PBS B Double Combinations
A B Double combination refers to a category of combination that consists of a Prime Mover truck towing two trailers which is where the "double" part of the name comes from. The B in the title refers to the connection between the two trailers which is done through a fifth wheel mounted on the back of the front (often called lead) trailer. The advantages of a B Double over the general access Prime Mover and Semitrailer are the additional cubic capacity due to the second trailer and gross weight due to the additional axle group. A B double requires a specific lead trailer, which is often smaller in cubic capacity due to having the fifth wheel mounted to the rear. An exception to this are Stag B doubles and Super B Doubles carrying 2x40ft containers.
Common prescriptive B Doubles generally operate under the National Class 2 B-double Authorisation Notice. This allows for general access for B doubles less than 19m in overall length (Or longer in some jurisdictions i.e 21m in Tasmania). Longer B Doubles up to 26m in length very commonly operate under this authorisation on a set of roads commonly refered to as the 'B Double Network'. This page contains information on PBS Combinations and their potential benefits when operating outside the authorisation notice.
When it comes to B Doubles that require PBS Certification it is almost exclusively for combinations that exceed the 26m prescriptive limit. These are commonly refered to as Super Bs or Super B Doubles. Maximum length is not caped and in some rare cases exceeds 30m but more typically is within the 26-30m envelope as it provides the potential for better access, especially east of Gatton into Brisbane. PBS B Doubles typically fall into three subcategories with the potential for a combination to be in two or even all three categories.
Long Wheelbase Prime Mover
High Cubic or Container capacity trailers
Higher combination mass Quad Quad or Quad Tri combinations
B Doubles with long wheelbase prime mover
Commonly referred to as a 27m B Double this combination allows the use of a 'full size' long wheelbase prime mover with a 'full size' set of trailers. The common standard for a prescriptive 26m double is a 34Pallet set of trailers which when coupled to a cab over or short bonent truck neatly fits under 26m. With a longer Prime Mover however it is not possible to package a 34Pallet trailer set to be under 26m, leading to operators having to use 10pallet lead trailers and reducing overall capacity to 32Pallets. This can result in a tradeoff between driver comfort and carrying capacity. A 27m PBS B Double can eliminate this tradeoff usually with little downslide as access is still good due to the overall or axle mass weights not being increased. It should be noted that these combinations need to pass the PBS Level 2 swept path requirements which is often not possible with existing older trailers that have the tri group to far backwards on the rear trailer. When it comes to new trailers the design can be tweaked to ensure compliance with PBS swept path requirements with even the longest T909, C509 or whatever prime mover you desire.
High Cubic or Container Capacity Trailers
With the additional overall length allowance trailer sets can be optimised for maximum pallet carrying capacity which can be as much as 42Pallets when using a short cab over prime mover. This represents an additional 8 pallets over the standard 34Pallet prescriptive design a productivity increase of 24%. Axle configuration can to tailored to the weight of freight carried. Lighter freight tasks can make use of a standard tri-tri configuration which provides great access as the 68.5t overall mass is not exceeded which eliminates bridge assessments. For heavier freight a Quad Tri or Quad Quad axle configuration can be used as detailed below.
Quad Quad and Quad Tri B Doubles
PBS Quad Quad and Quad Tri Super B Doubles have been around for a number of years now and have provided operators with increased overall mass weights (Up to 77.5t or 73t respectivly) and payloads, along with approved network access in Vic, Tas and NSW and access being approved via permit for QLD. This combination is therefore a great option for both Container, General and Refrigerated Freight.
What are the different types of PBS Quad Quad Super B combinations?
The most common types of PBS Quad Quad Super B Doubles are units capped at 30mtrs in total length and can meet the HPFV Vic and NSW Reference Vehicle dimension requirements, as this provides the best access to set networks.
Combinations such as the 30m Quad Quad B Double Skel provide container operators with the option of moving two heavy 40ft boxes direct form port to container parks, whilst the 30m Quad Quad B Double Vans add increased palletized space up to 42Pallets as per above and additional mass weights up to 77.5T.
How can BTT engineering help you get the most out of your PBS B Double combination?
BTT Engineering works with both you and your trailer manufacturer to ensure your combination meets the PBS Build Standards and individual states access requirements. Also offering assistance with obtaining the required Telematics, Weighing systems, Access Permits and any additional NHVAS Accreditation Modules needed to fully maximize your new PBS Combination.
Related PBS services & other combinations we can assist with
PBS B Double combination FAQs
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It depends on the axle configuration, it can range from 68.5t for a tri-tri configuration to 77.5t for a quad quad configuration.
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Typically up to 30 meters, however slightly longer may be allowed in some jurisdictions like Victoria.
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Both combinations can provide great benefits, the advantages of a B Double are that it is only two trailing units not three which can reduce capital and operating costs and that it is easier to package in more pallets (up to 42) whilst remaining under 30m overall length which is essential if you want to travel into Brisbane.