Longer Semi-Trailers (LSTs) are 15.65m articulated trailers legally authorised for use on roads in Great Britain under amendments to the Road Vehicles (Authorisation of Special Types) (General) Order 2003 (STGO) introduced on 31 May 2023. They may be up to 2.05m longer than a standard 13.6m semi-trailer while retaining the existing UK 44 tonne gross vehicle weight limit.
The additional trailer length increases load volume without increasing permitted weight. A 15.65m LST can carry up to 60 UK pallets (1200 x 1000mm), typically providing around a 15% increase in cubic capacity compared with a standard-length trailer. This makes Longer Semi-Trailers particularly effective for high-volume, lower-density freight where load space rather than weight is the limiting factor.
- Higher pallet capacity per journey
- Reduced trip frequency for equivalent freight volumes
- Lower mileage and fuel consumption per pallet moved
- Reduced CO2 emissions per unit of freight transported
Operation is subject to defined dimensional, axle and manoeuvrability requirements under the STGO framework. The key legal and technical parameters are outlined below.
What is a Longer Semi-Trailer?
A Longer Semi-Trailer is an articulated trailer authorised to operate in Great Britain at up to 15.65m in trailer length under the STGO framework. It is longer than a standard 13.6m semi-trailer but does not benefit from any increase in the normal UK gross vehicle weight limit.
The main purpose of an LST is to increase load volume rather than payload weight. This makes it particularly suitable for operations carrying high-cube, lower-density freight where pallet count and cubic capacity are more limiting than gross mass.
In practice, LST suitability depends on route geometry, loading profile, manoeuvrability requirements and the operator's ability to use the additional trailer length efficiently. For some operations, a standard trailer remains the better fit if the work is weight-limited or route-constrained.
Legal Status of Longer Semi-Trailers in Great Britain
Longer Semi-Trailers became permanently authorised for use on roads in Great Britain on 31 May 2023 following amendments to the Road Vehicles (Authorisation of Special Types) (General) Order 2003 (STGO).
The national LST trial began in January 2012 and concluded on 29 February 2024. During the trial period, trailers operated under Vehicle Special Orders. Following completion of the trial, LSTs moved into permanent statutory authorisation under the STGO framework, subject to its specified operating conditions.
Because LSTs exceed the dimensional limits applied under standard GB and EU type approval rules, they do not fall within conventional approval schemes. Instead, they are authorised through STGO provided the trailer complies with the required dimensional, axle configuration and turning performance criteria.
This authorisation applies to Great Britain only. LST combinations are not intended for international road transport where standard European dimensional limits continue to apply.
Dimensional and Compliance Requirements
- Maximum trailer length: 15.65m, up to 2.05m longer than a standard UK semi-trailer
- Maximum overall vehicle combination length: 18.55m
- The 18.55m limit includes the tractor unit; extended or aerodynamic cabs permitted under Directive 96/53/EC Article 9a cannot be used where this overall length would be exceeded
- Trailer must be tri-axle
- A rear steer axle is required to assist manoeuvrability and reduce tyre scrub
- The vehicle combination must comply with turning circle requirements, remaining within a swept path corridor of 5.3m inner radius and 12.5m outer radius
- Maximum UK gross vehicle weight: 44 tonnes
Additional Capacity and Operational Impact
A 15.65m LST can accommodate up to 60 UK pallets (1200 x 1000mm) in a single-deck configuration, representing up to four additional pallets compared with a standard 13.6m trailer. Double-deck configurations can increase total pallet positions further, depending on deck layout and aperture specification.
Where operations are cube-limited, this increase in volume can reduce delivery frequency by approximately one trip in every 6.5, subject to route structure and load profile.
Unladen trailer weight increases marginally due to the additional structure and steering components. Payload calculations should be assessed carefully to ensure continued compliance with the 44 tonne gross vehicle weight limit.
Double-deck LSTs can be specified to achieve comparable deck apertures to standard-length equivalents, subject to detailed design.
Chassis Designs and Specification Options
Extended-length trailer development predates the national LST scheme. Rear steer systems were introduced to manage tyre wear and turning performance, and multiple chassis formats are available to suit operational requirements.
- Straight-frame chassis
- Step-frame chassis
- "Wedge" chassis designs
- Double deck and lifting deck configurations
- Self-tracking or positive steer rear axle systems
- Variable body length up to 15.65m
Specification should be aligned with route constraints, loading method, axle weight distribution and required turning performance.
General Arrangement Drawing
The diagram shown is an example general arrangement for a straight-frame curtainsider Longer Semi-Trailer at 4.2m overall height. Dimensions can be tailored to suit operational requirements, including deck height, body length, axle configuration and aperture specification.
The preview image is a low resolution JPG. The downloadable PDF provides the full technical layout including side elevation and plan-view dimensions.
360 Viewer
Take a virtual walk around in our 360 panoramic viewer.
Scene menu buttons on the left of the viewer window allow you to navigate around the trailer to look at specific features.
Example shown is a wedge chassis design with full-length lifting deck platform.
Image gallery
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Indicative pricing & availability
Price: P.O.A.
Available to pre-order
