Guidance & Reports on the UK Department for Transport’s trial of longer semi-trailers for articulated goods vehicles

The UK’s Department for Transport (DfT) recently released a statement saying that “Legislation will be laid to safely roll out of longer semi-trailers for articulated goods vehicles on roads from 31 May.”


The Department for Transport (DfT) began a trial of longer semi-trailers (LSTs) for articulated goods vehicles in January 2012. The operational trial aims to see if using longer semi-trailers brings about anticipated environmental and economic benefits. The trial is expected to save over 3,000 tonnes of CO₂ with overall economic benefits estimated at £33 million.

The trial involves longer semi-trailers of 14.6 metres and 15.65 metres in length (17.5 metres and 18.55 metres total vehicle lengths respectively). The trailers must operate within the UK’s existing domestic weight limit (44 tonnes for vehicles of 6 axles).

The trial was originally scheduled to run for a maximum of 10 years from 2012 with a total allocation available of 1,800. In 2017 the government agreed to increase the number of LSTs by an additional 1,000 and to extend the trial by 5 years to 2027. This increase will take the number of LSTs from 1,800 to approximately 2,800.

Participation in the trial is on a voluntary basis and at the participants’ own risk. DfT can’t guarantee that the use of the longer semi-trailers will continue to be permitted beyond the end of the trial period.

Guidance for participants

Data requirements and trial evaluation

DfT’s trial of longer semi-trailers is a research project which has been established to monitor, evaluate and understand the use of these vehicles. Operators taking part in the trial must collect data on their use of the trailers and submit it regularly to DfT’s independent trial evaluators, Risk Solutions every 4 months.

Risk Solutions can be contacted at 00441925 413 984 or for guidance and data recording templates.

Vehicle special orders for longer semi-trailers

Operators participating in the trial must apply to the Vehicle Certification Agency (VCA) for a vehicle special order (VSO) to use their longer semi-trailers commercially. Trial participants must sign an undertaking agreeing to certain terms before they apply to VCA. VCA will inform DfT when it issues a VSO to an operator.

Operating longer semi-trailers without a VSO is illegal and may invalidate insurance policies covering the use of these vehicles.

The secondary market for longer semi-trailers

Once participants have obtained longer semi-trailers, they are free to purchase vehicles from each other (the allocation quota moving with the vehicle). A new operator would have to apply for the necessary VSO.

Operators must notify DfT of their intention to purchase a longer semi-trailer from another participant to ensure they meet our allocation criteria.

The allocation itself has no monetary value and must not be bought or sold. Only the vehicle can be bought or sold.

Moving vehicles between sites for demonstration purposes

The Road Vehicle (Authorisation of Special Types) (General) Order 2003 permits longer trailers to be used on public roads for ‘tests and trials’ purposes, without a VSO. Schedule 11, Part 2 of the order gives a more precise definition of what is meant by tests or trials. It defines this term as including the use of vehicles or trailers for demonstration purposes. However, only a court can provide a definitive view of whether a particular activity fits the terminology used in the legislation, so if manufacturers are in doubt they should seek legal advice.

No prior authorisation from DfT is required as long as the use is in accordance with the requirements and conditions set out in the order. Section 38 covers requirements as to length. One of the conditions is that the vehicle is un-laden. Another is that the police should be given 2 clear working days’ notice. For those companies who hold an ‘O’ licence, the ESDAL (electronic service delivery for abnormal loads) system provides a web-based notification facility.

Manufacturers who do not themselves hold an ‘O’ licence should contact their local police force’s abnormal loads officer, who should be able to advise on the notification procedure.

Northern Ireland and Europe

The trial applies only to roads in Great Britain. Operators wanting to go to Northern Ireland in a longer semi-trailer must obtain an additional VSO from the Department for Infrastructure (DfI):

The longer semi-trailers do not comply with standards in force in other European member states so cannot be used for international traffic in mainland Europe.