for articulated coupling of the trailer to a lead trailer or prime mover, and a group of ground wheels for the trailer at or towards its rear: 35 wherein the front chassis section is a structural unit that includes multiple beam sections linked by one or 3167583_1 (GHMatters) P89639.AU 22/02/12 -7 more structural plates whereby to minimise the vertical extent of the front chassis section and thereby the deck height above ground of the floor of the trailer, while accommodating movement of the front chassis section over 5 said wheels of the lead trailer or prime mover during a turning manoeuvre. The floor of the B trailer of the first or second aspect or of the trailer of the third aspect may be substantially 10 straight, which can advantageously allow forklifts to drive therealong, but preferably includes a step down rearward of the trailer's front chassis section for increased cargo capacity. The floor of the B trailer may further include a step up rearward of the step down. As 15 such a sunken central chassis portion can be defined, between the steps, which is lower than the other, wheel clearing, portions of the chassis. Similarly the floor of the A trailer may be substantially straight but preferably includes a step down rearward of the A trailer front 20 chassis portion for increased cargo capacity. Preferably, the stepped down portion of the A trailer floor sits below an upper extent of the A trailer trailing chassis section. The deck height of the floor above ground i.e. the height 25 of the upper surface of the floor above ground, at the front chassis section is preferably less than 1.4m, more preferably less than 1.1m. The aforesaid vertical extent of the front chassis section of the B trailer in the first and second aspects of the invention, or of the trailer in 30 the third aspect of the invention, is preferably 125mm or less, for example about 100mm. The tyre outside diameter of the first group of ground wheels in the first and second aspects of the invention, 35 or of the wheels accommodated by the front chassis section in the third aspect of the invention, is preferably less than 900mm, most preferably of outside diameter between 3167583_1 (GH Matters) P89639.AU 22/02/12 - 8 750 and 900mm. In a preferred arrangement, these wheels and the second group of ground wheels that are at or towards the rear of the B trailer (or of the trailer in the third aspect of the invention), are of the same 5 diameter. In the first aspect of the invention, the deck of the A trailer may be in substance higher than the deck of the B trailer. Alternatively, the A trailer may be of drop deck 10 construction with a step down in the floor and chassis at the rear of the front chassis section. There are preferably two, three or four lengthwise spaced wheel axles in each group of ground wheels. 15 Preferably, the structural unit at the front chassis section of the B trailer in the first and second aspects of the invention, or of the trailer in the third aspect, has upper and lower structural plates linking the multiple 20 beam sections. Each beam preferably includes a horizontally elongate vertical web of material extending in a longitudinal direction. The upper structural plate conveniently provides part of the floor of the relevant trailer and thereby preferably extends the full width of 25 the trailer. The lower structural plate is preferably smooth faced on its undersurface whereby to reduce snagging or wear through contact with mud guards or other elements of the underlying wheel assemblies during turning manoeuvres of the trailer set; i.e. in preferred forms of 30 the invention the lower plate is or incorporates a skid plate. Typically, at least the front chassis section of the B trailer in the first and second aspects of the invention, 35 or of the trailer in the third aspect, does not include a conventional coaming rail. In one convenient substitute coaming facility, a plate or beam of the front chassis 3167583_1 (GHMatters) P89639.AU 22/02/12 - 9 section at each side preferably includes slots for receiving hooks of vertical curtain-tensioner assemblies that are attached to and travel with curtains providing side components of the cargo enclosure. 5 The cargo trailer set may be a B-double trailer set, or a pair of cargo trailers for a triple 20 trailer set or other road train. Optionally, a trailer per the B trailer of the above trailer set could be used as a single trailer 10 behind a prime mover. In a fourth aspect, the invention provides a cargo trailer for a cargo trailer set, the trailer having a chassis, a floor for carrying palletised cargo, and an enclosure for 15 the cargo, the chassis including a front chassis section having a coupling element engageable for articulated coupling of the trailer to a lead trailer or prime mover, and a group of ground wheels for the trailer at or towards its rear, optionally the floor of the trailer is front to 20 rear at a substantially uniform deck height above ground, and its front chassis section is a structural unit, whereby to minimise the vertical extent of the front chassis section and thereby the deck height above ground of the floor of the trailer, while accommodating movement 25 of the front chassis section over said wheels of the lead trailer or prime mover during a turning manoeuvre, and wherein the trailer further includes one or more of the preferments or options for the first, second and third aspects of the invention, as described above. 30 The various aspects of the invention are complementary, each aspect may incorporate features described in respect of one or more of the other aspects. 35 As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not 3167583_1 (GHMatters) P89639.AU 22/02/12 - 10 intended to exclude further additives, components, integers or steps. Brief description of the drawings 5 The invention will be further described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a side elevation of a B-double cargo trailer set according to an embodiment of the invention: 10 Figure 2 is a similar view of the A trailer alone: Figure 3 is a plan view of the chassis and floor construction of the B trailer, with the floor largely cut 15 away: Figure 4A is a cross-section on the line 4-4 in Figure 1; Figure 4B is an enlargement of circle 4B in Figure 4A: 20 Figure 5A is a front elevation of the B trailer depicting the arrangement for longitudinally tensioning the curtains: 25 Figure 5B is a plan view of a front portion of the B trailer depicting the arrangement for longitudinally tensioning the curtains: Figures 5C and SD detail portions of Figure 5A; 30 Figure 6 shows details of the arrangement of Figure 5A; Figures 7 and 8 are plan views of the ratchet mechanism; and 35 Figures 9A, 9B and 9C are side elevation views of B double trailer sets in accordance with various embodiments of the 3167583_1 (GHMatters) P89639.AU 22/02/12 - 11. invention. Detailed description of embodiments of the invention The illustrated B-double cargo trailer set 10 includes a 5 lead or A trailer 20 and a rear or B trailer 50. Each trailer 20,50 has a chassis 22,52, a floor 24,54 for carrying palletised cargo, and an enclosure 26,56 for the cargo. As is common for these kinds of trailer sets, the A trailer cargo enclosure is 24 feet in length, i.e. 7.475 10 metres, while the B trailer cargo enclosure is 45 feet in length, i.e. 13.72 metres. The respective enclosures 26,56 include a roof 27,57, front and rear walls 28a,28b;58a,58b and side curtains is 30,60 that are attached to an upper rail (not shown) at respective edges of the roof. The curtain is slidable along its upper rail to selectively open and close the respective side of the trailer for loading and unloading cargo. The roof 27,57 and other internal components are 20 supported by a framework of posts and other elements (not shown). The chassis 22 of A trailer 20 includes a pair of laterally spaced primary front to rear steel beams 32 that 2S extend from a front chassis section 33 to a trailing chassis section 34 that is behind the cargo enclosure 26 and has a first tn-axial group 35 of ground wheels 36 for the trailer set 10. Wheels 36 carry tyres of type 245/70R 19.5, i.e. an outside diameter of about 835mm, smaller 30 than those of standard prime movers and cargo trailers (e.g. hR 22.5 tyres). It will be seen that front chassis section 33 is significantly higher than trailing chassis section 34: the two are linked by tapered inclined segments 37 of main chassis beams 32. Front chassis 35 section 33 of A trailer 20 has a coupling element 38, e.g. a depending king pin, mounted centrally for articulated coupling of the trailer with a socket of a cooperable 3167583_1 (GHMatters) P89639.AU 22/02/12 - 12 coupling element of a prime mover. The A trailer has a substantially uniform deck height of about 1.43 metres, i.e. the conventional deck height of s standard curtain-sider trailers and of the upper deck of drop deck trailers. The deck height of the B trailer 50 is also flat and is more or less level, but is somewhat lower at about 1.09 10 metres at the front and sloping down to about 1.06 metres at the rear. It is preferably less than 1 .lm at the rear. This is similar to the lower deck height of drop deck trailers but is here achieved by different means. A second tn-axial wheel group 65 for the trailer set 10 comprises is wheels 66, also carrying tyres of type 245170R 19.5, and is disposed at or towards the rear of the trailer. At the front of trailer 50, instead of a raised deck the chassis 52 has a front section 53 comprising a structural unit that includes multiple beam sections linked by vertically 20 spaced upper and lower structural plates 70,71 (Figs. 3 and 4A) extend the full width of the trailer and are therefore rectangular in plan. The structural unit 53 is of a sandwich type construction. The beam sections of structural unit 53 are welded between and to these plates 25 and include thinned front sections 62a of the two main chassis I-beams 62 that extend the full length of the trailer. It will be seen in Figure 1 that these chassis beams each include a section 62b behind front chassis section 53 in which the lower edge is tapered between the 30 two depths of the chassis beams, i.e. 400mm and under 100mm. There are two further longitudinal beam sections 72,73 at each side between plates 70,71, located outside main beam segments 62a, plus front and rear transverse beam segments 74,75 and a pair of central transverse 35 segments 76 that support a central coupling element 68. This element, e.g. a king pin, is engageable with a socket 39 of a coupling element 40 (Fig. 2). The coupling element 3167583_1 (GHMatters) P89639.AU 22/02/12 - 13 40, or 'fifth wheel' in this embodiment, is upstanding from trailing chassis section 34 of the A trailer 20. The vertical extent of the structural unit comprising front chassis section 53 is 125mm or less, typically 100mm. In 5 this embodiment the beams, within the structural unit 53, are 60mm high and the plates 70,71 are 8mm thick so the unit 53 is about 76mm deep. Upper structural plate 70 of chassis front section 10 structural unit 53 provides the forward part of the floor 54 of the B trailer 50, as best seen in Figure 4A: the balance of the floor is provided by floor plating 55 (Fig. 3) fixed atop chassis beams 62 and reinforced by a frame 76 of steel joists and bearers. The lower structural plate 15 71 has a smooth undersurface and is designed to provide minimum but snag-free clearance over the mud guards 37 of wheels 36 during a turning manoeuvre. In alternative arrangements, the plates 70, 71 of front 20 chassis section 53 may be in sections instead of a full width plate as illustrated, or the front chassis section 53 may comprise multiple narrowly spaced cross-members rather than a few beam segments sandwiched by plates to create smooth surfaces over the tyres. 25 It will be appreciated from Figure 1 that the height of front chassis section 33 of the A trailer 20 is such as to accommodate wheels on a prime mover drawing the B double set that are substantially larger than the wheels 36,66. 30 The latter are thus smaller wheels than are conventional on prime movers, e.g. wheels of tyre type 11 R 22.5. This allows the trailing chassis section 34 of the A trailer to hang down substantially relative to the deck height of the A trailer. By then coupling this arrangement with the 35 special thin chassis section 53 at the front of B trailer chassis 52, a uniform lower deck height is obtained in the B trailer and a substantially greater cargo volume 3167583_1 (GHMatters) P89639.AU 22/02/12 - 14 achieved below the roof line - greater than with a drop deck trailer of similar length. In the depicted trailers, the vehicle trailer height is set at 4.3 metres, the standard regulation height, but it is thought feasible to 5 obtain a permit for 4.6 metres given the lower centre of gravity achieved by the lower deck height (the current regulation is that a minimum 50% of the trailer deck must be blow 1200mm in order to have the overall height over 4.3m and up to 4.6m). In this way, a double benefit can be 10 obtained. Both trailers are provided with conventional retractable stands 80 for propping the front end of the trailer when it is unsupported by a lead trailer or prime mover. Both 15 trailers would also typically be provided with longitudinally extending coaming rails 82,92 at each side, but on the B trailer, a conventional coaming rail does not extend into the area of the front chassis section 53 because it will be below the level of structural plate 71 20 and may thereby strike the mud guards 51 of wheels 36 in a turning manoeuvre. The coaming rail is employed as a hook point for the vertical curtain tensioner devices that travel with the curtain along its rail and are spaced along the length of the curtain and of the trailer. Figure 25 4B iilustrates a preferred arrangement by which the hooks of the trailer's curtain may be attached in the absence of the combing rail. At locations along its length spaced to complement the spacing of the curtain hooks (typically 600mm) the front chassis section 53 includes cutouts 103 30 at the edges of its lower plate 71. The cutouts 103 permit access upwardly into the interior of the chassis section 53. Therein short longitudinal rails 105 are mounted. To secure the curtain hook 105, an operator passes the hook 104 upwardly through the opening 103 and engages the rail 35 105, and then tensions the hook's strap. Alternatively, hook receiving slots might be formed in the side walls of the unit 53. 3167583_1 (GH Matters) P89639.AU 22/02/12 - 15 Alternatively, a conventional coaming rail can be transitioned into the front chassis section 53 and a reduced height coaming facility, for example by continuing 5 only the top edge of the combining rail, welded to the chassis section. A modification to suit the very thin form of the front chassis section 53 of B trailer 50 is the location of the io ratchet devices for longitudinally tensioning the curtain. A suitable arrangement is shown in Figures 5A to 8. Here, the curtain 60 at each side is secured to a vertical pole 95 rotatably supported in brackets 96, 97 at top and bottom of the end wall 58a. A ratchet mechanism 98 under is lower bracket 97 includes a hand lever 99 for rotating pole 95 against a ratchet (not shown) for tensioning the curtain. The ratchet mechanism 98 is attached to a front face of a front wall of the trailer. As is shown in figure 6, the ratchet mechanism 98 is positioned wholly above a 20 lower surface at the lower plate 71. As such no portion of the ratchet mechanism 98 projects downwardly beyond the plate 71 so as not to present a snagging point to interfere with the prime mover and/or lead trailer. 25 In general, curtain tensioning can be achieved by the use of ratchets at the front, or of an over centre device or by having the curtains pinned at the front and tensioned at the rear. 30 Figures 9A, 98 and 9C illustrate trailer sets at 10A, 10B and 10C in accordance with alternative embodiments of the invention. The trailer 10A includes a lead trailer 20 as in trailer 35 set 10 of Figure 1, and a B trailer 50A. The trailer 50A includes a front chassis section 53A of similar construction to chassis section 53. Rearward of the front 3167583_1 (GHMatters) P89639.AU 22/02/12 - 16 chassis section 53A the floor 54A steps down at, step down 93, by about 490mm. Further rearward of the step down 93, the floor 54A is stepped up, at step up 100. The chassis of trailer 50A is thus segmented into the forward chassis 5 section 53A, a central chassis section 53B and a rearward chassis section 53C. The central chassis section 53B, defined by steps 93, 100 sits below a height required for wheel clearance to 10 maximise the internal cargo carrying volume of the trailer. The central chassis section 53B sits as low as ground clearance will permit. In this embodiment, the step down 93 is about 3700mm from the front of the trailer. This distance corresponds to a minimum distance required 15 to clear the lead trailer's wheels 36 during turning manoeuvres extended to accommodate a discrete number of standard pallets in the lengthwise direction. A standard pallet typically has a footprint of about 1170mm by 1170mm. Thus, the front chassis section neatly 20 accommodates three standard pallets in a longitudinal direction, and the front chassis section 53A can carry a total of 12 typical, 1500mm high, pallets (3 along by 2 across by 2 high). 2S The step up 100 is similarly positioned as far rearward as possible as will allow clearance for the trailer's wheel 66A and allow each of the sunken central chassis section 53B and the rearward chassis section 53C to accommodate a discrete number of standard pallets along their length. 30 The trailer 50A is referred to as a double drop deck because it includes two steps. The described trailer 50A has a clearance under its front chassis section of about 1015mm and as such is adapted to cooperate with the lead 35 trailer 20 including its smaller than conventional wheels and lower than conventional fifth wheel height. It is contemplated that a similar double drop deck construction 3167583_1 (GHMatters) P89639.AU 22/02/12 - 17 might be applied to a trailer adapted to cooperate with a lead trailer or prime mover having conventional wheels and a conventional fifth wheel height. As such the height of the front chassis section 53A varies depending on the 5 fifth wheel height (which of course relates to the wheel size) of the prime mover or lead trailer. By way of example the trailer 50A could be modified to cooperate with a prime mover having standard ground wheels and a standard fifth wheel height by elevating the front chassis 10 section 53A to have a ground clearance of about 1250mm and by making a corresponding increase in the size of the step down 93 whereby the cargo carrying volume is reduced only in the front section of the trailer. 15 The trailer set 10B includes the B trailer 50A and a drop deck lead trailer 20A. The lead trailer 20A includes a front chassis section 33A which is relevantly similar to the front chassis section 33 of the trailer 20. About 3700mm from the front of the trailer, the chassis is 20 stepped down at step down 101, by about 480mm. Thus increasing the cargo carrying capacity rearward of the step down 101. The stepped down cargo carrying portion of the chassis 33B is made up of beams which project horizontally, rearwards to define rearward chassis portion 25 34. As such the chassis portions 33B and 34 are horizontally aligned. The step down 101 is located so that each of the chassis portions 33A and 33B neatly accommodate a discrete number 30 of standard pallets. The trailer set 10C includes the B trailer 50A and a double drop deck A trailer 20B. The double drop deck trailer 20B varies from the drop deck trailer 20A in that 35 its step down 101A is deeper than the step down 101 (it is about 710 mm deep) and rearward of the rear cargo carrying portion of the chassis 33B prime there is a step up 102 to 3167583_1 (GHMatters) P89639.AU 22/02/12 - 18 the rear, ground wheel carrying, portion of the chassis 34. As such the rear cargo carrying portion of the chassis 33B' is positioned as low as ground clearance will permit and the rear chassis portion 34 s stepped up to a height 5 sufficient to accommodate wheels and suspension, etc. In this embodiment the step up 102 is about 220mm high. It will be understood that a variety of modifications of the illustrated arrangements are possible within the io concepts of the invention. For example, the A trailer may also be formed with a low deck and the front section 33 of the chassis constructed in a fashion similar to the front section 53 of the B trailer chassis 52, either in an arrangement of minimised deck height with standard prime is mover wheel diameters, or to complement a prime mover with smaller diameter rear wheels, e.g. wheels of an outside diameter less than 900mm, e.g. in the range 750 to 900mm (e.g. tyre types 245170R 19.5 or 255170R 19.5). With such a configuration, the deck height in both trailers can be 20 the same or substantially the same minimised deck height. These alternative A trailer constructions are within the ambit envisaged by the present inventive concept. The various illustrated B trailers may be employed in a 25 single trailer set with a prime mover fitted with rear wheels similar in size to the illustrated A trailers. In another optional modification, any of the trailers may be fitted with a mezzanine deck in an arrangement known 30 per Se. This is especially advantageous with the uniform low deck B trailer, as drop-deck trailers fitted with mezzanine decks require different height pallets for maximum utilisation of the available space. The trailer will of course readily also accept currently used load 35 restraint devices such as side gates, sliding gates and load restraint curtains. 31675831 (GHMatters) P89639.AU 22/02/12 - 19 It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of 5 these different combinations constitute various alternative aspects of the invention. 3167583_1 (GHMatters) P89639.AU 22/02/12