WO2025073010A1 - An improved arrangement for an articulated vehicle, super a-double trailer - Google Patents

Abstract

A trailer for use as part of an articulated vehicle, and suitable for use as the lead trailer of a Super A-double vehicle, or as the first and/or second trailer of a B-triple vehicle, the trailer including: a frame for supporting a cargo, the frame including a front end and a rear end;a front coupler at the front end for pivotable coupling to a prime mover or another trailer or dolly; a plurality of support axle assemblies mounted on the frame and disposed generally near the rear end for operatively supporting ground engaging wheels, the support axle assemblies being spaced apart along the frame, a front axle of the plurality being laterally fixed, a second axle assembly being spaced towards the rear end of the frame being fixed or steerable, and a third axle assembly in the plurality of support axles being steerable.

Description

AN IMPROVED ARRANGEMENT FOR AN ARTICULATED VEHICLE, SUPER A- DOUBLE TRAILER Technical Field [0001] The present technology relates generally to articulated vehicles. [0002] Arrangements of embodiments are suitable for trailers in what is known as a Super A- Double vehicle arrangement, or as the first and/or second trailer of a B-triple vehicle arrangement. [0003] It should be appreciated that the present technology is not limited to those uses only. Embodiments of the invention relate to an arrangement which improves the cornering performance, in terms of swept path maximum, of an articulated vehicle up to 36.5 metres long. Background Art [0004] Articulated vehicles, in particular B-double and B-triple vehicles, are used extensively for road transportation of heavy and oversized loads. [0005] They can be difficult, or dangerous, to manoeuvre on public road systems. [0006] The size of these B-double and B-triple vehicles, has resulted in their access being restricted in metropolitan areas in many Australian states, including New South Wales, Victoria and South Australia to Level 2A, 26 metre length B Double. [0007] As a response to this kind of restriction, there have been numerous proposals for improving manoeuvrability. However, the proposals either are not suited for use in relation to B-double or B-triple vehicles, or involve excessive complexity and cost. [0008] The present invention seeks to provide an arrangement preferably suited for use in Super A-Double and B-triple vehicles, which substantially ameliorates one or more of the abovementioned disadvantages. Summary of Invention [0009] Broadly, the present technology provides a vehicle that, for a given length, complies with more stringent performance-based standards than current vehicles, in that the vehicles have a reduced maximum width of a swept path in a prescribed 900 low speed turn. [0010] This reduced swept path width may enable approval for operation on a greater range of approved networks of the public road system. [0011] According to one aspect of the present invention there is provided a trailer for use as part of an articulated vehicle, and suitable for use as the lead trailer of a Super A-double vehicle, or as the first and/or second trailer of a B-triple vehicle, the trailer including: a frame for supporting a cargo, the frame including a front end and a rear end; a front coupler at the front end for pivotable coupling to a prime mover or another trailer or dolly; a plurality of support axle assemblies mounted on the frame and disposed generally near the rear end for operatively supporting ground engaging wheels, the support axle assemblies being spaced apart along the frame, a front axle of the plurality being laterally fixed, a second axle assembly being spaced towards the rear end of the frame being fixed or steerable, and a third axle assembly in the plurality of support axles being steerable. [0012] According to another aspect of the present invention there is provided a trailer for use as part of an articulated vehicle, the trailer including: a frame for supporting a cargo, the frame including a front end and a rear end; a front coupler at the front end for pivotable coupling to a prime mover or another trailer or dolly; a plurality of support axle assemblies mounted on the frame and disposed generally near the rear end for operatively supporting ground engaging wheels, the support axle assemblies being spaced apart along the frame; wherein the front coupler includes a king pin mounting plate with a plurality of king pin receivers. [0013] In an embodiment the front coupler includes a king pin mounting plate with a plurality of king pin receivers. [0014] In an embodiment the king pin mounting plate includes two king pin receivers, 100mm apart along a longitudinal axis. [0015] In an embodiment the third axle assembly in the plurality of support axle assemblies is self tracking. [0016] In an embodiment the third axle assembly in the plurality of support axle assemblies includes a steering mechanism that is controllable to pivot the ground engaging wheels between 0 and 25 degrees to either side of a longitudinal direction defined by a longitudinal axis extending along the frame from front to rear. [0017] In an embodiment the ground engaging wheels pivot 14 degrees left or right. [0018] In an embodiment the third axle assembly in the plurality of support axle assemblies includes a steering mechanism that is selectively lockable. [0019] In an embodiment the third axle assembly in the plurality of support axle assemblies includes a steering mechanism that is automatically lockable into a straight position when the trailer is travelling over a selected speed. [0020] In an embodiment the trailer frame is 14600mm long, but it could be 9m, 10m, 11m, 12m, 13m or 14m or 15m or 16m long. [0021] In an embodiment the plurality of support axle assemblies is spaced apart from one another by 1350mm. The axle assemblies could be spaced apart by 1000mm, 1100mm, 1 200mm or 1400mm or 1500mm. [0022] In an embodiment the third axle assembly in the plurality of support axle assemblies is spaced from the rear end of the trailer frame by 2330mm. [0023] In an embodiment the plurality of support axles is underslung. [0024] In an embodiment the third axle assembly with steering assembly includes an underslung suspension arrangement. [0025] In an embodiment the underslung suspension arrangement includes one or more air springs. [0026] In an embodiment the second axle assembly with steering assembly is mounted on an underslung suspension arrangement. [0027] In an embodiment the coupler is a downwardly depending king pin or traction pin. [0028] In an embodiment the king pin is spaced from the front of the trailer frame by 1620mm. The king pin could be spaced from the front of the trailer by 1400, 1450, 1500, 1550, 1 600 or 1650 or 1700 or 1750 or 1800mm. [0029] In an embodiment there is a dolly provided, which is configured to be mounted under the king pin. [0030] In an embodiment the dolly includes a frame with a pair of spaced apart support axle assemblies. [0031] In an embodiment the axle assembly spacing on the dolly is 1350mm. The axle assemblies could be spaced apart by 1000mm, 1100mm, 1200mm or 1400mm or 1 500mm. [0032] In an embodiment the spacing between the king pin and the rear end of the trailer is 12980mm. [0033] In an embodiment there is a rear coupling at the rear end of the frame for coupling to a dolly of a like trailer disposed at a rearward position behind the trailer. [0034] In an embodiment the rear coupling is set in from the rear end of the trailer by 300mm. [0035] In an embodiment the dolly is 3300mm from the centre of an end of a coupling arm and a fifth wheel or turntable disposed on the frame between the two dolly axle assemblies. [0036] In an embodiment there is provided a second front coupler at the front end of the frame, to provide a different pivot point for further improved manoeuvrability at low speed. [0037] According to a further aspect of the present technology there is provided an articulated vehicle including: a prime mover or tractor unit with a driver’s cab and a fifth wheel; and a trailer for use as part of an articulated vehicle, and suitable for use as the lead trailer of a Super A-double vehicle, or as the first and/or second trailer of a B-triple vehicle, the trailer including: a frame for supporting a cargo, the frame including a front end and a rear end; a front coupler at the front end for pivotable coupling to a prime mover or another trailer or dolly; a plurality of support axle assemblies mounted on the frame and disposed generally near the rear end for operatively supporting ground engaging wheels, the support axle assemblies being spaced apart along the frame, a front axle of the plurality being laterally fixed, a second axle assembly being spaced towards the rear end of the frame being fixed or steerable, and a third axle assembly in the plurality of support axles being steerable. [0038] In an embodiment the articulated vehicle includes a dolly which includes a frame with a pair of spaced apart support axle assemblies and a pivoting coupling arm extending from the frame, and a fifth wheel or turntable disposed on the frame between the two spaced apart support axle assemblies. [0039] In an embodiment the steering mechanism includes a control mechanism, such as for example a mechanism that is hydraulically, pneumatically or electrically operable. [0040] In an embodiment the steering axle is controlled by a hydraulic, pneumatic or electrically operable locking mechanism by which the, or each, steerable axle is able to be held against steering above a nominal speed. [0041] In operation, in an embodiment the steering by the, or each, steering axle is permitted only during low speed travel, such as when required for tight turns, such as encountered in built up areas. At higher speeds at which the, or each, steering axle is locked, the steering axle performs in the same way as a fixed axle. In operation the multi-axle system is configured to overcome the cornering performance restrictions applicable to longer B- doubles greater than 26 metres in overall length. Brief Description of Drawings [0042] To enable a clearer understanding, an embodiment of the invention will hereinafter be described with reference to the drawings, and in those drawings: [0043] Fig.1 is a side elevation view of a trailer assembly showing two trailers and a dolly, the trailer assembly connected to a prime mover; [0044] Fig.2 is an isometric view from above and a left side of a different trailer assembly from that shown in Fig.1 and without the side walls of a trailer body; [0045] Fig.3 is a side view of a rear portion of the trailer frame which shows three supporting axle assemblies mounted thereon, with the third one at a rear end of the trailer frame being underslung and steerable, the front two being fixed; [0046] Fig.4 is an underside view of the rear portion of the trailer frame as shown in Fig.3 with the third supporting axle being steerable and underslung, the front two being underslung and fixed; [0047] Fig.5 is an isometric view from the rear end of the trailer frame of the underslung and steerable support axle assembly shown in Figs.3 and 4; [0048] Fig.6 is a plan view of the underslung third support axle assembly; and [0049] Fig.7 is a side section view from the middle, of the underslung third support axle assembly. Description of Embodiments [0050] Referring to the drawings there is shown a trailer generally indicated at 10. The trailer is for use as part of an articulated vehicle 100, and is suitable for use as the lead trailer 10 of a Super A-double vehicle 100, or as the first and/or second trailer of a B-triple vehicle. [0051] The trailer 10 includes a frame 20 for supporting a cargo (not shown), the frame 20 including a front end 22 and a rear end 24. [0052] The trailer 10 also includes spaced apart walls 12 which retain and protect the cargo. There can also be a refrigerator unit 15. [0053] There is a front coupler 30 at the front end 22 for pivotable coupling to a prime mover 50 or another trailer or dolly 70, as well as a plurality of support axle assemblies 40 mounted on the frame 20 and disposed generally near the rear end 24 for operatively supporting ground engaging wheels 45. [0054] The coupler is a downwardly depending king pin 31 or traction pin. The king pin is spaced from the front of the trailer frame by 1620mm. The king pin could be spaced from the front of the trailer by 1400, 1450, 1500, 1550, 1600 or 1650 or 1700 or 1750 or 1 800mm. To facilitate improved manoeuvrability a second location for the king pin can be provided. The king pin is removable from a plate which has two spaced apart king pin receivers along a longitudinal axis and may be relocated in a position 100mm along from the main coupling location. The king pin may be threaded, or bayonet fitted, or fitted with a transverse pin or other suitable fastening method. [0055] The support axle assemblies 40 are spaced apart along the frame 20, a front axle 41 of the plurality 40 being fixed so that the wheels stay in line with the trailer’s longitudinal axis 99, a second axle assembly 42 being spaced towards the rear end 24 of the frame 20 being either fixed or steerable, and a third axle assembly 43 in the plurality of support axles 40 is steerable. [0056] The second axle assembly 42 or third axle assembly 43 in the plurality of support axle assemblies may be steerable automatically or passively, or it may be driven by a drive system so as to force a change in direction relative to the longitudinal axis 99. [0057] Axle 46 of the steerable axle assembly is supported underneath by a trailing arm 49. At the end of the trailing arm 49 is an airbag 48 for spring suspension of the axle 46. [0058] A steering mechanism 60 in one form is self tracking which includes a steering pin 61 and steering arms 62, the latter pivotally mounted at ends of the underslung axle 46. The steering arms 62 are at one end operatively mounted to a wheel hub 47 on which the wheels 45 rotatably mount. Since there is a lateral offset between the steering pin centre 61 and the tyre contact patch, the steering arms 62 can maintain a track themselves using the adhesion resistance between the tyre and the road. The arms 62 turn under the influence of the friction between the tyre 45 and road. [0059] There may also be a drive system which can drive the steering arms 62 even when the friction does not change the angle, a hydraulic ram 51 can change the angle of the steering arms 62, the ram connected to a sensor or a mechanism which monitors the angle between the prime mover 50 and the trailer frame 10, or the front trailer 10 and the rear trailer 10a, or the dolly and the rear trailer 10a. [0060] The third axle assembly in the plurality of support axle assemblies includes a steering mechanism that is controllable to rotate the ground engaging wheels between 0 and 25 degrees to either side of a longitudinal direction defined by a longitudinal axis extending along the frame from front to rear. [0061] The steering mechanism 60 has a lock that can be selected or automatically lockable over a selected speed. [0062] To facilitate the increased manoevrability the trailer frame is 14600mm long, but it could be 9m, 10m, 11m, 12m, 13m or 14m or 15m or 16m long. [0063] The plurality of support axle assemblies is spaced apart from one another by 1350mm. But to amend the manoeuvring performance the axle assemblies could be spaced apart by 1 000mm, 1100mm, 1200mm or 1400mm or 1500mm. [0064] The third axle assembly in the plurality of support axle assemblies is spaced from the rear end of the trailer frame by 2330mm to provide the selected manoeuvrability. [0065] The dolly 70 provided, is configured to be mounted under the trailer 10A king pin 31. The dolly 70 includes a frame with a pair of spaced apart support axle assemblies. The axle assembly spacing on the dolly is 1350mm. The dolly axle assemblies could be spaced apart by 1000mm, 1100mm, 1200mm or 1400mm or 1500mm. [0066] The spacing between the king pin and the rear end of the trailer is 12980mm. [0067] There is a rear coupling 75 at the rear end of the frame for coupling to a dolly of a like trailer disposed at a rearward position behind the trailer. [0068] The rear coupling is set in from the rear end of the trailer by 300mm. It is a Ringfeder coupling. [0069] The dolly is 3300mm from the centre of an end of a coupling arm and a fifth wheel or turntable disposed on the frame between the two dolly axle assemblies. [0070] There is provided a second front coupler at the front end of the frame, to provide a different pivot point for further improved clearance at low speed. [0071] The front coupler includes a king pin mounting plate with a plurality of king pin receivers. The king pin mounting plate is mounted to the underside of the front of the trailer frame and includes two king pin receivers, 100mm apart along a longitudinal axis. The idea is that, while the radius of turn may end up slightly larger, the trailers may not hit one another on tight turns. [0072] An articulated vehicle 100 is shown, which includes: a prime mover or tractor unit with a driver’s cab and a fifth wheel; and a trailer for use as part of an articulated vehicle, and suitable for use as the lead trailer of a Super A-double vehicle, or as the first and/or second trailer of a B-triple vehicle, the trailer including: a frame for supporting a cargo, the frame including a front end and a rear end; a front coupler at the front end for pivotable coupling to a prime mover or another trailer or dolly; a plurality of support axle assemblies mounted on the frame and disposed generally near the rear end for operatively supporting ground engaging wheels, the support axle assemblies being spaced apart along the frame, a front axle of the plurality being laterally fixed, a second axle assembly being spaced towards the rear end of the frame being fixed or steerable, and a third axle assembly in the plurality of support axles being steerable. [0073] The articulated vehicle 100 includes a dolly 70 which includes a frame with a pair of spaced apart support axle assemblies and a pivoting coupling arm extending from the frame, and a fifth wheel or turntable disposed on the frame between the two spaced apart support axle assemblies. [0074] The steering mechanism includes a control mechanism, such as for example a mechanism that is hydraulically, pneumatically or electrically operable. [0075] In an embodiment the steering axle is controlled by a hydraulic, pneumatic or electrically operable locking mechanism by which the, or each, steerable axle is able to be held against steering above a nominal speed. IN OPERATION [0076] In operation, in an embodiment the steering by the, or each, steering axle is permitted only during low speed travel, such as when required for tight turns, such as encountered in built up areas. At higher speeds at which the, or each, steering axle is locked, the steering axle performs in the same way as a fixed axle. In operation the multi-axle system is configured to overcome the cornering performance restrictions applicable to longer B- doubles greater than 26 metres in overall length. [0077] The embodiments described provide additional articulation increasing the manoeuvrability creating improved vehicle performance and handling. This advancement gives the combination reduced regulatory restrictions allowing this 34-metre class 3A PBS (performance based standards) combination to meet the same performance standards as a much smaller 26 metre class 2B PBS combination making this vehicle combination the longest vehicle ever to be built for Australian roads and approved by Australian regulatory authorities to be utilised in metropolitan areas of Australia. [0078] That is, the vehicle can be 35.5m long, (PPS Vehicle Class 3A / 36.5 metre vehicle) but is approved and operates as a 2B performance standard, same as a 26 metre vehicle. [0079] The conditions for approval for this type of trailer appear below, demonstrating the increased maneuvrability through a very wide range of suburban and urban settings: Transport for New South Wales (TfNSW) [0080] NSWOBM01Heavy Vehicle Movement - New South Wales On Board Mass Monitoring (OBM) On Board Mass Monitoring 1. The vehicle must have an On-Board Mass (OBM) system that has been approved by Transport Certification Australia (TCA) and that meets the requirements of the Interim OBM Mass Monitoring Business, Operational and Technical Requirements issued by TCA.2. When an OBM system type approved by TCA becomes available for use in the IAP, all vehicle combinations operating under this permit will be required to transition to an OBM system that is type approved by TCA for use in the IAP, at a timeframe specified by Roads and Maritime. “OBM system that is type-approved by TCA” means On-Board Mass scales or weighting devices or load cell systems capable of accurately measuring vehicle axle and gross weights that are type-approved by Transport Certification Australia.3. The OBM system must be maintained, operable and calibrated at least once every six months, commencing with calibration prior to the commencement of its use under this permit 4. The operator must provide OBM system calibration reports for each vehicle to their IAP Service Provider within five days of a calibration being completed. The IAP Service Provider will provide calibration reports to Roads and Maritime.5. Roads and Maritime must be provided with reports from the OBM measuring systems in the format and timeframes as provided in the Interim OBM Mass Specifications. Where a permit issued to multiple vehicles, the conditions specified in Clauses 1 to 5 apply to each vehicle listed in the PBS Vehicle Approval. [0081] NSWPBSIP01As this is an in-principle vehicle, the customer must supply the following information when the ‘as built’ vehicle is requiring road access: • The vehicle drawing number and date • Any relevant PBS Design Approval and Vehicle Approval • The in- principle approval that has been provided by the NHVR In the event that the above information is not provided, the ‘as built’ vehicle will be considered a ‘new’ application and will be subject to further assessment including bridge and third party rail assessments. The ‘as built’ vehicle and route must be identical to the in-principal application in order for Transport Roads and Maritime Services to expedite the access application. Whilst geometric access will be the same any variations between the in-principle vehicle and ‘as built’ vehicle (i.e. axle spacings) will be subject to further assessment including bridge and third party rail assessments. Additionally any variations to the initial assessed route will require further assessment. [0082] RAMPBS01The combination must not exceed the following masses on route 465512. Steer Axle -6.5t Drive Axle -14t Lead Trailer - 17t Dolly - 14t Rear Trailer -17t [0083] FM01Operator must have a fatigue management plan that identifies sufficient suitable rest opportunities for the vehicle on the route. [0084] RMSSE01The vehicle must be fitted with all of the following advanced safety equipment o Autonomous Emergency Braking o Electronic Stability Control o Electronic Brake Distribution o Lane Departure Warning System o Underrun protection fitted to the front, sides and rear of the vehicle [0085] TMA01The hauling unit/s identified in this permit must be enrolled and monitored in Telematics Monitoring Application (TMA) or the Intelligent Access Program (IAP). A current Certificate of Enrolment must be carried in the hauling unit/s, which indicates enrolment in TMA or IAP. In Principle - Department of Transport - Victoria [0086] APBSPIP01NHVR Case No: 465512 for Alvaro Transport Pty Ltd requesting an ‘In Principle’ approval to operate a 34.25m A-Double (3-2-3) combination on journey ID:13UDI-1 v38 at the mass of 68.5tonnes tonnes. [0087] An assessment has been conducted by the VicRoads Asset Services for the submitted 34.25m A-Double (3-2-3) combination with a gross mass of 68.5tonnes. [0088] The vehicle combination meets the required specifications for access on the nominated route Network for the approved mass of 68.5 tonnes. In order to travel at the approved mass the operator must use the nominated route. [0089] Consent for an "In-Principle" approval is granted to allow the vehicle combination at the approved gross combination mass of 68.5tonnes on the VicRoads managed roads, nominated routes and specified network (if applicable). [0090] The operator must adhere to the specified operating conditions per PBS In-Principle Assessment IP1687. [0091] Please note should there be any changes to the mass or dimensions of the vehicle a bridge reassessment of the route will be required. [0092] VRTP04Permission must be obtained and carried from the Department of Transport prior to traversing any railway track where the heavy vehicle overall combination length exceeds 26.0m. Contact must be made to the "Over Dimension Load Team" via the following communication channels email: odlpermit@transport.vic.gov.au, mobile: 0417 054626. For further information relating to the process please see https://transport.vic.gov.au/ways-to-travel/road/over-dimensional-load-permits Wyndham City Council movement - Report of Damage

heavy vehicle damages assets or infrastructure, contact must be made with Traffic and Transport Department of Wyndham City Council via 039742 0777 with receipt of the advised damage from the road manager. A written statement of the damage must be recorded and provided in writing to the road manager prior to repairs of the damaged infrastructure or asset. Penrith City Council

movement - Report of Damage event heavy vehicle damages assets or infrastructure, contact must be made with Alexx Alagiah of Asset Management via 0247327584 with receipt of the advised damage from the road manager. A written statement of the damage must be recorded and provided in writing to the road manager prior to repairs of the damaged infrastructure or asset. Travel Transport for New South Wales (TfNSW) [0095] RS01Restricted Speed Condition - Speed on Specific Roads Speed restriction - The heavy vehicle is restricted to a maximum speed limit of 90 kph on the approved route, except where a traffic sign indicates a lower speed limit. [0096] NSWPBSL3Map03ACompliance with any listed conditions applicable to the area or route shown on the PBS 3A HML network or PBS 3A GML and CML network maps available at www.rms.nsw.gov.au/pbsmap [0097] It will be understood to persons skilled in the art of the invention that many modifications may be made without departing from the spirit and scope of the invention. [0098] It is to be understood that any prior art publication referred to herein does not constitute an admission that the publication forms part of the common general knowledge in the art. [0099] In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

Claims

CLAIMS: 1. A trailer for use as part of an articulated vehicle, and suitable for use as the lead trailer of a Super A-double vehicle, or as the first and/or second trailer of a B-triple vehicle, the trailer including: a frame for supporting a cargo, the frame including a front end and a rear end; a front coupler at the front end for pivotable coupling to a prime mover or another trailer or dolly; a plurality of support axle assemblies mounted on the frame and disposed generally near the rear end for operatively supporting ground engaging wheels, the support axle assemblies being spaced apart along the frame, a front axle of the plurality being laterally fixed, a second axle assembly being spaced towards the rear end of the frame being fixed or steerable, and a third axle assembly in the plurality of support axles being steerable.

2. The trailer in accordance with claim 1 wherein the third axle assembly in the plurality of support axle assemblies is self tracking.

3. The trailer in accordance with claim 1 or 2 wherein the third axle assembly in the plurality of support axle assemblies includes a steering mechanism that is controllable to rotate the ground engaging wheels between 0 and 25 degrees to either side of a longitudinal direction defined by a longitudinal axis extending along the frame from front to rear.

4. The trailer in accordance with any one of claims 1 to 3 wherein The trailer in accordance with claim 1 wherein the third axle assembly in the plurality of support axle assemblies includes a steering mechanism that is selectively lockable.

5. The trailer in accordance with any one of claims 1 to 4 wherein the third axle assembly in the plurality of support axle assemblies includes a steering mechanism that is automatically lockable into a straight position when the trailer is travelling over a selected speed.

6. The trailer in accordance with any one of claims 1 to 5 wherein the trailer frame is 14 600mm long.

7. The trailer in accordance with any one of claims 1 to 6 wherein the trailer is 9m, 10m, 11m, 12m, 13m or 14m or 15m or 16m long.

8. The trailer in accordance with any one of claims 1 to 7 wherein the plurality of support axle assemblies is spaced apart from one another by 1350mm.

9. The trailer in accordance with any one of claims 1 to 8 wherein the axle assemblies are spaced apart by 1000mm, 1100mm, 1200mm or 1400mm or 1500mm.

10. The trailer in accordance with any one of claims 1 to 9 wherein the third axle assembly in the plurality of support axle assemblies is spaced from the rear end of the trailer frame by 2 330mm.

11. The trailer in accordance with any one of claims 1 to 10 wherein the plurality of support axles is underslung.

12. The trailer in accordance with any one of claims 1 to 11 wherein the third axle assembly with steering assembly includes an underslung suspension arrangement.

13. The trailer in accordance with any one of claims 1 to 12 wherein the underslung suspension arrangement includes one or more air springs.

14. The trailer in accordance with any one of claims 1 to 13 wherein the second axle assembly with steering assembly is mounted on an underslung suspension arrangement.

15. The trailer in accordance with any one of claims 1 to 14 wherein the coupler is a downwardly depending king pin or traction pin.

16. The trailer in accordance with any one of claims 1 to 15 wherein the king pin is spaced from the front of the trailer frame by 1620mm.

17. The trailer in accordance with any one of claims 1 to 16 wherein the king pin is spaced from the front of the trailer by 1400, 1450, 1500, 1550, 1600 or 1650 or 1700 or 1750 or 1 800mm.

18. The trailer in accordance with any one of claims 1 to 17 wherein there is a dolly provided, which is configured to be mounted under the king pin.

19. The trailer in accordance with any one of claims 1 to 18 wherein the dolly includes a frame with a pair of spaced apart support axle assemblies.

20. The trailer in accordance with any one of claims 1 to 19 wherein the axle assembly spacing on the dolly is 1350mm.

21. The trailer in accordance with any one of claims 1 to 20 wherein the axle assemblies on the dolly are spaced apart by 1000mm, 1100mm, 1200mm or 1400mm or 1500mm.

22. The trailer in accordance with any one of claims 1 to 21 wherein the spacing between the king pin and the rear end of the trailer is 12980mm.

23. The trailer in accordance with any one of claims 1 to 22 wherein there is a rear coupling at the rear end of the frame for coupling to a dolly of a like trailer disposed at a rearward position behind the trailer.

24. The trailer in accordance with any one of claims 1 to 23 wherein the rear coupling is set in from the rear end of the trailer by 300mm.

25. The trailer in accordance with any one of claims 1 to 24 wherein the dolly is 3300mm from the centre of an end of a coupling arm and a fifth wheel or turntable disposed on the frame between the two dolly axle assemblies.

26. The trailer in accordance with any one of claims 1 to 25 wherein there is provided a second front coupler at the front end of the frame, to provide a different pivot point for further improved manoeuvrability at low speed.

27. An articulated vehicle including: a prime mover or tractor unit with a driver’s cab and a fifth wheel; and a trailer for use as part of an articulated vehicle, and suitable for use as the lead trailer of a Super A-double vehicle, or as the first and/or second trailer of a B-triple vehicle, the trailer including: a frame for supporting a cargo, the frame including a front end and a rear end; a front coupler at the front end for pivotable coupling to a prime mover or another trailer or dolly; a plurality of support axle assemblies mounted on the frame and disposed generally near the rear end for operatively supporting ground engaging wheels, the support axle assemblies being spaced apart along the frame, a front axle of the plurality being laterally fixed, a second axle assembly being spaced towards the rear end of the frame being fixed or steerable, and a third axle assembly in the plurality of support axles being steerable.

28. The articulated vehicle in accordance with claim 27 wherein the articulated vehicle includes a dolly which includes a frame with a pair of spaced apart support axle assemblies and a pivoting coupling arm extending from the frame, and a fifth wheel or turntable disposed on the frame between the two spaced apart support axle assemblies.

29. The articulated vehicle in accordance with claim 27 or 28 wherein the steering mechanism includes a control mechanism, such as for example a mechanism that is hydraulically, pneumatically or electrically operable.

30. The articulated vehicle in accordance with claim 27, 28 or 29 wherein the steering axle is controlled by a hydraulic, pneumatic or electrically operable locking mechanism by which the, or each, steerable axle is able to be held against steering above a nominal speed.