Fixed Double Deck Trailers

Why fixed deck trailers are used

Fixed double deck trailers are typically used in operations where pallet heights, freight dimensions and loading methods remain relatively consistent between journeys. This allows the upper deck position to be optimised around a known operating profile without requiring adjustable deck mechanisms.

Because the upper platform remains permanently fixed, the trailer structure is generally simpler than mechanically adjustable or hydraulically operated alternatives. This can help reduce acquisition cost, tare weight and long-term maintenance requirements whilst still delivering substantial volumetric gains over a conventional single deck trailer.

Many fixed deck trailers are configured specifically for pallet network, retail and trunking operations where high pallet throughput, repeat loading patterns and loading efficiency are prioritised over deck flexibility.

Trailer geometry can also be tailored to suit different operating requirements, including step-frame, straight-frame and wedge chassis layouts depending on the required aperture distribution, freight profile and internal height strategy.

How chassis geometry affects internal height

Fixed double deck trailer design is influenced by the height of the tractor unit fifth wheel, typically around 1250 mm in the UK. Because the trailer neck sits above the tractor unit chassis, internal height is naturally more restricted at the front of the trailer.

Behind the landing legs, the tractor unit no longer sits beneath the trailer. This allows step-frame and wedge chassis layouts to reduce floor height towards the rear, increasing available aperture height where most of the double deck load space is used.

Step-frame designs use a pronounced drop behind the landing legs, while wedge layouts slope gradually downwards towards the rear. Straight-frame layouts maintain a more consistent floor height throughout the trailer length.

Upper deck configurations

Upper deck length is usually determined by the available internal height and the type of freight being carried.

Full-length fixed upper decks can maximise pallet capacity, with some trailers accommodating up to 52 UK pallets where freight height and aperture distribution allow.

Many step-frame pallet network trailers use a shorter 3/4 length upper deck from the landing leg area rearwards. This keeps the rear section suitable for standard pallet heights on both levels, while leaving the swan-neck area available for taller, irregular or non-divisible freight.

Curtainsider and box van configurations

Fixed deck curtainsiders provide full side loading access using forklifts and are widely used for palletised freight distribution.

Fixed deck box van trailers are commonly used for retail, parcel and high-cube distribution operations where aerodynamic performance, load security or weather protection are priorities.

Because the upper deck is fixed in position, box van trailers typically require a two-tier tail-lift system to provide access to both deck levels during loading and unloading.

Pallet network fixed deck trailers

Many UK pallet network double deck trailers are step-frame fixed deck curtainsiders designed for repeat hub-to-hub distribution, where side access, loading speed and predictable freight profiles are important.

Pallet network "Deckers" commonly refer to a specification of step-frame curtainsided fixed deck trailer well suited to pallet network operators.  These freepost (only one side pillar at the neck) trailers will be tri-axle on either 19.5" mini single or 17.5" twin tyres.  The upper fixed deck has mesh panels in the floor to improve visibility for the forklift loaders.  The upper deck is likely to extend from the neck position rearwards, allowing larger loads to be positioned on the swan-neck.  The body (including fixed rear panel) will be EN 12642-XL rated and the curtains will have an extended track so that curtains wrap around the rear to prevent fouling during loading ('Clearspan').